| In this experiment, kumquat was chose as the plant material, two types of soil (karst soil and acid soil) from Karst areas were used as potted matrix, after inoculated with arbuscular mycorrhizal fungi (AMF) in Glomus mosseae,(G.m) and Glomus etunicatum (G.e), the effects of AMF on drought resistance of Kumquat under drought conditions were conducted. The results are as follows:1. Under drought stress, after inoculated with AMF, the mycorrhizal colonization frequency (F%), infection intensity (M%), vesicle abundance (V%) of whole root system and infection intensity (m%) of infected root fragments were significantly lower than the normal water treatment. In any moisture conditions, growing in the same soil, the four infection rate indexes of kumquat inoculated with G.e were higher than that with G.m; In different types of soil, the four infection rate indexes of kumquat growing in acid soil and inoculated with G.e were more higher than that in karst soil treatment; On the other hand, the four infection indexes of kumquat inoculated with G.m growing in karst soil was significantly higher than that in acid soil treatment. Experimental results show that, no matter what types of the soil the kumquat grew in, compared with the inoculated with G.m treatment, the infection rates of kumquat inoculated G.e treatment were stronger. It demonstrates that a good symbiosis can be formed between Ge and kumquat root system. Under drought conditions, the ability to adapt drought stress of G.e is stronger than that of G.m.2. Under normal water conditions, compared with non-AMF treatment, when kumquats grew in the same soil inoculated with AMF, SOD, POD activity and GSH content of their leaves increased in different extents; MDA content of leaves and roots relative conductivity were lower in different degree. Under drought stress, compared with the normal water treatments, SOD, POD activity and GSH content of each kumquat treatment had decreased trends in different magnitude; however, SOD, POD activity and GSH content of the kumquat inoculated with AMF treatments were still higher than the non-AMF treatments, and the difference was significant; while the MDA content in leaves and root relative conductivity of kumquat were on the rise, but MDA content in leaves and roots relative conductivity of kumquat inoculated with AMF treatments were significantly lower than those with non-AMF treatments.3. Compared with normal watering treatment, under drought stress, kumquat’s stomatal conductance (Gs), transpiration rate (Tr), chlorophyll content (Chl) and net photosynthetic rate (Pn) of kumquat had different reduced extend. It indicates that Water metabolism and photosynthesis of kumquat are inhibited. In addition, under drought stress, compared with normal watering treatment, kumquats inoculated with AMF, the water use efficiency of leaves improved to varying degrees. Growing in the same soil, compared with the non-AMF and drought treatment, kumquat inoculated with AMF treatments, the value of Chl, Pn, Gs and Tr were increased to different extents. In particular, Pn, Gs and Tr of kumquat inoculate with G.e treatment are higher than those of their G.m inoculated treatment.4. Under normal water conditions, growing in the same soil, the leave Mg2+-ATPase and Ca2+-ATPase activity of kumquat inoculated AMF treatments were significantly higher than those with non-AMF treatments. Under drought stress, two kind of ATPase activity in kumquat leaves had different decreased trend, while the ATPase activity of kumquat inoculated with AMF treatments were significantly higher than those with non-AMF treatments.5. Under normal water conditions, growing in the same soil and inoculated with AMF, the indexes of kumquat growth potential (such as plant height, root length and root volume)、root system activity and dry matter accumulation were higher than those with the non-AMF treatments. Under drought stress, root system activity of each kumquat treatment was significantly lower than that of normal moisture conditions treatment; in the same soil, root system activities of kumquat inoculated with AMF were significantly higher than those with non-AMF treatments, The order of kumquat root activity showed the trend:inoculated with G.e treatments> inoculated with G.m treatments> with non-AMF treatments; Root system activity level sequence of kumquat growing in different soils inoculated with G.e treatments showed the trend:the acid soil treatments> karst soil treatments, and the results varyed significantly. Under drought stress, compared with normal water treatments, the indexes of kumquat growth potential and dry matter accumulation have a different degree of reduction. Overall, under drought stress, the increase growth effect of kumquat growing in karst soil and inoculated with AMF was more significant, and its dependence to AMF was higher than that in acid soil.In summary, AMF can alleviate damage of water stress on leaves and root of kumquat, enhance water retention and drought tolerance and maintain relatively higher physiological metabolism and function. Ultimately, it shows a certain synergy effect for kumquat growth. In addition, under drought stress, the promoting effect on drought resistance and growth of kumquat inoculated with G.e treatment were higher than inoculation with G.m. Therefore, Glomus etunicatum (G.e) will choose as one of the dominant arbuscular mycorrhizal candidate strains for kumquat growing in the karst dry region to improve water retention capacity and drought resistance. This study should provide theoretical inference for improving kumquat production and promoting fruit yield in karst area. |
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