Compensatory Growth of Soybean after Shade during Vegetative Promotes Root Nodule Recovery

Background: The recovery growth of soybean after environmental stress, especially shade stress, is essential for soybean to alleviate the yield loss caused by shade. Although the mechanism of recovery growth on leaves has been intensely researched, little is known about the mechanism of compensatory growth on soybean nodule formation. Methods: This study aimed to investigate the effect of recovery growth after shade on soybean nodule formation and the distribution of carbohydrates in root nodules. Four shade treatments, including vegetative period shade (VS), reproductive period shade (RS), total growth period shade (TS) and no shade as control (CK), were applied on monoculture soybean by using a black mesh shading net with light transmittance of 50%. Result: The aboveground dry weight, nodule number and weight and grains yield were lowest in TS and those values in VS were higher than in RS. Compared with RS, VS increased the nodule weight by 75.6% and the sucrose and starch content by 19.3% and 15.6%, respectively. We suggested that, compared with RS, VS improved the compensation growth of soybean and promoted the carbohydrate distribution into nodules, ultimately reducing the negative effect on soybean nodule formation and yield production.