Micrometeorology and physiology of sugarcane crop during water stress
Water stress is the single most important factor limiting yield in plants. The effects of water stress on the micrometeorology and physiology of sugarcane were investigated using the rainshelter facilities provided at the South African Sugar Association Experiment Station, Mount Edgecombe. Sugarcane variety NCo37 6 was stressed at the age of seven months during the first ratoon crop. Plant extension rate (PER) together with microclimatic measurements including radiation interception, and leaf and canopy temperature were measured continuously. Photosynthesis and leaf water potential were also measured on a daily basis together with the volumetric soil water content. Among the yield-determining processes, plant extension rate was the first to be significantly affected 10 days after onset of water stress. The leaf water potential (ΨL measured at this stage was -0.7 MPa. Leaf area index and radiation interception were the next processes to be affected. A significant decrease in photosynthetic rate occurred 19 days after onset of water stress when the ΨLwas at -1.0 MPa. More than 50% reduction in radiation use efficiency occurred 24 days after imposing water stress and the ΨLmeasured at this stage was -1.5 MPa. Recovery from the first stress as far as plant extension rate and photosynthesis were concerned, occurred within 3 to 4 days after irrigation was resumed. When the same sugarcane plants were stressed for a second time, it took fewer days for plant extension rate and photosynthesis to be severely affected as compared to the stress imposed during the first time.