The American Rose, p. 15, Oct. 1958.
Male Controls Sprouting
Edward B. Risley
Durham, N. H.

A REVIEW of data collected in 1955 has revealed evidence that the particular rose variety used as the pollen parent may influence the length of time that must pass before the seeds will germinate. When the pollen has a direct effect on the seed tissues, other than the embryo, the effect is known as xenia. The color of the seed of the pollen parent has long been known to control the color of the kernels on an ear of corn, and this is cited as the classic example of xenia. In other plants, xenia is rare.

The twelve lots of seeds listed below were harvested without drying and put in moist sphagnurn moss in polyethylene bags in a refrigerator on September 23 and 24, 1954. In all cases the female parent was Skinner's Rambler. The number of days until the first seeds germinated (the stratification period) was recorded for each cross.

Rose varieties crossed in 1954

The difference between longest and shortest stratification period was 90 days. The majority of the seeds in each cross germinated soon after the first ones. No other obvious variable was in operation and the difference is thought to be due to some direct effect the pollen parent had on the seed coat or on the chemical nature of dormancy in this case.

CybeRose note: Risley overlooked cold tolerance — the ability of a plant to grow at low temperatures. A heat-loving plant may refuse to grow long after its chilling requirement had been satisfied. The male parents could be contributing genes for the production of specific fatty acids that influence cold tolerance. Unsaturated fatty acids allow growth at lower temperatures; saturated fatty acids limit low temperature growth. If this is what is happening, then this is not a case of xenia (influence of pollen on maternal tissues) because only the embryo is affected.

It is worth noting that Queen of the Lakes, one of Brownell's "Sub-Zero" roses, was bred for hardiness in the north. No doubt the reluctance of this variety to grow in cold weather contributes to its hardiness. Diamond Jubilee, on the other hand, was bred from Marechal Niel, another rose that stops growing at low temperatures, but lacks a proper dormancy that would allow it to survive repeated cycles of freeze and thaw.