Changes in endogenous abscisic acid
and indole-3-acetic acid in developing seeds and pods among three
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.