Vinayak H. Lokhande

Investigation of arsenic accumulation and tolerance potential of Sesuvium portulacastrum (L.) L.

Sesuvium portulacastrum (L.) L., a facultative halophyte, is considered a suitable candidate for the phytoremediation of metals. An investigation of As accumulation and tolerance was conducted in Sesuvium plants upon exposure to As(V) (100-1000 μM) for 30 d. Plants demonstrated a good growth even after prolonged exposure (30 d) to high As(V) concentrations (1000 μM) and a significant As accumulation (155 μg g⁻¹ dry weight) with a bioaccumulation factor of more than ten at each concentration. The results of shoot and root dry weight, malondialdehyde accumulation, photosynthetic pigments, and total soluble proteins demonstrated that plants did not experience significant toxicity even at 1000 μM As(V) after 30 d. However, metabolites (total non-protein thiols and cysteine) and enzymes (serine acetyltransferase, cysteine synthase and γ-glutamylcysteine synthetase) of thiol metabolism, in general, remained either unaffected or showed slight decline. Hence, plants tolerated high As(V) concentrations without an involvement of thiol metabolism as a major component. Taken together, the results indicate that plants are potential As accumulator and may find application in the re-vegetation of As contaminated sites.

Sesuvium portulacastrum (L.) L. a promising halophyte: cultivation, utilization and distribution in India

Seapurslane, Sesuvium portulacastrum (L.) L. (Aizoaceae) is a pioneer, psammophytic facultative halophyte naturally growing in the subtropical, mediterranean, coastal and warmer zones of the world. The plant is utilized as a vegetable by the local peoples as well as forage for domestic animals in the coastal area. Environmentally, it is utilized for the bioreclamation of saline soil in the arid and semiarid regions and an alternative culture to problematic soils. The Sesuvium clones collected from the coastal regions of India lead to conclusions with respect to its geographical distribution and prospective utilization in the bioremediation of coastal and saline areas, as an emerging source of secondary metabolite-phytoecdysteroids in sericulture industry and cultivation on large scale for food as well as forage, of this underutilized, neglected wild and also cultivated plant species.

Morphological and molecular diversity analysis among the Indian clones of Sesuvium portulacastrum L.

Sesuvium portulacastrum L. (seapurslane) is a halophyte used as pioneer species in sand dune fixation and stabilization of saline soil. Studies on the morphological and molecular diversity were carried out for the 14 clones of Sesuvium collected from the different coastal regions of India. Significant differences were observed for morphological traits viz., length, width, diameter and area of leaf, internodal distance and stem diameter for different clones when compared with the clone from Gujarat state (GJ1). A UPGMA dendrogram for morphological traits based on the Pearson’s similarity coefficient clustered the clones into three groups considering 80% polymorphism as criteria. Molecular diversity among the clones was studied using Randomly Amplified Polymorphic DNA (RAPD), Internal Transcribed Spacer (ITS) and markers specific to Ac homologous region. Of the total 749 RAPD loci amplified with 70 random primers, 294 were polymorphic with 39.25% diversity. A phylogenetic tree constructed with UPGMA and SHAN, grouped the clones into three major clades based on RAPD data. The molecular diversity studied with ITS and markers specific to Ac homologous region revealed 37.50% and 66.66% polymorphism and clustered the clones into three and four clades, respectively. The genetic diversity analysis revealed wide variations among the S. portulacastrum clones, reflecting a high level of diversity within the species which might be due to anthropogenic impact and geographic environmental conditions. Further, the various clones from the different eco-geographic coastal localities might have originated from native places of wild abundance. To the best of our knowledge, this is the first attempt to evaluate both morphological and genetic diversity among the Sesuvium clones collected from the distant habitats of the coastal regions of the India.

Differential growth, physiological and biochemical responses of niger (Guizotia abyssinica Cass.) cultivars to water-deficit (drought) stress

The present study demonstrates the effect of polyethylene glycol-8000 (PEG) and percent field capacity (FC%)-induced water-deficit stress on growth, water status, productivity and various biochemical parameters in Guizotia abyssinica Cass. cultivars (IGP 76, GA 10, No. 71 and IGPN 2004) at seedling and maturity stages of the plant. Cultivar GA 10 showed higher, IGP 76 and No. 71 moderate, and IGPN 2004 least reduction in percent seed germination given PEG stress treatments (0, 10 and 20%). A similar pattern was observed for decreased growth and water content of the seedlings and plants of the cultivars exposed to both kinds of water-deficit stresses. The productivity (number of capitula per plant, number of seeds per capitula and 1,000-seed weight) and total chlorophyll content of cultivar IGPN 2004 was significantly higher in comparison to other cultivars given different FC% treatments (100, 80 and 60%). Significantly higher accumulation of proline, glycine betaine and total soluble sugars and lower damage to membrane lipids under increased water-deficit stress (i.e., at 80 and 60% FC) conditions in cultivar IGPN 2004 suggested its more tolerance capacity to water-deficit stress in comparison to other cultivars. Besides, antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) partially demonstrated variations in the tolerance of the cultivars to water-deficit stress. The results suggest that cultivar IGPN 2004 could be considered as more tolerant, and IGP 76 and No. 71 as moderately tolerant, whereas GA 10 was more sensitive to water-deficit stress.

Hairy root induction and phytoremediation of textile dye, Reactive green 19A-HE4BD, in a halophyte, Sesuvium portulacastrum (L.) L.

Highlights • Hairy roots induction from A. rhizogenes NCIM 5140 strain in Sesuvium.• Textile dye degradation and color removal using hairy roots.

