Salinity Dependent Photosynthetic Response and Regulation of Some Enzymes in Halophytes from Indian Sundarbans

Abstract

The Environment and Ecosystem of tropical and subtropical coastal zone is marked with unique geophysical characters like sea surges with tidal waves, upland discharges, rapid sedimentation, substrate erosion and episodic cyclones. Mangroves are representing a genetic adaptation of a large variety of plant community of different families to a typical saline environment and are best developed on shorelines of tropical world particularly in vast areas of tidal influence. The mangroves are specially suited for the inhospitable environmental condition and thus pose a lot of challenging problems to the biologists. The main feature of mangroves is in their ability to successful colonization under constant physiological stress (Chaudhuri 1996). These plants grow by developing some morphological, physiological and reproductive adaptation (Zimmermann 1983; Das 1999). This vegetation provides a multidimensional beneficial impact on coastal ecosystem in the form of production and protection. This vast greenery nurses several estuarine habitats and mitigate the violence of cyclonic effect (Hogarth, 1999). Recently, these economic and ecologically utility plant communities are under severe threats world-wide. Hence, conservation and management of such ecosystem is a front-line issue to the scientific world. It is well established that biodiversity of the mangrove vegetation is getting degraded to a large extent all over the world due to human interference and tectonic activities. Mangrove ecosystems currently cover 146,530 km2 of the tropical shorelines of the world (FAO 2003). This represents a decline from 198,000 km2 of mangroves in 1980, and 157,630 km2 in 1990 (FAO 2003). These losses represent about 2.0% per year since 1980–1990, and 0.7% per year within 1990–2000. These figures show the magnitude of mangrove loss, and hence the potentiality of mangrove restoration programme. In the Indian subcontinent (extends between 21o31' 22°30' N and 88°10′ 89°51′ E), two important river systems, namely the Ganga and Brahmaputra, constitute the largest delta formation where the vast mangrove vegetation thrives with highest species diversity. Given the marked uniformity of zonation pattern, mangrove communities may be useful in interpreting minor changes in coastal conditions and serving as biological indicators. In the Sundarbans delta, there has been a very slow tilting of the coast due to tectonic uplift in the northwestern part (India) and subsidence in the east (Bangladesh). This has a major