山桃叶片光合生理参数对土壤水分的响应特征

Response Characteristics of Photosynthetic Physiological Parameters of Prunus davidiana leaf to Soil Moisture

为探明山桃幼苗叶片光合生理特性对土壤干旱胁迫的响应规律,明确干旱胁迫下山桃幼苗的光合作用特性,以期为山桃幼苗的水分栽植管理提供理论依据。本研究以3 a生山桃幼苗为研究对象,模拟设置土壤相对含水量(RWC)为90.49%~30.28%共5个水分梯度,采用便携式光合仪Li-6400,测定分析不同土壤水分条件下山桃叶片的光合光响应曲线,筛选适宜的光合光响应模型,探讨山桃叶片净光合速率(P_(n))、光合光响应参数、蒸腾速率(T_(r))和水分利用效率(WUE)对土壤水分的响应规律。土壤水分可显著影响山桃幼苗叶片的光合作用和蒸腾作用,直角双曲线修正模型可较好模拟不同土壤水分条件下山桃叶片光合光响应曲线。山桃叶片表观量子效率、最大净光合速率、光饱和点、光补偿点和暗呼吸速率随土壤水分的降低均呈现先升高后降低的趋势,在RWC为59.68%~74.26%时光照生态幅较宽,利用弱光能力较强。随土壤水分的降低,山桃叶片P_(n)和T_(r)呈现先升高后降低的变化趋势,分别在RWC为74.26%和59.68%下达最高值,而WUE表现为先降低后升高的趋势,在RWC为90.49%下达最高值。高水分条件下山桃叶片P_(n)、T_(r)和WUE显著高于低水分条件,适宜的水分条件可显著提升山桃叶片的光合能力。随干旱胁迫的加重,山桃叶片呈现T_(r)比P_(n)更加敏感的响应表现,呈现出干旱胁迫下以降低蒸腾作用提升水分高效利用的生理特性。

In order to explore the response of photosynthetic physiological characteristics of leaves of Prunus dawidiana seedlings to soil drought stress,and to clarify the photosynthetic characteristics of P.dawidiana seedlings under drought stress,so as to provide theoretical basis for water planting management of P.davidiana seedlings.In this study,three-year-old P.davidiana seedlings were used as the research object,and five water gradients with soil relative water content(RWC)of 90.49%-30.28%were simulated.The portable photosynthesis instrument Li-6400 was used to measure and analyze the photosynthetic light response curves of P.davidiana leaves under different soil moisture conditions,and the suitable photosynthetic light response model was screened to explore the response of net photosynthetic rate(P),photosynthetic light response parameters,transpiration rate(T_(r))and water use efficiency(WUE)of P.dawidiana leaves to soil moisture.Soil moisture could significantly affect the photosynthesis and transpiration of the leaves of P.dawidiana seedlings.The modified rectangular hyperbola model could better simulate the photosynthetic light response curve of P.davidiana leaves under different soil moisture conditions.The apparent quantum efficiency,maximum net photosynthetic rate,light saturation point,light compensation point and dark respiration rate of peach leaves increased first and then decreased with the decrease of soil moisture.When the RWC was 59.68%-74.26%,the light ecological range was wide and the ability to use weak light was strong.With the decrease of soil moisture,P_(n)and T_(r)of P.dawidiana leaves increased first and then decreased,and reached the highest values at RWC of 74.26%and 59.68%,respectively,while WUE decreased first and then increased,and reached the highest value at RWC of 90.49%.The P_(n),T_(r)and WUE of P.dawidiana leaves under high water conditions were significantly higher than those under low water conditions,and suitable water conditions could significantly improve the photosynthetic capacity of P.dawidiana leaves.With the aggravation of drought stress,the leaves of P.dawidiana showed more sensitive response to T_(r)than P_(n),showing the physiological characteristics of reducing transpiration and improving water use efficiency under drought stress.