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 carbohydrates through photosynthesis and may die unless the cause of its chlorophyll insufficiency is treated, although some chlorotic plants, such as the albino Arabidopsis thaliana mutant ppi2 are viable if supplied with exogenous sucrose[1].
Contents |
Etymology
Chlorosis is derived from the word Chloris or from the Greek Khloros meaning "greenish-yellow," "pale green," "pale," "pallid" or "fresh".
Causes
Chlorosis is typically caused when leaves don't have enough nutrients to synthesise all the chlorophyll they need. It can be brought about by a combination of factors including:
- a specific mineral deficiency in the soil, such as iron; [2]
- a soil pH at which minerals become unavailable for absorption by the roots [3]
- poor drainage (waterlogged roots) [3]
- damaged and/or compacted roots [3]
- pesticides and particularly herbicides may cause chlorosis, both to target weeds and occasionally to the crop being treated.
- exposure to sulphur dioxide
Of course, the exact conditions would be different for different plants. For example, Azaleas prefer unusually acidic soil and rice isn't troubled by waterlogged soil.
Chlorosis in viticulture
Like many other plants, grape vines are susceptible to chlorosis, and 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 greater problem in viticulture. To deal with the Phylloxera blight, 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 were common in 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 in France this specific form of chlorosis was termed chlorose calcaire. 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.[4][5]
Treatments
Specific nutrient deficiencies (often aggravated by high soil pH) may be corrected by supplemental feedings of iron, in the form of a chelate or sulphate, magnesium or nitrogen compounds in various combinations.
References
- ^ Kubis S, Patel R, Combe J, et al. (August 2004). "Functional specialization amongst the Arabidopsis Toc159 family of chloroplast protein import receptors". Plant Cell 16 (8): 2059–77. doi:. PMID 15273297.
- ^ Koenig, Rich and Kuhns, Mike: Control of Iron Chlorosis in Ornamental and Crop Plants. (Utah State University, Salt Lake City, August 1996) p.3
- ^ a b c Schuster, James. "Focus on Plant Problems - Chlorosis". University of Illinois. http://www.urbanext.uiuc.edu/focus/chlorosis.html. Retrieved 2008-12-22.
- ^ Jancis Robinson, ed (2006). "Chlorosis". Oxford Companion to Wine (3rd ed.). Oxford: Oxford University Press. pp. 170. ISBN 0-19-860990-6.
- ^ Jancis Robinson, ed (2006). "Rootstock". Oxford Companion to Wine (3rd ed.). Oxford: Oxford University Press. pp. 591–3. ISBN 0-19-860990-6.
|
|||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
