Light Response Characteristics Under Soil Water Stress In Leaves Of Lonicera Japonica And Ziziphus Jujuba Var.spinosus.

In recent years,the change of precipitation pattern make frequent extreme drought,soil water deficit estricts the vegetation recovery and reconstruction more frequently.Yimeng mountain area is a typical representative of the northern mountainous region soil area,Lonicera japonica and Ziziphus jujuba var.spinosus.are widely distributed in the area of water-saving forestation and medicinal economic shrubs.Under the background of climate change,soil extreme drought probability showed a trend of increase,seriously restrain the growth and development and production of flos lonicerae.Therefore,on the basis of predecessors’ research work,we choose 3 year old honeysuckle and Ziziphus jujuba var.spinosus.as the experimental materials,forestry experiment stations in Shandong Agricultural University in the greenhouses in pot experiment and soil moisture control survey,as well as the photosynthesis,chlorophyll fluorescence measurements.To obtain the soil saturated water content to plant net photosynthetic rate to zero within the scope of the multistage soil moisture gradient,illuminates the response to soil moisture change regularity of every index.Define the two plants photosynthetic efficiency significantly reduce the scope of extreme drought water.This paper is to build support for science to extreme drought under the background of Yimeng mountain area honeysuckle productivity loss reduction and efficient water management system of adaptation measures.(1)The light response curves of Lonicera japonica and Zizyphus jujuba show the similar rule with the increase of light intensity: rise rapidly before slowly rising to a stability maximum value.Within the scope of the saturated water content to the lowest water content,photosynthetic parameters of the threshold response to soil moisture showed obvious regularity,namely with the loss of the RWC,the parameters were reduced after first rise to the maximum,Pn of Lonicera japonica reached the highest when RWC was 79.59%,and Zizyphus jujuba reached maximum when RWC was 65.06%;WUE of honeysuckle reached the peak levels when RWC was 79.59% and zizyphus jujube was 86.51%.By analysing the various parameters on the response regularity of soil moisture,RWC=29.71% and RWC=38.53% for Lonicera japonica stomatal mechanism turning point(RWCSL-NSL).(2)Compared to Lonicera japonica and Ziziphus jujuba,the Lonicera japonica’s Pnmax was 18.3μmol·m-2·s-1,but the Ziziphus jujuba’s Pnmax was 17.19μmol·m-2·s-1 under the suitable water condition,Lonicera japonica has the higher photosynthetic capacity.But Ziziphus jujuba could maintain a higher level of photosynthetic rate in a large scale of light and haven’t obvious phenomenon of photoinhibition,It could maintain the wider light of higher Pn relative to Lonicera japonica and better to adapt the highlighty.Lonicera japonica and Ziziphus jujuba’s Φ were highest when Pn reached maximum water points,and Ziziphus jujuba’s Φ was higher than the Lonicera japonica under various water points,showed a greater ability to capture under the weak light of light quantum.Lonicera japonica and Ziziphus jujuba’s LUE of leaves showed single-peak curve responsed to light intensity of the process,the LUE of two tree species showed obvious threshold response under different soil moisture,Lonicera japonica and Ziziphus jujuba respectively reached the maximum in RWC was 79.59%,65.06% and Lonicera japonica’s LUE was always higher than Ziziphus jujuba and it’s light utilization status was also better.(3)Moderate water stress is helpful to improve the PSⅡ reaction center of electron transfer and conversion efficiency Lonicera japonica and Zizyphus jujuba,thus to improve plant photosynthetic capacity,excessive soil moisture has certain help to eliminate the photoinhibition,but will affect the plant the photochemical efficiency of PSⅡ and electron transfer activity,etc.,which is harmful for the improvement of plant photosynthetic productivity.With the decrease of soil moisture,Fo of Lonicera japonica and Zizyphus jujuba increases gradually,Fm,Fv/Fm,ΦPSⅡ and qP decreased,PSⅡ reaction center occured reversible inactivation and serious phenomenon of photoinhibition.And at the beginning of the drought,by the heat dissipation energy consume gradually increasing,Lonicera japonica and Zizyphus jujuba can effectively avoid the damage of photosynthetic mechanism excess light energy,the increase of NPQ is a kind of passive adaptation of plants to adversity photoinhibition.It reduces the photochemical efficiency,but can make the two tree species reduce the photosynthetic productivity caused by light inhibition of greater losses when subjected to drought stress from light damage.(4)According to the Lonicera japonica and Ziziphus jujuba’s Pn,Tr and WUE critical value of the effectiveness of the lowest and highest soil moisture,which could divided soil moisture into different threshold range,and we proposed the grading standards of soil water availability and productivity of Lonicera japonica and Ziziphus jujuba.Lonicera japonica soil moisture classification: when RWC<11.44%,"no production of inefficient water";RWC between 29.10%~36.40%,"low production and high efficiency water";RWC between 36.4% and 79.59% "High yield and high efficiency water";when RWC>79.59%,for the "high yield and low efficiency water".The Ziziphus jujuba soil moisture classification: when RWC<11.32%,"no production of inefficient water";when the RWC was between 38.53% and 41.05%,"low production and high efficiency water";When RWC was between 41.05% and 65.06%,"High yield and high efficiency water";when RWC>65.06%,"high yield and low efficiency water".In summary,Lonicera japonica and Ziziphus jujuba are adaptable to arid environments when they are exposed to drought,the amount of light consumed by heat dissipation increases gradually,which can effectively avoid the damage of photosynthetic mechanism under drought stress from light damage,reduce light suppression caused by the greater loss of photosynthetic productivity.But the two kinds of species have different drought resistance,Lonicera japonica can achieve higher net photosynthetic rate under the appropriate water,and its light energy use efficiency is higher,and Ziziphus jujuba high ability to adapt to high light intensity,in a wide light intensity within the range to maintain a stable net photosynthetic rate,and weak light has a strong ability to use.According to the different drought resistance of the two tree species,the relative water content of the soil should be between 36.4 ~ 79.59% and 41.05 ~ 65.06% in the actual production and water management,so that the Lonicera japonica and Ziziphus jujuba can reach the higher productivity level.