Stress Comparison Among Four Main Salts In Salt-alkalized Soil On Kochia Sieversiana

According to the characters of the salt components in salt-alkaline soil, four salts including two neutral salts (NaCl and Na2SO4) and two alkalic salts (NaHCO3 and Na2CO3), were selected to treat the seedlings of Kochia sieversiana at various concentrations. The relative growth rate (RGR), malondialdehyde (MDA), and water content were determined to analyze and compare the physiological responses of K. sieversiana to four single salt stresses. The stress traits of four simplex salts and differences among them were discussed in order to lay a foundation for clarifying the mechanism of natural mixed salt-alkaline stress.The results showed as follows: (1) For K. sieversiana, the tolerably maximal concentrations of different salt stresses were different. The sequence from high to low was NaCl (1000 mmol. L-1), Na2SO4 (800 mmol. L-1), NaHCO3 (600 mmol. L-1), and Na2CO3 (175 mmol. L-1). It is clear that the tolerably concentration for neutral salt was higher than that for alkalic salt, especially for Na2CO3, its tolerably concentration was the lowest and only 175mmol L-1. This suggested that there was dissimilar stress intensity for different simplex salt stress to plant.(2) The growth of K. sieversiana was not inhibited, on the contrary, was stimulated under lower neutral salt stress (below 300 mmol L-1 NaCl or 50 mmol L-1 Na2SO4). Under alkalic salt or neutral salt over certain concentration stresses, the growth of K. sieversiana was obviously inhibited, and effects of inhibition increased with increasing the concentration of salt. By comparing at the same concentration of Na+, the inhibiting effects of alkalic salts were greater than that of neutral salt. The orders of inhibition intensity of four salts to the shoots or roots of K. sieversiana were same, and all were Na2CO3>NaHCO3>NaCl>Na2SO4.(3) Under Na2SO4, NaCl, and NaHCO3 stresses, the MDA content was nearly not changed with increasing salinity, whereas the MDA content was obviously increased under Na2CO3 stress, which showed that the cellular membrane system could be injured and metabolism could be interfered in Na2CO3 stress, and could not be injured in other three kinds of salt stress.(4) The inhibiting extents of four salts to roots were stronger than that to shoots.(5) Under four salt stresses, the water content of k. sieversianna decreased with increasing salt concentration. However, relative high water content still remained even under an intense salt stress, which might be a trait of K. sieversiana to resist salt-alkaline stress. According to the all of above, we can get a conclusion as follows. The stress effects of four main salts in natural salt-alkaline soil on plant are different. Taking K. sieversiana for an example, the deleterious order is Na2CO3>NaHCO3>NaCl>Na2SO4.The neutral salt, especially Na2SO4, is less harmful, and the alkalic salt, especially Na2CO3, is more harmful. Hereby, a scientific judge of salt-alkalization degree and recovery difficulty for salt-alkaline soil could be achieved, by analyzing the species and content of anion in a salt-alkaline soil.