Efeito do estimulante vegetal triacontanol sobre crescimento inicial e mecanismos fisiológicos de tolerância a seca de cana-de-açúcar.

Abstract

The sugarcane (Saccharum spp.) is one of the main crop of Brazil, of great economic importance that contributes to the sugar and ethanol production. Drought is one of the most limiting factors in the sugarcane productivity and an alternative to reduce the negative effects of stress is the application of vegetable biostimulants.. Foliar application of the biostimulant triacontanol (TRIA) has been used in different crops to reduce adverse effects, but it is still an effect on sugarcane have not been studied. Therefore, the objective of this study was to evaluate the effect of TRIA on the growth and drought tolerant of sugarcane. The experiment was carried out in a greenhouse with cultivar RB92579. The experimental design was a randomized complete block design with a 4x2 factorial design: four levels of TRIA (0, 10, 40 and 160 μM) and two water regimes (irrigated and drought stress) with five replications. The applications of TRIA in the aerial part of the plant occurred 30 and 60 days after planting (DAP). These plants were physiologically and biochemically evaluated at two intervals: six days (drought stress) and two days (rehydration) after the onset of treatment at 120 days after planting. The irrigated plants that received 160 μM TRIA level was more effective ingrowth, with increase in the height, number of leaves, leaf area, stalk dry mass, besides promoting the increase in the chlorophyll content. With drought stress imposed all plants independent of the various levels of TRIA, the reduction of leaf water potential, the relative water content, the gas exchanges, furthermore, the same plants presented a reduction in effective quantum of photosystem II and chlorophyll content. Under drought stress the plants that received the highest TRIA level showed showed higher increases in total soluble carbohydrate content, and little variation of proline and amino acids concentrations. Plants under drought stress presented lower activity antioxidant enzymes of superoxide dismutase and lipid peroxidation when TRIA was applied 160 μM, while the activity of catalase and ascorbate peroxidase enzymes were not altered by TRIA applications. The160 μM TRIA level application contributed to growth of irrigated sugarcane, but even with positive results, the data sets suggest that concentrations up to 160 μM TRIA level are insufficient to significantly reduce the symptoms of drought stress in sugarcane.