| Using four-year-old potted plants of Prunus cerasifera var atropurpurea, Prunus×cistenena'pissardii', Prunus wrasifers'nigra'as materials which artificial controlled the soil water to add NaCl. The soil salt contents were set as CK (0.042%), 0.1%, 0.2%, 0.3% and 0.4% respectively. Leaf membrane lipid peroxidation, antioxidant enzyme activity, osmotic adjustment substance contents, photosynthetic characteristics, pigment contents and leaf coloration changes under different salt treatment of the three plants were studied. The salt-resistant ability of tree plants were evaluated comprehensively using subordinate function method which provides the theory basis for the anti-salty variety's selective breeding and the color-leaf plant's cultivation and application in saline areas.The results showed as follows: with the increased of soil NaCl contents, salt injury rate and the salt injury index increased; Leaf relative conductivity, MDA contents, oxygen free radical production rate continued to rise; Antioxidant enzymes, proline and soluble sugar first increased and then decreased; Soluble protein contents of P. cerasifera var atropurpurea and P.×cistenena'pissardii'came down with rise of stress, but in P. wrasifers'nigra',the soluble protein content was first increased and then decreased; In all of the tree plants, Na+, Cl- contents in leaves were increased, but K+ content was decreased. It is very possible that proline and soluble sugar are the most important osmotic adjustment substance in P. cerasifera var atropurpurea and P.×cistenena'pissardii', but in P. wrasifers'nigra'the osmotic regulation is conducted by the intercoordination of proline, soluble sugar and soluble protein; With the rise of NaCl concentration, net photosynthetic rate, transpiration rate and stomatal conductance of the three plants decreased, intercellular CO2 in P.×cistenena'pissardii'and P. wrasifers'nigra'increased, but in P. cerasifera var atropurpurea, it was deceased at first and then increased. That indicated that photosynthesis of P.×cistenena'pissardii'and P. wrasifers'nigra'were inhibited mainly by non-stomatal factors, but in P. cerasifera var atropurpurea photosynthetic was inhibited mainly by stomatal factors under light salt stress, and by non-stomatal factors in heavy salt stress. With the rise of soil NaCl contents, leaves pH in P.×cerasifera var. atropurea increased, but in the other plants it was no significant change. Anthocyanin, flavonoids, chlorophyll and carotenoids in all of the tree plants were decrease under NaCl stress, except anthocyanin of P. cerasifera var atropurpurea and P.×cistenena'pissardii'in the fifth day of treatment. With the increase in stress,"L*-value"and"b*-value"increased more obviously, but"a*-value"maintain a downward trend. Correlation analysis showed that in the three plants, anthocyanin is the main pigments determined the leaves color under salt stress, followed is chlorophyll, flavonoids and carotenoids had less impact. After salt treatment, the leaves brightness values increased, and leaf color turn to yellow-green from deep purple. P. cerasifera var atropurpurea leaves color has no significantly change under 0.1% NaCl treatment. P.×cistenena'pissardii'began to turn green obviously in the fifteenth days on treatment, but P. wrasifers'nigra'leaves corlor has no obvious difference under every treatment. The anthocyanin content was positively related with enzymes PAL and CHI.The salt-resistant ability was evaluated comprehensively using subordinate function method and the main results was P. cerasifera var atropurpurea had stronger salt-resistant ability, followed P. wrasifers'nigra', P.×cistenena'pissardii'had poor salt-resistant ability,and the salt-tolerant thresholds were 0.349%,0.261%,0.327% of soil salt content. |
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