Effects Of Salt And Alkaline Stress On The Growth And Physiological Metabolisms Of Different Leaves In Avena Sativa Seedlings

Avena sativa is a kind of herbaceous plant that belongs to Avena of Gramineae. It is a worldwide cultivation crop with high nutrition value. As it has no strict requirement of soil condition,it can be planted in many types of soil. It is also a traditional and ideal food in saline and alkaline regions. In recent years, A. sativa has been taken as a alternative crop for the improvement of saline-alkaline soil because of its higher salt-alkaline tolerence. In order to elucidate the effects of saline and alkaline stresses on the growth, photosynthesis and physiological metabolisms of leaves from different positions, we take A. sativa seedling as the material, using NaCl and NaHCO3to simulate saline and alkaline stresses. And we determined the contribution and response mechamism to saline-alkali stress of leaves from different positions under saline-alkali stress.Then, we deeply understood the growth and physiological metabolism function of leaves from different leave position,changes after stresses, and provided a theoretical basis for the regulation of sativa seedings.The main research results and conclusions were as follows:(1) Lower concentration (100mmol/L) of saline and alkaline stresses take little effects on the survival rate of A. sativa seedlings, but different results were found under higher concentration. High concentration alkaline stress can lead to death of A. sativa seedlings. Under saline and alkaline stresses, the leaves of different positions of A. sativa seedlings have been significantly inhibited, and the inhibition of alkaline stress to a greater extent than saline stress. The second leaf blade had the highest biomass.(2) The chlorophyll a, chlorophyll b and total chlorophyll contents in leaf blades of different positions were promoted under saline stress, and the promoting effects under low concentration (100mmol/L) were greater than that under high concentration (200mmol/L). There was a reverse effect of alkaline stress on chlorophyll, the inhibition were enhanced with increasing alkalinity. The changing trend of chlorophyll were increased firstly and then decreased with rising leaf position under both stresses, and the highest chlorophyll content was found in the second leaf.(3) The net photosynthetic rate (Pn) and stomatal conductance (Gs) of A. sativa seedlings were promoted under low concentration saline stress, but were inhibited under higher saline stress. Both intercellular carbon dioxide concentration (Ci) and ranspiration rate (Tr) were inhibited under saline stress. Water use efficiency of leaves was promoted under saline stress, but the promoting effects under low concentration (100mmol/L) were greater than that of under high concentration (200mmol/L).The net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate of A. sativa seedlings were inhibited under alkaline stress, and the inhibition was heightened with increasing alkalinity. Water use efficiency (WUE) was promoted under low concentration alkaline stress but inhibited by high concentration alkaline stress. The intercellular carbon dioxide concentration (Ci) in leaves of different position were accelerated under alkaline stress, and thus the higher the concentration, the more obvious the acceleration. With the leaf position rising, the net photosynthetic rate and water use efficiency of A. sativa seedlings were decreased and then increased, stomatal conductance (Gs) and transpiration rate of leaves were declined.(4) The Na+concentration in leaves of different position were increased whereas the K+concentration decreased under saline and alkaline stresses. The increasing extent of Na+and decreasing extent of K+under alkaline stress were higher than that under saline stress. In order to resist the Na+toxicity and osmotic stress resulted from the saline and alkaline stresses, A. sativa accumulated a large number of Cl-and SO42-content was also increased at the same time.With leaf position rising, the changing trends of inorganic cations of Na+Ca2+and Mg2+contents were all decreased firstly and then increased. On the contrary to changing trend of K+contents, inorganic anions of Cl-and NO3-contents had the same changing trends with Na+, Ca2+and Mg2+contents, and SO42-and H2PO4-contents increased and then decreased. The highest or lowest contents of inorganic ions were found in the second leaf position.