Apparent competition between vegetative phase and fruiting phase
Carbohydrate to Nitrogen Ratio
(This appears to be the nucleus of a unifying model of floral induction. It unites photoperiodism, shading, girdling, temperature variations, humidity, and other conditions on the basis of their effect on the carbohydrate:nitrogen ratio. Root-bound plants, for example, would be expected to receive less nitrogen, relative to their potential for photosynthesis. Girdling and binding would trap carbohydrates above, while allowing nitrogen to move upwards from the roots. Scapes or stems removed from a plant would receive no more nitrogen from the roots, while retaining their carbohydrates. In other words, any condition—external or internal—that affects the carbohydrate:nitrogen ratio could influencing flowering and fruiting.)
Roberts (1927)
How do very poorly
vegetative trees become strongly vegetative by being placed in a short
photoperiod? The change in percentage of nitrogen appears directly related to
the fall in specific gravity due to a reduced carbohydrate content. With the
respiration of carbohydrate material there is a corresponding
liberation of available nitrogen, as NIGHTINGALE (3) has found in the tomato.
If carbohydrate respiration is a liberator of nitrogen forms which make for
increased growth then carbohydrate accumulation must have previously been a
binder of those nitrogen forms. Does carbohydrate accumulation inhibit
vegetative extension? Do accumulating reserves cheek growth as well as
accumulate after growth in length is checked? That could be an interpretation
of the reduced growth of girdled trees. Girdling so changes other factors that
this evidence might be weak. The relation of amount of elongation to
composition in the shade-and-girdling series does, however, appear
suggestive. The probable, if not apparent, relation of carbohydrate
accumulation to reduced growth has many practical applications in connection
with such questions as dwarfness, period of growth, ''old age" in trees,
partial etiolation, the rest period, as well as with blossom bud formation.
Separating stems from plants
Beaton (1861)
Mr. Knight made an experiment for getting early Potatoes to seed by planting them on a ridge, and when the plants were ready to bloom he washed away the soil of the ridge to prevent them making young tubers, and so force the whole strength of the plants or roots into the stems and foliage to see if that would force them to seed. Another form of that experiment is applicable to all bulbs and tubers which form roots on the flowering-stems, as the Japan Lilies and others do. Pot such bulbs or tubers with the neck of the bulbs just at the surface, and when the stem is an inch or two put an empty pot over it, introducing the stem through the hole at the bottom of the pot, then earth up the stem, and when it roots and fills the upper pot separate from the bulbs, then cross it.
Neil O. Anderson, Breeding and Genetics (2007)
Most hybridizing in private and public sector breeding programs has been conducted in greenhouse conditions. Viehmeyer and Uhlinger (1955) developed a ‘water culture’ method to accommodate situations of limited greenhouse space. This technique was accidentally discovered after chrysanthemum stems cut for use as pollen sources were allowed to senesce in a vase and produced seeds. In 1951, the water culture method was re-tested with cut stems placed in jars of water, in lab conditions (ambient temperatures and light conditions), and proved successful in seed production. Subsequent trials demonstrated that seed could be ripened in darkness, seed viability and % seed set were equal to in situ ripening, and seed maturation occurred 2-4 wks. Earlier (Viehmeyer and Ulhlinger, 1955).
B: New Varieties of Potatoes from Seeds (1846)
In autumn, soon after
the appearance of the first heavy frosts, let the potato balls or apples be
gathered, macerated in water, the seeds separated from the pulp, and placed in
some convenient place in the shade, to dry; after which they may be packed up
in an air-tight box or bottle, and kept until required for use. As few of
the early sorts produce blossoms, in order to produce seeds from them, deprive
the plant of its tubers as they appear, and keep the runners from which they
proceed above ground, by not earthing up the plant, and blossoms and seeds will
soon appear.
Knight: On raising new and early Varieties of the Potato (1820)
Having fixed strong stakes in the ground, I raised the mould in a
heap round their bases, and in contact with them: on their south sides I
planted the Potatoes from which I wished to obtain seeds. When the young plants
were about four inches high, they were secured to the stakes with shreds and
nails, and the mould was then washed away, by a strong current of water, from
the bases of their stems, so that the fibrous roots only, of the plants, entered
into the soil. The fibrous roots of the Potatoe are perfectly distinct organs
from the runners, which give existence, and subsequently convey nutriment, to
the tuberous roots; and as the runners spring from the stems only of the
plants, which are, in the mode of culture I have described, placed wholly out
of the soil, the formation of tuberous roots is easily prevented; and whenever
this is done, numerous blossoms will soon appear, and almost every blossom will
afford fruit and seeds
Traub: Artificial Reversal of Growth Dominance in Amaryllids (1935)
In a large number of trials, self or cross pollinated flowers of
excised amaryllid scapes, especially those of Hippeastrum, placed in
water or nutrient solution, have in the great majority of cases produced seeds.
Within limits, the number of seeds per capsule seems to be largely a function
of the relative size ("fleshiness") of the peduncle
Caldwell: At Long Last—Seeds On Lycoris squamigera (1979)
So in the flowering season of 1976 I went back to work on L. squamigera, using pollen from L. sanguinea, L. sprengeri, L. chinensis, L. "Sperryi" and from a new unidentified
yellow lycoris that looks much like L. squamigera. Reciprocal
crosses were made. I cut about 40 scapes, labeled them and hung them in light
shade in my greenhouse. For a time they made progress; seed capsules fattened
in an encouraging way. However, in September when they were fully ripened it
was a disappointing task to shell out the capsules, umbel after umbel, and find
no seed. But one scape looked particularly good and, sure enough, when I peeled
away the capsule covering, there they were—three large, shiny, hard black
seeds, one of them fully 3/8" in diameter. This may sound absurd but plant
breeders will understand—it was like finding gold nuggets after a 20-year
search!
Allen: Experiment's on Mr. Pell's Farm (1845)
The grain was cut when the straw presented a yellow appearance
four inches above the ground. At that stage of its growth, a milky substance
could be expressed readily from the kernels, by gentle pressure of the
forefinger and thumb. It was allowed to remain three days on the field, when it
was carried to the barn and threshed out immediately. It weighed 64 lbs. per
bushel, and sold for 12 1/2 cents above the market price by weight. A
few acres were left standing, and cut three weeks after, when others in the
neighborhood harvested their wheat. This proved small, shrivelled, and weighed
56 lbs. per bushel. The straw had lost its most nutritious substances, was much
lighter than that cut earlier, and was consequently less valuable. Mr. Pell
thinks that after the stem turns yellow near the ground (there being no
connection between the root and the tassel), the kernel wastes daily. By early
cutting, nearly all the saccharine matter is preserved in the straw, and it is
thus rendered almost as valuable for fodder as hay.
