Sauren Das

An adaptive feature of some mangroves of Sundarbans, West Bengal

Mangrove taxa, apart from their morphological characters, have some unique leaf anatomical features which are very much related to their adaptation as the plants grow in unstable, variable and saline environments with regular tidal influence. Special stomatal structures with extended cuticles render the transpiration rate in many taxa. The presence of glandular and non-glandular hairs on the abaxial and/or adaxial leaf surfaces in some taxa are related to salt secretion of these plants. Comparatively large amounts of water storage tissues occur in the hypodermal or mesophyll tissue of the leaves, reflecting the adaptive nature of mangroves in their stressful habitat. The occurrence of terminal tracheids helps with capillary water storage within the leaf. The coriaceous nature of the leaves in some taxa is due to the presence of sclereids within the mesophyll region. It is noted thatHeritiera is unsuitable to the highly saline habitat of the Sundarbans forest region because of some anatomical peculiarities.

Salinity-imposed changes of some isozymes and total leaf protein expression in five mangroves from two different habitats

Abstract A comparative account of the polymorphic expression of two antioxidative enzymes (Peroxidase and Superoxide dismutase), two hydrolyzing enzymes (Esterase and Acid phosphatase) and total proteins was estimated both qualitatively and quantitatively from the leaves of five mangroves (Bruguiera gymnorrhiza, Excoecaria agallocha, Heritiera fomes, Phoenix paludosa and Xylocarpus granatum) from two different habitats (in situ habitat of Sundarbans and their replicas from ex situ habitat in fresh water condition) and discussed. The higher amount of total protein occurred in fresh water plants compared to their Sundarbans counterparts. The increment of total protein ranged among 156% to 5.7%. Gel electrophoresis experiments revealed that in most of the cases there were extra numbers of protein bands expressed with relatively low molecular weight in saline habitat. In all salinity imposed plants, there were sharp increases in band intensity and the number of isoforms of investigated enzyme. Peroxidase increment in saline plants ranged from 257–139%. Similarly, SOD was estimated at 247–147% in saline habitats. Increments of Esterase and Acid phosphatase varied from 287–154% and 293–139%, respectively.

Differential expression of physiological and biochemical characters of some Indian mangroves towards salt tolerance

Mangroves are physiologically interesting as potential models for stress tolerance and as sources of alternative ideas about physiological strategies relevant at the ecosystem level. Variation in habitat has great impact on the physiological behavior and biochemical expression level of a particular plant species. Five species of mangroves, growing in saline and fresh water conditions were assessed for their ecological fitness in two different habitats. Assessments were based on some physiological and biochemical parameters measured from the fully exposed mature leaves under saline (15–27 PPT) and non-saline (1.2–2 PPT) conditions. Among the five species considered for investigation Bruguiera gymnorrhiza, Excoecaria agallocha and Phoenix paludosa grow luxuriously in the Sundarbans forest, while the rest two (Heritiera fomes, Xylocarpus granatum) are scanty. A comparative account of photosynthetic efficiency, chlorophyll content, mesophyll and stomatal conductance, specific leaf area, photosynthetic nitrogen use efficiency, total foliar free amino acids and differential expression of some antioxidant isoenzymes in leaf were estimated between the saline and non-saline plants. Elevated assimilation rate coupled with increased chlorophyll content, increased conductance and higher specific leaf area in non-saline condition indicates ability of these mangroves to grow even under minimal substrate salinity. The optimum PAR acquisition for photosynthesis in B. gymnorrhiza, E. agallocha and P. paludosa was higher under salt stress, while the maximum assimilation rate was lower in control plants. The opposite trend occurred in H. fomes and X. granatum, where the peak photosynthesis was lower under non-saline conditions even at a higher irradiance than in the saline forest. The isoform patterns of peroxidase, acid phosphatase and esterase indicated considerable difference in regulation of these enzymes due to salt stress and /or reverse adaptation.

