The effects of water stress on the chemical composition of soybean shoot parts at different growth stages and assimilate distribution to the seeds at different nodal positions

The response of soybean [Glycine max (L) Merrill] cv. Akiyoshi to three moisture levels at three growth stages was investigated in a glasshouse experiment. Percent leaf nitrogen was reduced by water deficit at late flowering and early podding but increased after rewatering. This parameter was not affected by water deficit at early flowering. Percent total available carbohydrate in the stem was reduced by water deficit except at late flowering but also increased after rewatering. Plants subjected to water deficit after early podding had higher available carbohydrate in the stem at maturity. Percent oil content was slightly increased in the seeds of plants subjected to water stress at early podding but percent protein was generally reduced by water stress. Total oil and protein yields were reduced by water deficit at all stages of growth. 14C retention was highest in the seeds of the main stem and lowest in those of the secondary branches, seeds at higher nodal positions on the main stem contained more 14C. The amount of 14C in seeds of the primary branches decreased with an increase in nodal position from the main stem. Distribution of 14C assimilates into the seeds of plants subjected to water deficit was reduced at all stages of growth. The resultant decrease in assimilate distribution to seeds will lead to a reduction in yield of soybean grown under conditions of water deficit. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 3, July (1999) pp. 66-7