Chlorosis
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2008-06-05T16:50:08Z
Tomas e
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/* Chlorosis in viticulture */ Variety -> cultivar, for this botanical article the botanically correct terminology rather than wine industry terminology seems appropriate
{{mergeto|Chlorophyll|date=February 2008}}
{{for|the form of anemia|Chlorosis (medicine)}}
[[Image:AlbinoPopcorn.jpg|thumb|right|300px|A popcorn plant with severe chlorosis (left) beside a normal plant (right).]]
In [[botany]], '''chlorosis''' is a condition in which leaves produce insufficient [[chlorophyll]]. As chlorophyll is responsible for the green colour of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to manufacture [[carbohydrate]]s through [[photosynthesis]] and may die unless the cause of its chlorophyll insufficiency is treated; some chlorotic plants, such as the albino ''Arabidopsis thaliana'' mutant ''ppi2'' are viable if supplied with exogenous sucrose<ref>[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=519198 Functional Specialization amongst the Arabidopsis Toc159 Family of Chloroplast Protein Import Receptors<!-- Bot generated title -->]</ref>. Specific [[nutrient]] deficiencies (often aggravated by high [[soil pH]]) produce chlorosis, which may be corrected by supplemental feedings of [[iron]], [[magnesium]] or [[nitrogen]] compounds in various combinations. Some [[pesticide]]s, particularly [[herbicide]]s, may also cause chlorosis, both to target [[weed]]s and occasionally to the [[Crop (agriculture)|crop]] being treated.
The reason [[Iron deficiency (plant disorder)|iron deficiency]] causes chlorosis is that iron is used in the [[active site]] of glutamyl-tRNA reductase, an enzyme needed for the formation of [[5-Aminolevulinic acid]] which is a [[Precursor (chemistry)|precursor]] of [[heme]] and [[chlorophyll]].<ref>A. Madan Kumar and Dieter Söll, Antisense ''HEMA1'' RNA Expression Inhibits Heme and Chlorophyll Biosynthesis in Arabidopsis, Plant Physiol, January 2000, Vol. 122, pp. 49-56 http://www.plantphysiol.org/cgi/content/full/122/1/49</ref>
==Chlorosis in viticulture==
[[Grape vine]]s are suscpetible to chlorosis just like many other plants, and the symptoms of iron deficiency tend to be common on soils rich in [[limestone]]. In the wake of [[The Great French Wine Blight]], when European ''[[Vitis vinifera]]'' were affected by ''[[Phylloxera]]'', chlorosis became a more problematic phenomenon in [[viticulture]]. To solve the Phylloxera problem, ''V. vinfiera'' was grafted onto [[rootstock]] based on American species of the ''[[Vitis]]'' genus, such as ''[[Vitis riparia]]'', ''[[Vitis rupestris]]'', ''[[Vitis berlandieri]]''. However, many of these were less adapted to the lime-rich soils that was common in many of [[French wine|France's vineyards]], in particular many of those that produced wines of top quality. Many grafted vines in lime-rich vineyards therefore showed signs of iron deficiency, and this specific form of chlorosis was termed ''chlorose calcaire'' in France. The problem was largely overcome by the selection of lime-resistant American vines as basis for hybrid vines used for rootstock material. However, since such rootstocks may be less than optimal in other respects, it is necessary for the viticulturalist to balance the need for chlorosis resistance against other viticultural needs. This is illustrated by one of the most common lime-resistant rootstocks, 41 B, which is a hybrid between ''V. vinifera'' cultivar [[Chasselas]] and ''V. berlandieri'', which generally has a sufficient, but not extremely high, Phylloxera resistance.<ref>{{cite encyclopedia |editor=[[Jancis Robinson]] | encyclopedia=[[Oxford Companion to Wine]] |edition= Third Edition |title=Chlorosis |year=2006 |publisher=Oxford University Press |location=Oxford |isbn=0-19-860990-6 |pages=170 }}</ref><ref>{{cite encyclopedia |editor=[[Jancis Robinson]] | encyclopedia=[[Oxford Companion to Wine]] |edition= Third Edition |title=Rootstock |year=2006 |publisher=Oxford University Press |location=Oxford |isbn=0-19-860990-6 |pages=591-593 }}</ref>
==Etymology==
Chlorosis is derived from the word [[Chloris]] or from the Greek ''Khloros'' meaning "greenish-yellow," "pale green," "pale," "pallid" or "fresh".
== References ==
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{{otherarticles|Physiological plant disorders|Physiological plant disorders}}
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