PHOTOSYNTHESIS RATE OF SUGARCANE GENOTYPES UNDER RAINFED CONDITIONS DURING TWO SEASONS

Abstract

The goal of the research was to study the physiological response of three varieties of sugarcane and establish differences based on their photosynthetic capacity in response to two seasons and the effect in yield and industrial quality. Three commercial varieties of sugarcane were evaluated under rain-fed conditions in two seasons of the year and at different times of the day, considering the photosynthetic rate and the varietal response in variables such as yield and juice quality (degrees Brix). The Mex 79-431 variety had the highest photosynthetic rate (46.39 mu molCO(2).m(-2).s(-1)) during the summer and was the most efficient variety in the use of photosynthetically active radiation (RFA), compared to CP 72-2086 (45.51 mu molCO(2).m(-2).s(-1)) and Mex 68 P-23 (37.34 mu molCO(2).m(-2).s(-1)). The varieties CP 72-2086 and Mex 79-431 were better adapted to the environmental conditions of the time of the year since they were superior to Mex 68 P-23 in the photosynthetic rate in both summer and winter, with averages of 13.5, 16.0 and 16.9 mu molCO(2).m(-2).s(-1), respectively. The Mex 68 P-23 variety was superior in yield but with a similar juice quality in the three varieties (23 degrees Brix). It is concluded that the environment influences the photosynthetic response of sugarcane plants since in winter there were reductions of up to 54\% with respect to summer.