Effects Of Shading On Leaf Colour And Physiological Characteristics Of Three Varieties Of Heuchera Micrantha

In recent years,the application of Heuchera micrantha in southwestern China is not universal.In order to exploit and utilize Heuchera micrantha resources reasonably,three varieties of Heuchera micrantha `Peach Flambe',Heuchera micrantha `Forest Worm',and Heuchera micrantha `Caramel' were selected in this study.There are four shading rate of 0%,30%,60% and 90% were set up to systematically studied the photosynthetic characteristics,leaf color changes and physiological response of the Heuchera micrantha varieties in different shading groups.This study further confirms the suitable growth environment of Heuchera micrantha varieties and provided the theoretical basis and data support for the introduction and application of Heuchera micrantha in southwestern China.The main results are as follows:(1)In terms of photosynthetic characteristics,the three varieties of Heuchera micrantha all showed obvious "midday depression of photosynthesis",which was caused by non-stomatal factors.The change trend of light response curve is basically similar:It increases rapidly first and then stabilizes gradually,and the excessive photosynthetic active radiation can caused the photosynthetic inhibition.`Caramel' has a lower light saturation point,which can effectively utilize the weak light for photosynthesis.It has a relatively good effect on the use of weak light,and photosynthesis is inhibited greatly under strong light.`Peach Flambe' and `Forest Worm' have a better use of strong light and are more adaptable to strong light environment.(2)From the view of leaf color,the leaf color of the three varieties of Heuchera micrantha gradually turned green with the decrease of light intensity.With the increase of shading degree,the contents of chlorophyll a,chlorophyll b,total chlorophyll and carotenoid in leaves increased,the degree of leaf coloration decreased,the contents of anthocyanin decreased,and the contents of phenylalanine ammonia lyase and soluble sugar related to its synthesis also decreased.For non-green leaf varieties of `Peach Flambe' and `Forest Worm' adequate light is conducive to the development of their ornamental value,but for green leaf of `Caramel',a good shading environment is conducive to the color of its green leaves.(3)According to the physiological response to light stress,malondialdehyde content of three varieties of Heuchera micrantha reached the highest value under full illumination,which indicated that strong light environment might damage the leaves.The change range of malondialdehyde in `Peach Flambe' was significantly larger than that in `Forest Worm' and `Caramel',indicating that the damage of `Peach Flambe' was more affected by strong light.These varieties' minimum or maximu of soluble protein contents,SOD activity and POD activity varied from the treatment time and shading groups,which indicated that shading time and shading degree could affect the resistance of these varieties comprehensively.Among them,`Peach Flambe' can produce protective response to the shading environment,`Forest Worm' can produce protective response to the light shading environment,and `Caramel' can produce protective response to the severe shading environment.Generally speaking,the most suitable conditions to `Peach Flambe',`Forest Worm',and `Caramel' is the shading conditions of 0%~30%,30%~60% and 60%~90% respectively.It could inferred that the red varieties of Heuchera micrantha prefer the strong light,and it could be arranged under the sparse forest with simple structure as ornament,and can also be matched with low shrubs;while the green varieties of Heuchera micrantha is more suitable for planting under the shade,such as dense forest or trees and shrubs with complex structure;and the mixed color variety one is between the two.