ABSTRACT
Water deficit is the primary limiting factor for successful yield of soybean (Glycine max L.) around the world, depending on its severity and duration, and has variable effects on several metabolic processes. Therefore, a pot experiment was conducted in a wire house at the National Research Centre, Cairo, Egypt, to examine the interactive effects of two levels of potassium fertilizer and water deficit on the distribution of
14C into biochemical components (ethanol soluble compounds, oil and protein) of three Japanese soybean genotypes, non-nodulating (NN) (En 1282), nodulating (N) (Eneri) and super-nodulating (SN) (En-b0-1). The potassium (K) fertilizer levels were 25 and 150 mg K2O kg soil-1. Sixty-five days after sowing (pod filling stage), soil moisture (SM) for plants was maintained at 80% FWC for control (WW) and no water was added considered as water deficit (WD). Plant leaves were collected at 0 (at the end of exposure time), 24, 48, and 72h for measuring photosynthetic activity, total lipids and protein. The highest amount of 14C was found in soluble carbohydrates after 24h in the three genotypes followed by oil and protein. K at a high level significantly increased
14C fixation by 20.4 and 26.8 % in non-nodulating and normal nodulating genotypes, respectively. High K had no effect on the super-nodulating genotype. The super-nodulating genotype was characterized by lower ability for
14C fixation than normally nodulating soybean at both K levels. K inhibited the detrimental effect of drought stress on photosynthesis, and this might be due to the role of K in CO2 fixation.
