Articles
Ecophysiology, early season productivity, and water relations of Gala apple trees under netting and evaporative cooling
Article number
1468_25
Pages
191 – 198
Language
English
Abstract
Apple production in the Goulburn Valley, Australia, is increasingly challenged by concurrent heat and radiation stress.
Protective netting is often deployed to mitigate these conditions.
However, the ecophysiological and productivity responses of young orchards remain poorly characterized.
This study evaluated the effects of low-shade (<25%) black and gray netting (permanent and temporary deployment) and overhead evaporative cooling (intermittently activated at air temperature >32°C) on microclimate modification, tree physiology, vegetative growth, and early-season productivity of young ‘Bigbucks’ Gala apple trees during the 2025-26 season.
Grey and black netting reduced peak solar radiation by 16 and 19%, respectively, with negligible effects on air temperature, except for a slight reduction (~0.7°C) under black netting during extreme conditions (>42°C). No effects of netting on vapor pressure deficit (VPD) were observed.
During extreme heatwaves (i.e., maximum air temperature ~43°C and maximum VPD ~6-8 kPa), trees under black permanent netting maintained higher stomatal conductance (0.20-0.22 mol m‑2 s‑1) than the unnetted control (0.12-0.14 mol m‑2 s‑1), while evaporative cooling most effectively preserved midday stem water potential (-1.5 MPa) compared to control trees (-1.8 MPa). Effective quantum yield of PSII was largely unaffected by treatments.
Permanent netting significantly increased trunk cross-sectional area (p<0.05), whereas flower cluster and fruitlet numbers were not influenced.
Low-shade black permanent netting improved physiological resilience and vegetative vigour under extreme summer conditions, and evaporative cooling effectively mitigated acute water stress, offering practical adaptation strategies for heat-sensitive apple production systems.
Protective netting is often deployed to mitigate these conditions.
However, the ecophysiological and productivity responses of young orchards remain poorly characterized.
This study evaluated the effects of low-shade (<25%) black and gray netting (permanent and temporary deployment) and overhead evaporative cooling (intermittently activated at air temperature >32°C) on microclimate modification, tree physiology, vegetative growth, and early-season productivity of young ‘Bigbucks’ Gala apple trees during the 2025-26 season.
Grey and black netting reduced peak solar radiation by 16 and 19%, respectively, with negligible effects on air temperature, except for a slight reduction (~0.7°C) under black netting during extreme conditions (>42°C). No effects of netting on vapor pressure deficit (VPD) were observed.
During extreme heatwaves (i.e., maximum air temperature ~43°C and maximum VPD ~6-8 kPa), trees under black permanent netting maintained higher stomatal conductance (0.20-0.22 mol m‑2 s‑1) than the unnetted control (0.12-0.14 mol m‑2 s‑1), while evaporative cooling most effectively preserved midday stem water potential (-1.5 MPa) compared to control trees (-1.8 MPa). Effective quantum yield of PSII was largely unaffected by treatments.
Permanent netting significantly increased trunk cross-sectional area (p<0.05), whereas flower cluster and fruitlet numbers were not influenced.
Low-shade black permanent netting improved physiological resilience and vegetative vigour under extreme summer conditions, and evaporative cooling effectively mitigated acute water stress, offering practical adaptation strategies for heat-sensitive apple production systems.
Authors
E.G. Bekele, M. Peavey, N.D. Swarts, A. Scalisi
Keywords
flower cluster, heat stress, microclimate, radiation stress, stem water potential, stomatal conductance
Groups involved
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