Physiological Mechanisms Of Low Temperature Tolerance Improved By Grafting In Melon

Cucumis melo L. belongs to the branch ofCucurbitaceae, the subordination ofCucumis, which is annual herbal vine. Melon is one of the major world fruits and hasan important status on horticulture in the world. It has a high economic value. But inthe northern China, spring cold limits the melon early listing. It has a bad effect onsubstantial economic increase. Nowadays,to use grafting techniques is aeffective wayto improve cold accumilation. With widely application of grafting techniques, it hassignificant effects on the improvement of cold tolerance in melon. But the theoreticalstudy about grafting techniques are inadequate. The subject focus on the index ofphysiological and biochemical and relevant gene expression on grafted seedling ofmelon and uses scion-root seedling as reference during chilling stress in order toinvestigate the internal mechanism about grafting improving cold accumilation,and toprovide basis of spreading about grafting techniques of melon. Now the subject obtainthe following results:1. The conductivity, content of MDA has similar level between grafted seedlingand scion-root seedling in low temperature tolerance from0h to12h.But these dataare low for scion-root seedling from12h to72h. The content of soluble sugar ingrafted seedling is much higher than that in scion-root seedling. The soluble proteinbetween grafted seedling and scion-root seedling are both decline at the beginning andthen rise. But the grafted seedling has a high growth trend during low temperaturetolerance of elevated stage. In opposite, the proline between grafted seedling andscion-root seedling are both rise at the beginning and then decline. But the graftedseedling has a high growth trend during low temperature tolerance of elevated stage.2. Grafted seedling has a high activity of SOD and CAT than scion-rootseedling. The activity of POD shows decline at the beginning and then rise. Graftedseedling’s activity of POD gets into a high growth trend earlier than scion-rootseedling. The activity of POD in grafted seedling has a high level than scion-root seedling.3The relative expression of CAT, APX and ERF1in grafted seedling of melonhas a high level than scion-root seedling. The three genes expression all rise at thebeginning and then decline in low temperature stress with the time going on, thenreaching the maximum at24h,48h and48h.But these genes have a flat trend duringthe process of decline. Grafted seedling and scion-root seedling have a rising trend inthe expression level of GS1. The grafted seedling has a high level in the gene of GS1than that in scion-root seedling.4. The expression level of DREB1,NAC and bZIP2is irregular in chilling stress.But these have a trend of rise at the beginning and then decline Overall and thenreaching the maximum at12h,24h and24h.