A variation on chloroplast development: The bizonoplast and photosynthetic efficiency in the deep-shade plant Selaginella erythropus

UNLABELLED • PREMISE OF THE STUDY Chloroplast development and structure are highly conserved in vascular plants, but the bizonoplast of Selaginella is a notable exception. In the shade plant S. erythropus, each dorsal epidermal cell contains one bizonoplast, while other cells have normal chloroplasts. Our quest was to (1) determine the origin of bizonoplasts, (2) explore developmental plasticity, and (3) correlate developmental changes with photosynthetic activity to provide insights unavailable in other green plants with more constrained development.• METHODS Bizonoplast development was studied in juvenile prostrate and older erect shoots of S. erythropus. Plastid plasticity was studied in plants cultivated under different light conditions. Chlorophyll fluorescence was measured and correlated with photosynthetic activity.• KEY RESULTS The bizonoplast originates from a proplastid, forming a distinctive upper zone rapidly after exposure to low light. In the prostrate shoots, the proplastid develops through early stages only. When the shoot becomes erect, the proplastid soon develops into a mature bizonoplast. Erect shoots have significantly higher photosynthetic efficiency than prostrate shoots. No bizonoplasts were found in the plants growing in high light, where 2-4 spheroidal chloroplasts formed, or with light from below.• CONCLUSIONS The upper zone develops above a normal-looking chloroplast structure to produce a bizonoplast. Bizonoplast developmental plasticity suggests that regular lamellar structure and monoplastidy are adaptations to deep shade environments. Such novel variation in S. erythropus is in stark contrast to known plastid development in other vascular plants, possibly reflecting retention of developmental flexibility in the basal clade, Lycophyta, to which it belongs.

Salt Stress: A Biochemical and Physiological Adaptation of Some Indian Halophytes of Sundarbans

Experiment was conducted with five typical mangroves (Bruguiera gymnorrhiza, Excoecaria agallocha, Heritiera fomes, Phoenix paludosa, and Xylocarpus granatum) both from Sundarbans (in-situ) and grown in mesophytic condition (ex-situ, in the Indian Statistical Institute’s premises) since 15–17 years. A comparative account on PAR utilization for maximum photosynthesis, stomatal conductance, total leaf proteins, and polymorphic expression of two antioxidative enzymes (peroxidase and superoxide dismutase) and two hydrolyzing enzymes (esterase and acid phosphatase) were estimated both qualitatively and quantitatively. The present work revealed that the net photosynthesis was higher in mangroves from mesophytic habitats than those of the native plants, but the PAR acquisitions for maximum photosynthesis were greater in most of the Sundarbans species, except H. fomes and X. granatum. At the same time, the stomatal conductance was remarkably depleted under salinity stressed habitats than those of the nonsaline counterparts and ranged between nearly 25 and 52%. Total leaf protein content form the above said taxa revealed that the increment of total protein occurred in mesophytic habitat and it was ranged between 156% (in P. paludosa) and 5.7% (in X. granatum). PAGE analysis revealed that in most of the cases there were extra numbers of protein bands expressed with relatively low molecular weight in saline habitat plants. In all salinity imposed plants, there were sharp increase in band intensity and number of isoforms of each enzyme. Peroxidase increment in saline plants was ranged between 257% (in Bruguiera) and 139% (in Excoecaria). Similarly, superoxide dismutase (SOD) was estimated as 247% (in Heritiera) to 147% (in Excoecaria) in saline habitats. Increments of esterase and acid phosphatase were varied from 287% (in Phoenix) to 154% (in Excoecaria) and 293% (in Bruguiera) to 139% (in Excoecaria), respectively. Salinity imposed increment of antioxidant enzymes proved their efficient scavenging ability to evolved reactive oxygen species (ROS), but these increments were relatively lower in Heritiera and Xylocarpus even though the net photosynthesis was higher. This might be related to their less adaptability in elevated salinity stress than those of the other three species investigated from the same regime. Among the plants grown in in situ condition, some taxa have the better ability of enzyme production, which might be correlated with the efficient stress management practice. A statistical relationship was observed between the total protein content and the investigated enzyme concentration, dependent on the habitat and discussed accordingly.

