The effect of Water limitation on Water Relations, growth and seed yield of four soybean (Glycine max merri.) genotypes

Abstract

Drought is one of the major constraints for soybean in Iraq. In order to investigate the effects of different soil moisture levels on the water relations ,mineral nutrients (K, Ca) content , growth and seed yield of four Glycine max genotypes, a split-plot experiment (using CRB design) with four replications was conducted .Irrigation regimes :50, 60 , 70 , 80 , and 100% of field capacity ,respectively and soybean genotypes : S , Pi , G and Lee were allocated to main and sub plots, respectively. The parameters that were measured are the leaf relative water content, K and Ca content , dry weight of shoot and root, root length, Yield component and plant seed yield . There was decrease in the leaf relative water content in plants under water deficit, treatment under water deficiency 60 and 50% of F.c had fall to 74.6 and 60.6%, respectively. when compared with the control plants (100% field capacity) 85.33 %.While osmotic potential increase to 0.716 and 0.647 . Genotype interacted significantly (P<0.05) with water level when studying osmotic potentials but not significantly with relative water content . Drought stress not affect significantly Ca and K uptake in plants . The genotypes considerably differed with respect to K uptake ,genotype Pi uptake more K 466.2 m mole Kg-1 than other genotypes . The results showed that dry matter accumulation were reduced due to water deficit. Water limitation also reduced pods per plant and 1000 seeds weight. Consequently, seed yield per plant under limited irrigation was considerably lower than that under well-watering. The numbers of pods per plant were the most affected yield components under drought stress. Lee genotype had the highest dry matter 8.9 g , pods per plant 81.84, 1000 seeds weight 15.2 g . The superiority of Lee genotype in plant seed yield 2.613 g resulted from higher pods per plant and 1000 seeds weight . S and Lee genotypes consumed large amount of water 1199.9 and 1158.5 mm ,while Pi and G genotypes consumed low amount of water 876.5 and 892.7 mm ,therefore the results show the possibility of the use of Pi and G genotypes in the less moisture . May be due to the osmotic adjustment which is one of the major adaptive mechanisms to survive drought.