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- Title
Seedling Growth in Phaseolus vulgaris L. The Early Growth of Cultivars Selected for Seedling Cold Tolerance.
- Authors
HARDWICK, R. C.; ANDREWS, D. J.
- Abstract
Silbernagel has described a test for selecting cultivars of L. which exhibit rapid seedling emergence at low temperatures, and using this test has identified three cold-tolerant cultivars. We have compared the growth of these cultivars with that of three control cultivars. Both at 25/20 °C and at 20/15 °C day/night temperatures, Silbernagel's cultivars emerged more rapidly than the controls. This was due to more rapid hypocotyl elongation, not to earlier germination. Rapid hypocotyl elongation was associated with high relative growth rates of the seedling axis and rapid loss in weight of the cotyledons. After emergence, cotyledons of all cultivars continued to lose weight at a constant exponential rate. Relative growth rates of the axes were not constant but declined with time. There was no evidence that genotypic differences in growth rates before emergence were reflected in growth rates after emergence. A simple quantitative analysis suggested that the decline in axis relative growth rate after emergence was due to a declining contribution from cotyledonary reserves. There were significant differences between cultivars in the initial weight of the seedling axis. Axis weight (A) was not linearly proportional to seed weight (S), but the curvilinear allometric relationship A = 0.0773 S satisfactorily accounted for most of the variation in initial axis weight between cultivars. In all cultivars, axis weights at emergence were smaller in the cool regime than in the warm, because low temperatures depressed axis relative growth rates relative to the rate of emergence. The biggest difference between the Q of relative growth rate, and of emergence rate, and hence the biggest effect of low temperature on axis weight at emergence, occurred in the cold-susceptible cultivar Seafarer. However, genotypic cold tolerance during the period when growth is dependent on reserves did not appear to guarantee cold tolerance during the main period of growth.
- Publication
Annals of Botany, 1981, Vol 47, Issue 2, p203
- ISSN
0305-7364
- Publication type
Article