Extrapolative microRNA precursor based SSR mining from tea EST database in respect to agronomic traits

Tea (Camellia sinensis, (L.) Kuntze) is considered as most popular drink across the world and it is widely consumed beverage for its several health-benefit characteristics. These positive traits primarily rely on its regulatory networks of different metabolic pathways. Development of microsatellite markers from the conserved genomic regions are being worthwhile for reviewing the genetic diversity of closely related species or self-pollinated species. Although several SSR markers have been reported, in tea, the trait-specific Simple Sequence Repeat (SSR) markers, leading to be useful in marker assisted breeding technique, are yet to be identified. Micro RNAs are short, non-coding RNA molecules, involved in post transcriptional mode of gene regulation and thus effects on related phenotype. Present study deals with identification of the microsatellite motifs within the reported and predicted miRNA precursors that are effectively followed by designing of primers from SSR flanking regions in order to PCR validation. In addition to the earlier reports, two new miRNAs are predicting here from tea expressed tag sequence database. Furthermore, 18 SSR motifs are found to be in 13 of all 33 predicted miRNAs. Trinucleotide motifs are most abundant among all followed by dinucleotides. Since, miRNA based SSR markers are evidenced to have significant role on genetic fingerprinting study, these outcomes would pave the way in developing novel markers for tagging tea specific agronomic traits as well as substantiating non-conventional breeding program.

Seedling Morphology of Three Mangrove Species and Its Taxonomic Implications

Seedling establishment is an important part of the life cycle of mangroves. Very early in the juvenile stage, they face adverse situations such as a variable and unstable substrate as well as a high-saline environment Therefore, the propagules should have some ability to float in saline water. Seedlings differ morphologically from the adult plants. Here, I examined the seedling growth stages in three species of mangrove:Aegialitis rotundifolia Roxb.,Aegiceras corniculatum (L) Blanco, andAvicennia marina (Forsk.) Vierh. that grow in the Sundarbans swamps of West Bengal. In all cases, fruits were the propagating units; seeds were inseparable from those fruits. Germination was rapid and required no dormancy period. The hypocotyi pierced the seed coat rather than emerging from the pericarp — a variation on the traditional viviparous type of germination. Seedlings then became exposed prior to abscission from parent plants. Based on germination patterns and differences in seedling morphology observed here, these species should be classified in a more relevant taxonomic group than was done previously.

Genetic variation in relation to adaptability of three mangrove species from the Indian Sundarbans assessed with RAPD and ISSR markers

Rich genetic polymorphism is important for plants to adapt to changes because it enables the plant to make anatomical, physiological and biochemical changes in response to abiotic stress. Geomorphologic characteristics, demographic interference and a cumulative decrease in freshwater influx in the Indian Sundarbans region have proved detrimental to some economically important plants. In this study, genetic polymorphism of three mangrove species, Xylocarpus granatum, Excoecaria agallocha, and Phoenix paludosa, was assessed using RAPD and ISSR molecular markers. X. granatum, already in distress in the Sundarbans, had the least genetic polymorphism, 14.56% in the RAPD analysis and 12.92% in the ISSR. Relatively higher genetic polymorphism was recorded for the profusely growing E. agallocha and P. paludosa: 24.66 and 26.4% in RAPD; 24.87 and 20.32% in ISSR analysis respectively. A UPGMA dendrogram constructed using the similarity matrix from RAPD, ISSR and combined data showed that for X. granatum, the least and highest salinity zones clustered together, whereas for E. agallocha and P. paludosa, higher and lower salinity areas clustered in different clades. Nei’s genetic diversity, calculated from RAPD and ISSR data, was also in accordance with 0.0637 and 0.0583 for X. granatum, respectively, much lower than 0.0794 and 0.0818 for E. agallocha and 0.0799 and 0.0688 for P. paludosa. This opposing degree of polymorphism might be attributed to the profusely growing E. agallocha and P. paludosa and precarious status of X. granatum throughout the Indian Sundarbans.