Northern Rio de Janeiro State University - UENF, Plant Physiology Lab, Av. Alberto Lamego 2000, 28013-602 Campos dos Goytacazes-RJ, Brazil; and Embrapa Meio Ambiente, Rodovia SP 340 km 127.5, 13820-000 Jaguariúna-SP, Brazil; and Corresponding author. Email:
Embrapa Meio Ambiente, Rodovia SP 340 km 127.5, 13820-000 Jaguariúna-SP, Brazil.
Funct Plant Biol. 2021 Apr;48(5):469-482. doi: 10.1071/FP20298.
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.
叶片在不同位置对光照可用性、温度和多种环境胁迫的动态波动的响应不同。目前的假说认为，大气中 CO2 浓度升高（e[CO2]）可以在树冠垂直剖面内补偿水分胁迫对叶片气体交换和咖啡豆质量特性的负面影响，与光和温度微气候相互作用在浆果发育的最后两个阶段。在水分限制的雨养条件下，进行了 5 年的自由空气 CO2 富集实验（FACE），观察到了阿拉伯咖啡（Coffea arabica L.）的响应。为了从垂直剖面中分为四层 50 厘米厚的层中采样的叶片，对依赖于光的叶片光合作用曲线（A/PAR）进行了建模。e[CO2]显著增加了总光合作用（AmaxGross）、表观量子产率效率、光补偿点、光饱和点（LSP）和暗呼吸速率（Rd）。作为特定阶段的响应，考虑到浆果成熟，从 A/PAR 计算出的所有参数在垂直剖面中的叶片位置均不敏感。在两个阶段，整个树冠剖面都没有观察到 AmaxGross 和 LSP 的逐渐增加，特别是在最低的两层，这表明叶片对光具有可塑性。在两个阶段，e[CO2]下观察到 Rd 与叶片温度（TL）呈负相关。在 e[CO2]下，气孔导度也与 TL 呈负相关，即使 TL 升高，也会减少叶片蒸腾和 Rd。这表明在 e[CO2]和水分限制下，咖啡叶片对高温的适应。在两个阶段，e[CO2]的衰减都发生在水分限制下，除了最低的两层，特别是在 A 和水利用效率方面。在 e[CO2]下，咖啡在中光和高光层中产生浆果，均匀分布在其中，与实际 CO2 下的不均匀分布形成对比。e[CO2]导致最高层的咖啡因含量增加，中光下的绿原酸和脂质减少，低光层中的糖水平升高。在有限的土壤水分下，咖啡对 e[CO2]的响应能力表现为单个叶片利用可用光和水的综合能力，从而导致新的繁殖结构在中光和高光层中的最终植物投资。
