Effects Of Grafting On Growth, Development,Physiological And Biochemical Indexes Of Chrysanthemum Under Heat Stress

Chrysanthemum morifolium is originated in China, which is one of the top-ten traditional famous flowers in China and one of the four most important cut flowers in the world. The high temperature limits their growth, development, the quality of florescence and industrialization, especially in Wuhan where the hot and humid climate lasts for a long time in summer. Although the grafting technology has been used in Chrysanthemum shaping for a long time, the study on its internal mechanism on Chrysanthemum is deficient. In order to reveal the effects of grafting on growth, development, physiological and biochemical indexes of Chryanthemum under heat stress, the seeds of Artemisia annua were sown in the early spring of2011and two cultivars of Chrysanthemum morifolium called’Zilong Xianzhao’and’Tanxianggou’were cut and grafted at different time. Then C.’Zilong Xianzhao’grafted seedlings and cuttings were selected as experiment materials exposing to different high temperature in artificial climate incubator, while some physiological and biochemical indexes were tested under40℃heat stress. Ornamental traits and some physiological and biochemical indexes of C.’Zilong Xianzhao’and C.’Tanxianggou’grafted seedlings and cuttings were also observed in the field. The major results are as follows:1. The growth of C.’Zilong Xianzhao’grafted seedlings and cuttings (SA-85and SB-85) under different heat stress (35℃,40℃and45℃) for0,2,4,8,16,24h and2,3,4and5d were separately observed. The results showed that the grafted seedlings under heat strees performed better than cuttings. Moreover, the heat resistance of those experiment materials cuould be distinguished under40℃heat stress. Under35℃heat stress for5days, there was slight heat damage phenomenon and survival rates were all above84%. In contracst, all the materials died under45℃heat stress. However, those materials showed varying thermal damage phenomena after8-16hours under40℃heat stress and completely different survival rate. The survival rate of grafted seedlings was more than80%, while the cuttings’was44.4%(SA-85) and22.4%(SB-85) respectively.2. The root/shoot ratio, the dry and fresh weight of aerial part and shoot, dry/fresh, and the protective enzyme activities of C.’Zilong Xianzhao’grafted seedlings and cuttings (SA-85and SB-85) were analyzed under40℃in artificial climate incubator.The results demonstrated that all the indexes of grafted seedlings were significantly better than the cuttings (SA-85and SB-85); the protective enzymes activities in leaves, roots and stems had different sensitivity. The protective enzymes activities in leaves and roots were more sensitive than in stems; besides, the SOD activity in leaves and POD activity in roots and stems reached their peak values spontaneously. Furthermore, there was significant differences among the protective enzymes activities of grafted seedlings’ healing part, stock part and scion part. The activities in healing part were highest, but in scion part were lowest.3. According to the results of physiological and biochemical indexes and ornamental traits of C.’Zilong Xianzhao’and C.’Tanxianggou’grafted seedlings and cuttings in the field, it suggested that grafting is a good way to make chlorophyll (a+b) content of C.’Zilong Xianzhao’and C.’Tanxianggou’grafted seeldings increase28.2%and46.1%respectively. The photosynthetic rate enhanced80.6%-109.5%and67.5%-98.3%, as well as the root vitality improved21.5%å'Œ48.9%, but the relative electrical conductivity of leaves reduced17.2%and31.4%. Apparently, grafting also increased the protective enzymes activities in spite of planting in the field. More importantly, there was similar trend of protective enzymes activities whether in the field or in artificial climate incubator. The grafted seedlings of two cultivars growed well during high temperature period in summer while the cuttings’leaves happened wilting or curling under heat stress. In addition, the bloom of the two cultivars’grafted seedlings advanced by7to10days compared to the cuttings and the flowering period extended10to14days. However, there was no difference in plant height, leaf and petal length and width between the grafted seedlings and the cuttings.This study was conducted to reveal the internal mechanism of improvement of heat resistance in grafting seedlings by detecting physiological and biochemical indexes. It provided us with an ideal simple method and theoretical basis for chrysanthemum planting in summer thereby promoting chrysanthemum industry in hot regions.