Relationship Between Photosynthetic Adaptability And Epicuticular Waxes Of Blue-leaf Hosta

Hosta,a perennial herb of Liliaceae,has been widely applied in gardens due to its strong shade resistance,simple cultivation methods,and high ornamental value.After years of cultivation,it has rich varieties and bright colors.With the in-depth study of breeders,leaf colors have become more and more multiplicity,many scholars believe that leaf colors account for a high proportion in the comprehensive evaluation of Hosta,while the waxy appendages of leaf epidermis have a great impact on leaf colors.In this paper,effects of cuticular waxes on the photosynthetic physiological characteristics of 3 cultivars of blue-leaf Hosta(H.‘Blue Angel’,H.‘Halcyon’ and H.‘Baby Bunting’)were studied,and the optimum culture conditions for the growth and enjoying of blue-leaf Hosta were obtained.And the relationship between photosynthetic physiology and wax content of 3 cultivars of blue-leaf Hosta under different light conditions was analyzed.This research selected the best growing conditions for cultivation and viewing,and provided theoretical guidance for the application of blue-leaf Hosta in gardens.The main findings are as follows:(1)Under sun light condition,the photosynthetic adaptability of cuticular waxes-covered leaves of 3 cultivars of blue-leaves Hosta was higher than that of cuticular waxes-free leaves,the photosynthesis diurnal variation exhibited a bimodal curve,and showed midday depression of photosynthesis.From the time when the net photosynthetic rate reached its peak,H.‘Baby Bunting’ showed better adaptability to strong light than that H.‘Blue Angel’ and H.‘Halcyon’,in other words,H.‘Blue Angel’ and H.‘Halcyon’ were more tolerant to shade.The net photosynthetic rate,water use efficiency and maximum photochemical efficiency of cuticular waxes-covered leaves were higher than those of the cuticular waxes-free leaves,while the transpiration rate was lower than that of the cuticular waxes-free leaves.(2)Under different light intensity treatments,there were difference in the photosynthetic capacity of leaves among 3 cultivars of blue-leaves Hosta,when light intensity were 50%,the Pn of H.‘Blue Angel’ reached maximum,followed by 30%.When the light intensity was 30%,the Pn of H.‘Halcyon’ reached maximum,followed by 50%.When the light intensity was 50%-70%,the Pn of H.‘Baby Bunting’ reached maximum.The adaptability to subdued light of H.‘Halcyon’ was better than H.‘Blue Angel’ and H.‘Baby Bunting’.(3)In terms of plant growth,H.‘Blue Angel’ and H.‘Baby Bunting’ were suitable for the sun light intensity of 50%-70%,while H.‘Halcyon’ was suitable for 50%,followed by 30%.(4)In terms of the leaf color,they were suitable for cultivation under 10%-30% light intensity,then the blade can reach the deepest blue.The darker blue the leaf was,the greater the ornamental value.(5)The waxes content of 3 cultivars of blue-leaves Hosta under different light intensity was negatively correlated with net photosynthetic rate and brightness,but not with chlorophyll content,and the correlation between wax content and other factors was not identical,which might be due to different genotypes.