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| Authors: | F.J. Peryea, R. Kammereck |
Abstract:
The severity of leaf chlorosis in iron-deficient fruit trees is often characterized using a semi-quantitative visual rating index that is subject to evaluator bias.
Analytical instruments are now available that provide a quantitative measure of leaf green color that could substitute for visual ratings.
We injected limbs of mature chlorotic pear trees (Pyrus communis cv.
Bartlett) with distilled water or a solution of 0.5% Fe (w/v) as FeSO47H2O on 17 July 1995. Treatments were replicated eight-fold.
On 18 August 1995, a Minolta SPAD-502 chlorophyll meter was used to measure the green color of 30 randomly sampled leaves located above the point of injection on each injected limb.
Average leaf green color was higher in the Fe-injected tree than in the water-injected tree of each experimental block (P=0.0003). Mean leaf green color (meanSD) averaged 34.73.8 SPAD units for the Fe-injected trees and 27.33.8 SPAD units for the water-injected trees.
The absolute increase in mean leaf color of 7.4 SPAD units was equivalent to a relative increase of 27 percent.
This result suggests a SPAD meter can provide an unbiased quantitative measure of the severity of leaf chlorosis associated by Fe deficiency, and confirms that mid-summer trunk injection of Fe can partially ameliorate Fe-chlorosi symptoms.
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