Effects Of Shade And Fertilization On Cold-resistance And Photosynthesis And Fluorescence Of Camellia Oleifera Seedling Leaves

The Camellia oleifera Abel.is one kind of typical arboreal oil tree plant in china with high comprehensive utilization value.The study object is the Camellia oleifera seedlings growing in Shucheng county located in Dabie Mountains of West Anhui,with different shading time and different fertilization quantity of processing.Based on the difference of the semi-lethal temperature in different time?including January,February,November and December?,the effects of shading time and fertilizer amount on cold resistance of Camellia oleifera seedling leaves are studied in this paper.The photosynthetic characteristics and chlorophyll fluorescence parameters of Camellia seedlings were measured and compared in different seasons with different fertilizer rate,and the fertilization effect on Camellia seedlings characteristics of Photosynthetics and fluorescence has been analyzed.The results were as follows:The shading time has a significant effect on the semi-lethal temperature of Camellia oleifera seedling leaves in November and December of the same year,but not for January and February of the next year.Regression simulation reveals that the relationship between the semi-lethal temperature?y?and shading time?x?follows the mathematical correlation of y=ax²-bx-c?R²= 0.8987*⁰.9116*?.Such equation suggests that with shading time increasing,the semi-lethal temperature drops in the first stage and then starts to grow,indicating that excessive shading time will reduce the cold resistance of Camellia oleifera seedling leaves.Fertilization obviously affects the semi-lethal temperature of Camellia oleifera seedling leaves in above four months.Regression analysis demonstrates that,for all time mentioned above,the relationship between semi-lethal temperature?y?and fertilizer amount?x?fits the model of y=k/?1+aexp?-?bx+cx²+dx3????R²=0.9929*⁰.9994*?,which means that the semi-lethal temperature will gradually decrease to a plateau?instead of infinitely low?with fertilizer amount increasing.Fertilization have different degree effect on Photosynthesis of Camellia seedlings.When the fertilizing amount is changed from 0 g / per-plant to 19 g / per-plant,the net photosynthetic rate is increasing with increasing fertilization.However,the net photosynthetic rate shows a downward trend with further increasing fertilizing amount.In this study,net photosynthetic rate,stomatal conductance,and water use efficiency of treatment 5 have the maximum daily mean value which are 9.907?mol.m^-2.s^-,0.0968 mol.m^-2.s^-,9.68,respectively,being 1.16,1.83,1.28 times of the control group's.In the treatment 5,intercellular CO2 concentration is minimal for 315.525?mol.m^-2.s^-,which is 0.85 times that of the control.And the regression simulation shows that fertilizing amount about 16.3g/per-plant is optimum value,which means that net photosynthesis of Camellia seedlings has the maximum daily mean value in this condition.So,the right fertilizing amount could promote the photosynthetic reaction of Camellia seedlings.The test found that,with different fertilization processing in summer and winter,Camellia seedlings' Fv/Fm and N_P,Q diurnal variation were respectively single-valley and a single-peak shape.In the summer,Fv/Fm minimum and N_P,Q maximum value both appear in 12:00-14:00;in the winter,the corresponding values appear in the morning and evening.This trend shows that,under different fertilization levels in summer and winter,PSIIreaction center liveness of Camellia seedlings leaves are subject to a certain degree of inhibition in 12:00-14:00,and in the morning and evening.while this inhibition is reversible.And by fertilizing treatment,fluorescence parameters shows a significant difference,which are Fv/Fm's daily mean value increasing from 0.55 to 0.71 in the summer?an increase of 1.3 times?and daily average increasing from 0.67 to 0.77 in the winter?an increase of 1.15 times?;furthermore,N_P,Q day mean decline from 1.65 to 0.85 in the summer?down 48.5%?,and day average also decrease from 1.28 to 0.71?down 44.5%?.In conclusion,Camellia oleifera seedlings in the test area can improve photosynthetic efficiency and resistance to hostile environmentby taking fertilization measure.