Effect Of Shading Intensity On Morphology And Physiological Characteristics Of Phoebe Bournei Seedlings

In this paper,the current seedlings of Phoebe bournei seedlings in Jindong Forest Farm were used as experimental materials,with full light,30%,50%,70%,90%,a total of 5 shade treatments to study the morphological growth and photosynthesis of Phoebe bournei seedlings with different shade strength.The main research conclusions of the characteristics,physiological characteristics,leaf anatomical characteristics and cold environment physiology are as follows(1)The 30%,50%,and 70%shaded environment can promote the growth of seedling height,ground diameter and leaf area of the seedlings of Phoebe bournei and the increase in the number of leaves per plant,as well as the development of roots in the underground(total root length)Increase,the number of lateral roots increases),and at the same time promote the accumulation of fresh weight,90%shading will cause the above growth indicators to be suppressed;specific leaf area index increases with increasing shade intensity;height-diameter ratio gradually increases with increasing shade intensity Increased,in which 70%and 90%of the shading treatment group was significantly higher than the control,and the seedling growth quality was relatively poor;the stem-to-root ratio index showed that the CK,30%,50%,and 70%shading treatment group had a more stable rhizome biomass allocation.90%shading treatment group showed obvious imbalance.The comprehensive analysis results of growth morphological indicators showed that the ranking results of seedling growth status of each shade treatment group from good to poor were:50%shading>70%shading>30%shading>CK>90%shading(2)From the perspective of chlorophyll fluorescence parameters,compared with the control group,the remaining shade treatment groups have no significant difference in the YII,Fv/Fm and Fv/Fo index values;qP and qN indicators indicate that heavy shading environment will The photochemical activity and photoprotection ability of seedlings are significantly reduced;shading will affect the light response curve of Phoebe bournei seedlings.The relationship between the maximum net photosynthetic rate of different shade treatment groups is:CK>50%shading>30%shading>70%Shading;from the perspective of leaf gas exchange parameters,compared with the control group,there was no significant difference in stomatal conductance and intercellular carbon dioxide concentration among the other shading treatments,but the net photosynthetic rate and transpiration rate increased with the shading intensity Gradually decreases.(3)The effects of different shades on the physiological characteristics of Phoebe bournei seedlings are as follows:Compared with the control group,the content of soluble sugar and soluble protein changes less in the shade environment of 30%and 50%,while 70%and 90%changes significantly under shading;the MDA content index indicates that 50%and 30%shading can reduce the plasma membrane peroxidation in seedlings to a certain extent;the free proline content in seedlings after shading is significantly lower than in contrast,the osmotic adjustment effect of cells was less affected;during the increase of shading intensity,the contents of chlorophyll a,chlorophyll b,total chlorophyll,and carotenoid showed an upward trend while the ratio of chlorophyll a and chlorophyll b gradually decreased;Affecting the absorption of N,P,K elements by the leaves,compared with the control group,the 30%and 50%shading environments have a smaller impact,and the 70%and 90%shading environments have a larger impact(4)The anatomical parameters of the leaf cross section of Phoebe bournei seedlings showed that there was no significant difference in leaf midrib thickness between the treatment groups except the 50%shade treatment group;leaf thickness,fence layer thickness,sponge layer thickness and fence layer and The ratio of sponge layer showed a downward trend with the increase of shading;the stomatal density under 90%shading environment was significantly lower than that of other shading treatment groups.(5)Compared with the control group,the content of soluble sugar and free proline in seedlings increased first and then decreased with the increase of shading intensity after cold environment,and the content of malondialdehyde and relative conductivity increased with the shading intensity It showed the opposite change trend,and the soluble protein content had little difference among the shade treatment groups.The changes of physiological indexes in the cold environment of each shade treatment group showed that the seedlings of Phoebe bournei grown after moderate shade environment had increased cold resistance.