不同土壤水分下山杏光合作用光响应过程及其模拟

Light response of photosynthesisand its simulation in leaves of Prunus sibirica L.under different soil water conditions

利用CIRAS-2型便携式光合作用测定系统,在黄土高原丘陵沟壑区,测定了山杏(Prunus sibirical L.)在8个土壤水分梯度下光合作用的光响应过程,并采用直角双曲线模型、非直角双曲线模型和直角双曲线修正模型对其进行拟合分析。结果表明:土壤相对含水量(RSWC)在56.3%—80.9%范围内,山杏在强光下能维持较高的光合作用水平,受到的光抑制不明显。在此土壤水分范围内,3个模型均能较好地拟合光合作用的光响应过程及其表观量子效率(Φ)、光补偿点(LCP)和暗呼吸速率(Rd),对Φ、LCP和Rd的拟合精度以非直角双曲线模型>直角双曲线修正模型>直角双曲线模型。但超出此范围(即RSWC<56.3%或RSWC>80.9%)时,山杏的光合作用在强光下会发生明显的光抑制,表现为光合速率随光强增加而明显降低,量子效率和光饱和点明显减小,此时只有直角双曲线修正模型能较好地拟合山杏光响应过程及其特征参数。结论:山杏光合作用正常的土壤水分范围在RSWC为56.3%—80.9%之间;直角双曲线修正模型能较好地拟合各种土壤水分下山杏的光响应过程及其特征参数;直角和非直角双曲线模型适用于正常水分下山杏光响应过程及其特征参数的模拟,但不能用于拟合胁迫水分(或光抑制)下的光响应过程。

Water deficit is one of the major limiting factors in vegetation recovery and reconstruction in loess hilly gully region.Prunus sibirica L.is one of the common trees grown in this region.However,studies on characteristics of photosynthesis in leaves of Prunus sibirica L.under water stress are limited. The objective of this study is to explore the effect of different soil water content on photosynthesis in leaves of Prunus sibirica L.to characterize the relationship between photosynthesis of Prunus sibirica L.and soil water content and to explore the applicability of different photosynthetic models in simulating light response of photosynthesis in Prunus sibirica L.under different soil water conditions,which will help us to further understand the photo-physiological characteristics of Prunus sibirica L.under water stress.The results will also help guiding cultivation of Prunus sibirica L.in the loess hilly gully region. By using CIRAS-2 portable photosynthesis system,the light responses of photosynthesis in leaves of two-year-old Prunus sibirica L.were studied under 8 different soil water conditions.And the light response curves of photosynthesis were fitted and analyzed by rectangular hyperbola model,non-rectangular hyperbola model and a modified model based on rectangular hyperbola model. Higher photosynthesis and less obvious photo-inhibition were observed in leaves of Prunus sibirica L grown in the region where the relative soil water contents（RSWC） were from 56.3% to 80.9%.The light response of photosynthesis,the apparent quantum yield（Φ）,the light compensation point（LCP） and the dark respiration rate（Rd） were well fitted by the three models.Among the three models,the non-rectangular hyperbola model fitted the data best;the rectangular hyperbola model fitted the data worst.When the RSWC exceeded the optimal range（56.3%RSWC80.9%）,obvious photo-inhibition and significant decrease in photosynthesis were observed in leaves of Prunus sibirica L.under strong light,light saturation point and quantum yield of photosynthesis also decreased significantly.Under this circumstance,only the modified rectangular hyperbola model could well fit light response of photosynthesis and the main parameters. The optimal range of RSWC for normal photosynthesis in leaves of Prunus sibirica L was from 56.3% to 80.9%.The modified rectangular hyperbola model could well fit light response curves of photosynthesis and the main parameters under all the different soil water conditions.The rectangular hyperbola model and non-rectangular hyperbola model could only be used to fit light response curves of photosynthesis and the main parameters under the optimal soil water conditions.