An adaptive inducible ecological tolerance strategy of Semibarbula orientalis (Web.) Wijk. & Marg. to desiccation stress

When exposed to dry conditions, plants become cognizant of desiccation signal and transfer it to cellular machinery to activate responses for adaptation. For protection against the injurious effects of desiccation inside the cells, lower plants have typical defense mechanism. Although bryophyte possesses capability to tolerate desiccation, yet unfavourable environmental conditions may be the reason for irreversible dryness of these miniature plants. Hence, the genera which are tolerant to desiccation have to be compelled to be recognised and propagated to conserve some precursor colonisers of ecosystem naturally. This study explores the effect of different desiccation levels in plants of Semibarbula orientalis collected from two locations. The two populations showed difference in the expression of antioxidative enzymes as well as photosynthetic pigments in their respective controls. Maximum increment in peroxidase activity was observed in 72 h desiccated plants, which was 59% higher in site 1, and 484% in site 2, than their respective controls. In the plants of site 2, maximum value (about 105% higher than control) of superoxide dismutase was seen at 48 h desiccation. However, a gradual decrement was observed in catalase, as the duration of desiccation increased. Highest value of chlorophyll content was seen at 48 h desiccation which was about 294% higher for chl a, 387% for chl b and 372% for total chl in site 1, whereas plants of site 2 revealed 269% increment in chl a, 1042% in chl b and 803% in total chl, than their respective controls. Our results are often explained on the premise of relationship between desiccation tolerance and atmospheric moisture (relative humidity), as the rate of desiccation has been reported to be faster at lower relative humidity and vice versa. Hence it is suggested that, desiccation and rehydration are not merely indicative of removal and addition of water, but also include a sequence of physiological and biochemical events, and the efficiency of such changes in different populations, under different environmental conditions highlights variation in the inducible response strategy.