Plant Light Competition Research Between Different Species Underdensity Constraint Conditions

Light is one of the most basic resources required by plant growth and reproduction.At the same time,light resources are often an important factor limiting plant growth and development,thus affecting the stability of population,community and even the whole ecosystem.The difference of local light competition enviroiment leads to a stronger negative feedback effect between the input of individuals to traits and the consumption of photo synthetic products in plant population.The essence of plant population density dependence effect is actually the competition effect of different individuals in plant population on similar resources.And studies have shown that light competition drives biodiversity loss.However,at the level of individual and population,the plant population density is high,the size of individuals within the population is not uniform,asymmetric light resource competition is not conducive to small individuals to obtain the same proportion of light resources,often in the state of light deficit,which leads to the small individual due to the accelerated reduction of leaf light resource interception and death.At the community level,when plants compete for light resources,shrubs and herbaceous shaded leaves under the canopy often improve the utilization efficiency and competitiveness of light resources by reducing the compensation point of light and extending the life of the leaves.Therefore,whether the strategies for individual plants competing for light resources vary due to canopy position,growth cycle and the presence of different species at different population densities,these relationships are still unclear.G enerally,this study selected two photosynthetic types crop,Zea mays L and Linum usitaiissimum Linn,and set up plant light competition control experiments with different planting densities to elminate weeded samples.For the control group,the artificial weeding treatment group was designed to track the plant height,aboveground biomass,photosynthctic characteristics,light response curve and leaf life traits from the emergence stage to the maturity stage,and the appropriate analysis of leaf light suitable for different canopy heights.The results showed that:(1)Between the herbicidal treatment group and the control group,the individual horizontal traits such as aboveground biomass of maize were significantly higher than the individual differences in the same treatment sample(F is much greater than 1,P<0.01),and the individual level of aboveground biomass of flax.The trait difference was significantly higher than the individual difference in the same treatment sample(F is much larger than 1,p<0.01);the difference in horizontal traits of maize between different densities is greater than the individual difference in the same density(F=12.863,p<0.01),different density The difference in horizontal traits between flax individuals was greater than the individual differences in the same density(F=19.492,p<0.01).As the plant growth cycle progressed,the horizontal traits of maize and flax plants increased,and there were significant differences between different growth cycles(Tukey-HSD test,p<0.01).(2)Compared with the herbicide treatment,the variation of individual characters in the plant population without herbicide treatment was greater,and the population density could explain that the variation of plant characters was less than that of the herbicide treatment,and the interspecific light competition had a stronger effect on plant characters.(3)The' plant population density is high,the photosynthetic adaptability of canopy leaves is reduced,and the rate of reduction of the grass sample removal is faster.(4)The changes of maximum net photosynthetic rate and dark respiration rate are actually different between different canopy.(5)Under the canopy,photoinhibition and photosynthetic adaptation were more likely to occur in plants with different species.Compared with the net photosynthetic rate of leaves,leaf life of individual plants is more affected by density than by weeds in the field,the purpose of this study is to provide a new perspective for revealing the mechanism of interspecific interactions in plant species by constructing strategies for competition,utilization and adaptation of light resources in the same plant population and among different species.Moreover,it will provide important theoretical basis for constructing the optimal population density and community structure.