INFLUENCE OF BORDEAUX MIXTURE AND ITS COMPONENT PARTS ON TRANSPIRATION AND APPARENT PHOTOSYNTHESIS OF APPLE LEAVES

Abstract

The influence of Bordeaux mixture and its component parts on the rate of photosynthesis and transpiration of Stayman Winesap apple leaves was measured in an environment-control chamber where temp., light, and humidity were controlled. Under the conditions of these expts. photosynthesis was reduced at least temporarily by applications of Bordeaux mixture regardless of the temp., light, humidity, or soil moisture conditions. The influence of Bordeaux mixture on the photosynthetic process is evidently primarily physiological rather than mechanical. The soluble Cu fraction within Bordeaux appears to be directly related to the retarding effect of this spray on photosynthesis. The temp. at which Bordeaux may be expected to instigate visible injury to apple foliage lies between 60[degree] and 70[degree] F. The transpiration rate of illuminated mature apple leaves appears to be uninfluenced or somewhat depressed by Bordeaux mixture and its component parts. The general effect of Bordeaux mixture applied to young apple trees growing under low soil moisture conditions was a slightly reduced rate of transpiration.