Examples of chlorosis and necrosis ?
- Chlorosis is loss of chlorophyll leading to yellowing of leaves. This symptom is caused by the deficiency of elements N,K,Mg,S,Fe,Mn,Zn & Mo. Some examples: Grape wine,Citron.
- Necrosis is the death of tissue, particularly leaf tissue. The tissue first turns brown and subsequently dies. This symptom is due to the deficiency of Ca,Mg,Cu &K. Example: Tomato.
- Note: Different plants respond differently to the deficiency of the same element.
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. vinifera 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.
Necrosis (from the Greek νεκρός, "dead", νέκρωσις, "death, the stage of dying, the act of killing") is a form of cell injury that results in the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma that result in the unregulated digestion of cell components. In contrast, apoptosis is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal.
Cells that die due to necrosis do not follow the apoptotic signal transduction pathway but rather various receptors are activated that result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the intracellular space. This initiates an inflammatory response in the surrounding tissue: Nearby phagocytes are prevented from locating and engulfing the dead cells. The result is a build-up of dead tissue and cell debris at, or near, the site of the cell death. A classic example is gangrene. For this reason, it is often necessary to remove necrotic tissue surgically, a process known asdebridement...