Articles
‘SURROUND’ PARTICLE FILM APPLICATIONS – EFFECTS ON WHOLE CANOPY PHYSIOLOGY OF APPLE
Article number
636_72
Pages
565 – 571
Language
English
Abstract
A chemically inert, reflective kaolin-based particle film (Surround WP, Engelhard Corp., Iselin, N.J.) has been developed in recent years as a physical barrier to repel insects, prevent disease spread and reduce the incidence of fruit sunburn on apple trees. This paper evaluates the potential use of Surround on 5 year-old apple trees (Malus x domestica Borkh. cv. Braeburn on M.9 rootstock) to reduce fruit sunburn damage and to examine its effect on net carbon exchange (NCE) rates. It is hypothesised that the particle film applications reduce surface temperature by increased light reflection, thus maintaining high stomatal conductance under excessive ambient heat stress conditions. At the leaf level, carbon assimilation rates over a wide range of incident light levels and temperatures were significantly lower on Surround-treated trees than the control trees.
However, neither leaf transpiration nor leaf stomatal conductance was affected by the particle film. Chlorophyll fluorescence measurements indicated greater quenching ability and lower photochemical yield of the white-washed leaves, confirming the photosynthetic response.
Differences in leaf gas exchange were due to the Surround leaves absorbing 20 % less light compared to the control leaves.
Whole-canopy NCE, measured with an open-top cuvette system, was not affected by Surround applications despite cuvette temperatures of up to 40°C. The different CO2 exchange results between individual leaves and the whole-canopy were probably due to improved light distribution in the canopy due to enhanced leaf reflection.
The particle film significantly reduced the numbers of fruit with visible sunburn damage, possibly due to 20 % lower fruit skin temperatures and/or reduced irradiance when compared to the control trees.
The beneficial temperature reduction by the Surround cover and the ease of washing off the particles from the fruit, make it a promising treatment for alleviating excessive heat stress and sunburn in apple trees grown in warm and dry locations.
However, neither leaf transpiration nor leaf stomatal conductance was affected by the particle film. Chlorophyll fluorescence measurements indicated greater quenching ability and lower photochemical yield of the white-washed leaves, confirming the photosynthetic response.
Differences in leaf gas exchange were due to the Surround leaves absorbing 20 % less light compared to the control leaves.
Whole-canopy NCE, measured with an open-top cuvette system, was not affected by Surround applications despite cuvette temperatures of up to 40°C. The different CO2 exchange results between individual leaves and the whole-canopy were probably due to improved light distribution in the canopy due to enhanced leaf reflection.
The particle film significantly reduced the numbers of fruit with visible sunburn damage, possibly due to 20 % lower fruit skin temperatures and/or reduced irradiance when compared to the control trees.
The beneficial temperature reduction by the Surround cover and the ease of washing off the particles from the fruit, make it a promising treatment for alleviating excessive heat stress and sunburn in apple trees grown in warm and dry locations.
Authors
J.N. Wünsche, L. Lombardini, D.H. Greer
Keywords
Malus x domestica, photosynthesis, chlorophyll fluorescence, light properties of leaves, sunburn incidence
Online Articles (89)