Nutrition and Heredity
de Vries: Nutrition and Selection (1909)
The recent researches of MAC LEOD and others clearly point to a very close relationship between nutrition and variability. For, broadly speaking, variability is really nothing more than differences in individual strength. The stronger a plant or a branch on a plant is, the greater is the likelihood of deviations in a positive direction; weak plants and sickly branches tend to fluctuate in the opposite direction.
Davis: Malnutrition and segregation in Oenothera (1921)
Traub: Reversal of Growth Dominance (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. Species in five Genera have been used in the experiments,— Hippeastrum, Crinum, Haemanthus, Zephyranthes and Narcissus. In Zephyranthes the number of seeds produced has been below expectancy, especially in the case of Z. Atamasco and Z. treatieae, which may be due in part to the relatively small size of the peduncle. Z. robusta, with a larger peduncle, produces a relatively larger number of seeds per capsule. Although abundant seeds have been secured from excised scapes of Crinum asiaticum, C. longifolium album and C. longifolium roseum, only an abundant number of fleshy fruits without seeds were produced in the case of C. augustum, a doubtful species which does not set seeds under Florida conditions. A Burbank hybrid Crinum produced many small seeds in each pod which were not viable. Approximately 5 percent of flowers on excised scapes of Haemanthus multiflorus have produced seeds.
Husmann: Currant-grape growing (1920)
It has been found that in order to make the blooms set and secure full yearly crops of grapes the vines must be ringed every year. This ringing consists of making two parallel incisions through the bark and cambium layer around either the trunk, the arms, or the canes of the vines and completely taking out the bark and cambium layer between the two parallel incisions. This does not interfere with the upward flow of the sap through the outer ring of undisturbed wood, but where the ringing occurs checks the returning flow while the ringed place is healing.The effects of ringing are a full setting of fruit and much larger berries and clusters. The ringing is done either with a large-bladed pocketknife or with special tools made for the purpose.
[Note: The currant-grape is seedless, but ringing — by trapping carbohydrates in the upper parts of the vine — increase fruit set. Compare with what Traub (above) found when a sterile crinum produced seeds, though they were not viable. I suspect that doubtful embryos, in partially fertile plants, might be encouraged to grow with an increased supply of nourishment.]
Marshall & Ellstrand: Selective seed abortion in wild radish (1986)
While selective seed abortion based on the paternal genotype has been discussed, it has not been demonstrated because separating effects of fertilzation and abortion is difficult. We overcame this difficulty by appropriate timing of stress after mixed pollination in wild radish. We pollinated full sib pairs of wild radish plants with mixtures of pollen from three donors. All plants were treated identically during pollination and fertilization. Ten days later, when seed abortion is a likely response to stress, one plant per pair was water stressed. Since all plants were treated identically at fertilization, any differences between control and stressed plants in the proportion of seeds sired by each donor must be a result of selective seed abortion. Such differences were found. Therefore, selective seed abortion by paternal genotype occurs in wild radish. This result is the first demonstration of this kind of control in plant reproduction and likely represents maternal choice.
Marshall & Whittaker: Effects of pollen donor identity on offspring quality in wild radish, Raphanus sativus (1989)
There were significant effects of paternity on two measures of early growth: leaf number and plant height. Paternal effects on three measures more closely related to fitness; final plant weight, day of first flower production, and total flower number were also significant. Under the conditions of this experiment, final plant weight was probably the best predictor of fitness. The pollen donor that sired the largest seeds in the previous experiment sired offspring that were largest after 8 weeks of growth. Half of the plants were grown under low-water conditions. Paternal effects on growth were not masked by the environmental effects. In fact, some paternal effects became stronger under stress.
Galloway: Effect of maternal and paternal environments on seed characters in Campanula americana (2001)
A number of studies have demonstrated that pollen quality and quantity varies with the environment and may affect an individual's ability to sire seeds (e.g., Young and Stanton, 1990; Delph, Johannsson, and Stephenson, 1997; Aizen and Raffaele, 1998; Lehtilä and Strauss, 1999 ). In natural populations, heterogeneous environments may lead to differences in siring ability among individuals due to variation in pollen quantity or quality. In the present experiment, the environment was constant across individuals within a paternal treatment. However, if the response of pollen characters to the environment varied among families (i.e., genotype-by-environment interaction), the family with the greatest amount of viable pollen may vary across environments. As a consequence, the paternal environment may bias paternity, resulting in a genetic source to the "environmental" paternal effects.
Galloway: Parental environmental effects on life history in the herbaceous plant Campanula americana (2001)
Maternal light environment also did not affect percentage germination (Table 2). However, the paternal light environment did influence germination percentage (Table 2). Seeds whose fathers grew under low-light conditions germinated in larger numbers than seeds from fathers in which light was not as limited (Fig. 2).
Etterson & Galloway: The influence of light on paternal plants in Campanula americana (2002)
Offspring trait expression is determined by the combination of parental genes and parental environments. Although maternal environmental effects have been widely characterized, few studies have focused on paternal environmental effects. To determine whether light availability influences pollen and offspring traits in the woodland herb Campanula americana, we reared clones of 12 genotypes in two light levels. In the parental generation we measured pollen number and size. Plants grown under high light produced more pollen grains per flower than those grown under low light. However, the response was genotype specific; some individuals responded little to changes in light availability while others substantially reduced pollen production. As a consequence, paternity ratios may vary between light environments if more pollen is associated with greater siring success. We crossed a subset of these plants to produce the offspring generation. The paternal and maternal light environments influenced offspring seed mass, percentage germination, and days to germination, while only maternal light levels influenced later life traits, such as leaf number and size. Maternal and paternal environmental effects had opposite influences on seed mass, percentage germination and days to germination. Finally, there was no direct relationship between light effects on pollen production and offspring trait expression.