Agronomic And Physiological Characteristics Of Different Rice Varieties With Salt Tolerance Under Salt Stress

With the increasing salinization of soil,how to effectively utilize salinization land has become an important problem restricting agricultural production.Rice is a moderately sensitive crop to salt stress,and its yield is greatly reduced under salt stress.Therefore,it is of great significance to elucidate the response and physiological characteristics of rice yield with different salt tolerance to salt stress for exploring the physiological mechanism of resistance to salt stress.In this study,five salt-tolerant rice varieties and two salt-sensitive rice varieties were used as materials,and five different salt concentrations(0,1,2,2.5 and 3 g kg-1)were set up.The main results show that:1.Compared with salt-sensitive rice,salt-tolerant rice varieties could tolerate higher salt stress concentration(2.5 g kg-1),and yield reduction was smaller under salt stress.Salt-tolerant rice varieties received higher yield due to their higher total spikelet quantity and seed setting rate.At the same time,a higher crop growth rate from tiller to jointing and from heading to maturity indicated that good agronomic traits are an important manifestation of strong salt-tolerant rice.2.Compared with salt sensitive rice varieties,in the middle of tillering stage,panicle stage and heading stage,salt-tolerant rice under salt stress showed better root activity and root morphology,root length,root diameter,root surface area,root oxidation,organic acid content in root secretion and so on.It is beneficial to the absorption of nutrients and ions in the roots.At the same time,Na+ was accumulated in rice roots,and less Na+was transported to shoot.These results indicated that the leaf morphology and physiology were the more important physiological mechanism for salt tolerance of rice varieties.3.Compared with salt-sensitive rice varieties,salt-tolerant rice varieties had higher antioxidant enzyme activity and non-enzyme antioxidant substance content,as well as higher content of organic osmotic regulatory substances such as fructose,trehalose,sorbitol and proline and abscisic acid content in leaves at the middle tiller stage,panicle stage and heading stage.At the same time,there are less Na+transported to shoot in salt-tolerant rice which kept higher K+/Na+ratio in leaves.Salt-tolerant rice varieties had good stomatal morphology and higher photosynthetic rate.These results indicated that the leaf morphology and physiology were the more important physiological mechanism for salt tolerance of rice varieties.These results indicated that the difference of yield between different salt tolerance rice was mainly caused by the physiological difference of salt tolerance at tillering stage,panicle stage and heading stage.These growth stages were the key period to determine the number of panicle,grain number per panicle and seed setting rate of rice.Good physiological performance of salt-tolerant rice in these critical growth stages is the basis for these rice varieties to obtain high yield.The study can be used to adjust breeding strategies and improve salt-tolerant cultivars adapted to saline-alkali land.