Whyte: Relationships of Developmental Physiology (1960)
For maximum production of grains in an annual cereal, growth processes are allowed to proceed to their end, until such time as the developmental processes and building of the grain exercise a completely inhibitive effect upon growth and the plant bearing the ripe fruit dies. Where optimal environmental conditions are available for fruiting, the straw is of little value, everything having been supplied to the grain. Where conditions are below the optimum, grain yields are lower and ripening more difficult, but the straw is of higher nutritive value for livestock. Growth has continued longer owing to the lower inhibitory effect of the development, and less building material is supplied to the grain.
The striking of an appropriate balance between growth and reproduction is the basis of good management of grassland for grazing or hay production.
Russell: Proliferous Character of the flower-salk of the Lilium Candidum (1835)
...the flower-stalk of the White Lily (Lilium Candidum), cut
immediately after the sepals have fallen, and kept in an upright position in a
cool and shady situation, will evolve from the axis of its bracteal leaves
distinct bulbs, capable of producing perfect plants. My attention was first
attracted to this curious fact by the kindness of a friend, some three or four
years since, and I have uniformly been successful in the result, whenever I
have renewed the experiment. But the vital energy is not only continued and
developed in the production of these hitherto adventitious bulbs, several of
the capsules even, ripened sound and vigorous seed.
Sterility and Gigantism
Knight: Upon the effects of very high temperature on some species of plants (1819)
The Melon. Plants of this species were trained upon a trellis near the glass, which was of the best quality, and these exhibited a greater degree of health and luxuriance, than I had ever before seen; but not a single flower ever unfolded; a great profusion of minute blossoms, nevertheless, appeared in succession at the points of the shoots, all of which perished abortively. I was much disappointed at the result of this experiment; from which I confidently expected to obtain fruit of the greatest excellence.
The Water Melon. A plant of this species, treated in the same manner as the melon plants above mentioned, grew with equal health and luxuriance, and afforded a most abundant blossom; but all its flowers were male. This result did not, in any degree, surprise me; for I had many years previously succeeded, by long continued very low temperature, in making cucumber plants produce female flowers only; and I entertain but little doubt, that the same fruit-stalks might be made, in this and the preceding species, to support either male or female flowers, in obedience to external causes.
Cook: Suppressed and Intensified Characters in Cotton Hybrids (1909)
Many plantings of Central American varieties of cotton in Texas
have been rendered completely sterile through the exclusive development of
vegetative branches from the axillary buds instead of fruiting branches, which
arise from extra-axillary buds. This behavior may be viewed as an
intensification of the vegetative tendency, which remains largely in abeyance
when the plants develop in a normal manner, as they are able to do after a few
seasons of acclimatization, that is, if the first plantings do not carry the
vegetative intensification to the point of complete sterility.
Cook: Cuzco Corn (1916)
The usual behavior of the Cuzco corn in the United States is to
produce plants of enormous size that mature very little seed, often none at
all. It has been taken for granted that the size of the plants should be in
proportion to the enormous kernels, and that our seasons were not long enough
to permit this type of corn to mature.
But in Peru one does not see these gigantic,
infertile plants, nor any indication that the corn crop requires a large amount
of heat to bring it to maturity. The impression one gets from the Peruvian
corn-fields is that the plants are not taller than with us and rather more
slender, the most striking peculiarity being the prevailing red color of the
foliage. The best development and largest ears of the Cuzco corn are found
in some of the higher valleys, at elevations between 9,000 and 11,000 feet, in
districts where the summer climate is cooler than in any of the corn-growing
regions of the United States.
Karpechenko: The production of Polyploid Gametes in Hybrids (1927)
Dominance of biennial over annual habit
Burbank: Methods and Discoveries 6:68 (1914)
Still greater interest attaches, perhaps, to hybridizing
experiment in which the parents were Shaffer's Colossal raspberry and the
Crystal White blackberry.
Some of the plants from this cross were of the
most tree-like proportions. Most of them, however, were barren, though they
bloomed freely. But there were exceptional ones that fruited, and selected
seedlings were grown from these through a series of generations. In the fourth
generation a plant appeared which was of such extraordinary characteristics
that it was given the name of Paradox.
This plant was in all respects a most
perfect combination of the two ancestral forms from which it sprang. The wood,
bark, leaves, blossoms, prickles, roots, and seeds could not by any test be
proved to be like one or the other. The fruit, produced in abundance, was an
oval, light red berry of good size, larger than that of either progenitor, and
of fair quality.
Many of the first generation descendants
of the Paradox were partially barren, though blooming freely. Sterility as to
fruit was often associated with gigantic growth.
Girdling and Grafting
JCH: Ringing Fruit Trees (1869)
This year the appearance of the three branches above the cut stem was one mass of white blossom, there being only one blossom on any other part of the tree; and there are at this time, besides numbers that I have removed, thirty-six Pears, healthy, and apparently going on to maturity.
Williams: An Account of a Method of hastening the Maturation of Grapes (1808)
I took annular excisions of bark from the trunks of several of my
Vines, and that the exposed alburnum might be again covered with new bark by
the end of autumn, the removed circles were made rather less than a quarter of
an inch in width. Two Vines of the White Frontiniac, in similar states of
growth, being trained near to each other on a south wall, were selected for
trial; one of these was experimented on (if I may use the term), the other was
left in its natural state, to form a standard of comparison. When the circle of
bark had been removed about a fortnight, the berries on the experimented tree,
began evidently to swell faster than those on the other, and by the beginning
of September showed indications of approaching ripeness, while the fruit of the
unexperimented tree continued green and small.
Nicolas: Sterility encountered in rose breeding (1927)
Paul's Scarlet Climber as an own root plant may be considered as
sterile, but a grafted plant will bear both self- and hand-pollinated seeds.
http://www.bulbnrose.org/Heredity/MassKnight1823.html
It was before well known to gardeners, that any thing which
checked the growth of a fruit tree, hastened the production of fruit.
On
two orange-trees from St. Michael's, which had never borne fruit, though we had
had them many years, we practised decortication, taking off a ring of the bark
of half an inch in width. In the following spring, this year, the gardener
expressed to me his surprize, that those limbs were literally loaded with
blossoms. He had not been in the secret. We pointed out to him the
decortication or ringing, or as we say, the "girdling," and it was
found, that while every other part of the tree was without blossoms, those
which were operated upon were far too greatly covered with them.
In this case we committed a mistake. The orange-tree puts forth only once in a
year ordinarily in our climate, or under favourable circumstances, twice.
