Studies On Physiological Characteristics Of Seed, One Year Old Seedlings And Two Year Old Transplanted Seedlings Of Wild Jujube Under NaCl Stress

In this paper, use the seeds, one year old seedlings and two year old transplanted seedlings of wild jujube（Ziziphus jujuba var. spinosa （Bunge） Hu） as the experiment material and were treated with differentconcentration of NaCl stress. This experiment studied the seed germination indices and changes of physiologicalcharacteristics of one year old seedlings and two year old transplanted seedlings of wild jujube. The results are asfollows:1. Seed germination of wild jujube has inhibits the NaCl stress. With increasing of NaCl concentrations, seedgermination rate, germination index and relative germination rate of wild jujube were decreased in different extents,and the length and growth rate of hypocotyls and radical of wild jujube were significantly inhibited. It possesses bettersalt tolerance during the stage of wild jujube seed germination, and the median lethal concentration and the lethalconcentration is108.22mmol·L^-1and207.66mmol·L^-1respectively treated by NaCl. The germination of seed issignificantly restrained when the concentration of NaCl is higher than100mmol·L^-1.2. When NaCl stress12days, with increasing of NaCl concentration, Na⁺content in root, steam and leaf of oneyear old seedlings and two year old transplanted seedlings of wild jujube were increased significantly. K⁺content inboth root and steam was decreased, while the K⁺content increased in the leaf, showed that leaf and steam was the mainorgan for Na⁺and K⁺storage in wild jujube. The NaCl stress have no significantly influence Mg²⁺content in leaves andsteam and Mg²⁺contents decreased in the root. Ca²⁺content in different tissue changed irregularly, the levels of changeMg²⁺content in leaf and stem was comparatively smooth out. Ratio of Na⁺/K⁺, Na⁺/Mg²⁺and Na⁺/Ca²⁺in differenttissue of one year old seedlings and two year old transplanted seedlings of wild jujube was increased gradually withincreasing in NaCl concentration. Indicating that the absorption selectivity of K⁺, Mg²⁺and Ca²⁺in root was affected byNaCl stress. With increasing of NaCl concentration, Na⁺-K⁺, Na⁺-Mg²⁺and, Na⁺-Ca²⁺transport selectivity ratio （SK、Na,SMg、Na, SCa、Na） declined with varing degrees compared to control. The ion contents in leave were always much higherthan those in other organs of one year old seedlings and two year old transplanted seedlings of wild jujube, and ratio ofNa⁺/K⁺in leaf were higher than root and steam, due to the stronger selective absorption capacity of K⁺by leaf of wildjujube under NaCl stress, and by maintaining high level of K⁺in leaf, being of significance for keeping the ionhomeostasis and maintaining the normal growth in leaf of seedlings and to reduce the damage of salt stress.3. Compared with the control, soluble protein, proline and soluble sugar content and Na⁺, K⁺content in leaves increased with the increase of NaCl concentration. Wherefrom inference that jujube seedlings used osmotic-adjustment substances to maintain osmotic balance of the aerial parts, reduce the water potential, and as to maintain thewater absorption capacity, to mitigate an adaptation mechanism of physiological drought. Thereby, wild jujube appearsto be of definite salinity tolerance ability.4. Under NaCl stress12days, biomass of seedling was decreased with increasing in NaCl concentration,, themembrane permeability and contents of MDA in leaves of one year old seedlings of wild jujube were increased; leafrelative water content were decreased. SOD, POD and CAT activities in leaf showed increase�'decrease tendency.When150mmol·L^-1treatment, POD and CAT activity in leaf reached the highest value, and maintain over of the75%relative water content. With increasing of NaCl concentration, the membrane permeability and contents of MDA inleaves of two year old transplanted seedlings of wild jujube were increased and leaf relative water content weredecreased. SOD and POD activities in leaf showed increase and then decrease tendency, while the CAT activity wasgradually rise. When150mmol·L^-1treatment, POD and CAT activity in leaf reached the highest value, and maintainover the70%relative water content. In a word, wild jujube was dependent on the leaves of reactive-oxygen-scavengingenzymes to reduce the damage NaCl stress.5. One year old seedlings of wild jujube was in NaCl stress, have net photosynthetic rate, transpiration rate,stomatal conductance, Fo, Fv/Fm and ΦPS II decreased; Ciand ETR was deceased at first and then increased. Under0¹00mmol·L^-1treatment, the total chlorophyll, chlorophyll a, chlorophyll b content of leaf to maintain a stable state,no significant differences among the treatments. Net photosynthetic rate was inhibited mainly by stomatal factors under0¹00mmol·L^-1stress, and by non-stomatal factors in other NaCl stress.