Relationship Between Soil Moisture Content and Superoxide Dismutase Activity in Soybean Leaves in Northeast China

Abstract

Soybean is a crucial source of plant protein and oil; However, a decline in yield has been observed. In this study, spring soybean varieties (Heinong 44 and Heinong 65) were selected to determine the effects of different soil moisture levels on changes in superoxide dismutase (SOD) enzyme activity. A water-cut treatment was conducted on potted soybean plants from the beginning of their flowering stage. The soil moisture content under different water-cut days was recorded, and the SOD activity of soybean leaves was determined. The results showed that the SOD activity of soybean leaves first increased and then decreased with a decrease in soil relative water content. The SOD activity under moderate drought stress was significantly higher than that under suitable water and mild drought conditions, and there was no significant difference between suitable water and mild drought conditions. The relationship between soil moisture content and SOD activity of the two soybean varieties was consistent with the Gaussian curve. When the relative soil moisture content was 34.7%–49.8%, the SOD activity was higher than that under suitable water and mild drought stress conditions. The SOD activity of soybean leaves was highest when the relative soil water content was 42.1%–42.8% under moderate drought stress. This research provides a theoretical basis for the rapid diagnosis of soybean drought stress.