Stable Carbon Isotope Discrimination (<i>δ</i><sup>13</sup>C) of Cotton Burrs and Seeds as a Season-Long Integrator of Crop Water Stress

Abstract

Plant-based irrigation management schemes typically use surrogates such as canopy temperature, alone, or in conjunction with environmental variables, to infer the degree of "crop stress" (biological strain) induced by drought. Few systematic studies of the relationship between "crop stress", as defined by such surrogates, and physiological estimates of water use efficiency (WUE) exist over both daily and seasonal time scales relevant to agronomic irrigation control. The systematic application of stable carbon isotope discrimination (δ 13 C) might allow post hoc evaluation of irrigation scheduling schemes and might also be a useful germplasm screening tool if the source(s) of variability can be uncovered and/or controlled. Results from preliminary efforts comparing leaf and cotton seed δ 13 C to season-long water deficits showed that seeds are more useful indicators of season-long water stress and water use efficiency during crop development.