Salinity in agricultutal terms is the excess of salts above the level plant require. Most often it poses constrains in the growth hence productivity of the category of plants called glycophytes, wherein falls major crops, therefore is a serious concern. It is often recognized as excess of sodium ions (sodicity) that imparts life threatening consequences in plant due to mal-textured soil hindered porosity and aeration leads to physiological water deficit. Mingling with other edaphic/environmental factors viz. precipitation, temperature, flooding, soil profile, water table exaggerates the catastrophe synergistically. Improper irrigations system, leaching fraction added with land clearing and deforestation have been marked as the major cause. The present review underlines the different sources of salinity stress and their physiological manifestations, toxicity responses alongwith tolerance in plants and management strategies in affected landscapes.

Causes of salinity and plant manifestations to salt stress: a review.

Summary
• The aim of this study was to determine whether guaiacol peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT) activities are effective in the protection and recovery of cowpea (Vigna unguiculata (L.) Walp.) leaves exposed to a salt-induced oxidative stress. The salt treatment (200 mm NaCl) was imposed during six consecutive days and the salt withdrawal after 3 d (recovery treatment). Control plants received no NaCl treatment.
• The salt treatment caused almost complete cessation of leaf relative growth rate in parallel with the transpiration rate. The restriction in leaf growth was associated with a progressive increase in membrane damage, lipid peroxidation and proline content. Salt withdrawal induced a significant recovery in both leaf growth rate and transpiration. Surprisingly, these prestressed/recovered plants showed only a slight recovery in leaf lipid peroxidation and membrane damage.
• Leaf CAT activity experienced a twofold decrease only after 1 d NaCl treatment, and salt withdrawal had no effect on its recovery. SOD activity did not change compared with control plants. By contrast, POX activity significantly increased after 1 d NaCl treatment and showed a significant recovery to levels near to those of control.
• In conclusion, it appears that the ability of cowpea plants to survive under high levels of salinity is not caused by an operating antioxidant system involving SOD, POX and CAT activities in mature leaves.

Superoxide dismutase, catalase and peroxidase activities do not confer protection against oxidative damage in salt‐stressed cowpea leaves

The study aimed to investigate the effects of an AM fungus (Glomus intraradices Schenck and Smith) on mineral acquisition in fenugreek (Trigonella foenum-graecum) plants under different levels of salinity. Mycorrhizal (M) and non-mycorrhizal (NM) fenugreek plants were subjected to four levels of NaCl salinity (0, 50, 100, and 200 mM NaCl). Plant tissues were analyzed for different mineral nutrients. Leaf senescence (chlorophyll concentration and membrane permeability) and lipid peroxidation were also assessed. Under salt stress, M plants showed better growth, lower leaf senescence, and decreased lipid peroxidation as compared to NM plants. Salt stress adversely affected root nodulation and uptake of NPK. This effect was attenuated in mycorrhizal plants. Presence of the AM fungus prevented excess uptake of Na+ with increase in NaCl in the soil. It also imparted a regulatory effect on the translocation of Na+ ions to shoots thereby maintaining lower Na+ shoot:root ratios as compared to NM plants. Mycorrhizal colonization helped the host plant to overcome Na+-induced Ca2+ and K+ deficiencies. M plants maintained favorable K+:Na+, Ca2+:Na+, and Ca2+:Mg2+ ratios in their tissues. Concentrations of Cu, Fe, and Zn2+ decreased with increase in intensity of salinity stress. However, at each NaCl level, M plants had higher concentration of Cu, Fe, Mn2+, and Zn2+ as compared to NM plants. M plants showed reduced electrolyte leakage in leaves as compared to NM plants. The study suggests that AM fungi contribute to alleviation of salt stress by mitigation of NaCl-induced ionic imbalance thus maintaining a favorable nutrient profile and integrity of the plasma membrane.

Contribution of Glomus intraradices inoculation to nutrient acquisition and mitigation of ionic imbalance in NaCl-stressed Trigonella foenum-graecum

Prosopis alba (algarrobo) is one of the most important salt-tolerant legumes used in the food and furniture industries. The effects of salinity on some growth and physiological parameters in algarrrobo seedlings were investigated. 17-Day-old seedlings were subjected to three salt treatments by adding NaCl to the growth medium in 50 mmol.L-1 increments every 24 h until the final concentrations of 0, 300 and 600 mmol.L-1 were reached. Only the highest NaCl concentration affected all of the considered parameters. Thus, 600 mmol.L-1 NaCl caused a significant reduction in root and shoot growth, but an increase in the root/shoot ratio. Leaf relative water content, nitrate content and nitrate reductase activity in leaves and roots were also decreased. At 300 and 600 mmol.L-1, the glycinebetaine content was significantly increased in both leaves and roots but this was not found for proline content. Total soluble carbohydrates increased only in roots. The results suggest that glycinebetaine enhancement may be important for osmotic adjustment in Prosopis alba under salinity stress.

/pdf/the-effects-of-salt-stress-on-growth-nitrate-reduction-and-1o3gt8a3gh.pdf

The effects of salt stress on growth, nitrate reduction and proline and glycinebetaine accumulation in Prosopis alba

Proline accumulation and glutamine synthetase activity are increased by salt-induced proteolysis in cashew leaves.

Salinity-induced effects on nitrogen assimilation related to growth in cowpea plants

The aim of this study was to test the hypothesis that salinity can affect indirectly the nitrate acquisition by a negative modulation triggered by glutamine accumulation Cowpea plants were exposed to a mild NaCl concentration (50 mM) in order to restrict growth and N-demand After 21 d, pretreated plants and control plants were supplied with 0, 5 and 10 mM of Ca(NO3)2 for 3 d in absence of NaCl Salt pretreated plants showed a great limitation in acquisition of NO3
 −, indicated by decline in the nitrate uptake rate, NO3
 − accumulation, nitrate reductase activity and protein content The restriction of NO3
 − utilization was positively associated with increased glutamine synthetase activity and glutamine accumulation, especially in roots

A. R. B. Melo

Papers

Salinity-induced effects on nitrogen assimilation related to growth in cowpea plants

Salinity affects indirectly nitrate acquisition associated with glutamine accumulation in cowpea roots