Leaf expansion and recovery from soil drying in soybean genotypes

Abstract

ABSTRACT Maintenance and recovery of the canopy area when drought stress is relieved may be critical for maintaining high productivity. In this study, experiments were conducted in controlled environments to evaluate leaf expansion and leaf necrosis of five soybean (Glycine max Merr. L.) genotypes undergoing soil-drying, followed by re-watering. Water-deficit stress was imposed by limiting daily watering. When soil water decreased to a severe defined level, full watering resumed for five days. Measurements of leaf expansion and necrosis were taken during water-deficit and recovery periods. Genotypic differences for critical soil-water thresholds at which leaf expansion rates decline were detected. Genotype “Benning” showed the sensitivity of expansion rates to soil-drying while “Geden Shirazu” showed leaf expansion tolerance to soil drying. All genotypes recovered expansion rates within one or two days. During recovery, the recently released cultivar ‘USDA-N8002ʹ had the highest leaf expansion rate among genotypes, compared to its well-watered plants. The high recovery potential of USDA-N8002 was largely attributable to high nighttime expansion recovery. This elite drought-tolerant cultivar, along with the commercial cultivar Benning, experienced the lowest levels of leaf necrosis. While all genotypes exhibited rapid recovery in leaf expansion following drought, variation in the extent of recovery and level of leaf necrosis indicates that these characteristics can be exploited to enhance drought resilience.