MORPHO-PHYSIOLOGICAL INDICATORS OF WATER STRESS ON SUGARCANE AS A FUNCTION OF IRRIGATION DEPTHS

The present study was developed to evaluate relationships between the water depths (rain and irrigation) and morphological (leaf area index) and physiological indicators (leaf temperature, leaf water potential and chlorophyll content in leaves) of water stress on sugarcane subject to different irrigation levels. The experiment was installed in October 2010 in Jaiba/MG, Brazil, in an area irrigated by a center pivot system with sugarcane in the fourth cycle. For the treatments, emitter nozzles were exchanged in each vain between pivots so that the depths applied related to 25, 50, 75, 100, 125 and 150% of evapotranspiration, with the irrigation management performed to meet 100% of the demand. The factors of leaf area index, leaf water potential, leaf temperature and leaf chlorophyll index were measured. The values obtained were subjected to analysis of variance and subsequently developed regressions. From the results, it was concluded that there was a trend of increased leaf area index (LAI) for sugarcane as increasing the water depth in the crop cycle; the increase in LAI was more pronounced in treatments that received more water; leaf water potential was lesser for smaller irrigation depths, with emphasis on the treatment that received less water (25%); leaf temperature was close to the air temperature in the treatment receiving the highest depths (100 and 150%) with a trend for an increased difference between the temperature of the leaves as reducing the water supply; the chlorophyll index (ICF) tended to increase as increasing the depths, with a slight drop in treatments receiving depths greater than 100% of the ETc.