Abstract

The overall coordination between gas exchanges and plant hydraulics may be affected by soil water availability and source-to-sink relationships. Here we evaluated how branch growth and mortality, leaf gas exchange and metabolism are affected in coffee (Coffea arabica L.) trees by drought and fruiting. Field-grown plants were irrigated or not, and maintained with full or no fruit load. Under mild water deficit, irrigation per se did not significantly impact growth but markedly reduced branch mortality in fruiting trees, despite similar leaf assimilate pools and water status. Fruiting increased net photosynthetic rate in parallel with an enhanced stomatal conductance, particularly in irrigated plants. Mesophyll conductance and maximum RuBisCO carboxylation rate remained unchanged across treatments. The increased stomatal conductance in fruiting trees over nonfruiting ones was unrelated to internal CO₂ concentration, foliar abscisic acid (ABA) levels or differential ABA sensitivity. However, stomatal conductance was associated with higher stomatal density, lower stomatal sensitivity to vapor pressure deficit, and higher leaf hydraulic conductance and capacitance. Increased leaf transpiration rate in fruiting trees was supported by coordinated alterations in plant hydraulics, which explained the maintenance of plant water status. Finally, by preventing branch mortality, irrigation can mitigate biennial production fluctuations and improve the sustainability of coffee plantations.

中文翻译：

---

灌溉和结果之间的相互作用对树枝的生长和死亡率，气体交换和咖啡树的水关系有影响。

摘要

气体交换和工厂水力之间的总体协调可能会受到土壤水的可利用性和源－汇关系的影响。在这里，我们评估如何分支生长和死亡，叶气体交换和代谢咖啡（受影响小粒咖啡L.）的干旱和果树。是否灌溉田间生长的植物，并保持满负荷或无负荷。在缺水的情况下，灌溉本身尽管叶片的同化池和水分状况相似，但对果树的生长没有显着影响，但显着降低了果树的树枝死亡率。结果增加净光合速率，同时增加气孔导度，尤其是在灌溉植物中。在所有处理中，叶肉电导和最大RuBisCO羧化率均保持不变。果树上的气孔导度高于非果树上的气孔导度与内部CO ₂无关浓度，叶面脱落酸（ABA）水平或ABA敏感性差异。然而，气孔导度与较高的气孔密度，较低的气孔对蒸气压亏缺的敏感性以及较高的叶片水力传导率和电容相关。植物水力学的协调变化支持果树叶片蒸腾速率的提高，这解释了维持植物水分状况的原因。最后，通过防止分支机构的死亡率，灌溉可以减轻两年一次的生产波动并提高咖啡种植园的可持续性。