Physiological Mechanisms Of Salt-alkaline Tolerance And Evaluation On Salt Tolerance Of Ping’ou Hybrid Hazelnut(corylus Heterophylla Fisch.× Corylus Avellana L.)

There is a large area of salt-alkali land in China; agricultural productivity is severely affected by salt-alkali stress which becomes one important factor of abiotic stresses. At present, Ping’ou hybrid hazelnut(Corylus heterophylla × Corylus avellana, Liaozhen 3) were wide cultivated as an excellent hazelnut variety, there are varying degrees of salt-alkali land types in northeast, north China and northwest of our country, where are major hazelnut growing areas, evaluation of salinity tolerance and study of saline-alkaline tolerance mechanism have great meaning for development of industrial culture in ‘Liaozhen 3’ Ping’ou hybrid hazelnut. Three types of salt-alkaline stress conditions were performed with Na Cl and Na2CO3, the pot experiment in salt-alkali stress simulation method was used to study the changes of the growth and physiology indexes in ‘Liaozhen 3’ Ping’ou hybrid hazelnut under different saline-alkali stresses, then Ping’ou hybrid hazelnut seedlings were treated with Na Cl under hydroponic conditions to study response to salt stress, saline-alkaline tolerance physiology mechanism was clarified; Single index and three cpmprehensive evaluated methods were used to analysed salt tolerance of eightteen hazelnut varieties and one hazelnut cultivar. The main results of this research are as following:1. The damage level was the fourth level under 250 mmol·L-1 neutral salt after 42 days; the damage level was the first or second level under high concentration Na2CO3 after 42 days. The plant height, newshoots length, number of leaves and total biomass of ‘Liaozhen 3’ Ping’ou hybrid hazelnut were inhibited apparently under salt-alkali stresses, the stem diameter widened with low salt-alkali stress concentration,while the ratio of root and shoot increased significantliy; The thickness of shoot epidermis, xylems, leaves and palisade tissue increased firstly, then decreased with the increase in concentration of saline-alkaline stress. The different damage degree were found with the order of Na Cl stress > mixed salt-alkaline stress > Na2CO3 stress on base of salt-alkali stress sympotom.2. The MDA contents of leaves increased gradually with the increase in concentration of saline-alkaline stress, the soluble protein and sugar contents raised firstly, then decreased, the proline contents increased significantliy; The ABA contents of leaves increased significantly, and ABA synthesis is more rapid under low concentration Na2CO3 stress,the(GA + IAA + ZR)/ABA ratio also reduced apparently compared with control. The correlation analysis indicated that the significant positive correlation was found between the(GA + IAA + ZR)/ABA ratio and the plant height, newshoots length and leaves, whereas the(GA + IAA + ZR)/ABA ratio and the root/shoot ratio are negative related. The succinic acid, citric acid, tartaric acid, malic acid and propionic acid contents raised in varying degrees under Na2CO3 stress in roots of ‘Liaozhen 3’ Ping’ou hybrid hazelnut; The succinic acid, citric acid and propionic acid contents decreased firstly, then increased with the increase in concentration of Na Cl stress, while the tartaric acid and malic acid declined constantly in roots; There is some accumulation in organic acid contents under mixed salt-alkaline stress in roots. The total contnets of organic acid accumulated under three salt-alkali stresses with the order of Na2CO3 stress > mixed salt-alkaline stress > Na Cl stress.The accumulation of organic acid in roots is one physiological response to salt stress in ‘Liaozhen 3’ Ping’ou hybrid hazelnut.3. The chlorophyll contents declined significantly under Na Cl stress, the photosynthetic indexes Pn, Gs, Tr, WUE, Ls, CUE and LUE descended with the increase in concentration of stress, the photosynthetic capacity of leaves declined obviously. The chlorophyll contents raised, Ci increased firstly, then decreased and other photosynthetic indexes decreased firstly, then increased, and finally decreased again with the increase in concentration of Na2CO3 stress, the influence degree is smaller under Na2CO3 stress than the other two