Abstract The frequency and severity of droughts and heat stresses are becoming a threat to crop production and food security in arid and semi-arid regions worldwide. To ameliorate both stresses simultaneously, micro-sprinkler systems are being proposed and their performance is investigated here for gray jujube trees planted in an arid region. The experiments focused on the effects of different levels of micro-sprinkler irrigation amounts on air temperature, relative humidity, vapor pressure deficit, leaf-level physiological processes, yield, and quality of the fruit. The experiment was carried out over a two-year period in a jujube orchard consisting of three micro-sprinkler irrigation levels that spray water at 2 mm d-1 (T1), 4 mm d-1 (T2), 6 mm d-1 (T3) and the control at the flowering to fruit set stage. Within the canopy volume, the application of micro-sprinkler cooling system was shown to decrease air temperature by 1 to 3 ℃ and enhance air relative humidity by 11 - 17% when compared with the control. The associated decrease in air temperature and increases in air relative humidity reduced the vapor pressure deficit (VPD) from 3 kPa to 2 kPa. The measured VPD reduction across treatments explained much of the measured differences in physiological responses (net photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency) at the leaf scale. The aforementioned physiological improvements increased the quantity and quality of the jujube fruit. The study adds to the growing literature that supports the use of micro-sprinklers as a cooling system to ameliorate the negative effects of droughts and heat under extreme heat stress conditions.

中文翻译：

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微气候和作物对微喷灌的响应

摘要 干旱和热应激的频率和严重程度正成为全球干旱和半干旱地区作物生产和粮食安全的威胁。为了同时改善这两种压力，人们提出了微喷水系统，并在此研究了它们在干旱地区种植的灰枣树的性能。试验重点研究了不同水平的微喷灌量对气温、相对湿度、水汽压差、叶片水平生理过程、产量和果实品质的影响。该实验在一个枣园进行了为期两年的时间，由三个微喷灌水平组成，喷水 2 mm d-1 (T1)、4 mm d-1 (T2)、6 mm d-1 (T3)和开花到坐果期的对照。在树冠体积内，与对照相比，微喷淋冷却系统的应用表明，空气温度降低了 1 至 3 ℃，空气相对湿度提高了 11 - 17%。空气温度的相关降低和空气相对湿度的增加将蒸汽压差 (VPD) 从 3 kPa 降低到 2 kPa。处理间测量的 VPD 减少解释了叶片尺度上生理反应（净光合速率、蒸腾速率、气孔导度和水分利用效率）的大部分测量差异。上述生理改善提高了枣果实的数量和质量。该研究补充了越来越多的文献，这些文献支持使用微型喷头作为冷却系统，以减轻极端热应激条件下干旱和高温的负面影响。