| At present,climbing plant,being used as vertical greening for landscaping,soil protection,ecological repair,bioremediation after mining,exists less variety,lower resistance and slower effect,ect.in the transitional climate zone.In this paper,Humulus scandens,widly distributed in domestic,was used as experimental materials.Firstly,soil agitation and shading had been set up in the wild population,including A-shallow tillage and shading,B-only shallow tillage,C-only shading and D-no tillage and no shading.Secondly,low temperature stress had been set up indoors.Some index,including germination rate and germination index of seed,physiological and biochemical characteristics of seedlings,etc were measured.Through self-thinning of population,the morphological plasticity,biomass allocation,competition mechanism,the relationship between density and biomass,the change of photosynthetic characteristics,the competitiveness of individual male or female plant,sex ratio of population,reproductive strategy were analyzed.The purpose was to study seed germination,seedling growth,self-thinning rule,and growth adaptability during the formation of H.scandens population,which would provide the basis for the popularization and application of H.scandens in environmental greening and ecological management.The results were as follows:(1)Shallow tillage and shading both had significant effects on germination index of seeds(P<0.01).Germination rate existed the largest difference between 12 days and 30 days.Shallow tillage promoted seed germination.Shallow tillage adding to shading treatment was more favorable to germination.And the order of germination index from high to low was A>B>D>C(i.e.shallow tillage and shading > only shallow tillage > no tillage and no shading > only shading).Low temperature had significant effects on physiological activity of leaf in different ages(P<0.01).SOD activity existed significant difference under the condition of different temperatures(P<0.01),and SOD activity of leaves at different age all decreased with the temperature decreasing.The effects of temperature on POD activity of seedling at different ages was larger.At low temperature,CAT activity of younger seedlings was lower than that of older seedlings.Under the condition of low temperature stress,the content of MDA,SS and Pro all were significantly increased(P<0.01).And the content of MDA at 1-and 2-leaf age both were higher than that of 3-,4-and 5-leaf age.(2)H.scandens population at the seedling stage existed significant self-thinning,in which population density decreased by 71%,in 60 days.When H.scandens changed from vertical growth to lateral growth,population density and plant height decreased significantly.Through self-thinning,stem traits of remaining plants existed a significant change,with the change order of internode length > main stem length > stem diameter,and internode length increased.The variation order of leaf traits was leaf area > petiole length > leaf thickness > leaf width > leaf length > total leaf number > remaining leaf number,and the order for root traits was total root length > root volume > root number > root length > maximal root length.After self-thinning,biomass of each component and biomass of individual plant both significantly increased,but the accumulated biomass per unit area was periodically dropped.Self-thinning had no significant effect on distribution rate of aboveground biomass(P>0.05),but highly significant effect on the ratio of leaf to stem and root to stem(P<0.01).A significant allometric relationship,among leaf biomass,root biomass and aboveground biomass,was found(P<0.01).Stem and aboveground biomass had the same growth trend,i.e.synchronous growth.But with the aboveground biomass increasing,leaf,petiole and root presented allometry growth.Aboveground biomass was significantly associated with leaf,stem,petiole and root biomass(P<0.01).The allometric relationship between stem biomass and density followed final yield constant rule.Biomass of leaf,petiole and root was not satisfied with anyone of-3/2 or-4/3 or-1 self-thinning rule.Total biomass of single plant and aboveground biomass were significantly correlated to density(P<0.01).For the remaining plants,the allometric relationship between aboveground biomass of single plant,total biomass and density followed final yield constant rule.(3)Self-thinning of seedlings had significant effect on Chla and Chl(a+b)(p< 0.05),but no significant effect on Chlb and Chl a/b.Through Self-thinning of seedlings,Pnof unit leaf area showed a downward trend.For the photosynthesis,T5 treatment was stronger than T3 and T4 treatments,and T6 treatment was stronger than T4 treatment.Self-thinning had significant effect on WUE and Ls of unit leaf area,no significant effect on Ci of unit leaf area,and no obvious regularity on Tr and Gs.When the density of H.scandens plant decreased from 43.33 strains/m2 to 17.33 strains/m2,the ratio of female to male gradually increased,in which there was a significant influence(P<0.01).The density of gender of mature seedlings both had highly significant on flower biomass and reproductive allocation,and existed highly significant interaction(P<0.01).The effect of density on flower biomass was greater than that of gender,but the effect of gender on reproductive distribution was higher than that of density.Population density and climbing height had no significant effect on seed weight of single inflorescence,and there was no significant interaction(P>0.05).Climbing height had no significant effects on seed number and 1000-grain seed weight of single inflorescence(P>0.05),but population density had highly significant effect on above two indicators(P<0.01),in which there was no significant interaction(P>0.05).Therefore,seed traits of H.scandens were not affected by the climbing height.In conclusion,the shallow tillage and shading were conducive to the germination of H.scandens seeds.Cold resistance of seedlings having 3-,4-and 5-leaf age were stronger than that only 1-and 2-leaf age.Through self thinning of seedlings,components continued to grow,and biomass gradually increased,but chlorophyll and photosynthetic rate per unit area decreased.The allometric relationship,including between stem biomass and density,between total biomass and density,etc.all followed final yield constant rule,.After self-thinning of mature seedlings,the number of female plant was far greater than that of male plant.The quality of seed was related to population density,but it was not affected by the climbing height.Therefore,H.scandens had the characteristic of strong self-adjustment ability and growth adaptability,which was preferred plant for vertical greening in the landscaping,soil protection,ecological repair,bioremediation after mining etc. |
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