Ringing or girdling should only be executed when the sap is in the greatest
possible degree of action. These limbs are not healthy, and we fear will not
hold their fruit, but the experiment shewed the principle in its clearest
light. The general rule is, to girdle when the tree is in its most rapid state
of growth, to make the decortication or ring larger or smaller according to the
vigour of the plant, but so little in all cases as to enable the tree to close
the wound during the same season. We made a similar experiment on a flowering
plant, the beautiful Passiflora Alata, and we threw it by this process into
flower, at a season in which it never flowers in the ordinary course of nature,
that is, in the month of August. Its usual time of flowering with us, is
October and April.
Jeffrey: Seeds on horseradish and Lilium candidum (1915)
Physiological sterility is frequently due to entirely different
causes than genetical lack of harmony, as for example in the horseradish or the
potato (Solanum). In the former it has been found possible to bring about the
formation of fertile seed by simply girdling the top of the subterranean
storage region of the plant, so as to prevent the undue descent of assimilates.
The common white lily, Lilium candidum, presents a similar condition, for here
the setting of seed takes place only when the leafy flowering axis is severed
from its bulb and kept in water.
Drinkard: Fruit-bud formation and development (1911)
Prof. Macoun: Proc. Soc. Hort. Sci. (1911)
It has been a little theory of mine, not borne out by any actual
experiments, that the formation of fruit-buds is due in part to the retardation
of the elaborated sap in the upper part of the tree. For instance, we find that
ringing a tree will cause the development of fruit buds. We find also that a
branch which is partly broken will fruit perhaps two or three years before the
other part of the tree. We find that a tree which is top-grafted will fruit
sooner than a tree which is not. It strikes me that there may be some relation
between the retardation of the elaborated sap by ringing, breaking or grafting
and the formation of fruit-buds. It has also been noted by fruit-growers that a
dry season is is followed by a good crop of fruit the next year.
Meehan: Budded Roses (1855)
Every body knows why a Pear is grafted on the Quince. The Quince
is naturally a shrub, ten or fifteen feet in height, and of the same natural
family of plants as the Pear, which will "take," or bud or graft,
freely on it; but in so doing, loses its tendency to become a tree, and while
thus assimilating in size to the Quince, gains an additional power to flower
and bear fruit. This is in accordance with the physiological doctrine, that
what tends to check the wood-forming principle of vegetation, increases its
power to blossom and bear. The Rose can be, and is, budded for the same reason,
though not for that reason alone.
American Farmer, 5(6):193 (1876)
A correspondent of the American Agriculturist says: "To obtain fruit from barren trees, take coarse, strong twine, and wind it several times about the lower limbs of a tree and tie it as tight as possible. The next spring all the top above the cord will be as white as a sheet, and there will not be one blossom below. A neighbor seeing his trees loaded with pears, used the same method with the same success."
Russell: To obtain
Fruit from Barren Trees (1859)
I wish to
describe to you a method of making fruit trees bear that I blundered on to.
Some fifteen years ago I had a small apple tree that leaned considerably. I
drove a stake by it, tied a string to a limb and fastened it to the stake: The
next year that limb blossomed full, and not another blossom appeared on the tree,
and as Tim Bunker said, "it got me a thinking," and I came to the
conclusion that the string was so tight, that it prevented the sap returning to
the roots; consequently, it formed fruit buds. Having a couple of pear trees
that were large enough to bear but that had never blossomed, I took a coarse
twine, wound it several times around the tree above the lower limbs, and tied
it as tight as I could. The next Spring all the top above the cord, blossomed
as white as a sheet, and there was not one blossom below where the cord was
tied. A neighbor seeing my trees loaded with pears, used this method with the
same result. I have since tried the experiment on several trees, always with
the same result. I think it a much better way than cutting off the roots. In
early Summer, say June or July, wind a strong twine several times round the
tree, or a single limb, and tie it, the tighter the better, and you will be
pleased with the result: the next Winter or Spring the cord may he taken off.
Noehden: Ringing Fruit Trees (1822)
The theory of this mode of pruning consists in suppressing the direct channel of the sap, and substituting for it from three to seven oblique branches, which, at certain distances, one above another, form a sort of forked passage that will only permit the sap to rise and descend slowly, obliging it to stop and form a great number of fruit buds. The experience of more than a century proves the goodness of this theory, when it is put in practice by skilful gardeners.
Noehden: Training Fruit Trees (espalier) (1822)
The essential point is to lay the branches in a horizontal position. For by training them in this way, the current of the sap is forced to assume a direction, in which it cannot move with the same quickness as it would in its natural channel, which is from the root straight upwards: and the diversion favours the process of forming fruit, by inducing, as has elsewhere been intimated, a slower motion of the sap, and thus affording time for the secretion and deposition of its particles.
Sir Francis Bacon: Delaying Roses (1635)
The Seventh is, the Girding of the Body of the Tree about with some Pack-threed; For that also, in a degree, restraineth the Sap, and maketh it come up, more late, and more Slowly.
Altered Conditions, Transplanting, Starving, Infection and Drought
Downing: The Van Mons Theory (1849)
It will be remembered that it is a leading feature in this theory that, in order to improve the fruit, we must subdue or enfeeble the original coarse luxuriance of the tree. Keeping this in mind, Dr. Van Mons always gathers his fruit before fully ripe, and allows them to rot before planting the seeds, in order to refine or render less wild and harsh the next generation. In transplanting the young seedlings into quarters to bear, he cuts off the tap root, and he annually shortens the leading and side branches, besides planting them only a few feet apart. All this lessens the vigor of the trees, and produces an impression upon the nature of the seeds which will be produced by their first fruit; and, in order to continue in full force the progressive variation, he allows his seedlings to bear on their own roots.
Genesee Farmer, 24(2): 88 (February, 1863)
The Balsam, or Lady Slipper, is well known. It has been greatly improved, and the flowers are now frequently as large and double as the rose. They should be transplanted once or twice, so as to check the growth of leaves, and favor the development of the flowers.
Burbank: Fragaria californica (1914)
We have seen that
plums and many other plants are stimulated to exceptional growth by precisely
such a change. But when the promising wildlings from the Yosemite were
transplanted to my gardens they ran to vines and produced very little fruit, although
in their native habitat they had borne abundantly.
Sorauer (1895) quoted by Wiggans 1918,
Mo. Agr. Exp. Sta. Research Bul. 32
Of our apple trees it is a well known fact that in warm insular climates they grow into magnificent foliate trees but remain unproductive of fruit.
Shomel: Corn Culure and Breeding. 51st Annual Report of the Indiana State Board of Agriculture XLIII (1901-1902).
In most seasons, cowpeas and soy beans, drilled between the rows of corn just after the last cultivation, give good results. These crops will produce from one to two and one-half tons of hay per acre and will increase the fertility of the soil. Where the soil is a rich prairie loam the soy bean is more successful than the cowpea. On such rich soils the cowpea run to vines and does not mature a seed crop.
