Salman Gulzar

Light, salinity, and temperature effects on the seed germination of perennial grasses

The germination requirements of four perennial halophytic grasses, Aeluropus lagopoides, Halopyrum mucronatum, Sporobolus ioclados, and Urochondra setulosa, were studied under control conditions in the laboratory. Treatments included two light levels (12 : 12 h light : dark period and 24-h dark environment), six salinity concentrations (0, 100, 200, 300, 400, and 500 mmol/L NaCl), and four temperature regimes (fluctuating day : night temperature regimes of 10° : 20°, 15° : 25°, 20° : 30° and 25° : 35°C), using a completely randomized block design. Best seed germination of all grasses was obtained in a distilled water control. Increase in salinity progressively inhibited germination of all species. For example, few seeds of H. mucronatum germinated above 300 mmol/L NaCl, while seeds of the other grasses germinated in up to 500 mmol/L NaCl. Optimal temperature regime for germination for all species was 20° : 30°C both for light- and dark-germinated seeds. At higher temperatures differences between light and dark treatments were not significant. Absence of light had no effect on the seed germination of U. setulosa and H. mucronatum; however, germination was lower in all salinity treatments. In the case of A. lagopoides, absence of light substantially inhibited the germination both in control and saline conditions. The light effect was marked in the case of S. ioclados, which showed very low germination in the absence of light both under saline and nonsaline conditions.

Salt Tolerance of a Coastal Salt Marsh Grass

Growth, water and osmotic relations were examined in the halophytic perennial grass Urochondra setulosa (Trin.) C.E. Hubbard from a population located on the coast of Arabian Sea near Karachi, Pakistan. Urochondra setulosa plants were grown in 0, 200, 400, 600, 800, and 1000 mM NaCl in a sand culture using sub‐irrigation. Number of leaves and tillers, root length and shoot length, fresh weight and dry weight of roots and shoots were highest in the non‐saline control and decreased with an increase in salinity. Some plants survived in salinities above 600 mM NaCl, but their growth was stunted and mortality was high. Maximum succulence as estimated from plant water content was found in 0 mM NaCl. Water potential, osmotic potential and stomatal conductance became more negative with an increase in salinity, while pressure potential decreased with increasing salinity. Percentage ash content of shoots did not vary with increases in salinity. Na+ and Cl− levels increased in shoots while K+ concentration decreased with increases in salinity.

Effects of salinity on growth, ionic content, and plant-water status of Aeluropus lagopoides

The effect of sodium chloride (NaCl) in the external medium upon the growth, plant–water status, and ionic content of Aeluropus lagopoides was studied. Plants grown in non-saline and 200 mM NaCl had the greatest fresh and dry weights. Increasing salinity (400 to 1000 mol m−3 NaCl) caused a decrease in fresh and dry weights of plants. The water potential and osmotic potential of shoots became more negative with an increase in salinity, which was associated with an accumulation of Na+ and Cl− in leaves. Shoot Ca2+, Mg2+, and K+ concentration remained constant in salinity treatments, while Na+ increased in salt treatments and reached greater than 4 mol m−3 g−1 dry weight.

Seed Germination Strategies of Desmostachya Bipinnata: A Fodder Crop for Saline Soils

Abstract Desmostachya bipinnata (L.) Stapf. (Poaceae), or drub, a perennial grass of near-coastal and inland deserts, is a potential fodder crop for either saline soils or where only brackish water is available for irrigation. The responses of D. bipinnata seeds under various salinity (0, 100, 200, 300, 400, and 500 mM NaCl), temperature (10°–20°, 15°–25°, 20–30°, and 25°–35°C) and light (12∶12-h dark∶light and 24-h dark) regimes were investigated. All seeds germinated under nonsaline conditions, however, increase in salinity resulted in a progressive decrease in germination, and few seeds germinated at 500 mM NaCl. Change in temperature had little effect on seed germination under nonsaline conditions, however, seed germination was inhibited under cooler saline conditions. The germination under saline conditions improved at warmer temperature regimes. Seed germination under nonsaline control in dark was similar to those of seeds germinated in light. However, at high salinities, seed germination was substantially inhibited in dark in comparison to those germinated in light. When ungerminated seeds were transferred to distilled water they germinated immediately, and those from higher salinity and temperature regimes had higher recovery. The ability of seeds to germinate over a range of salinity and temperature regimes suggests possibilities for sustainable use of this species as a cash crop in saline soils.

The influence of genes regulating transmembrane transport of Na+ on the salt resistance of Aeluropus lagopoides

Plantlets of Aeluropus lagopoides (Linn.) Trin. Ex Thw. were grown at different NaCl concentrations (26, 167, 373 and 747mM) for 3, 7 and 15 days; their growth, osmotic adjustment, gas exchange, ion compartmentalisation and expression of various genes related to Na+ flux was studied. Plantlets showed optimal growth in non-saline (control; 26mM NaCl) solutions, whereas CO2/H2O gas exchange, leaf water concentration and water use efficiency decreased under all salinity treatments, accompanied by increased leaf senescence, root ash, sodium content and leaf osmolality. A decrease in malondialdehyde (MDA) content with time was correlated with Na+ accumulation in the leaf apoplast and a concomitant increase in Na+ secretion rate. A. lagopoides accumulated a higher concentration of Na+ in root than in leaf vacuoles, corresponding with higher expression of V-NHX and lower expression of PM-NHX in root than leaf tissue. It appears that V-ATPase plays a vital role during Na+ transport by producing an electromotive force, driving ion transport. Leaf calcium increased with increasing salinity, with more rapid accumulation at high salinity than at low salinity, indicating a possible involvement of Ca2+ in maintaining K+:Na+ ratio. Our results suggest that A. lagopoides successfully compartmentalised Na+ at salinities up to 373mM NaCl by upregulating the gene expression of membrane linked transport proteins (V-NHX and PM-NHX). At higher salinity (747mM NaCl), a reduction in the expression of V-NHX and PM-NHX in leaves without any change in the rate of salt secretion, is a possible cause of the toxicity of NaCl.

