'''Black Leaf''' is a physiological disease that affects some grape varities such as [[Concord grape|Concord]]. It is essentially a [[potassium]] deficiency that causes the leaves on a vine to turn purple and eventually black as [[chlorophyll]] is lost. For wine growers this lack of chlorophyll inhibits the vines ability to transmit sugar to the grape, leaving the resulting grapes with a low [[brix]] count that may be less then ideal for wine making. <ref> R. Irvine & W. Clore ''The Wine Project'' pg 31 Sketch Publications 1997 ISBN 0-9650834-9-7 </ref>

== References ==

<references/>

== External Links ==

* [http://www.ajevonline.org/cgi/content/abstract/49/4/367 Photosynthesis and Chlorophyll Fluorescence in Blackleaf-Affected Concord Leaves] - American Society for Enology and Viticulture

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