Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Av. Peter Henry Rolfs, s/n, Viçosa 36570-900, Brazil.
Laboratorio de Ecología Funcional y Ecosistemas Tropicales, Escuela de Ciencias Biológicas, Universidad Nacional Costa Rica, Avenida 1, Calle 9, Heredia 863000, Costa Rica.
Tree Physiol. 2021 Jan 9;41(1):35-49. doi: 10.1093/treephys/tpaa116.
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.
气体交换和植物水力之间的整体协调可能会受到土壤水分供应和源库关系的影响。在这里，我们评估了干旱和结实对咖啡（Coffea arabica L.）树的枝条生长和死亡率、叶片气体交换和代谢的影响。在田间生长的植物进行了灌溉或不灌溉，并保持了全果负荷或无果负荷。在轻度水分亏缺下，灌溉本身并没有显著影响生长，但在结实的树木中显著降低了枝条死亡率，尽管叶片同化物库和水分状况相似。结实增加了净光合速率，同时增强了气孔导度，特别是在灌溉植物中。无论处理方式如何，胞间导度和最大 RuBisCO 羧化速率均保持不变。结实树木的气孔导度高于非结实树木，与内部 CO2 浓度、叶片脱落酸（ABA）水平或 ABA 敏感性差异无关。然而，气孔导度与较高的气孔密度、较低的气孔对水汽压亏缺的敏感性以及较高的叶片水力传导率和电容有关。结实树木中较高的叶片蒸腾速率是由植物水力的协调变化来支撑的，这解释了植物水分状况的维持。最后，通过防止枝条死亡，灌溉可以减轻两年生生产波动，提高咖啡种植园的可持续性。
