Single Leaf Carbon Exchange and Canopy Radiation Use Efficiency of Four Peanut Cultivars1

Abstract

Abstract Knowledge of the interception of solar radiation by crop canopies and the use of that radiation for carbon assimilation is essential for understanding crop growth and yield as a function of the environment. A field experiment was conducted in 1990 at Gainesville, FL to determine if differences in single leaf carbon exchange rate (CER), canopy radiation interception, radiation use efficiency (g dry matter produced per unit of solar radiation intercepted), and increase in seed harvest index with time exist among several commonly grown peanut (Arachis hypogaea L.) cultivars. Four cultivars (Early Bunch, Florunner, Marc I, and Southern Runner) were grown in field plots on a Kendrick fine sand (a loamy, siliceous, hyperthermic Arenic Paleudult) under fully irrigated, intensive management. Total crop and seed dry matter accumulation were determined, and canopy radiation interception measured at weekly intervals. CER of uppermost, fully expanded sunlit leaves were determined at midday at 2-wk intervals. Single leaf CER's were similar among cultivars (25 to 35 μmol CO2 m-2 s-1) and relatively stable throughout most of the season, before declining during late seed filling. Although interception of radiation differed somewhat among cultivars during early canopy development, total crop dry matter accumulation was linearly related to the cumulative amount of radiation intercepted by all four cultivars (r2=≥0.99). Radiation use efficiency was similar among all cultivars with a mean of 1.00 g dry matter accumulated per MJ of intercepted solar radiation. The increase in seed harvest index with time was linear (r2≤0.94) and the rates of increase were similar among the Early Bunch, Florunner, and Marc I cultivars (0.0058 d-1), but lower (0.0043 d-1) for the later maturing Southern Runner cultivar. Results from this study indicated that the primary differences among these four cultivars were in early-season development of the leaf canopy and resultant radiation interception and the rate of seed growth, rather than the capacity to assimilate carbon dioxide.