Effects Of Shading On Wild Impatiens Omeiana Hook.f.

Impatiens omeiana were used as experimental material in this study. A pot experiment was conducted to study the changes in morphology, anatomical structure and characteristics of flowering under different shading(full light,45%shading,70%shading and 95%shading), and effects of different light intensity on growth, physiological and photosynthetic characteristics was investigated. The aim was to clear the light-tolerance of Impatiens omeiana. At the same time we expected to provide theoretical foundation for protecting and using Impatiens omeiana. The results showed that:The growth of height, basal diameter and leaf area of Impatiens omeiana increased, but the number of leaves and branches reduced significantly under shading treatment. With increasing of shade degrees, blade length/width increased, showed that leaf became long and narrow. Leaves appear anxious and falls under all lighting conditions, growing very weak.Leaf thickness, leaf weight ratio, the thickness of palisade tissue and the ratio of palisade tissue to spongy tissue significantly of Impatiens omeiana decreased under shading, spongy tissue thickness had no remarkable changes.Appropriate shading promoted biomass accumulation of Impatiens omeiana, biomass of aboveground and underground were larger under 45% and 70% shade than full light and 95%shade. The order of aboveground water content was 95%>70%>45%>full light, in contrast underground water content followed by full>45%>70%>95%shade.The content of chlorophyll a and chlorophyll a+ b in leaves increased and then decreased with increasing of shade degrees, it has the maximum value under 70% shade. As the extent of shading increasing, the chlorophyll b content increased but the chlorophyll a/b ratio decreased significantly. The net photosynthetic rates were double——peak curve under the full sunlight treatment and 45% shade, having the midday depression of net photosynthetic, while the net photosynthetic rates were single——peak curve under the other treatments. The order of average net photosynthetic rat, transpiration rate and stomatal conductance was 45%shade>70%shade>full light>95% shade, the order of stomatal limitation was full light> 45%shade> 70%shade> 95%shade, the order of intercellular CO2 concentration and vapor pressure deficit was 95%shade> full light> 70%shade> 45%shade. It indicated that it was helpful to photosynthetic process of Impatiens omeiana under 45% shade and 70% shade, full light and 95% shade had the opposite effect. With the increase of shade ratio, the ratio of average net photosynthetic rate to average Photosynthetically Active Radiation(PAR) and the apparent quantum yield (?) increased, but light saturation point(LSP), light compensation point (LCP)and dark respiration(Rd) declined to produce a certain ecological adaptability to low light.As the increased of shade degrees, the activity of SOD enzyme, POD enzyme and CAT enzyme first increased and then decreased, it has the maximum value under 45% and 70% shade. The MDA content reduced with the increased of light intensity. It can reduced the injured of membrane system and be conducive to the growth of plants under 45% and 70% shade.Only under the treatments of shading can the Impatiens omeiana bloom. Plant has the largest flower number under 45% shade, followed by 70% shade, and their flowering time same, are 26d.Under 95% shade, it has the minimum flower number, only 14d. The size of corolla part of Impatiens omeiana Hook.f.increased significantly under 70% shade. The results showed that 45% and 70% shade has the best morphology and ornamental value. Fruit number per plant and the seeds number of individual fruit has a maximum under 70% shading, but the fruit-setting ratio and fruit weight has a maximum under 95% shading. The effect of different shading treatment on Pollen-ovule ratio was very small, it is 116802.In conclusion,45% and 70% shad treatment can enhance the photosynthesis and the activity of antioxidant enzymes of Impatiens omeiana, reduce the damage of membrane systems, it is beneficial to plant growth and improve the plant's ornamental value. It is not conducive to plant growth under full light and 95% shade.