Herbert (Amaryllidaceae) (1837) - Camellias
p 367:
The reason that the seedlings raised by some nurserymen are so
very inferior is, that their plants are in the most luxuriant growth; and it
cannot be expected that seed gathered from individuals growing with freedom and
vigour, should not be more disposed to reproduce the natural form of the plant,
than to yield the fine cultivated varieties, which are to be obtained from them
when almost diseased by repletion.
p 370:
Having cultivated the myrtle-leaved above twenty-five years, I
never saw that variety bear an anther in my collection, except one season, when
all the flowers on every plant of the kind had them, and they were found in two
or three late flowers last year; but the seedlings reared from its pollen, of
which great expectations were entertained, proved to be the worst I had ever
raised, and it seemed that whatever peculiarity of the season inclined the
flowers to deviate from their usual double form, and approach nearer to the
fertile single-flowered original, disposed also the pollen to generate single
seedlings. I have seen the myrtle-leaved with anthers at Mr. Knight's nursery,
though the circumstance has been so rare in my own collection; perhaps it may
be connected with the more or less luxuriant growth of the plant.
http://www.bulbnrose.org/Heredity/DrinkardFruitBud1911.html
Prof. Blake: Proc. Soc. Hort. Sci. (1911)
I think from certain observations that the peach is perhaps more
susceptible than the apple to differences of fertilizer treatment and other
conditions. In the experiments in New Jersey, it has been quite noticeable that
sometimes a check to the trees, such as attacks of scale, results in very large
fruit. During the past two or three years some winter injury has occurred, and
those trees which have not been too severely injured produced very large
specimens, even though there was a very large crop on the tree.
Prof. Drinkard: Proc. Soc. Hort. Sci. (1911)
Reed, at the Virginia Station, has reported a case where a blight
of some kind had caused the blooming of certain trees in the fall of the year,
and he attributed the premature blooming to the influence of the blight. There
is no doubt that the cessation of vegetative growth has a marked influence on
fruit-bud formation, but to what extent they are correlated I cannot say.
Nicolas: Rose Infections (1933)
Summer defoliation is not always due to
disease, although diseases will precipitate it. Summer defoliation did not
bother our fathers before the introduction of Austrian Briar blood. Austrian
Briars will lose their foliage early because it matures early. It is the nature
of the beast that nothing can change, and all their hybrids inherit that
character in a greater or lesser degree. When the foliage is mature, the
"cortex" or film of corky material that heals the pores where the
leaf is attached to the branch begins to form, the leaf receives less and less
nutrition from the plant and drops at the least provocation, spray or dust
notwithstanding.
[This may relate to the apparent sterility of R. foetida. If the
plant is not allowed to go dormant (usually being "forced" to grow by a foreign rootstock),
it may compete with the fruiting phase — drawing back nutrients needed to
ripen fruit and seed. Would girdling help?]
American Agriculturist, 2(6): 179 (1843) by S. S.
The writer visited an amateur strawberry gentleman this spring, who had various kinds. His Hovey bed was taken peculiar care of, so that he could present his friends some. The writer asked him if they had borne well? He replied they were very large—he would find him one; after some little time, one was found, very large, and if strawberries were raised, to be looked at, or taken in small quantities, like medicine, then under the present treatment, they would answer. The runners of these vines in the garden referred to, were four feet long. Mr. Longworth says a plant in his garden, in one year, covered with runners three square feet of ground. Now no plant can do both; make a large amount of stems, foliage, and runners, and bear fruit or berries at the same time.
Shock
Popenoe: Origin of the Banana (1914)
Seeds may be produced in an ordinarily sterile variety as a result
of environmental conditions, if there is any basis of fact in the story given
to O. W. Barrett by a Porto Rican native, who advised: "Get a stool
of bananas growing rapidly in shallow soil by the addition of artificial
fertilizers; let one bunch of fruits set; but before that ripens, cut down all
but one of the stems in the clump. The remaining shoot, 'thinking it has but
one more chance to perpetuate its kind before being killed,' on account of the
tremendous shock to the more or less connected stem bases in the clump, at once
produces a small bunch of somewhat abnormal fruits, some of which will contain
seeds."
Schulz: Hardgrove Shock Treatment (1954)
As soon as the flower stalk begins to wilt it is cut off; also cut
off all the leaves except the very small center ones. Lift the amaryllis from
the pot and cut back the roots to about two inches. Then repot in fresh soil
and set the plant in a shady place until the leaves begin to lengthen. At this
point, you can put it back with your other amaryllis, if you wish, and it will
very likely show another bloom stalk.
Root-bound / Root pruning
The Garden: Root-Pruning (1892)
The Floral World 4(7): 223 (July, 1869)
Hoya Bella Culture.—W. G., Salop.—This is by no means an expensive subject. You can get a thrifty little plant anywhere for half-a-crown. If you procure a plant at once, shift it into a pot one size larger, and place in an average temperature of 70°. Previous to potting, give the foliage a thorough sponging with warm water and a little soft soap, if in any way infested with scale or mealy bug, and then syringe with clear water, A thoroughly-drained pot and a light porous soil are indispensable requisites to the successful culture of this beautiful little Hoya. The compost should consist of two parts fibry peat, one part leaf-mould, and a good sprinkling of sand, small crocks, and nodules of charcoal. Stop the leading shoots to promote a bushy growth, and towards the end of August lessen the water supply, and place near the glass to thoroughly ripen the wood. This must be done in a careful and judicious manner, so that no sudden check is experienced. In the winter a temperature of 55° will be sufficiently high, and just enough water must be given to keep the foliage fresh. Shift early in February, and place in a growing temperature, as already advised. After a flowering size is attained, keep the roots rather pot-bound, as the plants then flower with greater freedom.
American Farmer, June, 1876
“Root-pruning
can be done at any season of the year; but it is easiest performed in spring.
The earth is then saturated with moisture, and is easily dug. Trees of three or
four inches diameter (apple or pear,) should have their roots cut off from
fourteen to eighteen inches from the trunk, [too near the stem ] and two and
two and a half to three feet deep, [deeper than necessary, the roots of trees
of that size never spread two feet below the surface.] Smaller trees should
have the roots cut shorter, and larger longer. As a rule, the radius of the
circle should be about five inches for every inch of diameter of the tree. The
trench should go deep enough to cut all lateral roots. Enough roots must be cut
to check the tree that the annual growth shall not exceed ten inches; and
whenever the tree replaces the roots cut, so as to make excessive growth, the
operation must be repeated."
In case of pear
blight, root-pruning must be done when the disease first appears. It will not do to delay, and, if well
performed, seldom fails to effect a cure. A good sharp spade should be used.