stress conditions.4. The Na+, Cl- contents increased significantly with the increase in concentration of Na Cl and mixed salt-alkaline stress in roots, shoots and leaves of ‘Liaozhen 3’ Ping’ou hybrid hazelnut; The Na+ contents accumulated obviously in shoot and are much smaller in shoots and leaves under Na2CO3 stress than neutral salt, the Cl- contents varied inapparently by Na2CO3 stress; the K+ contents declined gradually with the increase in concentration of the three saline-alkaline stresses in roots, and varied inapparently in shoots and leaves under Na2CO3 stress; The K+/Na+ ratio decreased significantly under Na Cl and mixed salt-alkaline stress in roots, shoots and leaves, The K+/Na+ ratio still maintain higher level in shoots and leaves under low concentration Na2CO3 stress; Na2CO3 stress causes different degrees of decrease of the Zn, B, Ca contents. There are obvious differences between three stress conditions in accumulation, balance and transport of mineral ions.5. With the increase in concentration of Na Cl, specific high-frequency resistance r, specific low-frequency resistance r1, specific intracellular resistance ri and specific extracellular resistance re of shoots decreased firstly, then increased, and finally decreased again. However, these parameters raised gradually with the increasing of Na2CO3 concentration, while r1 and re reduced slowly by mixed salt-alkaline treatments. The significant negative correlation was found between the sum of five cations and four EIS parameters r1, re, relaxation time τ, and distribution coefficient of relaxation time Ψ. EIS is an effective means of studying the ablity of tolerance salt-alkaline stress, the shoots of ‘Liaozhen 3’ Ping’ou hybrid hazelnut might be tolerant of 200 mmol·L-1 Na2CO3 stress while they could be resistant to 100~150 mmol·L-1 under Na Cl stress, and the ability of tolerance mixed salt-alkaline stress could be in between Na Cl and Na2CO3 stress.6. ‘Liaozhen 3’ Ping’ou hybrid hazelnut seedlings were treated with Na Cl under hydroponic conditions to study growth and physiological response to salt stress. The results showed that the sympotom of salt stress aggravated gradually, and the length of root, biomass declined with the increase in concentration of Na Cl; The photosynthetic indexes Pn, Gs, Tr, Ls, WUE and respiration intensity decreased significantly; The relative conductivity of leaves and Ci increased gradually with the increase in concentration of stress; The ultrastucture of chloroplast in leaves varied apparently, the chloroplasts swelled and deformation, the granum and stroma lamellae structures were blurred, the thylakoids degenerated.7. The net growth of plant height, biomass of eightteen hazelnut varieties and one hazelnut cultivar were inhibited apparently under salt-alkali stresses, while the ratio of root and shoot increased obviously; The relatve conductivity, MDA, proline, soluble protein and sugar contents of leaves increased significantliy; The chlorophyll contents declined; gradually with the increase in concentration of saline-alkaline stress, the contents raised firstly, then decreased, the contents increased significantliy; The photosynthetic indexes Pn, Gs, Tr, Ls, WUE decreased in different degrees; The thickness of shoot epidermis and palisade tissue/spongy tissue ratio of leaves increased slightly. According to the changes of growth and physiological indexes in nineteen hazelnut varieties under salt stress, the fourteen indexes: the plant height, ratio of root and shoot, chlorophll contents, relative conductivity, Pn, Gs, Ci, Tr, thickness of shoot epidermis, palisade tissue/spongy tissue ratio in leaves, MDA, proline, soluble protein, soluble sugar contents were chosen, which related to salt-tolerance, the salt tolerance coefficient of fourteen indexes were standardized by method of subordinate function, salt tolerance of eightteen hazelnut varieties and one hazelnut cultivar was evaluated by subordinative function, principal component analysis and clustering analysis, B-21, 83-33, 84-545, Liaozhen 4, 84-237, 81-21 were found be stronger salt-tolerant varieties and Liaozhen 1, Yuzhui, Liaozhen 7 are weaker salt-tolerant varieties, the basis of hazelnut introduction was provided for saline-alkaline area.