An experiment was conducted to determine the effects of nutritional level and flower location on factors related to flower, pollen, and ovule production, and to determine what developmental patterns would be modified to mediate any observed changes. Plants subjected to high nutrient levels developed larger leaves, more branches, more flowers on both the main stem and the branches, and opened their first flowers 6 days sooner than plants at lower levels of nutrients. Total flower number increased from 72.2 to 626.8 per plant, with most of the increase produced on the primary branches. The number of pollen grains in the entire androecium averaged 14,685, but significantly increased with higher nutrient levels and decreased with the stage of plant maturity (nodal position on the plant). The number of ovules also increased with nutrient level and decreased with maturity stage. Average ovule number decreased from about 129 in flowers at nodes produced early in the growth cycle to about 100 in flowers produced at later nodes. Despite highly significant plasticity in numbers of both pollen and ovules, the Pollen/Ovule Ratio (average 132.7) did not vary significantly with either nutrient level or plant maturity stage. Path analysis, which decomposes correlation coefficients into direct and indirect effects of factors influencing development, indicated that nutrient level had a very strong direct effect on the number of primary branches and on the number of primary-branch flowers, as well as very strong indirect effects on the latter. The primary-branch flowers directly determined over 67% of the total flower number, and indirectly determined about 24% jointly with secondary-branch flowers, and over 3% jointly with main-stem flowers. The direct effects of secondary-branch flowers and mainstem flowers were 3.8% and 0.3%, respectively. The relationship among components of yield is slightly additive. Direct determination of yield was 74.6% by the number of flowers per plant, 0.6% by the number of ovules per flower, 3.8% by the number of seeds per ovule, and 1.1 % by the weight per seed. The proportion of yield jointly determined by flower number and the developed seeds per ovule was 15.3%. It was concluded that allocation of resources increases to both male and female functions under conditions of high nutrient levels, and pollen/ovule ratios are consistent within a plant despite significant plasticity in numbers of pollen grains and ovules.
Vasek, Frank C.; Weng, Vincent; Beaver, Robert J.; and Huszar, Charles K.
"Effects of Mineral Nutrition on Components of Reproduction in Clarkia ungucilata,"
Aliso: A Journal of Systematic and Evolutionary Botany:
4, Article 15.
Available at: http://scholarship.claremont.edu/aliso/vol11/iss4/15
© 1987 Frank C. Vasek, ,Vincent Weng, Robert J. Beaver, Charles K. Huszar
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