| The effects of salt stress on the growth of Crimson grape test tube seedlings (Vitis vinifera L. Crimson) were studied by adding NaCl to culture medium, and the mitigating effects of different concentration of NdCl3 on salt stress-induced inhibition were meanwhile examined. The results showed as following:1. Under condition of 0.1% NaCl, all growth indexes of the NaCl-treated plantlets are better than those of the controls. Interestingly, 0.1% NaCl concentration can break the "domestication" phenomenon and activate the growth of Crimson test-tube seedlings. When the concentration of NaCl reached to 0.2%, the root numbers, root length and leaf numbers were significantly reduced and were negative correlated with NaCl concentration. 20~40 mg·L-1NdCl3 promoted the growth of Crimson test-tube plantlets, and the best concentration was 40 mg·L-1,when it is higher than 80 mg·L-1, NdCl3 suppressed the growth of Crimson test-tube plantlets and showed the dosage effects. We also found that 20~80mg·L-1 NdCl3 significantly alleviated the salt stress-induced growth inhibition when NaCl was higher than 0.2% concentration during the first 20 days, the effectively alleviative concentration of NdCl3 under salt stress is 20mg·L-1. However, after 25 days, both high concentration of NdCl3 (80mg/L) and NaCl inhibited the growth of the test-tube plantlets.2. Chlorophyll contents of the Crimson test-tube plantlets increased and photosynthetic rate improved under condition of 0.1% NaCl concentration. The reason for this is possibly that low concentration of NaCl can not do harm to Crimson test-tube plantlets, but only be as stimulating factor to promote the relative metabolism of the plantlets. However, when the concentration of NaCl was higher than 0.2%, the chlorophyll contents and photosynthetic rate of Crimson test-tube plantlets decreased, and was significantly negative correlated with NaCl concentration. This was consistent with previous reports. Similar to the growth response, 20~40mg·L-1 NdCl3 also improved chlorophyll contents and photosynthetic efficiency. But when the concentration of NdCl3 was above 80 mg·L-1, it gave rise to suppressive effects. Therefore, certain concentration of NdCl3 can improve the chlorophyll contents and photosynthetic rate under salt stress, but higher concentration of NdCl3 produces negative effect.3. SOD and POD activity of the Crimson test-tube plantlets were higher than that of controls under condition of 0.1% NaCl from the beginning to the end. But under middle concentration of NaCl stress, SOD and POD activity first increased then declined as time. Moreover, activity of SOD and POD decreased significantly under high concentration of NaCl, leading to the growth inhibition of the test-tube plantlets. On the one hand, 0.1% NaCl concentration is not harm to the growth of Crimson test tube plantlets. On the other hand, no significant difference in MDA and PMP contents was observed between NaCl-treated (0.1% NaCl) and control. Additionally, under condition of 2% NaCl concentration, although test tube plantlets were suppressed, they could survive via reducing oxidative stress by increasing SOD and POD activity. However, when the plantlets were treated with 0.3% and 0.4% NaCl concentration, PMP and MDA contents increased greatly. It suggests that concentration of NaCl has already exceeded test tube plantlet 's adaptation ability. We found that the plantlet's leaves had a symptom of crimple, yellow and brown spot at the leaf edge. Under condition of 0.2% NaCl, 20~40mg·L-1 NdCl3 improved SOD and POD activity of the Crimson test-tube plantlets. Accordingly, membrane permeability and MDA contents reduced gradually. Surprisingly, when NdCl3 concentration rises to 80mg·L-1, both POD and SOD activity reduced, and MDA contents was already higher than those of NaCl-treated plantlets. These results showed that alleviative effects of NdCl3 to salt stress on Crismon grape test tube plantlets are concentration-dependent. That is, low concentration of NdCl3 has alleviative effects on Crismon grape test tube plantlets, while high concentration has damage effects under NaCl treatment.
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