Anatomical and physiological modifications of micropropagated 'caipira' banana plants under natural light

Abstract

Research about the use of natural light associated to changes in sucrose levels demonstrated potential in promoting in vitro hardiness of tropical climate species, as well as reducing production costs. However, little is known about physiological and structural changes that happen in the process. This study evaluated the physiological and anatomic performance, and ex vitro survival of micropropagated banana plants in response to cultivation conditions, in the stage of in vitro rooting. Shoots of the ‘Caipira’ cultivar were cultivated in MS medium, supplemented with 1 mg L–1 NAA and 6 g L –1 agar, in which the following treatments were applied: two sucrose concentrations (15 g L –1 or 30 g L –1) and two cultivation conditions (Natural light – greenhouse and Artificial light – growth chamber). At the end of 45 days, the contents of chlorophyll a, b and total, the relative water content in the tissues, anatomic characteristics and the ex vitro survival were evaluated. Effects of growth environment and sucrose concentration were observed on micropropagated ‘Caipira’ banana anatomy, physiology and survival. In vitro rooting of the shoots under natural light in the medium containing 15 g L–1 or 30 g L–1 sucrose promoted major alteration in the increase of palisade and spongy parenchyma, as well as reducing leaf water loss and plant death. The results obtained in the present study confirm the potential of the use of natural light as a substitute for artificial light for micropropagation of tropical species. Key words: Musa spp., solar light, carbohydrate, water loss, anatomy.