Analysis Of Physiological Effects On Four Rice Germplasms Genotype To Salinity Stress

Salt-tolerant genotype rice‘FL478',‘JX99',‘Pokkali'and salt sensitive genotype rice‘IR29'were used as test materials.The studies from the aspect of growth and development effect,regulation of carbohydrate metabolism,physiological biochemical response,K⁺?Na⁺absorption and distribution,and photosynthetic physiological characteristic in four rice germplasms were tested and analyzed under soil salt treatments of 0 g·kg^-1,1 g·kg^-1,2 g·kg^-1,3 g·kg^-1,4 g·kg^-1and 5 g·kg^-1in rainproof greenhouse.This study aimed to unveil the physiological effects of salt tolerance in Rice germplasms salt tolerance genotype under salinity stress,and the salt tolerance mechanism of rice was further clarified.This study aimed at helping to provide theoretical basis on salt-tolerant gene as well as the breeding of new salt-tolerant rice varieties.The experimental results after measurement are outlined in the following submission:It was observed at the end of the study that,salinity stress inhibited rice growth,plant height,and aerial biomass.Moreover,the increase of salt concentration in soil resulted in the decrease of the number of tillers,smaller leaf area and withering of leaf of rice.In regulating carbohydrate metabolism,the activity of SPS and SS was increased to promote the accumulation of sucrose and total soluble sugar,which contributed to the relief of cell osmotic pressure,maintenance of normal life activities,and the improvement of the stress resistance of plants with low salt stress.Additionally,SS and SPS activity decreased,and sucrose,total soluble sugar synthesis and accumulation in leaves decreased showing that the growth and development of the plant were inhibited more obviously under high salt stress.The accumulation of sucrose and soluble sugar in salt-sensitive'IR29'plants was more than as observed in salt-tolerant germplasm'JX99'and'Pokkali',whereas the growth and development of the salt-sensitive plants were significantly inhibited under salt stress.It may be inferred that the sucrose and soluble sugar synthesized and accumulated in IR29plants were largely used to relieve cell osmotic pressure and to participate in stress physiology recovery.Nonetheless the sugar supply for plant growth and development is insufficient,resulting in inhibited growth and development.For physiological and biochemical response mechanism,the salinity stress was observed to inhibit the synthesis and accumulation of the chlorophyll in rice.Thus,the chlorophyll content in rice leaves decreased with the increase of salt stress concentration.Nevertheless,the chlorophyll content of salt-tolerant germplasm was significantly higher than that of salt-sensitive ones.Correspondingly,the Malondialdehyde concentration of salt-tolerant rice and salt-sensitive varieties were increased with the strengthening of salt stress,which resulted in increased cell membrane permeability.However,the Malondialdehyde concentration of salt-tolerant rice was significantly lower than that of the salt-sensitive varieties,depicting that the leaf membrane damage of salt-tolerant rice was significantly lesser than that of the salt-sensitive rice.The relative water content of leaf and leaf sheath in 4 rice varieties decreased under salt stress,but critical saturation deficit of water of leaves and leaf sheaths both showed an upward trend.Among them,the critical saturation deficit in sensitive germplasm R29 greatly enhanced,whereas the relative water content in salt-tolerant germplasms slightly decreased.The proline concentration,P5CS??-OAT and SOD activities in rice leaves were increased at first and then decreased with the increasing salt stress concentration.Again,the proline concentration,P5CS,?-OAT and SOD activities of salt-tolerant rice and salt-sensitive varieties reached the maximum at 3 g·kg^-1and 2 g·kg^-1salt concentration,respectively,yet still,the proline concentration,P5CS,?