ABSTRACTThe sugarcane crop in Brazil, remains in the field throughout the year and is therefore subject to wide variation of the environment in different seasons. During the winter in some sugarcane producing regions, it is common the simultaneous occurrence of low temperature and water deficit, affecting plant physiological processes. In order to survive the adverse conditions, plants acclimate and show responses that confer differential tolerance in sugarcane cultivars. The temperature variation affects directly the kinetic and thermodynamic of the biochemical reactions and thus the plant physiological responses. The water stress has varying impact on agricultural productivity depending on the cultivar, the intensity and phenological stage at which it occurs. The water stress effects on sugarcane are harmful when occurring in the initial phase of establishment of plants, as well as of intense growth. Water stress and low temperature lead to oxidative stress, but the consequences are not well understood in sugarcane plants. The abiotic stresses also affect root to shoot communication, affecting stomatal responses and thus photosynthesis. The aim of this study was to test the hypothesis that more tolerant sugarcane cultivars to water stress and/or to low temperature have carbon metabolism (photosynthesis and carbohydrate metabolism) less susceptible to these environmental factors, probably due to the efficient roots to shoots communication and oxidative damage protection. To achieve this aim we will study the effects of the low temperature and/or water stress occurrence on photosynthesis (gas exchange and photochemical activity), on carbohydrate metabolism (carbohydrate accumulation and enzyme activity), oxidative metabolism and root to shoot communication in two sugarcane genotypes, with different characteristics.
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