TEMPERATURE EFFECTS ON COTTON ROOT HYDRAULIC CONDUCTANCE

Soil temperatures on the Texas High Plains are below the optimum for cotton root growth and function. Cool root-zone temperatures reduce the water absorption and hydraulic conductance of roots. Our objective was to determine the response of cotton (Gossypium hirsutum L.) root hydraulic conductance to temperature and the ability to acclimate to cool root-zone temperatures. Plants were grown in hydroponic culture in a greenhouse with root-zone temperature controlled at 30-degrees-C. Root-zone temperature was decreased to 18-degrees-C for a 14-day acclimation period at 36 days after planting. At 2-day intervals during the acclimation period the hydraulic conductance of a plant root system was measured at temperatures ranging from 30 to 7-degrees-C using a pressure chamber. Root conductance declined as temperature decreased from 30-degrees-C, declining at a slower rate at lower temperatures. Conductance at 18-degrees-C averaged 43% and at 7-degrees-C averaged only 18% of that at 30-degrees-C. Conductance of all plants responded similarly to temperature, indicating that there was no apparent acclimation of conductance to the 18-degrees-C temperature.