Diurnal Fluctuation of Leaf‐water Potential of Corn as Influenced by Soil Matric Potential and Microclimate1

Abstract

AbstractWater stress during critical growth periods is frequently the limiting factor in crop production. However few data are available on the variation of plant water status under field conditions. The object of this work was to quantify the effect of soil matric potential on plant water status. Sweet corn (Zea mays L.) was grown on a Varina sandy loam soil to determine the effect of the microclimate and irrigation on leaf water potential. Soil water stress was imposed naturally and by use of automated portable shelters that covered the plots during rainfall.Leaf‐water potential was closely related to the diurnal change of incoming energy. A maximum leaf‐water potential of −1.5 bars occurred just prior to sunrise. The minimum value, which occurred during the peak radiation load or stress, was dependent on soil matric potential and stage of plant development. Before tasseling, soil matric potentials of −0.08 and −0.60 bar at the 15‐cm depth in irrigated and nonirrigated plots resulted in minimal leaf‐water potentials of −12 and −18 bars, respectively. After tasseling, soil matric potentials were −0.07 bar at the 15‐cm depth in the irrigated and −3.0 bars in the nonirrigated plots, and the same minimal leaf‐water potential of −18 bars developed for both. Under the same radiation load, minimal leaf‐water potential of irrigated plants was −12 bars before tasseling and − 18 bars after tasseling. The results demonstrate the need to evaluate the influence of environmental stresses and soil water deficits on leaf‐water potential and associated physiological processes.