Salt Resistance Difference Of Rootstocks And Its Effect On The Salt Resistance Of Cucumber Seedlings

Soil secondary salinization is the main problem in protected horticulture, and grafting is the effective method of improving crop salt resistance. Salt resistance of rootstocks and its effect on the salt resistance of cucumber seedlings were studied in this paper. The research consisted of three experiments: salt resistance evaluation of different rootstocks experiment, salt resistance mechanism of different rootstocks experiment, grafting effects on the salt resistance of cucumber seedlings. The main results were as follows:1. This experiment studied that 22 species of rootstocks during seedling stage were evaluated under salt stress. (NaCl concentration: 50, 100, 150 and 200 mMNaCl). Salt injury index of rootstock were used to detect the salt resistance of rootstock. Rootstocks could be clustered to two groups, Chunbaiyu, Zaoqingyidai, Jizaoxiuyu (Cucurbit pepo L.cv.), TiejiangjunF1(Cucurbita moschata Duch.cv.) were sensitive to salt stress whereas the other species of rootstocks were tolerant to salt stress, and the salt resistant rootstocks could be clustered to three subgroups, Xiaoganhugua, Tongxinhugua, Hanlongbiyu and Chaofeng8848(Lagenaria siceraria Standl. var. clavata Makino cv.) showed the highest salt resistance, Heizinangua(Cucurbit ficifolia cv.) exhibited tolerant, whereas the other thirteen species showed more salt resistance.2. Salt-tolerant mechanism was studied using different rootstocks (Heizinangua, Chaojiquanwang and Chaofeng8848) as material .The rootstock effect was assessed by yong plant at different NaCl concentrations (0, 50, 100, and 150 mM NaCl). The results showed that the dry weight of shoot and root, fresh weight of shoot and root, plant height, stem diameter and leaf number of rootstock seedlings showed decline significantly with the NaCl concentration increasing. However, the shoot biomass reduction induced by salinity was more than that of root. Under the same salt concentration, Heizinangua reducing extent was maximal. Pn, Tr and Gs of rootstock seedlings showed decline significantly with the NaCl concentration increasing, but F₀ and Fv/Fm were contrary. Under the same NaCl concentration stress, the relatively conductance, SOD activity, POD activity, Pro content and MDA content of Heizinangua descending extent were maximal, but the Chaofeng8848 descending extent were minimum. The Na content of rootstocks tended to increase significantly with the increasing of salt concentration, and the Na content of leaf was significant lower than that of root, however, the stem had ability to accumulate high concentrations of Na. So the salt tolerance size is the same as the seedlings in the field: Chaofeng8848＞Chaojiquanwang＞Heizinangua.3. This experiment studied the growth and physiological characteristic of grafted (root: Chaojiquanwang, Heizinangua, Chaofeng8848; scion: Jinchun-2) under NaCI stress (NaCl concentration: 0, 50,100,150 mM). The results showed that the dry weight of shoot and root, fresh weight of shoot and root, plant lengh, stem diameter, leaf number and leaf area of grafted and self-root seedlings showed decline significantly with the NaCl concentration increasing, but self-root seedlings decline more significantly. Pn, Tr and Gs of grafted seedlings is higher than self-root seedlings. TheΦPSâ…¡and Fv/Fm of self-root seedlings were decline significantly with the NaCl concentration increasing. The relatively conductance and MDA content increased remarkably, whereas Pro content of self-root seedlings were significant lower than that of grained seedlings. The Na content of grafted seedlings was significant lower that of self-root seedlings, but the K content was contrary. New insights into the mechanisms by grafting that play critical roles in plant resistance to salt.