The Study On Physiological Mechanisms Underlying Atriplex Canescens In Response To Salinity And Drought

Drought and salinity are not only the main factors affecting the ecological environment around the world, but also restricting the production of agriculture. Growing plants are extremely important for improving salinity land, while the saline areas gradually expanded. However,halophytes can evolve a variety of mechanisms to adapt to drought and salt environment. A.canescens is a perennial semi-evergreen shrubs and grow well under drought and salt environment whitch has typical salt bladders. Currently salt-secreting mechanisms can improved after adding NaCl drought resistance has not been reported. It is an important species for sand-fixing and improved saline soil, but also as a good saline desert grassland.At present, domestic and foreign scholars do a lot of research about Atriplex species respond to salt and drought stress on physiological mechanism, but the physiological mechanisms about A.canescens in response to salinity and drought are rarely reported. Therefore, this paper use A.canescens with salt stress treatment, osmotic stress treatment and drought stress treatment, by its growth situation, photosynthetic, Na+ and K+ content, osmotic adjustment response to salt and drought stress on physiological mechanism. The main conclusions are as follows:1. A. canescens is a highly salt-tolerant plants. Compared with the control, at 100 mmol/L NaCl treatment A. canescens seedlings fresh weight, dry weight and plant height were significantly increased 13%,15% and 20%; however, 200 and 400 mmol/L NaCl did not substantially affect its biomass, A. canescens seedlings still grow normally. With NaCl concentration increased, the net photosynthetic rate increases; when 100 mmol/L NaCl, stomatal conductance and transpiration rate were significantly higher 1.8 and 1.9 times than control, but was not affected when the 200 and 400 mmol/L NaCl; water use efficiency rise sharply at 400 mmol/L NaCl, may be due to high salt concentration resulting A. canescens seedlings stomatal closure. Under different NaCl treatment, a large number of Na+ regionalization in vacuoles, on the other hand also transferred Na+ to salt bladders, to reduce the Na+ toxic effects on cell metabolism and keep the body Na+/K+balance.2. Under salt stress, A. canescens seedlings accumulate inorganic ions(Na+, K+, etc.) and organic osmolytes(proline, betaine, etc.) to reduce the osmotic potential and improve their water status, to maintain a highly osmotic adjustment capacity. Besides, the contribution of Na+increases with Na Cl concentration from 2% to 48.8%; the contribution of K+ decreases with NaCl concentration from 33.8% to 9.2%. Under high concentrations(200 and 400 mmol/L NaCl), the contribution of proline and betaine increased significantly, about 3.8% and 8.1% under 400mmol/L NaCl.3. Osmotic stress treatment significantly inhibited A. canescens seedlings growth. Under-0.2MPa and-0.5 MPa osmotic stress A. canescens seedlings fresh weight, dry weight and plant height are decreased 21.6% and 39.7, 22.2% and 43.1%, 20.5% and 42.5 compared with control.However, adding 100 mmol/L NaCl effectively alleviate the inhibitory effect of osmotic stress.Compared with-0.2 MPa, fresh weight, dry weight and plant height are increased by 11.3%, 9.4%and 11.2% in-0.2 MPa+100 mmol/L NaCl treatment. Compared with-0.5 MPa, fresh weight and dry weight are increased 13.7% and 13.9% in-0.5 MPa+100 mmol/L Na Cl treatment. Under osmotic stress treatment, transpiration rate, net photosynthetic rate and stomatal conductance were significantly lower than control. Compared with single osmotic stress treatment, after adding NaCl the net photosynthetic rate were significantly increase. In addition, when A. canescens seedlings subjected to different osmotic stress, it can maintain the stability of higher K+ content, increase proline content and betaine content, reduce osmotic potential, maintain a high moisture content to let seedlings grow well.4. Compared with the control, the biomass and net photosynthetic rate decreased significantly under drought stress. While the fresh weight, dry weight, plant height and root length are decreased 47.5%, 37.1%, 20.2% and 14.4%; transpiration rate, net photosynthetic rate and stomatal conductance decreased respectively 26.6%, 10.8% and 34.8% compared with control.Added 100 mmol/L Na Cl not only can alleviate the inhibitory effect of drought on plant, but also their net photosynthetic rate and transpiration rate returned to control levels. On the other hand,maintain the stability of the ground portion of K+ content is another important strategy to adapt to arid environment. Therefore, the amount by increasing osmotic adjustment ability and stay hydrated condition, thereby promoting plant growth and increase their drought resistance.