Effect of Temperature and Light stress on the Morphology Physiology and Secondary Metabolites of Withania somnifera L Dunal and its potential as Herbicide on the Himalayan weeds

Abstract

newline ABSTRACT newlineWithania somnifera, a multipurpose medicinal plant of the Himalayan region was selected for the present study. The plant possesses antioxidant, antitumor, anti-inflammatory, antistress, immunomodulatory, hematopoetic, anti-ageing, anxiolytic, anti-depressive rejuvenating properties and influence various neurotransmitter receptors in the central nervous system. Withanolides, secondary metabolites present in W. somnifera, have neuron regenerative property. In the present study, the plant was subjected to two abiotic stresses, namely, temperature and light in order to see their impact on morphological, physiological, biochemical parameters and on neuroactive constituent (withanolides). Seedlings were raised in the university nursery and one month old potted seedlings were grown in different temperature and light treatments. For temperature treatments the seedlings were exposed to five temperature conditions (8and#730;C, 18and#730;C, 38 and#730;C, 48and#730;C and 58and#730;C). Seedlings grown at 22and#730;C were treated as control plants. Similarly, one month old plants were exposed to different light regimes comprising of 8 hrs, 12 hrs, 16 hrs, 20 hrs and 24 hrs, while control plants were given 14 hrs light. The growth of the plants due to stress treatments was found to be affected. Both temperature and light treatments caused significant decrease in stem length, root length, fresh weight and dry weight in all the treatments except 8 hrs and 12 hrs photoperiods where there was marginal increase in stem length. Changes in leaf area, membrane stability and relative water content was also observed and these l protein, carotenoids, tocopherol, ascorbic acid and alkaloids decreased. The antioxidant enzymes like superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, glutathione S-transferase, DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2 -azino-bis-3ethyl benzthiazoline-6-sulphonic acid) enhanced due to stress treatments. Withanolides were found to be higher in high temperature and long photoperiod treated plants. W. somnifera was found to have protective mechanism against oxidative damage by maintaining higher enzymatic and non-enzymatic antioxidants. The plant was found to have herbicidal properties against four tested weeds of the Himalaya, i.e., Chenopodium album, Achyranthus aspara, Ageratum coenyzoides and Parthenium hysterophorus. The plant extract decreased seed germination and seedling growth of weeds.