Physiological Response Characteristics Of Sugar Beet Seedlings Under Neutral Salt And Alkaline Salt Stress

Sugar beet?Beta vulgaris L?is the main sucrose crop with special growth characteristics,and it is an important dominant cropin barren areas with stronger salt-alkali tolerant.Therefore,this experiment simulate mixed salt stress?Na₂SO₄ + Na Cl?and mixed alkali stress?Na₂CO₃ + NaHCO₃?,explore sugar beet seedling growth,physiological response and adaptation characteristics under the mixed forced neutral salt and alkali salt conditions,the 0%?CK?,0.5%,0.7%,0.9% neutral salt?Na₂SO₄: NaCl,mole ratio of 2:1?and alkaline salt?Na₂CO₃: NaHCO₃,mole ratio of 2:1?were mixed into the test pot.then,the KWS0143 and Beta464 were planted in the test pots,and determine the germination rate,biomass and chlorophyll content,cell membrane permeability,osmotic regulation substances content,antioxidant enzyme activity,plant hormones of sugar beet seedlings under different processing conditions.The main results were as follows:?1?With the increasing of the concentration of salt and alkali,germination rate of sugar beet seedlings gradually decreased,while dry weight of it increased first and then decreased.The dry fresh weight of sugar beet seedlings under the conditions of 0.5% and 0.7% salt or alkali were significantly higher than those of control,and the dry fresh weight of sugar beet seedlings under the conditions of 0.9% salt or alkali were significantly lower than those of control.The growth status of early stage sugar beet seedlings under the conditions of Na₂CO₃+NaHCO₃ is better than those of Na₂SO₄+Na Cl,but the growth status of sugar beet seedlings is the opposite with the prolongation of stress time.?2?With the increasing of the concentration of salt and alkali,The total chlorophyll content of sugar beet seedlings increased first and then decreased.The total chlorophyll content of sugar beet seedlings under the conditions of 0.5% salt or alkali were higher than those of control,the total chlorophyll content of sugar beet seedlings under the conditions of 0.7% salt or alkali were significantly higher than those of control,and the total chlorophyll content of sugar beet seedlings under the conditions of 0.9% salt or alkali were significantly lower than those of control.The order of chlorophyll a/b value under different concentrations were 0.9% > control > 0.7% > 0.5%.?3?With the increasing of the concentration of salt and alkali and the prolongation of stress time,the cell membrane permeability of sugar beet seedlings leaves gradually increased.The cell membrane permeability of sugar beet seedlings leaves under the conditions of 0.7% and 0.9% salt significantly higher than those of control,There are differences between the cell membrane permeability of sugar beet seedlings leaves under the conditions of 0.5% salt and those of control.The cell membrane permeability of sugar beet seedlings leaves under the conditions of alkali significantly higher than those of control.The order of sugar beet seedlings leaves MDA content were 0.9% salt> 0.7% salt> 0.5% salt> control and the third sampling > the second sampling > the first sampling,there are significant differences between leaves MDA content of two sugar beet seedlings under the conditions of alkali and those of control.?4?Three kinds osmotic regulation substances content?praline,soluble protein and soluble sugar?in the two sugar beet seedlings changed regularly with the increasing of the concentration of salt and alkali,with the increasing of the concentration of salt and alkali and the prolongation of stress time,the soluble sugar content of sugar beet seedlings increased first and then decreased.Three kinds osmotic regulation substances content of sugar beet seedlings under the conditions of 0.5% salt or alkali were higher than those of control,those of 0.7% salt or alkali were up to maximum,and those of 0.9% began to fall.Three kinds osmotic regulation substances content of two sugar beet seedlings under the conditions of 0.9% salt were significantly higher than those of control,three kinds osmotic regulation substances content of two sugar beet seedlings under the conditions of 0.9% alkali were significantly lower than those of control,The accumulation of soluble sugar in the leaves under the conditions of alkali were higher than those of salt,however,the accumulation of soluble protein in the leaves under the conditions of alkali were lower than those of salt.?5?The SOD,POD,CAT,APX activity of sugar beet seedlings increased first and then decreased.The activity of antioxidant enzymes of sugar beet seedlings under the conditions of 0.7% salt or alkali were up to maximum,and the activity of antioxidant enzymes of sugar beet seedlings under the conditions of 0.9% salt or alkali were significantly lower than those of control.The GSH content of sugar beet seedlings leaves under the conditions of mixed salt gradually increased,those of mixed alkali increased first and then decreased,and those of 0.9% alkali were up to maximum,alkali stress bring greater harm to sugar beet seedlings.?6?The accumulation of hormones in the sugar beet seedlings leaves changed irregularly with the increasing of the concentration of salt and alkali.The auxin content of sugar beet seedlings under the conditions of mixed salt increased first and then decreased.The ABA contents of sugar beet seedlings under the conditions of 0.5% salt were higher than those of control,then the abscisic acid content of sugar beet seedlings gradually decreased.The ZR content of sugar beet seedlings gradually decreased with the increasing of the concentration of salt.With the increasing of the concentration of alkali,The IAA,ZR,BR content of sugar beet seedlings gradually decreased,and the ABA content gradually increased.The value of IAA/ABA,ZR,ABA and BR/ABA under the conditions of high concentration?0.9%?salt or alkali gradually decreased.