Study On The Relationships Between Ectomycorrhizal Fungi And Cold Resistance Of Eucalyptus

Symbiosis of ectomycorrhizal fungi and trees is commonly in nature, some trees would grow badly or die without symbionts.It was reported that ectomycorrhizal fungi could increase the surface area of roots to absorb nutrients and water,promote the ability of absorption of water and nutrients,which were all beneficial for the growth and resistance of plants.Pisolithus tinctorius and Scleroderma polyrhizum are two important large-size ectomycorrhizal fungi,both of which can form ectomycorrhiza with Pine,Eucalyptus and Acacia,and promote the growth of host plants and increase the resistance of host plants.But so far there is no report about inoculating Pisolithus tinctorius and Scleroderma polyrhizum to Eucalyptus to increase their cold resistance.In this paper,on the basis of screening of culture mediums and culture condition of Pisolithus tinctorius and Scleroderma polyrhizum, 3-month-old cutting seedlings of Eucalyptus were inoculated with them. Two months latter,mycorrhiza were identified.To study the change of the growth,physiology and biochemistry of Eucalyptus systematically,six temperature gradients were designed:10±1℃,5±1℃,0±1℃,-3±1℃, -5±1℃and -10±1℃.The main results were as fellows:1.In aspect of the preparation of ectomycorrhizal preparation,PDA was the optimum culture medium for both Pisolithus tinctorius and Scleroderma polyrhizum.On this culture medium,they both grown well and hypha of them germinated quickly.The optimum culture condition of them was 27±1℃under dark condition.According to the results of observation,Pisolithus tinctorius was golden yellow,and there was no obvious difference between the older hypha(in the center)and the new one(on the edge).The older hypha(in the center)of Scleroderma polyrhizum was dark yellow,and the new one(on the edge)was golden yellow.Two kinds of Ectomycorrhizal fungi both secreted pigment and changed the color of culture medium to be brown-and-yellow.2.Cutting the roots properly of Eucalyptus promoted the infection of bacterium.Identification of mycorrhiza showed that roots of Eucalyptus became larger and appeared infuscate.The hypha,hartig net inside the mycorrhiza and emanating phyphae were observed obviously through microtomy sections.3.Growth indexes showed that inoculation of Pisolithus tinctorius was more favorable to the growth of GL₉ and GLWC₃.90 days after inoculating,the height and leaves number of GL₉ had increased 65.84% and 35.74%respectively,and there was remarkable difference at 0.01 level;There was no remarkable difference between branches number of GL₉ and that of the CK;The height,leaves number and branches number of GLWC₃ had increased 52.21%,39.82%and 42.26%respectively;The average of height,leaves number and branches number of GL₉ was as 8.290 time,14.666 time and 2.234 time respectively as that of GLWC₃.4.The vary of POD,SOD,CAT and content of soluble sugar of GL₉ inoculated by two-mixed bacterium were more remarkable;But the vary of these indexes of GLWC₃ was more remarkable when it was inoculated by Scleroderma polyrhizum at room temperature.Inoculating Scleroderma polyrhizum to GL₉ and culturing their seedlings under -5±1℃could improve their POD,SOD,CAT activities and content of soluble sugar.But it was better for GLWC₃ to inoculate Scleroderma polyrhizum and culturing seedlings under -10±1℃in a short time.