Respostas biométricas e fisiológicas ao deficit hídrico em cana-de-açúcar em diferentes fases fenológicas

Abstract

Resumo -O objetivo deste trabalho foi avaliar as respostas biométricas e fi siológicas de cana-de-açúcar (Saccharum spp.) ao defi cit hídrico (DH), em diferentes fases fenológicas. Os genótipos IACSP 94-2094 e IACSP 96-2042 foram submetidos a DH nas fases de crescimento inicial, crescimento máximo e de acúmulo de sacarose no colmo. O delineamento experimental foi inteiramente casualizado. A suscetibilidade ao DH foi determinada pela redução de matéria seca do colmo e do conteúdo de sólidos solúveis no caldo. O defi cit hídrico causou redução nas trocas gasosas, nas três fases fenológicas, em ambos os genótipos. Foi observada menor altura das plantas, menor acúmulo de matéria seca do colmo e de sólidos solúveis, e redução no número e comprimento de entrenós, apenas na fase de crescimento inicial, no clone IACSP 96-2042. Na fase de crescimento inicial, observou-se tolerância ao DH no genótipo IACSP 94-2094, com evidências de aclimatação fi siológica, e redução na produção de fi tomassa e de sólidos solúveis no genótipo IACSP 96-2042, como resposta à menor condutância estomática e à menor efi ciência aparente de carboxilação da fotossíntese. Independentemente da fase fenológica, o genótipo IACSP 94-2094 foi tolerante ao defi cit hídrico, pois manteve a produção de fi tomassa mesmo com redução das trocas gasosas.Termos para indexação: Saccharum, crescimento, fotossíntese, seca. Biometric and physiological responses to water defi cit in sugarcane at different phenological stagesAbstract -The aim of this work was to evaluate the biometric and physiological responses of sugarcane (Saccharum spp.) to water defi cit (WD), during different phenological phases. Genotypes IACSP 94-2094 and IACSP 96-2042 were subjected to WD conditions during the initial, maximum and sucrose accumulation phases. The experiment was carried out in a completely randomized design. Susceptibility to WD was established by reduction in stalk dry matter and soluble solids. Water defi cit reduced leaf gas exchange in all phenological phases of both genotypes. Lower plant height, less stalk dry matter and soluble solids, and reduction in number and length of internodes were only observed during the initial growth phase of the IACSP 96-2042 clone. In the initial growth phase, tolerance to WD was observed for IACSP 94-2094, with evidence of physiological acclimation, and for IACSP 96-2042 in reduction phytomass production and its soluble solid content, caused by lower stomatal conductance and lower apparent carboxylation effi ciency which limit photosynthesis. Regardless of the phenological phase, genotype IACSP 94-2094 was tolerant to WD, since its phytomass production was maintained even with impairment of leaf gas exchange.

Variation in the sugar yield in response to drying-off of sugarcane before harvest and the occurrence of low air temperatures

“…In sugarcane, water loss to the atmosphere and excessive dehydration are controlled by stomatal closure. This is the first defense mechanism used by the plant to adapt to the availability of water in the soil (Machado et al 2009). …”

PHYSIOLOGICAL RELATIONSHIPS IN Aleurites fordii Hemsl. SEEDLINGS

“…In this same context, Yordanov et al (2003) state that in a water deficit condition, the first defense adopted by the plant would be the restriction of the stomatal opening. Thus limiting photosynthesis, and consequently, the TR and avoiding loss of water content by the leaves (Machado et al, 2009). …”

Water stress indices for the sugarcane crop on different irrigated surfaces

“…The lack of water for the crop in the tillering period affects the immature tissues of the plant and ultimately damages the processes of storage of sugar (Machado et al, 2009). …”

“…According to Machado et al (2009), water deficit in sugarcane is the main responsible for the variability in plant growth and yield. In the present study, it was possible to observe that, during the initial months of sugarcane growth, there were limitations of the rainfall in 2014 for the region, agreeing with the data presented by IEA (2015) ( Table 1).…”