The Effects Of Morphological Plasticity And Physiological Stress Ability Of Pedicularis Kansuensis Under The Shading

In view of the existing practical problems such as few varieties of flowers,frequent pests and diseases,resistance decline and ornamental recession,etc,to screen the wild flowers with strong resistance and high ornamental vaule to serve the sustainable development of landscaping based on the rich wild ornamental flower germplasm resources in western Sichuan Plateau.In this paper,wild Pedicularis kansuensis in high radiation region was planted under three shading gradients(0,35%,70%)for experimental material.The component traits,biomass distribution,morphological plasticity,activities of antioxidant enzymes,resistance,photosynthetic pigments and photosynthetic parameters were involved and analyzed to reveal the survival strategies and growth characteristics of P.kansuensis in different light environments,which would provide some basis for the development and utilization of wild ornamental flowers in high radiation areas.The main results were as follows:(1)Component traits:The stress of shading had significant effects on leaf traits,stem traits and root traits of P.Kansuensis(P<0.05).Leaf traits and stem traits both reached the maximum when the shading degree was 35%.With the shading degree increasing,both stem and leaf traits showed a decreasing trend and got the minimum under the condition of 70%shading.The number of root,root length and rhizome diameter gradually decreased with the shading degree increasing.The effect of shading on flower traits of P.Kansuensis was the least,only there was significant influence on rachides length and flower number.(2)Biomass and distribution ratio:The stress of shading had a highly significant effects on biomass and biomass distribution of P.Kansuensis(P<0.01).The effect of shading on above-ground biomass was greater than that of underground biomass.With the shade degree increasing,the component biomass,including stem,leaf,floral axis,flower and fruit all were increased first and then decreased,and these index all reached the maximum under the 35%shading,but minimum under the 70% shading.The distribution ratio of underground biomass and root-shoot ratio reached the maximum under the control,and they gradually decreased with the shading degree increasing.The distribution ratio of leaf,flower and fruit biomass reached the maximum under 35% shading,then they decreased when shading degree was 70%.That’s to say,light shading was good for the accumulation of above-ground biomass.(3)Component biomass correlation:There was a significant correlation between stems biomass and other biomass,and the correlation coefficient was above 0.940(P<0.01).In particular,the correlation between stem biomass and above-ground biomass was the highest with the correlation coefficient of 0.993.Root biomass had a biggest correlation with total biomass and a smallest correlation with plant height,with the correlation coefficient of 0.971 and0.718,respectively.Plant height had a biggest correlation with stem biomass with the correlation coefficient was 0.929.The correlation between above-ground biomass and total biomass reached 100%.(4)Resistance to physiology:The stress of shading had significant effects on the activity of antioxidant enzymes and noxious substances of P.Kansuensis(P<0.01).The activity of POD、CAT、SOD reached the maximum under the condition of 35% shading,then these enzyme activity were significantly reduced with the shade degree increasing.The content of MDA and H2O2 gradually increased with the increase of shading.The content of MDA and H2O2 was not obvious difference between the control and 35% shading,but significantly increased under the condition of 70% shading.Severe shading aggravated the degree of membrane lipid peroxidation of P.Kansuensis,which was not conducive to plant growth.The stress of shading had significant effects on resistance material and metabolites of P.Kansuensis(P<0.01).The content of T-AOC、OPC、TP、SP reached the maximum value under the condition of 35% shading,but the content significantly reduced with the shading degree increasing.The content of anthocyanins and flavonoids decreased with the shading degree increased,and reached the maximum value under the control,the minimum under the 70% shading.Therefore,mild shade was conducive to the accumulation of resistant substances and metabolites,which improved plant resistance.(5)Photosynthetic pigment:The stress of shading had significant effects on photosynthetic pigment content of P.Kansuensis(P<0.01).The contents of Chla,Chlb,Chl(a+b)significantly increased with the shading degree increasing,and reached the maximum value under the condition of 35% shading,the minimum under the control.With the shading degree increasing,the content of Car increased first and then decreased with the minimum under the 70%shading.When shading degree increased,the content of Chl(a/b)decreased first then increased and reached the highest in the control,the lowest under the 35% shading.Therefore,moderate shade contributed to the accumulation of photosynthetic pigments and improved photosynthetic efficiency.(6)Photosynthetic parameters:The stress of shading had significant effects on the gas exchange parameters and photosynthetic parameters of P.Kansuensis(P<0.01).Pn,Gs,Tr presented a downward trend with the shading degree increasing and reached the maximum vaule in the control.With the shading degree increased,the Ci increased with the maximum value under the 70% shading.When light irradiation increased,photosynthetic parameters(Pn,Gs,Tr and Ci)basically presented a same change trend,in which Pn,Gs and Tr three parameters gradually increased and Ci always decreased.The Pmax,LSP,LCP and Rd of P.Kansuensis presented a downward trend with the increase of shade degree,and reached the maximum value under the control,but the lowest under the 70% shading.P.Kansuensis had a larger LSP and a smaller LCP,which indicated it had stronger ability to adapting to light.Therefore,the control and mild shading were beneficial to photosynthesis of P.Kansuensis,which could improve its utilization of light energy.In summary,P.Kansuensis has strong adaptability to light and blossom both in high radiation and low radiation.35% shading was conducive to growth and development of P.Kansuensis,in which plant presented better growth characteristics,physiological resistance and photosynthetic characteristics,showing a certain resistance to shading and plasticity,could be introduced domestication.Therefore,the light intensity should be reasonable adjusted while artificial introduction and cultivation,to avoid excessive shading of growth environment,so as to increase the number of flowers and enlarge the rachis and make full use of its ornamental value.