Endogenouscis,trans-Abscisic Acid and Pea Seed Development: Evidence for a Role in Seed Growth from Changes Induced by Temperature

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Abstract
Measurements were made using GC/MS SIM1 of the effects of temperature on cis,trans-ABA levels in developing ovules and embryos of two pea genotypes contrasted in seed size. These effects were then related to differences in the growth of the pods, seeds, embryos, and testae. In both genotypes high temperatures hastened the onset and rate of logarithmic and then linear growth, greatly shortening the duration of pod and seed development but without greatly altering seed size. Cis,trans-ABA was most concentratedx in the ovules immediately after fertilization. It also accumulated in the embryo, more rapidly in the larger-seeded line, during seed maturation. The stage when accumulation in the embryo began was the same irrespective of temperature. Accumulation ceased when the pods started to desiccate. The effects of different constant temperatures on the maximum levels of embryo cis,trans-ABA were relatively small and confounded in one genotype by variation in ovule abortion and in the other by differences in the stage when cis,trans-ABA accumulation ceased. However, when plants were transferred from 13 °C to 29 °C at two different stages during seed maturation, further seed growth was greatly inhibited coincident with a substantial increase in embryo cis-trans-ABA. The results suggested a role for cis,trans-ABA in the control of cotyledon enlargement during the linear phase of seed growth.