M. Sajid Aqeel Ahmad

Relationship between Callus Growth and Mineral Nutrients Uptake in Salt-Stressed Indica Rice Callus

ABSTRACT One month old rice calli were exposed to 0, 50, and 100 mol m−3 sodium chloride (NaCl) in the liquid LS basal medium supplemented with 2.5 mg L−1 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.5 mg L−1 kinetin. Callus relative growth rate (RGR; fresh) of both cultivars indicated a progressive decrease; however, callus dry weight increased as the NaCl level increased in the culture medium. Salinity stress increased the callus sodium (Na+), manganese (Mn2+), and magnesium (Mg2+) contents while potassium (K+), calcium (Ca2+), and iron (Fe2+) contents decreased. ‘Basmati-385’ showed less reduction in callus RGR, K+, and Ca2+ contents and a larger increase in callus dry weight, Na+, Mn2+, and Mg2+ contents as compared to ‘Basmati-Karnal’. However, the reverse was true for Fe2+ contents. K+/Na+ and Ca2+/Na+ ratios generally decreased under salt stress. Overall, reduction in callus relative growth rate was found to be inversely correlated with decrease in K+, Ca2+, and Fe2+ uptake and directly correlated with increased Na+ and Mg2+ concentration in callus tissue.

Soil-Plant Relationships in the Arid Saline Desert of Cholistan

The inland vegetation of saline patches in the Cholistan desert faces extreme environmental conditions including predominantly salt stress and limited resource availability. Changes in the salinity gradients may lead to gradual variation in response of individual plant species that ultimately affect community structure and composition. The present study was conducted to determine spatial distribution of individual species along a salinity gradient in the Cholistan desert in relation to their life form and tolerance limits. The results showed variable responses of these species in spatial distribution against the salinity gradient. The plants differed considerably in their tolerance level due to development of differential adaptive strategies under extreme salinities. Excretory species like Aeluropus lagopoides and Sporobolus ioclados dominated the sites with highest salinities along with the leafy succulent Suaeda fruticosa. Stem succulents dominated moderate salinities along with spreading stoloniferous Ochthochloa compressa and tussock grass Cymbopogon jwarancusa. Non-succulent Cressa cretica and tussock grass Lasiurus scindicus were mainly distributed to sites with lower and moderate salinities, while non-succulent plants dominated the lowest salinity site. Of the soil physico-chemical characteristics in the Cholistan desert habitats, salinity may have a direct effect on the life form and survival strategies of occurring plants. Thus, the difference in spatial distribution of individual species along salinity gradients suggested that salinity alone is not a responsible factor to determine community structure, but plant tolerance limits and their life habits are also important.

POTASSIUM AND CALCIUM UPTAKE IN MASHBEAN UNDER LEAD AND CHROMIUM STRESS

Plants of two mashbean genotypes were exposed to 20 or 40 mg L−1 of lead (Pb) or chromium (Cr) along with controls in a completely randomized design (CRD). Application of both metals (lead and chromium) caused a significant reduction in all growth parameters as compared with control. In addition, severe inhibition in potassium (K+) and calcium (Ca2+) uptake was observed with the increasing concentration of both metals in the root medium. Chromium was more toxic in reducing both cations as compared to same dose of lead. Overall, Pb and Cr contents of the root, stem and leaves increased under both metal stresses. In addition, both metals mainly accumulated in the aerial plant parts (stem and leaves).