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Effects of nitrogen form on the photochemical efficiency of PSⅡ and antioxidant characteristics of Jerusalem artichoke seedling under salt stress
- WANG Lei, LONG Xiao-hua, HAO Lian-xiang, LIU Zhao-pu
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2012, 21(1):
133-140.
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In order to study the effect of different nitrogen form on the physiology of Jerusalem artichoke seedling under the salt stress, a sand cultural study was carried out under the nitrogen nutrition (NH4+/NO3- as 4/1, 1/1 and 1/4) and salt stress. 1) The treatment of low concentration of salt stress had a little effect on the inhibition of plant growth, but high concentration of salt stress could remarkably inhibit Jerusalem artichoke growth. Under the same salt concentrations, the dry weights, relative moisture content, plant height and leaf area of Jerusalem artichoke increased with the proportions of NO3--N augment.2)With the increasing of salt concentration, PSⅡ system was significantly damaged, but the increasing of the proportions of NO3--N could reduce the damage degree of the PSⅡ system and improve ΦPSⅡ, Fv, Fv/Fm, Fv/Fo, Fm/Fo and qP. Especially, nitrogen nutrition had the highest light use efficiency at the ratio of NH4+/NO3- as 1/4. For example, under 100 mmol/L NaCl stress, compared with the treatment at the ratio of NH4+/NO3- as 4/1, ΦPSⅡ, Fv, Fv/Fm, Fv/Fo, Fm/Fo and qP of the treatment at the ratio of NH4+/NO3- as 1/4 increased by 1.03, 1.15, 1.05, 1.26, 1.20 and 1.05 times, respectively.3)Too much salt supply could cause the imbalance of plant cell osmotic, however, under the same salt concentration, the increasing of the proportions of NO3--N could significantly promote soluble sugar and soluble protein production and the transfer to the roots, then maintained the balance cell osmotic effectively under salt stress.4)Under the salt stress, the membrane lipid peroxidation usually occurred in plants cells, but the proportions of NO3--N augment could promote the SOD, POD, CAT and APX activity which had a function of eliminating reactive oxygen species, then alleviated membrane damage which the excessive accumulation of reactive oxygen species caused in cell. For example, under 100 mmol/L NaCl stress, compared with the treatment at the ratio of NH4+/NO3-as 4/1, SOD, POD, CAT and APX activities of the treatment with NH4+/NO3- as 1/4 were improved by 1.19, 1.08, 1.18 and 1.11 times, respectively. So with respect to NH4+-N, the increase of the proportions of NO3--N was more conducive to increase the accumulation of dry matter and water content, improve the activity of intracellular protection enzyme, maintain the stability of PSⅡ system and cell osmotic balance, then enhanced the resistance of Jerusalem artichoke to salt stress.