A correspondent of the American Agriculturist says: "To obtain fruit from barren trees, take coarse, strong twine, and
wind it several times about the lower limbs of a tree and tie it as tight as
possible. The next spring all the top above the cord will be as white as a
sheet, and there will not be one blossom below. A neighbor seeing his trees loaded
with pears, used the same method with the same success.”
Gardeners' Chronicle, June 13, 1908
Cymbidiums—plants in a root-bound
state are always more productive of flower-spikes.
Garden and Forest, 7: 247 (June 20, 1894)
Cypripedium insigne
We formerly had trouble in getting Cypripedium insigne to flower well, because we made the mistake of having very thrifty plants. They were treated to manure-water, and were green and vigorous, but when the time for flowering came the plants simply continued to grow and look strong, and did not flower. We now keep them in the coolest place in summer to prevent any second growth that might be induced by heat, and have left off giving manure-water except to such as are root-bound and really need it.
We are trying Cattleyas and Laelias in a large, cool and airy structure for the summer, and they have improved in looks already. Small houses have a tendency to become overheated in the hot months of the year, far beyond the requirements of these plants. This causes the growths to mature early, and a second growth ensues. The plants are thus deprived of the absolute rest so beneficial in winter and conducive to satisfactory flowering.
The Garden, 63: 377 (May 30, 1903)
Cockscombs
Balsams, Celosias, and other plants must be potted into their flowering pots before they become root-bound or they suffer a check. Cockscombs, on the other hand, are apt to grow away and refuse to produce their combs unless a check is given during the early period of growth. As soon as the combs are developed the plants require liberal treatment in every way and a gentle bottom heat.—J. Jaques. Wendover.
The Culture of Vegetables and Flowers from Seeds and Roots (1892)
Sutton and Sons
Cockscombs
The ideal Cockscomb is a dwarf, well-furnished plant, with large, symmetrical, and intensely coloured combs. Seeds of a first-class strain will produce a fair proportion of such plants in the hands of a man who understands their treatment. Sow in seed-pans filled with rich, sweet, friable loam, and place in a brisk temperature. Transfer the seedlings very early to small pots, and shift on until the size is reached in which they are to flower. Directly they become root-bound the comb will be formed.
Vick's Magazine, 9: 336 (1886)
Primula sinensis
There is a very general custom of removing all flowers as a means of retarding the flowering period; but this is a mistaken impression, and instead of retarding or checking the flowers it is certainly shortening the season by the succession of bloom spikes coming much sooner than they would otherwise have done where the first flowers were allowed to develop. The only means of checking the early flowering of Primulas is to repot them as advised directly the pots are filled with roots. They will then continue growing instead of sending up flowers. This is the secret of having late Primulas in first-rate condition, for if once they are allowed to become root-bound up come their flowers. A small quantity of soot added to the soil is very beneficial.—
A. Waters, in Journal of Horticulture.
The Garden Under Glass (1917) by William F. Rowles
Schizanthus
A good open soil and firm potting will suit schizanthuses with no attempt at shading. Never should they want for water, while to allow them to remain root-bound is a deadly sin, the punishment for which is premature flowering and puny plants. It was at one time delivered to me as a doctrine that these plants would not bear feeding. This I have proved to be a heresy, for besides adding chemical stimulants liberally to the soil I have fed them with liquid cow manure and frequently top-dressed them with Peruvian guano.
American Agriculturist, 3:29 (1844)
Pear-Training superseding the necessity of Root-Pruning.—Going over the pear quarter at the royal gardens at Versailles, I found from the head-gardener that he considered the tying-down the branches a sufficient check to overgrowth, without the assistance of root-pruning, except as regards any very free-growing varieties. Nothing could, to my mind, exceed the neatness and good-bearing of the pear-trees; they were of a conical shape and all the branches tied down so as to present the appearance of a conical chandelier, and of course much more bearing-wood obtained than in the trees which were stunted by root-pruning.
Art of Natural
Bonsai by David Joyce (2006)
Craetaegus oxycantha (May Hawthorn)
Do not let dry
out or let get root bound even though root bound trees flower better.
Azalea (satsuki) and Azalea (kurume)
Root-bound trees
flower too much, and some flowers must be removed to avoid weakening tree.
Journal of
Horticulture and Cottage Gardener 23:119 (August 6, 1897)
Tree
Carnations.—All the earliest rooted Carnations are growing rapidly and fast
filling their pots with roots. They must have weak stimulants every time they
need water, clear soot water, or that made from cow manure being good for them;
or, better still, artificial manure applied to the surface of the soil at
intervals of two or three weeks. If neglected in this respect growth comes to a
standstill, and flower spikes appear before they are wanted. Plants that are
allowed to become root-bound early in the season are almost certain to come
into flower in early autumn long before they are wanted. We have found it a
good plan to place into larger pots any that are likely to become root-bound
too early.
Choice Stove and
Greenhouse Flowering Plants, 157-158 (1869)
Benjamin Samuel Williams
Thyrsacanthus.
T.
Schomburgkianus.—This fine Acanthaceous plant, which is perhaps better known
under the name of T. rutilans, forms one of the most attractive and graceful
plants for winter blooming with which we are acquainted. The leaves are
oblong-lanceolate, tapering to a sharp point, and dark green in colour. The
flowers are tubular, bright scarlet, borne in long pendulous racemes, which
give the plant its peculiar graceful and elegant appearance. It is an abundant
bloomer, producing its vivid flowers through the whole winter and spring
months, and is a most glorious object for table decoration. The soil we find
best adapted for it is a good light loam, with the addition of some
well-decomposed manure and leaf mould, and a portion of silver sand. The plants
should be kept growing as fast as possible until they attain a considerable
size, and then kept root-bound, which will induce them to blossom more freely.
After this, if the drainage is kept in good order, a little fresh soil is all
that is necessary for a year or two, and then a batch of young plants should be
ready to succeed the older ones. It requires a liberal supply of water and
heat. Native of New Grenada.
Garden and Forest, 6:506 (1893)
Carnations may be
grown outdoors to advantage during the summer, and when lifted and potted in
the fall can be stored for a time in the pit or frame. In this way a regular
supply of these useful flowers can be assured. Bouvardias should be treated in
the same way for the summer, but after being lifted they require a higher temperature,
and, therefore, had better not be placed in the frame. If kept warm and treated
to a little stimulating food occasionally, the plants will soon become
root-bound, when they will flower freely all winter long.
American
Gardening, 24:701 (December 19, 1902)
Making the Most
of the Cold Frame and Hot Bed
I. Forcing
Cauliflower
Early vegetables
are always appreciated and cannot be had too early to suit people who are
expecting forced vegetables, and there is none that gives greater satisfaction,
on the whole, than early Cauliflower. It is also a pleasure to the grower to
cultivate subjects that give results so uniformly good as may be obtained from
any of the many stocks of forcing Cauliflower obtainable to-day.
