Photoperiodically Induced Changes in Seed Growth Rate of Soybean as Related to Endogenous Concentrations of ABA and Sucrose in Seed Tissues |
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Authors: | MORANDI ELIGIO N; SCHUSSLER JEFFREY R; BRENNER MARK L |
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Institution: | * MSU-DOE Plant Research Laboratory, Michigan State University East Lansing, MI 48824, USA
Department of Horticultural Science and Landscape Architecture, University of Minnesota St Paul, Minnesota 55108, USA |
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Abstract: | Short-day photoperiods can increase the partitioning of assimilatesto filling seeds of soybean (Glycine max L. Merr.), resultingin higher seed growth rates. The plant growth substance ABAhas been implicated in the regulation of assimilate transferwithin filling soybean seeds. Thus, we hypothesized that anincreased concentration of endogenous ABA in seeds may enhancesucrose accumulation and seed growth rate of soybeans exposedto short-day photoperiods. Plants of cv. Hood 75 were grownin a greenhouse under an 8-h short-day photoperiod (SD) until11 d after anthesis (DAA) of the first flower, when half ofthe plants were transferred to a night-interruption (NI) treatment(3 h of low-intensity light inserted into the middle of thedark period). Plants remaining in SD throughout seed developmenthad seed growth rates 43% higher than that of plants shiftedto NI (7·6 mg seed1 d1 vs. 5·3 mgseed1 d1). On a tissue-water basis, the concentrationof ABA in SD seeds increased rapidly from 7.6 µmol l1at 11 DAA to 65·2 µmol l1 at 18 DAA, butthen declined to 6·6 µmol l1 by 39 DAA.In contrast, the concentration of ABA increased more slowlyin NI seeds, reaching only 47·4 µmol l1by 18 DAA, peaking at 57·0 µmol l1 on 25DAA, and declining to 10·2 µmol l1 by 39DAA. The concentration of sucrose in SD embryos peaked at 73·5mmol l1 on 25 DAA and remained relatively constant forthe remainder of the seed-filling period. In NI, the concentrationof sucrose reached only 38·3 mmol 11 by 25 DAA,and peaked at 61·5 µmol l1 on 32 DAA. Thusin both SD and NI, sucrose accumulated in embryos only afterthe peak in ABA concentration, suggesting that ABA may havestimulated sucrose movement to the seeds. The earlier accumulationof ABA and sucrose in SD suggests that ABA may have increasedassimilate availability during the critical cell-division period,thus regulating cotyledon cell number and subsequent seed growthrate for the remainder of the seed-filling period. Glycine max L. Merr. cv. Hood 75, soybean, assimilate partitioning, abscisic acid, photoperiod, source-sink |
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