The New Zealand Institute for Plant and Food Research Ltd, Hawke's Bay Research Centre, Havelock North, New Zealand.
School of Science, University of Waikato, Hamilton, New Zealand.
Ann Bot. 2024 May 13;133(7):969-982. doi: 10.1093/aob/mcae024.
Plant water status is important for fruit development, because many fleshy fruits contain large amounts of water. However, there is no information on vascular flows of Persea americana 'Hass' avocado. The aims of this research were to explore the impact of drought stress on the water relationships of the 'Hass' avocado plant and its fruit growth.
Well-watered and water-stressed 'Hass' avocado plants were compared. Over 4 weeks, water flows through the shoot and fruit pedicel were monitored using external sap flow gauges. Fruit diameter was monitored using linear transducers, and stomatal conductance (gs), photosynthesis (A) and leaf and stem water potentials (Ѱleaf and Ѱstem) were measured to assess the response of the plants to water supply.
In well-watered conditions, the average water inflow to the shoot was 72 g day-1. Fruit water inflow was 2.72 g day-1, but there was water loss of 0.37 g day-1 caused by the outflow (loss back into the tree) through the vascular tissues and 1.06 g day-1 from the fruit skin. Overall, fruit volume increased by 1.4 cm3 day-1. In contrast, water flow into fruit of water-stressed plants decreased to 1.88 g day-1, with the outflow increasing to 0.61 g day-1. As a result, increases in fruit volume were reduced to 0.4 cm3 day-1. The values of A, gs and sap flow to shoots were also reduced during drought conditions. Changes in the hourly time-courses of pedicel sap flow, fruit volume and stem water potential during drought suggest that the stomatal response prevented larger increases in outflow from the fruit. Following re-watering, a substantial recovery in growth rate was observed.
In summary, a reduction in growth of avocado fruit was observed with induced water deficit, but the isohydric stomatal behaviour of the leaves helped to minimize negative changes in water balance. Also, there was substantial recovery after re-watering, hence the short-term water stress did not decrease avocado fruit size. Negative impacts might appear if the drought treatment were prolonged.
植物水分状况对果实发育很重要，因为许多肉质果实含有大量水分。然而，关于鳄梨 Persea americana 'Hass' 的维管流尚无信息。本研究旨在探讨干旱胁迫对‘哈斯’鳄梨树及其果实生长的水分关系的影响。
比较了充分浇水和受水分胁迫的‘哈斯’鳄梨树。使用外部 sap 流量计监测了 4 周以上的茎和果实花梗的水流。使用线性传感器监测果实直径，并测量气孔导度（gs）、光合作用（A）和叶片和茎水势（Ѱleaf 和 Ѱstem），以评估植物对供水的响应。
在充分浇水的条件下，茎的平均水流入量为 72 g day-1。果实水流入量为 2.72 g day-1，但通过维管束组织流出（回流到树中）和从果实皮中流出 0.37 g day-1 和 1.06 g day-1，导致水分损失。总的来说，果实体积每天增加 1.4 cm3。相比之下，水分胁迫下进入果实的水流减少到 1.88 g day-1，流出量增加到 0.61 g day-1。因此，果实体积的增加减少到 0.4 cm3 day-1。干旱条件下，A、gs 和茎 sap 流到茎的数值也降低了。干旱期间花梗 sap 流、果实体积和茎水势的每小时时间进程的变化表明，气孔的反应阻止了果实中更大的流出量。重新浇水后，观察到生长速率的大幅恢复。
总之，在水分不足的情况下，鳄梨果实的生长减少，但叶片的等水气孔行为有助于将水分平衡的负面变化降到最低。此外，重新浇水后有大量恢复，因此短期水分胁迫不会减小鳄梨果实的大小。如果干旱处理延长，可能会出现负面影响。