Last year we used
a selected strain of Snowball for the purpose, though any of the dwarf Erfurt
varieties are suitable.
It is high time
to commence operations by the sowing of a pan of seeds in the greenhouse. Our
first sowing is already up, and when these are transplanted, another sowing will
be made and successions made until about six sowings have been put in. The
demand, of course, will have to govern the quantity grown, but we find it
impossible to have too many heads.
The first
transplanting of the plants is done into 2 1/2-inch pots, placing the seedling
at the side of the pot, instead of in the centre. This will be found a great
preventive against "damping off," as it is termed—it may also be
called water-pot fever. Potting off young seedlings of any description may be
much more rapidly done in this way, and the percentage of loss considerably
reduced by this simple means. It is a well-known fact, too, that when a plant
begins to feel the sides of the pot it rapidly progresses.
When the plants
are ready for a shift, they are transferred into 4-inch pots, using at this
time a good, rich, light soil. A temperature of 50 to 55 degrees at night is
most suitable. Given these conditions, it will not be long before a 6-inch pot
will be needed.
If it is intended
to finish the crop in pots, the final shift may be to a 7-inch at this last
potting.
We prefer to
finish the crop in a hotbed made up about March 15, planting out. By that time
the plants will have become somewhat root-bound, which is a desirable
condition, since it checks the tendency to leaf production and hastens the
formation of the flower head. This state is an important one to be observed,
for if planted out before this the depth of the average hotbed will not suffice
as head room, and the foliage will become crippled and often frozen by getting
in contact with the glass. The use of mats is avoided, reliance being put upon
the latent heat from the soil to keep up the required temperature. Warmth at
the roots and a cool top will perfect finer heads than where the plants are
coddled and become puny from lack of light and air.
The above details
apply to all the earliest batches. The later sowings are planted in cold
frames, without the aid of fermenting materials. These last lots are planted in
frames that enjoy shade from the heat of midday. Cauliflowers delight in cool
treatment and in late spring require protection from sun, or the foliage
suffers, and consequently the heads are of poor color and quality.
If any crop
appears to come on slowly and a break in the supply is thereby threatened, use
nitrate of soda in the water given, and the result will be magical. It is not
desirable to use the nitrate in a general way, as it has a tendency to make the
heads too large. Small ones are always preferred by the epicurean. —E. O. O.
The Garden
[London] 54:42 (July 16, 1898)
Zonal Pelargoniums do not require any
particular mixture of soils. In fact, poor soil to my thinking is better than
rich combinations. The latter tend to the growth of leaves at the expense of
flowers. My compost for these at all seasons is that which has done duty for
other plants—Chrysanthemums and the like—and another most important item is to
use comparatively small pots. When root-bound they flower most profusely.—H. C.
The Garden
[London] 54:390 (Dec 12, 1898)
Zonal Pelargonium
Guillon Mangilli.— I doubt if there is a better all-round zonal than this old
variety. It is a very reliable winter bloomer, and there is no trouble to cut
good trusses from it from November onwards. For summer flowering it is
excellent, producing large heads of bloom in great profusion all through the
season if the plants when root-bound are occasionally fed with weak liquid
manure. I have plants of it now in 8-inch pots carrying about two dozen
trusses, and these have given me a lot of bloom for cutting from the middle of
June, and will continue to do so up to the close of the autumn. For the flower
garden it answers better than the majority of double kinds, not making such
gross growth as many of them, the flowers resisting heavy rains fairly well.
Cutting struck in April and grown along freely will make good plants in 6-inch
pots for winter blooming, and one-year-old plants cut back early in May, shaken
out a little when they break, and replaced in pots one size larger, will
furnish a quantity of bloom during the dull months of the year.— J. C. B.
The Garden
[London] 54:390 (Dec 12, 1898)
GERANIUMS FOR WINTER AND SPRING BLOOMING.
With the many and
beautiful varieties of zonal Geraniums now in commerce, a house having a
comfortable temperature can now be made very gay during the dull months of
winter by specially preparing the plants for the purpose. For producing plants
for winter blooming, the best way is to take stout cuttings in February. When
rooted, grow them on as hardy as possible, shifting into 4 1/2-inch pots before
they become pot-bound, keeping them close to the glass and giving abundance of
air. At the beginning of June stand them in a sheltered position in the open
air on a bed of ashes, pinching the growths when of sufficient length, and
assisting the roots with liquid manure as soon as the 6-inch pots, which will
be large enough for the plants to flower in, are becoming pretty well filled
with roots. A good fibrous loam and some coarse sand suit them well. Keep all
summer trusses of bloom picked off, and remove into a temperature of 50º early
in October. Their somewhat root bound condition will induce flowering better
than larger pots at this season. Even during the winter a gentle current of
fresh air must be given in open weather to prevent the plants becoming drawn.
For the production of large quantities of bloom during April, May, and June,
plant out spring-struck cuttings along the edge of a Peach house or vinery
border, allowing a distance of 2 1/2 feet between each and planting in a
compost of good holding loam and a little leaf-mould and coarse sand. This
mixture not only produces a short-jointed firm growth, but also allows of the
plants being lifted in autumn with a good ball attached. Pinch the growths as
soon as sufficiently advanced and train the plants by means of stout wooden
hooks or pegs. Continue this practice till the end of August, never allowing
the plants to suffer from want of water. About the middle of September well
water the plants, and a few days later carefully lift each with as much soil as
possible and pot firmly into 10-inch pots, placing in a frame and keeping
rather close for a fortnight. When established in their new quarters, give
plenty of air, and in October remove to a cool, airy position in the greenhouse,
or even a cool vinery or Peach house. When growing freely in spring, assist
twice a week with diluted liquid manure. Plants so treated will produce a
plentiful and continuous supply of good trusses of bloom. It is best to throw
away the old plants and raise a fresh lot every year. J. C.
Window
Gardening,153-154 (1898)
Henry T Williams
Vallota Purpurea,
Is one of the
finest Amaryllis, and is the most easily managed. They are not at all
particular as to soil, will grow in any, but prefer the same as recommended for
other Amaryllis But few plants answer as well or make as fine display for the
window. Unlike most other plants, they do not require shifting but will grow
from year to year in the same pot, tub or box without a change of soil, or
other care than to give them plenty of water while flowering or in their
growing state, and moderate watering the balance of the season. The foliage
being persistent they require attention the whole year, but they can be kept
under benches, in a light cellar or in any light room away from the frost
during the winter, and in summer anywhere out of doors upon the piazza, the
lawn, or if in pots, plunge in the border. They require but little pot room, in
fact do better when root bound. The writer had a clump in a small tub last
season that gave forty-one spikes of bloom; the plant was but five years from a
single bulb. It is truly one of the finest, cheapest and most desirable cape
bulbs.