Differential Osmotic Adjustment to Iso-osmotic NaCl and PEG Stress in the in vitro Cultures of Sesuvium portulacastrum (L.) L.

The influence of iso-osmotic (−0.7 MPa) NaCl and PEG stress on growth, osmotic adjustment and antioxidant defense mechanisms was investigated in the in vitro cultures of Sesuvium portulacastrum (L.) L. The decreased relative growth rate (RGR) and water content of PEG-stressed calli in comparison to NaCl was found to be correlated with differences observed in the energy expenditure for the maintenance of osmotic balance. Osmotic adjustment in the NaCl-stressed calli favored higher accumulation of saline ions and soluble sugars, whereas PEG-stressed calli confirmed increased levels of organic osmolytes (proline, glycine betaine and soluble sugars). Permeability of Na+ ions across the membrane revealed increased relative electrolytic leakage (REL) in NaCl-stressed calli, however non-penetrating and highly viscous solution of PEG amplified the peroxidation of membrane lipids. Increased activities of superoxide dismutase and catalase displayed efficient removal of toxic reactive oxygen species in comparison to ascorbate peroxidase in the calli exposed to iso-osmotic stress. These findings suggest that differential tolerance potential to iso-osmotic NaCl and PEG stress in terms of osmotic adjustment appears to be the prime defense mechanism of Sesuvium for its survival under iso-osmotic stress conditions at the expense of reduced growth and water content.

In vitro culture, plant regeneration and clonal behaviour of Sesuvium portulacastrum (L.) L.: a prospective halophyte

An efficient plant regeneration protocol using axillary shoots of the salt accumulator halophyte, Sesuvium portulacastrum (L.) L. was established and in vitro responses of six Sesuvium clones were studied. The shoot and root induction responses to cytokinins and auxins in clone MH (Maharashtra) were concentration specific. Significantly the highest number of shoots, average shoot elongation and percent shoot regeneration per explant were observed on MS medium supplemented with 40 μM 2-isopentenyl adenine (2iP) followed by 20 μM benzyladenine (BA). Higher cytokinin (60 μM), however, inhibited shoot induction and shoot length. The lower concentrations (5 or 10 μM) of α-napthaleneacetic acid (NAA) proved more effective for root induction, number of roots and average root length. Well-developed plantlets were successfully hardened and established in the field with more than 85 % survival rate. In vitro response of six Sesuvium clones cultured on MS + 20 μM BA revealed higher multiplication rate in clone MH and KA (Karnataka, India) compared to other clones. The results offer the prospect of selecting clones of this species with characteristics desirable for utilization and/or restoration in specific ecological zones.

Biochemical and physiological adaptations of the halophyte Sesuvium portulacastrum (L.) L., (Aizoaceae) to salinity

Sesuvium portulacastrum is a dicotyledonous halophyte. The responses of different clones of Sesuvium to salinity were analysed by measuring changes in growth, biomass accumulation, water content, osmolytes accumulation, oxidative damage, antioxidant enzymes and inorganic ions. In addition, microscopic observations were made to discern any changes in the stem anatomy of Sesuvium under salt stress. Reduced growth, biomass accumulation and tissue water content correlated with an increase in NaCl concentrations (200–800 mM), except at 200 mM NaCl, where an improvement in the parameters was observed among all clones, specifically in MH1 (Maharashtra). Increased osmolytes (proline, glycine betaine and total soluble sugars) and the accumulation of Na+ ions, without affecting K+content, were recorded in all clones. Higher malondialdehyde content and greater relative electrolyte leakage were evident in addition to increased catalase and superoxide dismutase activities under salt stress. Increased cortical cell size and cortex diameter of the stem were observed upon 200–400 mM NaCl stress; decreased thickness was seen at higher NaCl concentrations. This study suggests the differential behaviour of Sesuvium clones which might be useful in the rapid selection of a potent clone (such as MH1) for the restoration of wetlands and desalination of saline soils.

Growth, physiological, and biochemical responses in relation to salinity tolerance for In Vitro selection in oil seed crop Guizotia abyssinica Cass.

The calli cultures of Guizotia abyssinica (niger) cultivars IGP 76 and GA 10 were exposed to different levels of salt treatments (0, 30, 60, and 90 mM NaCl), in order to evaluate growth, physiological, and biochemical responses. A significant decrease in relative growth rate and tissue water content of GA 10 calli than IGP 76 under salt-stress conditions was associated with higher sodium ion accumulation. Osmotic adjustment revealed by the osmolytes (proline, glycine betaine, and total soluble sugars) accumulation was significantly higher in IGP 76 salt-stressed calli as compared to GA 10. The sustained growth and better survival of IGP 76 calli was correlated with lower malondialdehyde content and increased superoxide dismutase, ascorbate peroxidase, and catalase activities and higher α-tocopherol content in comparison to GA 10. The higher osmolytes accumulation and presence of better antioxidant system suggested superior adaptation of IGP 76 calli on salt-containing medium for prolonged periods in comparison to GA 10. The regeneration frequency, organogenesis, and acclimatization response of the plants derived from salt-adapted calli was comparatively lower than the plants derived from control calli of IGP 76. The growth, physiological, and biochemical characterization of the salt-tolerant regenerated plants exposed to stepwise long-term 90 mM NaCl treatment revealed no significant changes in comparison to the control. Thus, our results suggests the development of an efficient protocol for in vitro selection and production of salt-tolerant plants in self-incompatible crop, niger, and an alternative to traditional breeding programs to increase the abiotic stress tolerance.