Features Of Photosynthesis-light Response And CO₂ Response Of Poplar In Different Soil Phenolic Acid Concentrations

In the cultivation of populus plantation in China,multi-generation continuouscropping is a commonly used cultivation and management model.It has been shown that multiple generations of continuous cropping will have significant adverse effects on populus productivity,root growth and development and soil physical and chemical properties,which are closely related to the accumulation of phenolic acids in soil,while the effects of soil phenolic acids on populus physiological processes,especially photosynthetic physiology,still need to be further studied.Changes in photosynthesis light response and CO₂ response processes ofpopulus leaves were measured under six phenolic acid concentrations?0.5X,1.0X,1.5X,2.0X,2.5X,3.0X?and control?0X?treatments at the Forest Experimental Station of Shandong Agricultural University?36°25'N,117°58'S?,one-year-old plants from cuttage pots of Populus euramericana'Neva'were used as test materials using the second generation populus rhizosphere soil phenolic acid content X as a reference,and fitted and analyzed using the photosynthetic response model.Main objective:To explore the response characteristics of photosynthesis efficiency of populus seedlings to different concentrations of phenolic acid stress in soil;to analyze the fitting effect and applicability differences of different photosynthetic models on light response and CO₂ response.Main results and conclusions:?1?Effect of soil phenolic acid stress on photosynthesis efficiency of populus.The degree of inhibition of populus photosynthesis increased gradually with the increase of soil phenolic acid concentration.When the concentration of phenolic acid exceeded 2.0X,the inhibitory effect was significantly exacerbated,as shown by a significant decrease in photosynthetic efficiency parameters such as net photosynthetic rate?P_n?,maximum photosynthetic rate(P_nmax),photosynthetic quantum efficiency???and carboxylation efficiency?CE?,which produced significant photoinhibition under intense light.?2?The main reasons why soil phenolic acid stress limits populus photosynthesis.The main reasons for the decrease of photosynthesis in populus changed with the increase of soil phenolic acid concentration.At low concentrations??1.5X?,the main reason is the limitation of stomatal factors,and the CO₂ supply of photosynthetic institutions is blocked;at high concentrations?more than 1.5X?,the main reason is the limitation of changing from stomatal factors to non-stomatal factors,and the photosynthetic capacity of photosynthetic institutions decreases.?3?Different photosynthetic models were fitted to the differences in light response and CO₂ response.The right angle hyperbolic correction model can better fit the photosynthetic light response and CO₂ response process under different soil phenolic acid concentrations,as well as the photosynthetic characteristic parameters such as light intensity and CO₂ saturation?LSP and LCP?,P_nmax,?,CE;and its fitting effect is better than that of the right angle hyperbolic,non-right angle hyperbolic,and exponential equations.