Its season of
flowering is August and September, and we have neither been able to coax or
drive it into flower at any other season.
House Beautiful
10(2): 81 (July 1901)
Plants for the
Terrace
Ida D Bennett
Hibiscus
In spite of the florist's claims
to the contrary, I do not consider the hibiscus a good bedder. A good summer
bloomer it certainly is, but it does better in pots sunk in the ground or in
the sand box, where it can be kept moist and will receive the morning sun. In
the open ground the tendency to excessive root-growth interferes with its
blooming. The hibiscus blooms well when root-bound, but must never be allowed
to dry out during the blossoming period, as this is the cause of the dropping
of the buds so much complained of. When plants are wanted for winter blooming,
bedding out in the spring and lifting in the fall may be wise, as the plants
will be in better shape for the winter blooming than if grown in pots and
allowed to bloom during summer.
In the house the
excessive root-growth of the hibiscus may be pruned if it threatens to require
too large a pot. To accomplish this with the best results and the least
trouble, I run a knife down through the soil on each side of the pot, slicing
off a good half of the roots. The remaining roots will quickly branch out into
many new feeding roots—the life of the plant—which will result in an early crop
of flowers. This will often bring a backward plant into bloom, and the habit of
blooming once established the plants will be found very reliable bloomers.
American Agriculturist, 52: 234 (April 1893)
Hibiscus not Flowering.—S. M. Wright. Clay Co., Ky.: The cause of failure of your Hibiscus sinensis to flower, after having been taken up from the garden, is a natural one. No shrub will thrive for a season after having been disturbed while in an active growing state. In disturbing its roots you have forced it into a premature rest, and its flowering buds were not developed. New buds will, in due time, form, and the plant will commence another season's growth. If the plants are expected to flower in winter, it will be much better not to take them out of the pot, but plunge them, so that the rim of the pots will be about an inch below the surface. Hibiscus have to be kept pretty well root-bound to flower freely.
Journal of Horticulture and Home Farmer, 56: 116 (January 30, 1906)
Acalypha Sanderiana
Well, I think a few remarks on stove flowering plants will not be out of place at this season. Beginning with Acalypha Sanderiana, this is a plant often neglected in the stove. I have heard the remark that it is not worth growing, simply because, through neglect, it has become root-bound in a small pot; then some day, when the stove is being overhauled, it is "shoved" into a pot several sizes too large for it. The result is that it grows to nothing but leaves and soft top growth, with an apology for a catkin here and there. If stuck under a glass in small pots in April, or even earlier, and given a shift as it requires, until it is put in a 7 in pot. (which is quite large enough to grow a specimen tree 3 ft or 4 ft high), a beautiful plant will result, with long catkins from the top to the rim of the pot. It should be grown as near the glass as possible, and given plenty of feeding when root-bound in its final pot.
American Florist, 2: 368 (May 1, 1887)
Calceolarias
During the whole period of a calceolarias' life it requires copious waterings, and should never be allowed to become dry. Water gently, but abundantly, and under the leaves and not over head except in the case of young plants in the frames. In warm, summer weather I usually sprinkled the little plants overhead early in the afternoon, so that they might be well dried before night. I never give manure water till after they get root-bound in their flowering pots, and then stop it when the plants come into bloom. Always keep them covered up dry in the event of muggy, misty, or wet weather.—Wm. Falconer
Floricultural Cabinet, July, 1854: 180
Amarylis Belladonna in Pots.—I recommend any of your readers who wish to cultivate this plant in pots, to try the following experiment:—keep the
plants constantly on a light shelf in the greenhouse, with a pan of wet sand unerneath them, which should never be allowed to become quite dry, not even in summer, when the plant is dormant. By this treatment some bulbs received from the Capo of Good Hope, which if not A. belladonna, can hardly be distinguished from that species, have flowered regularly every autumn in great luxuriance. They should never be fresh potted unless the roots split the pots, which some of mine have done, and of course the foregoing treatment must not be adopted till the bulbs have rooted themselves. This management was adopted accidentally as regards these bulbs, having been ordered, under the suggestion of the Rev. W. Herbert, for Brunsvigia Josephinae and multiflora, which were received at the game time, and which now flower regularly every other year. For some fifteen years before, I never succeeded in getting any of them to flower. The ordinary cause of failure in the cultivation of B. Josephinae is too much heat in winter, and want of moisture in summer,—J. R.
Humidity
The Avocado, a Salad Fruit from the Tropics USDA B.P.I. Bull. 77. p. 31-32 (1905)
G N
Collins
Extension of season is an important desideratum,
especially in the direction of later fruiting forms, the desirability of which
is considered farther on. Advance in this direction is likely to be made by the
introduction of new varieties and, perhaps, by extending the cultivation of the
trees to regions of more continuous moisture where the season of flowering can
be to some extent controlled. The tree flourishes in many localities where it
fails to bear fruit, and, as with the mango, this sterility is usually found in
localities of almost continuous humidity. Under such conditions an artificial
check, such as root pruning, has been found to induce flowering and the setting
of fruit. This can easily be overdone, however, in which case the trees will
bear one large crop and then die.
Some of the most
prolific trees are those grown in rather small depressions of porous rock in
southern Florida, where the plants are, in a manner, root-bound, while the
porous nature of the rock affords good drainage. There are a number of ways in
which the growth may be checked and the yield increased. The baring of the
roots to the sun would appear a very satisfactory method. A custom of hacking
the trees to make them bear is practiced by the Indians of Mexico. In any case
where the fruiting is induced by artificial means the season will be more or
less under control.
The Mango in Porto Rico, USDA B.P.I Bull. 28. (1903)
G N Collins
The fact that the tree may thrive in a given locality and yet fail to produce fruit should always be kept in mind. It may be considered as proven that the mango will be prolific only in regions subjected to a considerable dry season. On the moist north side of Porto Rico the trees grow luxuriantly, but they are not nearly so prolific nor is the fruit of such good quality as on the dry south side, and in the very dry region about Yauco and at Cabo Rojo the fruit seemed at its best, while its abundance was attested by the fact that fine fruit was selling as low as 12 for a cent. In Guatemala and Mexico the mango was found at its best only in regions where sever dry seasons prevailed.
