Effects of different concentrations of polyethylene glycol 400 (PEG 400) on viability, relative water content, total chlorophyll content, total soluble protein and antioxidant enzymes activities of protocorm-like bodies (PLBs) of Aranda Broga Blue Bell orchid hybrid were determined. Different concentrations of in vitro drought-inducing chemical, PEG 400 at 0, 5, 10, and 15% (v/v) were used in this study. From the results obtained, lower concentration of PEG 400 at 5% produce minimum impact on the relative water content and morphological changes of treated PLBs. Percentage of viable PLBs at 5% PEG 400 treatment showed no significant difference with the control PLBs. However, significant reduction in total chlorophyll content and total soluble protein content of PLBs verified that supplementation of PEG 400 into Vacin and Went medium caused severe interruptions on various biochemical processes. Excessive production of free radical molecules increased the total activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Specific localization, affinity and role of these enzymes resulted in different patterns of their overall activity. These findings suggested that the PLBs of Aranda Broga Blue Bell were drought tolerant orchid explants at low intensity of in vitro drought stress condition.
Key words: PLBs, Polyethylene glycol, Drought stress, Chlorophyll content, Antioxidant enzyme.
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