Muhammad Zaheer Ahmed

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.

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.

Growth patterns of Phragmites karka under saline conditions depend on the bulk elastic modulus

Salt stress is known to hamper steady-state water flow, which may reduce plant growth. This research was aimed to study the roles of leaf turgor, osmotic adjustment and cell wall elasticity under saline conditions which may reduce biomass production in Phragmites karka (Retz.) Trin, ex. Steud. (a marsh grass). Plants were grown in 0, 100 and 300 mM NaCl and harvested on 3, 7, 15 and 30 days to observe periodic changes in growth and water relations. Leaf number, relative growth rate, and relative elongation rates were higher in the non-saline control than in the plants grown under saline conditions. Plants showed a rapid decline in leaf growth rate (7–15 days) in 300 mM NaCl compared with a delayed response (15–30 days) in 100 mM NaCl. Leaf water potential decreased with increases in salinity after the third day of exposure whereas osmotic potential decreased after the fifteenth day. Low leaf turgor (Ψp) on the third day indicated an initial phase of osmotic stress under saline conditions. Plants maintained higher Ψp in 0 and 100 mM than in 300 mM NaCl. Differences between mid-day and pre-dawn water potential and water saturation deficit were higher in 300 mM NaCl than with other treatments. Water potential and hydraulic capacitance at turgor loss point decreased whereas bulk elastic modulus increased in 300 mM NaCl. Maintenance of turgor and growth at 100 mM NaCl could be related to efficient osmotic adjustment (use of K+ and Cl–), higher WUEi, and lower bulk elasticity whereas poor growth at 300 mM NaCl may have been a consequence of low turgor, decreased cell hydraulic capacitance and higher bulk elastic modulus.

POTENTIAL OF HALOPHYTES AS CATTLE FODDER: A CASE-STUDY IN PAKISTAN

Good quality water and arable land are needed to grow conventional crops to provide food for human and animal population. However, burgeoning world population leading to wide spread urbanization and industrialization is aggressively sharing these resources. A solution may be found in using saline water and salinized lands to produce quality animal feed from salt tolerant plants. In this study, two halophytic grasses (Panicum antidotale and Desmostachya bipinnata) were tested for their potential to replace conventional cattle fodder in the diet of cattle. Four trials were conducted in which cow calves were fed diets containing above mentioned halophytes alone or in combination with conventional fodders (wheat and maize). Weight gain in animals fed diets supplemented with halophytes were generally at par with or in few cases marginally better than those on conventional fodder. For instance, P. antidotale increased the calf weight around 15% when used as green and 8% in case of hay. Feeding Berseem (Trifolium alexandrinum, 15% crude protein) as the only source of concentrate in a diet containing D. bipinnata sustained weight only for about 6-7 weeks after which it started to decrease. Supplementing the diet with a regular concentrate was subsequently needed to restore weight gain. Halophytes as green/hay/concentrate were as good as conventional fodder regarding dressed meat. The protein content of meat was showing increasing trend when replacing conventional fodders with halophytes, particularly 20% protein was higher in meat when Prosopis juliflora pods and Manilkara zapota were used as concentrate and P. antidotale as hay in diet.

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