Teores de pigmentos fotossintéticos e estrutura de cloroplastos de Alfavaca-cravo cultivadas sob malhas coloridas

Abstract

The Alfavaca-cravo is a medicinal specie which produces an essential oil effective in the combat of several organisms. Therefore, the understanding of the physiologic behavior and physiological responses of this behavior to environmental conditions becomes necessary to improve methods of cultivation. In this context, the aim of this study was to evaluate the effect of the intensity and quality of the light on concentration of chlorophyll and carotenoids and on chloroplasts structure of Alfavaca-cravo (Ocimum gratissimum L.). The plants with 5.0-6.0cm were submitted to the following treatments: full sunlight and 50% of shade under blue, red and black nets during 120 days. The chlorophyll and carotenoids concentration were analyzed through spectrophotometer and the structure of chloroplast was analyzed by transmission microscopy. Plants maintained under full sunlight had the lowest chlorophyll a and b concentration and the highest carotenoids concentration. However, plants cultivated under black net had the highest production of chlorophyll a and b. The lowest chloroplasts density was found in plants under black net. In the treatments with 50% of shade was verified more elongated chloroplasts. Alfavaca-cravo plants grown under full sunlight and blue net had chloroplasts with larger areas and starch grains with larger perimeters. The changes on the pigments concentration and structure of chloroplasts showed a chromatic adaptation of Alfavaca-cravo to the variation of the intensity and quality of the light. This can improve photosynthetic performance under different luminosity conditions.