Spectral variation and radiation use efficiency in a wheat genotype trial [Variação espectral e eficiência de uso da radiação fotossinteticamente ativa em ensaio com genótipos de trigo]

Abstract

Field radiometry measurements are used to quantify the spectral variation and the solar radiation use efficiency of biomass production (εF), in an experiment with 20 wheat genotypes cultivated at the experimental site of the University of Taubaté in Taubaté, São Paulo State, Brazil, during the period from May to October of 1999. The crop was irrigated on a weekly basis in order to supply water close to soil field capacity. Eight radiometric measurements were taken with the field spectroradiometer Spectron SE-590, from plant emergency through physiological grain maturity. These measurements were transformed into the normalized difference vegetation index (NDVI) that, along with the photosynthetic active radiation (PAR) data, were used to calculate the accumulated absorbed PAR (AAPAR) over the crop growing season in order to estimate the values of εF. The result showed that εF presented a significant variation among genotypes and that the field radiometric technique is a promising tool to identify genotypes with high εF, and furthermore, for biomass production, the use of solar radiation, in the photosynthetic process, is much more relevant than AAPAR.