| Humulus scandens has the characteristics of sex differentiation of dioecious plants,dependence of climbing plants on external support,and short life span of herbaceous plants.The climbing ability determines the potential of light seeking,the short life requires the quick adaptation strategy to the light change,and the sex differentiation requires the male and female plants to adopt the coordinated growth change to the light condition,so as to ensure the survival and continuation of the species.It is of great practical significance to study the expression and response strategy of Humulus humulus to light adaptation,to the protection and utilization of wild plant resources,to the ecological environment treatment and to the sustainable application of Chinese herbal medicine.The paper used Humulus scandens as experimental material to study the shading of male and female by setting 4 light gradients of total illumination,mild,moderate and severe shading(0,25%,50%,75%).Including the effects of morphological indicators,physiological indicators and reproductive indicators.The main findings are as follows:(1)Component traits:Shading had significant effect on leaf traits(P<0.05),but had no significant effect on root traits(P>0.05).Leaf length,leaf width,total leaf number and total leaf area increased firstly and then decreased with increasing shade.Shading had a significant effect on stem traits of Humulus scandens(P<0.01),and the order of influence was: stem length>stem diameter>Internode length.Stem diameter,stem length and internode length first increased with shading and then decreased with moderate shading.Gender has a significant effect on leaf and stem traits(P<0.05).The leaf length and leaf width of the female were significantly larger than that of the male.The total leaf area and total leaf area of the male were significantly larger than that of the female(P<0.05),and the single leaf area of the female was significantly larger than that of the male(P<0.05).The stem diameter and stem length of male were significantly larger than that of female(P<0.05).The results showed that Humulus scandens can increase the leaf area to increase the amount of weak light captured,increase the aboveground biomass to escape the shadowy environment and obtain the light source.(2)Component biomass :Shading had different effects on the biomass accumulation of Humulus scandens.Shading had significant effects on root biomass allocation and total biomass(P<0.05),but had no significant effect on leaf and stem biomass allocation(P>0.05).The order of biomass affected by shading was as follows: total biomass>root biomass allocation>stem biomass allocation>leaf biomass allocation.The total biomass and stem distribution ratio increased firstly and then decreased with shading,while the leaf distribution ratio decreased firstly and then increased with shading.Gender only had significant effect on total biomass(P<0.01),but had no significant effect on biomass allocation of leaves,stems and roots(P>0.05).With the increase of shading degree,Humulus scandens will first allocate biomass to the components that can slow down or overcome the shading conditions to reduce the damage caused by stress to plants,and control the proportion balance between leaves and stems.The results showed that Humulus scandens had a strong growth strategy to deal with shading stress.(3)Protective enzyme activity:Shading had a significant effect on the activities of various protective enzymes of Humulus scandens.With the increase of shading degree,the activity of SOD and POD increased,and reached the maximum value in severe shading.The activity of CAT in moderate shade was significantly higher than that in light shade(P<0.05),but there was no significant change in no shade and light shade(P>0.05).The order of influence of shading on protective enzyme activity was: SOD>POD>CAT.Gender had a significant effect on SOD,POD,CAT activity(P<0.05).The SOD,POD,CAT activity of male plants were significantly higher than that of female plants.The effect of sex on the activity of the protective enzyme was: SOD>POD>CAT.The effect of shade on the activity of protective enzyme was much greater than that of sex.Under shading stress,Humulus scandens can reduce the damage caused by shading by increasing the enzyme activity through self-regulation.(4)Metabolites:Shading had a significant effect on MDA and metabolites(P<0.05).MDA increased with the increase of shading degree.As the shading degree increases,SS increased gradually,and SP increased firstly and then decreased.PRO increased gradually and reached the maximum in severe shade.The influence of shading on MDA and metabolites was as follows: MDA>SP>PRO>SS.SP of female plants was significantly smaller than male plants(P<0.05),while PRO was the opposite.The effect of shading on MDA and metabolites was greater than that of gender.(5)Photosynthetic pigment:Shading had a significant effect on the pigment content of Humulus scandens(P<0.05),but there was no significant difference in the content of pigment in sex(P>0.05).Chla,Chlb and Chla+b increased firstly and then decreased with the increase of shading degree,and the maximum value is obtained in moderate shade.The order of influence of shading on the pigment content of Humulus scandens was as follows: Chla+b>Chlb>Chla>Chla/b.(6)Reproductive traits:Shading had different effects on the morphology of Humulus scandens flowers.Shading had significant effects on the width of ovary,the number of small flowers,the diameter of inflorescence,the number of inflorescence layers,the length of flower handle,and the length of flower axial(P<0.05).The width of ovary increased with the increase of shading degree.With the increase of shading degree,the number of florets increased firstly and then decreased,and the light shade increased by 12% compared with the no shade.The diameter of inflorescence decreased gradually with the increase of shading degree,and that of severe shading was significantly smaller than that of no shade by 50%,and the decrease between mild shade and severe shade was the largest.The number of inflorescence layers decreased significantly by 26% in severe shade than in light shade.With the increase of shading degree,the length of flower handle first became longer and then became shorter,and the shortest was obtained in the middle shade.The order of effect of shade on flower morphology were as follows: floret number>pollen size>ovary width>cluster axial length>pollen activity>cluster handle length>inflorescence diameter>inflorescence layer number>anther length.Shading had a significant effect on the total biomass(P<0.05).With the increase of shading degree,the total biomass of Humulus scandens increased firstly and then decreased.Shading had a significant effect on reproductive distribution(P<0.05).When shading degree increased,reproductive allocation first decreased and then increased,and reached the maximum at no shade.The breeding index decreased firstly and then increased with the increase of shading degree,and reached the minimum value in moderate shade.In summary,Humulus scandens is highly adaptive to light and still performs normal metabolic activities in moderate shade.It has good morphological plasticity and physiological stress,and is a herb with certain resistance to negative and resistance.Humulus scandens has an extremely strong self-regulation ability and growth adaptability,which can increase the development potential and utilization value in landscape greening,ecological restoration,soil conservation and slope protection. |
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