ISHS Acta Horticulturae 732: VIII International Symposium on Canopy, Rootstocks and Environmental Physiology in Orchard Systems
EFFECT OF HAIL ON PHOTOSYNTHESIS, CHLOROPHYLL FLUORESCENCE, STOMATAL CLOSURE AND EVAPOTRANSPIRATION OF APPLE LEAVES |
| Authors: | I. Tartachnyk, M.M. Blanke, M.B. Jackson |
| Keywords: | Malus domestica Borkh., apple, hail, photosynthesis, stomata, stress physiology, transpiration, water |
| Abstract:
The incidence of hail during the growing season in European fruit orchards is on the increase. Our objective has been to study the effects of hail damage on water loss, stomatal closure and photosynthesis of apple leaves and duration of recovery processes. Photosynthesis was examined by porometry and chlorophyll fluorescence by quenching analysis. Evapotranspiration from ruptured leaf tissue was assessed by both porometry and thermal emission photography. Stomatal apertures were studied using silicone imprints. Measurements of chlorophyll fluorescence showed a dramatic decrease in electron transport rate, confirming porometer readings showing a decline in CO2 assimilation at a time when photochemical quenching (qP) decreased by half. This sharp fall in photochemical quenching and electron transport was followed by a partial recovery within 5 minutes. 'Hail' damage increased water loss due to evaporation from torn edges. Thermal emission pictures identified temperature gradients in concentric rings around sites of 'hail' injury with a distinct drop in temperature of up to 2°C. This cooling indicated enhanced water loss from the injured tissue. Leaf stomata closed within 3 minutes of 'hail' and remained closed for 3 hours before partially re-opening. This temporary stomatal closure is interpreted as an adaptation mechanism that prevents excessive water loss from the leaves. | |
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