Seminar on Research & Development of Fruit Trees (1980)
Mangoes show generally good growth and production throughout Jamaica. The problem areas include Manchester and the North coastal areas including some areas of St. Ann. In some of these areas, the mango achieves good vegetative growth, but fruiting is poor and at best biennial or less regular. (Mathias - personal communication), pointed out that the variety Ann, grows well on the marl soils of St. Ann's Bay, with good fruiting and fruit characteristics. The variety when transferred to Lima in St. James, however, did not reproduce those same fruit qualities etc. The mango can grow well on a wide range of soil types and needs a long dry period for flowering and fruit set. The occurrence of heavy rainfall and strong winds during this period will reduce mango yields drastically.
Atmospheric Pressure
High atmospheric pressure and fruit trees (1929)
I V Michurin
In some years, in the latter part of August, there is a long period of constant high atmospheric pressure (between 760 and 770 mm.). This, according to my observations, greatly affects the organisms of perennial plants and forces some of them to bloom again in the autumn.
In such cases, certain varieties of apple, cherry, mountain ash, bird cherry, and others have a second budding.
In such years a second flow of sap is also observed in hybrid seedlings, and against which we cannot take any measures; but in selecting we must not reject such damaged hybrids as lacking hardiness.
Science 2(27): 178 (August 10, 1883)
Influence of diminished atmospheric pressure on the growth of plants.—Experiments conducted by Wieler at Tübingen show, that, all other external conditions being the same, plants will grow more rapidly under diminished atmospheric pressure. Thus, if a specimen of the common Windsor bean (Vicia faba) be grown in a receptacle in which the pressure of the air can be controlled, it will be found to grow faster until the pressure has been diminished to 100-300 mm.; the normal pressure under which the ancestors of the plant have flourished being, of course, not far from 760 mm. If, however, the pressure is reduced below the smaller figure given above, the rate of growth diminishes. Wieler found that the curve of growth of the sunflower is about the same as that of the bean. It was further shown by his experiments, that growth is retarded by increased puressure until the minimum is reached at 2-2 1/2 atmospheres, from which point there is again an increase. Although the short abstract of these interesting results so far published is meagre in the extreme, it indicates that the field entered upon by Wieler (and by Bert in France) may compel us to revise some notions now held in regard to the adaptation of plants to their surroundings in past ages, and at the present time upon high mountains.—(Botan. zeit., July 6.) G.L.G.
The Physiology of Plants, Volume 2 (1903)
Wilhelm Pfeffer
A diminution of the atmospheric pressure usually causes a distinct acceleration of growth in strongly aerobic plants, and this appears to attain its maximal value when the pressure falls to between a quarter and a seventh of an atmosphere. Growth may then be accelerated to two or three times its original rapidity in some plants (Wieler), while Jaccard observed that potatoes grew seven times more rapidly under such circumstances. The result is due partly to the decreased density of the oxygen, and partly to the decreased air-pressure. Experiments performed by diluting air with indifferent gases show that a reduced partial pressure of oxygen does act as an accelerating stimulus to growth, and the fact that different authors are not in precise agreement as to the respective parts played by these two factors probably shows that the duration of the experiments and the nature of the plant are of considerable importance. Wieler found that a mere diminution of air-pressure produced no effect upon growth, possibly because his experiments lasted for a shorter time than those of Jaccard and Schaible. That duration is a factor of great importance is shown by the fact that prolonged tension may at first produce a retardation, but subsequently an acceleration of growth.
It is possible that the decreased air-pressure acts by removing a portion of the external pressure antagonizing turgor, and hence increasing the tension exerted by the internal osmotic pressure upon the cell-wall. In any case, however, the action is a stimulatory one, for a correspondingly increased tension of the cell-wall does not produce any mechanical acceleration of growth. This mechanical theory of Schaible's is in fact based upon an erroneous view as to the importance of turgor in growth. Apparently, therefore, either a decrease of air-pressure or a diminution of the partial pressure of oxygen may act as stimuli accelerating growth, although if the time of exposure is short the period of induction may not be sufficiently prolonged for the production of a perceptible result. [Vochting observed (Bot. Ztg., 1892, p. 94) that a reduction of the percentage of oxygen to 3 per cent, suppressed the formation of root-hairs on the roots of the potato.]
Plant-Geography upon a Physiological Basis (1903) p. 69-70.
Franz Wilhelm Schimpe
I. ATMOSPHERIC PRESSURE
As Wieler and Jaccard have shown, the pressure within the stratum of the atmosphere in which plants grow does not at all correspond to the absolute optimum pressure for the growth of plants. On the contrary, a diminution of the partial pressure of the oxygen—for the latter only, and not the total atmospheric pressure, comes into question—occasions an acceleration in growth until a certain low pressure is attained, which is constant for each species, and beyond which any further diminution in pressure causes a retardation in the rate of growth. We find this absolute optimum atmospheric pressure for growth to be in the case of Helianthus annuus about l00 mm., but for Vicia Faba about 200 mm. Again, an increase in atmospheric pressure above 760 mm. (or the corresponding pressure of oxygen) up to about 2 1/2 atmospheres occasions a retardation, but after that an acceleration in growth. There are therefore for growth two absolute optima of atmospheric pressure, both of which differ considerably from the pressures that prevail in the inhabited stratum of air, the one being at a far lower, and the other at a far higher oxygen-pressure.
According to Jaccard a decrease in the pressure of oxygen occasions not only more rapid growth, but also richer branching in the axes and roots, as well as an increase in the size of the leaves.
Floricultural Cabinet, July, 1854: 180
Atmospheric Influence On Plants.—The pressure of the atmosphere has a decided influence on the form and life of plants. From the abundance of their leafy organs provided with porous openings, plants live principally in and through their surfaces; and hence their dependence on the surrounding medium. Animals are dependent rather on internal impulses and stimuli; they originate and maintain their own temperature, and, by means of muscular movement, their own electric currents, and the chemical vital processes which depend on and react upon those currents. A species of skin respiration is an active and important vital function in plants; and this respiration, in so far as it consists in evaporation, inhalation, and exhalation of fluids, is dependent on the pressure of the atmosphere. Therefore it is that alpine plants are more aromatic, and are hairy and covered with numerous pores. For according to zoonomic experience, organs become more abundant and more perfect in proportion to the facility with which the conditions necessary for the exercise of their functions are fulfilled, as I have elsewhere shown. In alpine plants the disturbance of their skin-respiration occasioned by increased atmospheric pressure, makes it very difficult for such plants to flourish in the low grounds. The question whether the mean pressure of the aerial ocean which surrounds our globe has always been the same, is quite undecided; we do not even know accurately whether the mean height of the barometer has continued the same at the same place for a century past. According to Poleni's and Toaldo's observations, the pressure would have seemed to vary. The correctness of their observations has long been doubted, but the recent researches of Carlini render it almost probable that the mean height of the barometer is diminishing in Milan. Perhaps the phenomena is a very local one, and dependent on variations in descending atmospheric currents.—Humboldt's Aspects of Nature.