261 International Journal of Bio-resource and Stress Management 2012, 3(1):001-017 Comparative Morphology and Anatomy of Few Mangrove Species in Sundarbans, West Bengal, India and its Adaptation to Saline Habitat Humberto Gonzalez Rodriguez1, Bholanath Mondal2, N. C. Sarkar3, A. Ramaswamy4, D. Rajkumar4 and R. K. Maiti4 1Facultad de Ciencias Forestales, Universidad Autonoma de Nuevo Leon, Carr. Nac. No. 85, Km 145, Linares, N.L. Mexico 2Department of Plant Protection, Palli Siksha Bhavana, Visva-Bharati, Sriniketan (731 236), West Bengal, India 3Department of Agronomy, SASRD, Nagaland University, Medziphema campus, Medziphema (PO), DImapur (797 106), India 4Vibha Seeds, Inspire, Plot#21, Sector 1, Huda Techno Enclave, High Tech City Road, Madhapur, Hyderabad, Andhra Pradesh (500 081), India Article History Abstract Manuscript No. 261 Mangroves cover large areas of shoreline in the tropics and subtropics where they Received in 30th January, 2012 are important components in the productivity and integrity of their ecosystems. High Received in revised form 9th February, 2012 variability is observed among the families of mangroves. Structural adaptations include Accepted in final form th4 March, 2012 pneumatophores, thick leaves, aerenhyma in root helps in surviving under flooded saline conditions. There is major inter- and intraspecific variability among mangroves. In this paper described morpho-anatomical characters helps in identification of family Correspondence to and genus and species of mangroves. Most of the genus have special type of roots which include Support roots of Rhizophora, Pnematophores of Avicennia, Sonneratia, Knee *E-mail: [email protected] roots of Bruguiera, Ceriops, Buttress roots of Xylocarpus. Morpho-anatomically the leaves show xerophytic characteristics. This morphological and anatomical response Keywords to local conditions may allow the trees to maximize their photosynthetic efficiency Most of the species are now endangered species due to environmental effects and Mangroves, morphology, anatomy, adaptation, human activities. saline environment 1. Introduction populations occurring between the latitudes of 30° N and S (Tomlinson, 1986). At one time, 75% of the world’s tropical The term “mangrove” refers to grouping of tropical trees and coastlines were dominated by mangroves. Unfortunately, shrubs that grows in the intertidal zone. Mangroves include mangrove extent has been significantly reduced due to human approximately 16 families and 40 to 50 species (depending on activities in the coastal zone. There are two centers of mangrove classification). According to Tomlinson (1986), the following diversity: the Eastern group (Australia, Southeast Asia, India, criteria are required for a species to be designated a “true or East Africa, and the Western Pacific) where the total number strict mangrove”: Complete fidelity to the mangrove environment, of species is approximately 40 and the Western group (West major role in the structure of the community and has the ability Africa, Caribbean, Florida, Atlantic South America, and Pacific to form pure stands. These plants possess morphological and North and South America) where the number of species is physiological adaptation to their habitat. They should be isolated only 8. taxonomically from terrestrial relatives. Thus, mangrove is a non-taxonomic term used to describe a diverse group of plants The Sundarbans- World largest delta and continuous mangrove 2 that are all adapted to a wet, saline habitat. Mangrove may typi- forest, covering about 10200 m of land and water within the cally refer to an individual species. Terms such as mangrove Ganga, Bramhaputra and Meghna delta, with some approximately community, mangrove ecosystem, mangrove forest, mangrove 6000 km of reserve forest located in Bangladesh and the rest aprroximately 4200 m2 reserve forest in West bengal, India. The swamp, and mangal are used interchangeably to describe the flora of the Indian Sundarban includes 26 true mangrove spe- entire mangrove community. cies, 29 mangrove associates, and 29 back mangrove species of 1.1. Distribution 40 families and 60 genera (Naskar and Guha Bakshi, 1995). Mangrove distribution is circumglobal with the majority of An overview of tropical mangrove community ecology, based PRINT ISSN: 0976-3988; 0NLINE ISSN: 0976-4038 © 2012 PP House 000001 Rodriguez et al., 2012 primarily on Australian Work, can be found in Robertson ultrafiltration system. Transpiration at the leaf surface creates and Alongi (1992). Li and Lee (1997) reviewed much of the negative pressure in the xylem. This causes a type of “reverse Chinese mangrove literature published between 1950 and osmosis” to occur at the root surface. The salt concentration 1995. Ellison and Farnsworth (2001) have recently published of xylem sap in the red mangrove is about 1/70 the salinity a general review of mangrove ecology. of surrounding seawater, but this is l0 times higher than in There is major inter- and intra-specific variability among normal plants. Black and White mangroves regulate ionic con- mangroves. For example, physiological differences have been centration by excreting salt through glands on the leaf surfac. identified between West African and Western Atlantic Avicennia This temperature sensitive enzymatic process involves active germinans (Saenger and Bellan, 1995) and distinct chemo- transport with energy expended. Xylem sap is 1/7 concentra- types have been described for A. germinans and Rhizophora tion of salt water. This is l0 times the concentration of the salt (Corredor et al., 1995; Dodd et al., 1995; Rafii et al., 1996). excluders. All three species exhibit to a small degree a combi- Variability may result from genotypic differences or from nation of both methods of salt regulation. The Red mangrove phenotypic responses to local environments. Mean leaf area stores and disposes of excess salt in the leaves and fruit. Black of Rhizophora mangle in Mexico, for example, is positively and White mangroves are capable of limited salt exclusion in correlated with annual precipitation and negatively correlated the roots. Lenticels and spongy tissue in roots and modified with latitude. This morphological response to local conditions branches facilitates gaseous exchange. In Black mangroves, may allow the trees to maximize their photosynthetic efficiency spongy pneumatopphores (up to l0,000 per tree) extend up to (Rico-Gray and Palacios-Rios, 1996a). Similarly, leaf area 20 cm above the sediment. Prop roots in the Red mangrove possess many lenticels which allow O diffusion with passage indices can be used to differentiate Rhizophora mangle from 2 basin and dwarf forest types in southeast Florida, USA (Araujo to underground roots by means of open passageways (aeren- et al., 1997). chyma). In the White mangrove, lenticels in the lower trunk obtain O for aerenchyma. Peg rootsand pneumatophores may 1.2. Ecological significance 2 be present when found in oxygen deprived sediments. With a low productivity, most ecologists today view them as Five species of mangroves (Bruguiera gymnorrhiza, Excoecaria highly productive, ecologically important systems. Major roles agallocha, Heritiera fomes, Phoenix paludosa and Xylocarpus of mangrove swamps are mentioned: granatum) were investigated with respect to their photosynthesis • It contribute to soil formation and help to stabilize the rate, chlorophyll content, mesophyll conductance, specific leaf system area, stomatal conductance and photosynthetic nitrogen use • It act as filters for upland runoff. efficiency under saline (15-27 PPT) and non-saline (1.8-2 PPT) • The systems serve as habitat for many marine organisms such conditions (Nandy et al., 2007). In this study, it was found that as fish, crabs, oysters, and other invertebrates and wildlife elevated assimilation rate coupled with increased chlorophyll such as birds and reptiles. content, more mesophyll and stomatal conductance and higher • It produces large amounts of detritus that may contribute to specific leaf area in nonsaline condition indicates that these productivity in offshore waters. mangroves can grow well even with minimal salinity in soil. • Mangrove forests serve as protection for coastal communities It has been documented that xylem anatomy and leaf tissue of against storms such as hurricanes. Laguncularia racemosa appeared to be modulated by salinity, • It also serves as nurseries and refuge for many marine organisms which led to a coordinated decline in hydraulic properties as that are of commercial or sport value. Areas where widespread salinity increased. Therefore, these structural changes would destruction of mangrove has occurred usually experience a reflect functional water use characteristics of mangrove leaves decline in fisheries. Many threatened or endangered species under salinity (Sobrado, 2007). reside in mangrove forests. High salinity levels (400 mM NaCl) reduces photosynthesis in • Mangrove forests are also important in terms of aesthetics leaves of Bruguiera parviflora, primarily by reducing diffusion of and tourism. Many people visit these areas for sports fishing, CO to the chloroplast, both by stomatal closure and by changes boating, bird watching, snorkeling, and other recreational 2 in mesophyll structure, which decreased the conductance to pursuits. CO2 within the leaf, as well as by affecting the photochemistry 1.3. Physiological adaptation of the leaves (Parida et al., 2004). Mangrove species use two major methods of internal ionic Morpho-anatomy play important