 |  |
| Bildiri Özetleri | |
| Ana Sayfaya Dönüş |
| Back To The Main List |
|
Metin TURAN, Yıldırım SEZEN University of Atatürk, Faculty of Agriculture, Department of Soil Science, Erzurum, Turkey Abstract Plant growth is limited with different environmental conditions. One of this conditions is salt stress that causes plant dies depending on the type of crops. Soil salinity is one of the most important agricultural problems in arid and semiarid climate conditions in different parts of the world. Almost 1/3of irrigated lands in the world is under the salinity problem. In Turkey approximately 1.5 million ha agricultural land has salinity problem because of missmanagement and environmental conditions. The rehabilitation of saline soils is time consuming and very expensive. Introduction Salinity has been recognized as a major agricultural problem in arid and semi-arid regions and miss management land and irrigation areas. Differences in salt tolerance among plant species have also been long recognized; however, the role that salt tolerance plays in causing differences in nutrient uptake and metabolism between various plants, among plant species, at different stages of growth is still a major concern among investigators, and has not been fully understood. So it requires joint effort of agronomist, biochemist, geneticist, plant physiologist, soil scientists among others (Pessarakli, 1991; Kawasaki et al., 1983). Plant performance usually expressed as a crop yield, plant biomass or crop quality, may be adversely affected by salinity-induced nutritional disorders. These disorders may result from the effect of salinity on nutrient availability, competitive uptake, transport or partitioning with in the plant. For example salinity reduces phosphate uptake and accumulation in crops grown in soil a primarily by reducing phosphate availability. Salinity dominated by Na+ salts not only reduces Ca2+ availability but reduces its transport and mobility to growing regions of plant, affecting the quality of both vegetative and reprocductive organs. Salinity can directly affect nutrient uptake as Na+ reducing K+ uptake or by Cl- reducing NO3- uptake. High concentration of Na+ and Cl- in the soil solution may depress nutrient-ion activities and produce extreme ratios of Na+/ Ca2+, Na+/ K+, Ca2+/Mg2+ and Cl-/NO3-. Salinity can cause a combination of complex interactions affecting plant metabolism or susceptibility to injury. Macro and Micro Nutrient Uptake : Salt salinity affects plant physiology through changes of water and ionic status in the cells (Kashem et al., 2000; Hasegawe et al., 2000). Ionic imbalance occurs in the cells due to excessive accumulation of Na+ and Cl- and reduces uptake of other mineral nutrients, such as K+, Ca2+, and Mn2+ (Lutts et al., 1999). External supplied Ca+2 has been shown to ameliorate the adverse effect of salinity in plants, presumably by facilitating higher K+/Na+ selectivity (Hasegawe et al., 2000). In many field studies, horticulturists and agronomists set out to test the hypothesis that N-fertilizer additions alleviate, at least to some extent, the deleterious effect of salinity on plants. Despite the lack of evidence indicating that N applied to saline soil or media above a level considered optimal under non-saline conditions improves plant growth or yield, a number of laboratory and greenhouse studies have shown that salinity can reduce N accumulation in plants (Pessarakli, 1991). Champagnol (1979), reviewed 17 publication and reported that, P, added to saline soils, increased crop growth and yield in 34 of the 37 crops studied. Similar to the effect of added N, added P did not necessarily increase crop salt tolerance. In most cases, salinity decreases the concentration of P in plant tissue (Güneş et al., 1999), but the results of some studies indicated salinity either increased or had no effect on P uptake. The role of K is vital for osmoregulation and protein synthesis, maintaining cell turgor and stimulating photosynthesis (Peoples and Koch, 1979). Higher levels of K+ in young expanding tissue is associated with salt tolerance in many plants (Gorham, 1993; Khatun and Flowers, 1995). NaCl also changes the anion concentrations in plants. A lowered supply of nitrite to growing leaves may be responsible for inhibition of growth under saline conditions (Hu and Scmidhalter, 1998). Maintaining an adequate supply of Ca2+ saline soil solutions is an important factor in controlling the severity of specific ion toxicities, particularly in crops which are susceptible to sodium and chloride injury (Maas, 1993). Salinity stress has stimulatory as well as inhibitory effects on the uptake of some micronutrients by plants. The uptake of Fe, Mn, Zn and Cu generally increases in crop plants under salinity stress (Alam, 1994). The detrimental effects of NaCl stress on the nutrition of bean plants are reflected in higher concentrations of Cl and Mn in roots and Cl, Fe and Mn in leaves and Cl and Fe in fruits (Carbonell-Barrachina et.al., 1998). Briefly, it is reasonable to believe that numerous salinity-nutrient interactions are occurring at the same time but whether they ultimately affect crop yield or quality depends upon the salinity level and composition of salts, the crop species, the nutrient in question and a number of environmental factors. References . Alam, S.M.,1994. Nutrient by plants under stress conditions. In: Pessarakli, M (Ed.), Handbook of Plant and Crop Stress. Marcel Dekker, New York, pp.227-246. . Carbonell-Barrachina, A.A., Burlo, F. & Mataix, I., 1998. response of bean micronutrient to arsenic and salinity. J. Plant Nutr, 21, 1287-1299. . Champagnol, F., 1979. Relationships between PO4 nutrition of plants and salt toxicity. Phosphorus Agri.76,35-43. . Gorham, J., 1993. Genetics and physiology of enhanced K/Na discrimination. In: Randall, P (Ed.), Genetic Aspect of Plant Mineral Nutrition. Kluwer, Dordrecht, pp.151-159. . Güneş, A., Inal, A., Alpaslan, M.& Çıkılı, Y., 1999. Effect of salinity on P induced Zn deficiency in peper plants. Tr.J. of Agriculture and Foresty 23,459-464. . Hasegawa; P., Bressan, R.A., Zhu, J.K. & Bohnert, H.J., 2000. Plant celluler and moleculer responses to high salinity, Annu. Rev. Plant Mol. Biol.51, 463-499. |