Variation of photosynthesis and carbohydrate levels induced by ethephon and water deficit on the ripening stage of sugarcane

Abstract

An important index for the ethanol industry is the sucrose yield in sugarcane, which is affected by plant ability to accumulate sucrose during ripening. Despite the known efficiency of treatments such as water restriction and the application of regulators to stimulate the sucrose storage in culms, little is known about the physiological responses of the plant that lead to ripening. In this context, the aim of this study was to evaluate the physiological responses of sugarcane to different ripening treatments. Two varieties, IACSP95-5000, with high yield, and IACSP94-2094, with moderate yield were subjected to water deficit or application of chemical regulator (ethephon 480 g ha-1) and both treatments associated. Growth, accumulation of carbohydrates in leaves and culms were measured. It can be concluded that the effects of ethephon on sugarcane are genotype-dependent. Ethephon stimulates sucrose accumulation in the culm and the photosynthate supply by the source in the responsive variety (IACSP95-5000). Such effects are not associated with growth restriction. In relation to the drought combined with the application of ethephon, the responsive variety shows increased sucrose content in culm at the same level as when ethephon is applied alone, hence treatments have no additive effects on sugarcane ripening.