Functional Plant Biology ( IF 3 ) Pub Date : 2021-01-11 , DOI: 10.1071/fp20298 Miroslava Rakocevic , Eunice R. Batista , Ricardo A. A. Pazianotto , Maria B. S. Scholz , Guilherme A. R. Souza , Eliemar Campostrini , José C. Ramalho
Leaves in different positions respond differently to dynamic fluctuations in light availability, temperature and to multiple environmental stresses. The current hypothesis states that elevated atmospheric CO2 (e[CO2]) can compensate for the negative effects of water scarcity regarding leaf gas exchanges and coffee bean quality traits over the canopy vertical profile, in interactions with light and temperature microclimate during the two final stages of berry development. Responses of Coffea arabica L. were observed in the 5th year of a free air CO2 enrichment experiment (FACE) under water-limited rainfed conditions. The light dependent leaf photosynthesis curves (A/PAR) were modelled for leaves sampled from vertical profile divided into four 50-cm thick layers. e[CO2] significantly increased gross photosynthesis (AmaxGross), the apparent quantum yield efficiency, light compensation point, light saturation point (LSP) and dark respiration rate (Rd). As a specific stage response, considering berry ripening, all parameters calculated from A/PAR were insensitive to leaf position over the vertical profile. Lack of a progressive increase in AmaxGross and LSP was observed over the whole canopy profile in both stages, especially in the two lowest layers, indicating leaf plasticity to light. Negative correlation of Rd to leaf temperature (TL) was observed under e[CO2] in both stages. Under e[CO2], stomatal conductance was also negatively correlated with TL, reducing leaf transpiration and Rd even with increasing TL. This indicated coffee leaf acclimation to elevated temperatures under e[CO2] and water restriction. The e[CO2] attenuation occurred under water restriction, especially in A and water use efficiency, in both stages, with the exception of the lowest two layers. Under e[CO2], coffee produced berries in moderate- and high light level layers, with homogeneous distribution among them, contrasted to the heterogeneous distribution under actual CO2. e[CO2] led to increased caffeine content in the highest layer, with reduction of chlorogenic acid and lipids under moderate light and to raised levels of sugar in the shaded low layer. The ability of coffee to respond to e[CO2] under limited soil water was expressed through the integrated individual leaf capacities to use the available light and water, resulting in final plant investments in new reproductive structures in moderate and high light level layers.
中文翻译:
CO 2浓度升高下阿拉伯咖啡全冠垂直剖面叶片气体交换和咖啡豆质量波动
在不同位置的叶片对光利用率,温度和多种环境胁迫下的动态波动的反应不同。当前的假设表明,大气CO 2(e [CO 2 ])的升高可以补偿水稀缺对冠层垂直剖面上的叶片气体交换和咖啡豆品质性状的负面影响,这与二者在光照和温度的小气候之间的相互作用有关浆果发育的最后阶段。在限水雨水条件下的自由空气CO 2富集实验(FACE)的第5年中观察到了阿拉伯咖啡的反应。光依赖叶片的光合作用曲线(A/ PAR)建模为从垂直剖面采样的叶子分为四个50厘米厚的层。e [CO 2 ]显着提高了总光合作用(A maxGross),表观量子产率效率,光补偿点,光饱和点(LSP)和暗呼吸速率(R d)。作为一个特定的阶段响应,考虑到浆果成熟,根据A / PAR计算的所有参数对垂直剖面上的叶片位置不敏感。在两个阶段,尤其是在最低的两个层中,在整个冠层轮廓上均未观察到A maxGross和LSP的逐步增加,表明叶片对光的可塑性。R的负相关在两个阶段均在e [CO 2 ]下观察到d到叶片温度(TL)。在e [CO 2 ]下,气孔导度也与T L呈负相关,即使增加T L也会降低叶片的蒸腾作用和R d。这表明在e [CO 2 ]和水限制下,咖啡豆适应了高温。除最低的两层外,e [CO 2 ]衰减均在水分限制下发生,特别是在A和水分利用效率两个阶段。在e [CO 2下],咖啡生产的浆果具有中等和较高的光度层,它们之间的分布均匀,与实际CO 2下的不均匀分布形成对比。e [CO 2 ]导致最高层的咖啡因含量增加,在中等光照下绿原酸和脂质减少,而阴影下的低层糖含量升高。咖啡在有限的土壤水分条件下对e [CO 2 ]的响应能力是通过综合的单个叶片利用可用的光和水的能力来表达的,从而使最终的工厂投资于中等和高光照水平的新生殖结构。