Rendimentos Agrícola e Forrageiro de Três Cultivares de Cana-de-Açúcar (Saccharum spp) em Diferentes Épocas de Corte

Abstract

Micropropagation of bananas results in a great quantity of cloned plantlets, produced in a reduced space and in a short period of time. Nevertheless, the anatomical structure of the leaves of the explants formed under in vitro conditions present a series of deficiencies, which result, most of the time, in great volumes of losses due to desiccation, during acclimatization. The objective of this work was to study the morph- anatomical modifications caused to the banana ´Prata ana´ explants, when submitted to high light intensities, and a reduction in sucrose supplementation in the culture media during multiplication and rooting phases. The experiment was established in the facilities of the Biofactory, at EMBRAPA Cassava and Tropical Fruit Crops, in the city of Cruz das Almas, Bahia state, Brazil. The explants were maintained in vitro, during a 65 days period, during which two different light intensities (a natural light and an artificial light environment), together with two different sucrose concentrations (15g L-1 and 30g L-1) in the culture media, with two different growth regulators (BAP and ANA) were tested. The development of the in vitro materials were evaluated by several parameters. The anatomical characterization, was done by the extraction of transversal sections of the explants leaves, in two distinct positions (P1 - medium vein and P2 - central portion of the leaf limb, having been measured the thickness of each of the tissues which composed the leaf mesophyl. In order to characterize the shape, density and topography of the stomata, paradermic cuts were proceeded in both surfaces of the leaves. Explants in both multiplication and rooting media, under artificial or natural light presented an organized differentiation of the mesophyl, with no abnormalities at all. The appropriate functioning of the stomata, could be analyzed by the relation between the average polar diameters over the average equatorial diameters, having been confirmed that in the multiplication phase, the best results in terms of the development of the explants were obtained under artificial light conditions, with a 30g L-1 sucrose supplementation. On the other hand, for the rooting phase, the best results were obtained under natural light conditions, with a 15g L-1 sucrose supplementation.