-OAT and SOD activities of salt-tolerant rice were significantly higher than those of salt-sensitive varieties.The simple correlation and partial correlation of soluble sugar,proline and P5CS were significantly positive under salinity stress.The salt tolerance characteristics of salt-tolerant rice were considered as physiological salt tolerance.The proline synthetase P5CS and?-OAT of salt-tolerant are both activated by salinity stress and through two pathways of proline synthesis?Glu?Pro and Orn?Pro?to promote the rapid and high accumulation of free proline,which showed stronger salt tolerance in salt tolerant rice.The order of salt tolerance was JX99>Pokkali>FL478>IR29 by fuzzy membership function method.K⁺and Na⁺absorption and accumulation were as well measured.It was observed that the accumulation of Na⁺and K⁺in different organs of rice plants with 4 genotypes had different responses to salt stress.That is,low salt stress(0-3 g·kg^-1)contrast to Na⁺in various organs,promoted the accumulation of K⁺in rice plant organs,in which leaf>sheath>root.Rice plants accumulated more Na⁺in all organs,in which root>leaf sheath>leaves,resulting in Na⁺/K⁺imbalance in all organs,which thereby decreased salt tolerance of plants and increased salt damage under high salt stress(4⁵ g·kg^-1).The leaf sheath is an important Na⁺-K⁺buffer stock mainly used to absorb and partition Na⁺to regulate the Na⁺/K⁺balance in the root,leaf and leaf sheaths so as to increase the salt resistance.The transport coefficients S_K⁺?⁺_Na,S_K⁺?⁺_Naa of leaf sheath and root of salt-tolerant rice were significantly higher than those of salt-sensitive rice.Leaf sheath of salt-tolerant type distribution at the same time to the blade active transport K⁺,K⁺to root,root restriction Na+capacity is much higher than salt sensitive,by increasing the content of leaf and root of K⁺,limit the Na⁺on the distribution of the blade,improve the leaf and root of K⁺/Na⁺,alleviate the osmotic stress,improve the resistance to salt,the salt sensitive rice roots and leaves of Na⁺accumulation is higher,maintaining high Na⁺/K⁺,leaf and root of the cell membrane permeability is bigger,the salt injury was obvious.Also,for the physiological biochemical response,the net photosynthetic rate of salt-sensitive rice was significantly higher than that of salt-tolerant rice,and a large amount of soluble sugar was synthesized and accumulated to alleviate osmotic stress and reduce salt damage under soil salt treatment process.Soil salt treatment with 1³g·kg^-11 resulted in a higher intercellular concentration of ¹²CO2,meeting the photosynthetic physiological requirements of rice.4⁵ g·kg^-11 soil salt treatment forced rice stomata to close,Ci/Ca value was to lower,the intercellular concentration of ¹²CO2 to decrease,and the AMC of salt-tolerant rice to significantly increase than that of salt-sensitive rice to increase ¹³CO2 utilization efficiency.RuBPCase activity of salt-tolerant rice was relatively high,and a large amount of 13CO2 was carboxylated by salt-tolerant rice RuBPCase.However,RuBPCase could only meet the needs of short-term life activities and maintain short life activities.The transpiration rate and stomatal conductance of salt-tolerant rice were significantly lower than that of salt-sensitive rice under 1³ g·kg^-11 salt treatment,salt resistant stomatal resistance increased,transpiration rate decreases,the vane steam pressure deficit value was high and relatively stable,and water retention capacity increased to maintain a normal supply of nutrients and water to the root system above ground.However,the transpiration rate and stomatal conductance of salt-sensitive rice IR29leaves increased significantly,and transpiration tension caused excessive water loss and osmotic stress intensification in salt-sensitive rice leaves.Leaf transpiration rate of salt-tolerant rice was significantly lower than that of salt-sensitive rice under salt stress of 4-5 g·kg^-1.However,WUE and stomatal limit values increased obviously,and the difference between varieties was not significant,but rather significantly higher than the salt sensitive type.The salt-tolerant type can reduce water loss by reducing stomatal conductance and transpiration rate,so that rice leaves can maintain higher water potential,improve leaf water use efficiency and adapt to salt stress.