Cultivation Method of Hevea brasiliensis Large Polytube-raised Buddings Ⅶ.Screening of Shading Rate
To understand the growth and photosynthetic characteristics of large polytube-raised buddings of Hevea brasiliensis under different shading environments,and to determine the appropriate light environment for the growth of large polytube-raised buddings,five shading were set,including CK(full light),S60,S70,S80 and S90(60%,70%,80%and 90%shading rate,respectively),to observe the growth index and photosynthetic parameters changes.The results showed that different shading rates had significant effects on the growth,photosynthetic parameters,leaf area and relative content of chlorophyll of top-leaf-whorls of large polytube-raised buddings of H.brasiliensis,and there were significant differences between the two types of embryo seedlings.The vigorous seedling index of large polytube-raised buddings increased at first and then decreased with the increase of shading rate.Compared with full light,shading significantly affected the out-nursery rate of large polytube-raised buddings,but had little effect on the survival of planting.The interaction between embryo seedling type and shading was obvious.Full light(CK)and excessive shading(S90)could significantly inhibit the growth of large polytube-raised buddings.The optimal shading rate of large polytube-raised buddings was different among different embryo seedlings.The growth performance of small seedling buds under S60 and tissue culture seedlings under S80 was the best.Therefore,appropriate shading measures should be selected according to embryo seedling types during the cultivation of large polytube-raised buddings of rubber trees.
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