Effects Of Different Grafting Methods On The Growth And Physiological Characteristics Of Cucumber Seedlings

Cucumber is one of the most important vegetable. Grafting is an effective measure to improve the resistantance of cucumber, and it has been applied in cucumber production. The traditional grafting methods such as insert-grafting and cleft-grafting methods have some disadvantages such as low efficiency of grafting, so they are limited in cucumber production. Root-cut-grafting is a new grafting method and is suited for cucumber, but there were few reports about the physiological mechanism of this method. In this study, the effects of different grafting methods on the growth of grafted cucumber seedlings were investigated, and the standard on the root-cut-grafting and the effects of grafting on the growth and quality of cucumber were conducted. The results were as follows:1. The effects of different grafting methods (cleft-grafting, insert-grafting and root-cut-grafting) on the growth and physiology properties of cucumber seedlings were investigated. The materials were Cucurbita ficifolia and Jinchun No.2 as stock and scion, respectively; more ungrafted plants were used as controls. The results showed that: effect of three grafting methods on the growth was no difference for 13 days of grafting being over, but height, dry weight and leaf area of root-cut-grafting cucumber were significantly higher than other two at 16 days after grafting. Besides, leaf area and stem diameter of grafted seedling were higher than the ungrafted. In addition, in the grafted seedlings, photosynthetic rate and amount of electron transfer in leaves increased and the content of K⁺, Ca²⁺, Mg²⁺, ZT and GA in bleaching sap ascended whereas the content of ABA decreased. Comparing root-cut-grafting with cleft-grafting and insert-grafting, the former displayed better than the latters in gas change ability, stomatal conductance transpiration rate, transpiration rate, root activity and more content of K⁺, Ca²⁺,Mg²⁺ and ZT. All of the above may be the cause for that root-cut-grafting is superior to other two grafting methods.2. The effects of different temperatures, lower (10℃/5℃), higher (40℃/35℃) and normal (25℃/20℃), on the growth and physiology properties of cucumber seedlings were investigated. The materials and grafting methods were the same as above. Compared with the control temperature, the results showed that the grafted and self-rooted cucumber seedlings were both injured under low and high temperature stress, but the injured index of the grafted cucumber seedlings was significantly lower than those of self-rooted under low temperature treatment, whereas the injured index of grafted seedlings under high temperature treatment were significantly higher than those of self-rooted seedlings, and the grafted seedlings with root-cut-grafting performed best among the three grafted methods. The leaves of seedlings under low and high temperature treatments contained more proline and soluble sugar, higher SOD and POD activities than those of controls. Meanwhile, the seedlings of low temperature treated and grafted had a better performance than high temperature treated and self-rooted ones seven days after recovery period, respectively. Therefore, it is concluded that "Figleaf gourd" was a proper rootstock for cucumber to improve the chilling resistance, but was not suitable for the higher temperature treatment; The root-cut-grafting method could improve the adaptability of cucumber seedlings to temperature treatment by increasing root activity and containing higher POD and SOD activities.3. The effects on cucumber seedlings of different controls that involved depth of stocks inserting (1 cm, 2 cm, 3 cm), length of blade sections (0.4 cm, 0.8 cm, 1.2 cm) and height of shoots (3 cm, 4 cm, 5 cm) were investigated. Jinchun No.2 as scion and Cucurbita ficifolia and Chaofeng as stocks were used. The results suggested that, when stocks were inserted into substances for 1 cm, scion dry weight was highest and leaf area was relatively larger; on the contrary, growth vigor behaved worse when 3 cm. Additionally, when the length of blade sections was 1.2 cm, grafting survival rate was lowest, rot rate was highest, and growth parameters such as dry weight of root, length of scions, leaf area showed the worst. Meanwhile, the above parameters were better in case of 0.8 cm treatment. Moreever treatment of shoots height did not affect grafting survival rate notably, and grafting survival rate keep lower when the shoot height was 4 cm. Above all, it was thought that the treatment, as depth of stocks inserting was 1-2 cm, length of blade sections was approximately 0.8 cm and height of shoots was around 3 cm, would be suitable for root-cut-grafting.4. Effect of three grafted methods (root-cut-grafting, insert-grafting and cleft-grafting) on the growth and fruit quality of cucumber. The materials were the same as those in first experiment. The results reflected that after grafting, the early growth vigor was accelerated and female flowers timing was put off, at the same time, the total yield of grafted cucumber was advanced markably. What's more, the fruit of grafted cucumber had increasing contents of soluble protein and free amino acid, however, the contents of water and soluble sugar were not significantly different from ungrafted, and decresing vitamin C content. Furthermore, fruit taste of insert-grafting was the worst. So the effect of three grafting methods on the growth, yield and fruit quality in the whole growth period showed no differences.