Response of Pour Grain Legumes to Water Stress in South-eastern Queensland. 11* Plant Growth and Soil Water Extraction Patterns

摘要

Growth and water use of soybean (Glycine max), black gram (Vigna mungo), green gram (V. radiata) nand cowpea (V. unguiculata) in response to water stress were evaluated in the field at Dalby in south- neast Queensland. Differing strategies of growth and water use which reflected the differential nexpression of dehydration avoidance and developmental plasticity in response to stress were identified namong species. nThe primary difference between strategies related to differences in dehydration avoidance. Soil nwater extraction during the initial phases of drought was faster, and leaf area development and plant ngrowth were relatively less affected, in soybean than in the Vigna spp. Where adequate soil water nexisted, these differences were sustained during the drought period but were reversed where soil nwater was limited. Soil water extraction by soybean occurred to greater depths, and to lower npotentials, than in the Vigna spp. nDevelopmental plasticity influenced growth pattern in the Vigna spp. to varying degrees. Drought nperiods invariably curtailed growth and hastened maturity in green gram and black gram, but rain nprior to maturity induced renewed growth in black gram. Moderate stress curtailed growth and nhastened maturity in cowpea, which also responded to late rains with renewed growth. Severe stress ninhibited growth and delayed development in cowpea indefinitely.