American Journal of Botany
Pastinaca sativa (wild parsnip) produces seeds on the primary, secondary, and tertiary umbels of the flowering stalk. Within plants, variation in seed weight is about twofold. Secondary and tertiary seed weight is 73% and 50% of primary seed weight, respectively. Maximum variation in seed weight between plants is sixfold when tertiary seeds from a small plant are compared to primary seeds from a large plant. Within an umbel order, variation in seed weight between plants is correlated with plant size. Under autumn germinating conditions in the laboratory, finalg erminationo f seedsf romd iffierenut mbel ordersd oes not diffierb ut smallers eedsg erminate more rapidly than larger seeds. Under spring germination conditions in the laboratory, significantly more primary and secondary seeds germinate than tertiary seeds and the rate of germinationi s independento f seed weight.F ield germinationo f seeds from diffierenut mbel orders produces similar results except that in the spring both secondary and tertiary seed germination is lower than that of primary seeds. These results suggest that with respect to seed germination characteristicss mall seeds may have a competitive advantageo ver large seeds in the autumn becauset hey germinatem ore quickly,b ut in the springs mall seeds area t a disadvantageb ecause they have lower overall germination. Because most germination in the field occurs in the spring, population recruitment from small seeds is likely to be substanially less than that from large seeds.
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American Journal of Botany, 71:6 (1984), pp. 795-802. http://www.jstor.org/stable/pdfplus/2443470.pdf
Copyright © 1984 Botanical Society of America. Posted with permission.