Comparative salt tolerance of perennial grasses.

Salt tolerance mechanisms of three perennial halophytic grasses (Aeluropus lagopoides (Linn.) Trin. ex Thw., Sporobolus ioclados (Trin.) C.E. Hubbard and Urochondra setulosa (Nees ex Trin.) Nees) were studied to determine if local species employ similar strategies to tolerate high salinity. We found different patterns of growth, water relations and ion uptake among the species tested. Aeluropus lagopoides and U. setulosa were grown in 0-1000 mM NaCl while S. ioclados in 0-500 mM NaCl under ambient conditions. Plants from nonsaline controls had larger fresh and dry weights. Increasing concentrations of salinity from 600 – 1000 mM NaCl for A. lagopodides and U. setulosa and 500 mM NaCl for S. ioclados caused high salinity stress. Water and osmotic potential of the plants increased with increasing salinity and pressure potential decreased slightly in all species. Stomatal conductance in all grasses decreased substantially with the increase in salinity. Ash content remained low (~12%) in both shoot and root of all grasses and showed little change with the increase in salinity except for S. ioclados, where in root it increased up to 35%. Na and Cl concentrations showed a small increase while Ca, Mg and K remained constant with increasing salinity. Various ion ratios for shoot and root also showed variation between the species tested.

Effects of salinity and ascorbic acid on growth, water status and antioxidant system in a perennial halophyte

Limonium stocksii is a potential commercial cut-flower crop for saline areas using brackish water. We therefore were interested to learn about the mechanism of its salinity tolerance. Plants grew well under lower saline conditions (300 mM NaCl) but higher salinities reduced growth. An increase in leaf osmolality and the management of salinity-induced oxidative stress are the key strategies employed. Exogenous AsA application improved the functioning of the AsA-dependent antioxidant system, leading to better growth.

Excreting and non-excreting grasses exhibit different salt resistance strategies

Salt marsh grasses are adapted to thrive under saline conditions by various combinations of traits. Some researchers suggested that salt excreting grasses would differ from non-excreting ones in these traits. However, little is known about the differential responses between these plant types. Here, we compared the growth and physiology of salt excreting and non-excreting grasses. Differences were found between the two grass types in leaf water content, accumulation of organic compounds and Na+ distribution which appeared to be linked with salt excretion. Additional studies on a number of halophytic grasses could help to identify key traits for salt resistance.

Is Soil Heterogeneity the Major Factor Influencing Vegetation Zonation at Karachi Coast

This study attempts to understand whether changes in edaphic factors are key players in regulating ecophysiological parameters in coastal plants. Some ecophysiological parameters of selected populations along the coastal gradient (dune and salt marsh zones) were investigated. Significant variation in soil parameters such as ECe, moisture and organic matter were found between dune and marsh zones. However, populations mostly displayed plant-type specific variations in ecophysiological parameters i.e., dicot species had more negative xylem pressure potential and higher chlorophyll and transpiration rates than monocots. In addition, some species specific responses were also observed. Despite these differences all the species displayed almost similar water-use efficiency. Significance of results obtained in this study is discussed.

SEED GERMINATION AND RECOVERY RESPONSES OF SUAEDA HETEROPHYLLA TO ABIOTIC STRESSES

E detection and accurate diagnosis of cytogenetic abnormalities together with assessment of immunophenotypic findings is essential for prognosis and therapeutic targeting of Chronic Lymphocytic Leukemia (CLL). Hyperleukocytosis (absolute leukocyte count exceeding 100,000 cells/mm3) in CLL has been clinically described in the literature but immunophenotypic and cytogenetic characteristics have not been explored. This study examined retrospective data from hematopathology reports of patients with typical CLL and the hyperleukocytic variant to compare clinical, immunophenotypic and cytogenetic differences between the two groups. We found consistent laboratory associations, particularly thrombocytopenia. Flow cytometry showed that hyperleukocytic CLL cells were immunophenotypically identical. Our data did not demonstrate any difference in the incidence of genetic abnormalities compared to other CLL cases. Our research suggests that development of hyperleukocytosis is an independent event from the mutational status of the immunoglobulin heavy chain variable (IgVH), a leading prognostic indicator. The impact of hyperleukocytosis in CLL on long term survival is still uncertain.Seed germination and recovery from salt stress of an annual halophyte Suaeda heterophylla (Kar. & Kir.) Bunge to different iso-osmotic concentrations (0, -0.46, -0.92, -1.38, -1.84, and -2.30 MPa) of NaCl and PEG-6000 at 15/25, 20/30 and 25/35oC in both 12-h temperature and light regimes and in complete darkness were studied. Maximum number of seeds germinated in distilled water and increase in concentrations of both NaCl and PEG-6000 decreased germination at all temperature regimes, light and dark conditions, with higher inhibition in NaCl than PEG-6000. Recovery of germination and viability of seeds were lower in NaCl than PEG-6000 both in the light and dark. Moderate alternate temperatures (20/30oC) and 12-h photoperiod were found to be the optimal for seed germination and recovery. Better seed germination of S. heterophylla when osmotic potential caused both by NaCl and PEG 6000 is lower, temperature regime of 20/30oC and light regime is for 12 h. Grant Funding Source: ABDEL REHMAN A. ALATAR