Submitted to: Pear International Symposium
Publication Type: Abstract only
Publication Acceptance Date: 9/1/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A major problem in arid and semi-arid regions is the excessive heating of tree canopy and fruits. Fruit temperatures may reach very high levels resulting in sunburn damage. The worldwide tendency towards more dwarfing orchards having reduced vegetative vigor, exacerbates the situation by exposing more fruits to direct sunshine. Coating the tree with a chemically yinert, reflective kaolin particle film ('Surround', Englehard Corporation, NJ, USA) reduced excessive heat damage. Exposed fruits had surface temperatures reduced as much as 10 degrees C by the application of 'Surround' and sunburn damage was reduced in commercial orchards in Chile, California, and Washington. There was a 25% increase in PAR light reflection and scattering within the canopy that improved color on shaded parts of red apples. The IR, UV, and blue regions were reflected by 'Surround'. The increased reflection of IR lowered fruit and leaf temperatures consequently reducing stress imposed on the tree. Stomatal conductance was higher for a longer duration in the afternoons with 'Surround' application for single leaves, as well as for whole trees. Increased stomatal conductance resulted in increased net photosynthesis and yield. The net increase in photosynthesis was likely due to the large enhancing effect of reduced canopy temperature that overcame the reduced PAR reaching the chloroplasts by 'Surround'. Treated apple trees resisted water stress due to a slower loss of water by transpiration. The beneficial temperature by the kaolin cover, the enhancement of photosynthesis and yield, the environmental inert effect, and the ease of washing off the particles from the fruits, make it an interesting tool for alleviating ex- cessive heat stress in apple and pear trees grown in warm and dry climates.