Changes in endogenous abscisic acid and indole-3-acetic acid in developing seeds and pods among three peanut genotypes
Kusakawa, H., H. Nojima, A. Isoda, and Y. Takasaki (Faculty of Horticulture, Chiba University, Matsudo, Chiba 27l, Japan)
Abstract: Plant hormones have been implicated in the correlative control of seed development processes. Endogenous Abscisic Acid (ABA) and Indole-3-Acetic Acid have been identified in the reproductive structures of legumes. ABA has been shown stimulate sucrose transport into filling seed. A high level of IAA is reported to coincide with the period of high meristematic activity in the cotyledons and of rapid pod growth. The object of this study was to determine the concentrations of ABA and IAA in seed and pod wall of three peanut genotypes, differing seed size.
In 1994, three peanut genotypes, Chibahandachi (Virginia type) Java 13 (Spanish type) and Nakateyutaka (derived by crossing Virginia with Spanish type) were cultivated in the field of Chiba University. The flowering time was adjusted uniformly by removing older flowers. From 7 to 20 days after flowering (DAF), pods were extracted and assayed as a whole. Thereafter, pod wall and seed tissues were separated, extracted and assayed independently. ABA and IAA levels were quantified using HPLC with diode array. Seed Growth Fresh weight of seed increased continuously up to 80 DAF. The increase was two fold in Nakateyutaka and Chibahandachi (large-seeded genotype) as compared to Java 13 (small-seeded genotype). Seed growth rate showed two peaks. The large seeded genotypes had earlier higher values than the small seeded genotype in early development. Rapid seed filling occurred between 30 and 40 DAF in the large-seeded genotypes. The levels of ABA in whole pods containing immature seeds were higher at 15 DAF in the small-seeded Javal3 than in the large-seeded Chibahandachi. The whole pod was separated into seed and pod wall from 20 DAF. The levels of ABA in the seed were lower from 25 to 40 DAF, and increased thereafter. The levels of ABA in the pod wall at 20 DAF were higher than in the seed. Genotypic differences in the maximum levels of ABA in seeds were observed during 60 to 80 DAF. ABA Ievels were different in the two large seeded types, higher in Chibahandachi than Nakateyutaka. During 50-80 DAF, there was no increase in the sucrose level of the seeds of Nakateyutaka. It is suggested that the level of ABA during the seed filling period may stimulate assimilate uptake.