Salt tolerance and salinity effects on plants: a review.

Halophytes, plants that survive to reproduce in environments where the salt concentration is around 200 mM NaCl or more, constitute about 1% of the worlds flora. Some halophytes show optimal growth in saline conditions; others grow optimally in the absence of salt. However, the tolerance of all halophytes to salinity relies on controlled uptake and compartmentalization of Na+, K+ and Cl- and the synthesis of organic compatible solutes, even where salt glands are operative. Although there is evidence that different species may utilize different transporters in their accumulation of Na+, in general little is known of the proteins and regulatory networks involved. Consequently, it is not yet possible to assign molecular mechanisms to apparent differences in rates of Na+ and Cl- uptake, in root-to-shoot transport (xylem loading and retrieval), or in net selectivity for K+ over Na+. At the cellular level, H+-ATPases in the plasma membrane and tonoplast, as well as the tonoplast H+-PPiase, provide the transmembrane proton motive force used by various secondary transporters. The widespread occurrence, taxonomically, of halophytes and the general paucity of information on the molecular regulation of tolerance mechanisms persuade us that research should be concentrated on a number of model species that are representative of the various mechanisms that might be involved in tolerance.

Salinity tolerance in halophytes

Salinity is a major abiotic stress limiting growth and productivity of plants in many areas of the world due to increasing use of poor quality of water for irrigation and soil salinization. Plant adaptation or tolerance to salinity stress involves complex physiological traits, metabolic pathways, and molecular or gene networks. A comprehensive understanding on how plants respond to salinity stress at different levels and an integrated approach of combining molecular tools with physiological and biochemical techniques are imperative for the development of salt-tolerant varieties of plants in salt-affected areas. Recent research has identified various adaptive responses to salinity stress at molecular, cellular, metabolic, and physiological levels, although mechanisms underlying salinity tolerance are far from being completely understood. This paper provides a comprehensive review of major research advances on biochemical, physiological, and molecular mechanisms regulating plant adaptation and tolerance to salinity stress.

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Mechanism of Salinity Tolerance in Plants: Physiological, Biochemical, and Molecular Characterization

What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.

The ecology of seeds

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Responses of woody plants to flooding and salinity

Effects of Salinity on Growth, Water Relations and Ion Accumulation of the Subtropical Perennial Halophyte, Atriplex griffithii var. stocksii

http://projects.mans.edu.eg/heepf/ilppp/cources/12/pdf%20course/1/pressure/osmotic%20soilsalinity25.pdf

The effect of salinity on the growth, water status, and ion content of a leaf succulent perennial halophyte, Suaeda fruticosa (L.) Forssk

Seed germination and early seedling growth of Atriplex griffithii var. stocksii from seeds collected from a saline desert habitat in Karachi, Pakistan, were studied. The seeds of A. griffithii did ...

Effect of salinity, temperature, and growth regulators on the germination and early seedling growth of Atriplex griffithii var. stocksii

Contributing authors.- Preface.- Foreword.- 1. How salts of sodium, potassium and sulfate affect the germination and early growth of Atriplex acanthocarpa (Chenopodiaceae) B. Gaylord, T. Egan.- 2. Halophyte eed germination M.A. Khan, B. Gul.- 3. Salt tolerance of some potential forage grasses of Cholistan desert of Pakistan M. Ashraf et al.- 4. Variability of fruit and seed-oil characteristics in Tunisian accessions of the halophyte Cakile maritima (Brassicaceae) M.A. Ghars et al.- 5. Salt tolerant plants from the great basin region of the United States D.J. Weber, J. Hanks.- 6. Role of calcium in alleviating salinity effects in coastal halophytes B. Gul, M.A. Khan.- 7. Calorespirometric metabolism and growth in response to seasonal changes in temperature and salt B.N. Smith et al.- 8. Evaluation of anthocyanin contents under salinity (NaCl) stress in Bellis perennis L. R.A. Khavari-Nejad et al.- 9. A comparative study on responses of growth and solute composition in halophytes Suaeda salsa and Limonium bicolor to salinity X. Liu et al.- 10. Alleviation of salinity stress of some Brassica species M. Ozturk et al.- 11. Saline tolerance physiology in grasses K.B. Marcum.- 12. Localization of potential ion transport pathways in thesalt glands of the halophyte Sporobolus virginicus Y. Naidoo, G. Naidoo.- 13. Cellular responses to salinity of two coastal halophytes with different whole plant tolerance: Kosteletzkya virginica (L.) Presl.and Sporobolus virginicus (L.) Kunth X. Li et al.- 14. Eco-physiological studies on Indian desert plants: effect of salt on antioxidant defense systems in Ziziphus spp. N. Sankhla et al.- 15. Sabkha edge vegetation of coastal and inland sabkhat in Saudi Arabia H.-J. Barth.- 16. Analysis of the soil conditions in salt grass (Distichlis spicata (L.) Greene) wild populations in semiarid coastal zone of Mexico A. Escobar-Hernandez et al.- 17. Comparative salt tolerance of perennial grasses S. Gulzar, M.A. Khan.- 18. Commercial application of halophytic turfs for golf and landscape developments utilizing hyper-saline irrigation M. DePew, P.H. Tillman.- 19. Salt tolerance of floriculture crops C.T. Carter, C.M. Grieve.- 20. Utilization of salt-affected soils by growing some Acacia species M.Y. Ashraf et al.- 21. Soil remediation via salt-conduction and the hypotheses of halosynthesis and photoprotection N.P. Yensen, K.Y. Biel.-22. Mechanism of cash crop halophytes to maintain yields and reclaim saline soils in arid areas H.-W. Koyro et al.- 23. Halophyte uses for the twenty-first century N.P. Yensen.- 24. Halophyte research and development: What needs to be done next? B. Boer.

M. Ajmal Khan

Papers

Effects of Salinity on Growth, Water Relations and Ion Accumulation of the Subtropical Perennial Halophyte, Atriplex griffithii var. stocksii

The effect of salinity on the growth, water status, and ion content of a leaf succulent perennial halophyte, Suaeda fruticosa (L.) Forssk

Effect of salinity, temperature, and growth regulators on the germination and early seedling growth of Atriplex griffithii var. stocksii

Ecophysiology of high salinity tolerant plants.

Germination strategies of halophyte seeds under salinity