Effects Of Different Salts On Halophyte And Nonhalophyte

According to United Nations Educational, Scientific and Cultural Organization (UNESCO) and the Food and Agriculture Organization (FAO) to incomplete statistics, the area of world saline soil is 0.95438 billion hectares. According to the report of Wang et. al.(1993), the area of Chinese total modern (activity) salinized soil is 0.554 billion acres, together with about 0.673 billion acres of residual salinized soil.Furthermore, there is about 0.26 billion acres of potential salinized soil. Beside these, due to the irrational agricultural irrigation measures, some secondary salinized soil continually appears which increases the area of the Chinese salinized soil, seriously influences Chinese agricultural production and the development of the Chinese agriculture. Due to the influence of the salinized soil to the growth of the crops and the increase of soil salinization, the utilizeation of cultivable land is seriously limited. That aroused the recognition for the salinized soil of many scientists all over the world. The problem of plant's tolerance to salt is mainly the tolerance to NaCl. The research is mainly focused on two aspects: First, the study of salt-tolerance physiology in halophytes; second, the study of the injurious physiology in nonhalophytes. Thereby we can understand how to ameliorate or increase the plants'salt-resistance. Thus, my study focused on research of the effect of different salts on absorption, transport, accumulation, and the function in halophyte Suaeda Salsa and nonhalophyte Nicotiana tabacum L.1. Suaeda SalsaSeedlings of Chenopodiaceae halophyte Suaeda Salsa were treated with 0, 50, 100, and 200 mmol/L NaCl, KCl and NaNO₃ respectively after germination. The fresh and dry weight, succulent level and ion content were then determined after treated for 15 and 30d. The results showed that: (1). The fresh and dry weight was promoted by NaCl and NaNO₃ at all concentrations, while inhibited by KCl; (2). The order of the succulent level under the three salt treatment was NaCl>NaNO₃>KCl; (3). The order of ion accumulation of Na⁺ was NaCl>NaNO₃>KCl, and Na⁺ content increased with the time course; The order of K+ was KCl>NaCl>NaNO₃, and the content varied with treatment time and concentration; The order of Cl- was KCl>NaCl>NaNO₃, and the content decreased with the time; (4). NaCl promoted the SOD activity of Suaeda Salsa, KCl inhibited it, while NaNO₃ had no obvious effect; (5). The effect of the three salts on the photosynthesis was different, NaCl promoted the Pn and Gs, while KCl was opposite to the NaCl treatment; (6). The effect of NaCl and NaNO₃ on Fv/Fm was not obvious, while they promotedΦPSâ…¡. On the other hand, KCl obviously inhibited both Fv/Fm andΦPSâ…¡; (7). The CPS of the three ions in the vacuole was the most in the compartments of leaf cells; (8). The response of Suaeda Salsa to NaCl was extremely significant and the Na⁺ and Cl- contents in Suaeda Salsa under 200 mmol/L NaCl after 30d were 13.5% and 10.1% respectively. It is obvious that S.salsa is an obligatory sodium and chloride hyperaccumulating halophyte.2. Nicotiana tabacum L.Seedlings of tobacco (Nicotiana tabacum L. var. NC82) at four-leaf stage were treated with Hoagland solution containing different concentrations of NaCl, NaNO₃ and KCl respectively. Results showed that: (1). The fresh and dry weights of tobacco seedlings treated with NaCl suffered different degree of inhibition, the fresh and dry weights of the seedlings treated with 25 mmol/L NaCl were close to the controls. NaNO₃ and KCl also exerted different degree of stress to tobacco seedlings. The inhibition of NaCl was the biggest; (2). The effect of NaCl, NaNO₃ and KCl on ions accumulation of tobacco seedlings were as follows: Na accumulation levels were NaCl>NaNO₃>KCl; K+ accumulation levels were promoted by KCl, but K+ accumulation was inhibited by NaCl and NaNO₃; Cl- accumulation levels were KCl>NaCl>NaNO₃; NO₃- accumulation levels were promoted by NaNO₃, but KCl inhibited it, NaCl effects was not obvious; (3). The initiative effects of NaCl, NaNO₃ and KCl on antioxidase SOD were NaCl>KCl>NaNO₃; (4). Concentrations of NaCl, NaNO₃ and KCl also inhibited photosynthetic processes. Pn and Gs of tobacco were inhibited by NaCl, NaNO₃ and KCl, while promoted the Ci; (5). On the other hand, the three salts also inhibited the maximum PSâ…¡efficiency Fv/Fm and actual PSâ…¡photochemical efficiencyΦPSâ…¡; (6). The CPS of K+ in all the cell compartments was the largest. The CPS of Na⁺ in the NaCl treatment was the largest in all the cell compartments except the vacuole, As for the CPS of Cl- in the 3 organelles except vacuole, thr order was NaCl>KCl. On the other hand, the CPS of Na⁺ in the NaNO₃ treatment in the vacuole was largest, while the Cl- was KCl>NaCl.Through the studies above, the response of Suaeda Salsa to NaCl was extremely significant and showed strong dependence, while the tobacco was opposite; it was sensitive to salinty. Its growth was inhibited under the 25 mmol/L NaCl condition. That indicated there was essential difference between the response of halophyte and nonhalophyte to salinty. They are determined by the availability of salt-tolerant gene. To fathome the essences of plant's salt-tolerance needs further study from the point of plant salt-tolerance genetic biology.