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Leaf spots caused by fungi occur due to the necrosis of plant tissues. These necrotic lesions, localised in area and shape, consist of dead and collapsed cells of the host leaves. [ 1 ] One distinct feature of fungal infections is that there may be visible spores in the centre of leaf spots. [ 7 ]
When lettuce is infected with INSV, it shows a number of symptoms, such as yellowing leaves, dead spots, and stunted growth. On the inner leaves there are patterns of necrosis and chlorosis. At the base of the ribs of infected lettuce plants there is significant necrosis and lesions. The necrotic tissue can look brown to dark brown.
The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who is often regarded as one of the founders of modern pathology. [2] Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated digestion of cell components.
Tomato, tobacco, legumes, cucurbits, sweet potatoes and banana are a few of the most susceptible plants, but it also infects other herbaceous plants. [2] F. oxysporum generally produces symptoms such as wilting, chlorosis , necrosis, premature leaf drop, browning of the vascular system, stunting and damping-off.
Calcium deficiency symptoms appear initially as localized tissue necrosis leading to stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips. Generally, the new growth and rapidly growing tissues of the plant are affected first.
Cucumber mosaic virus (CMV) is a plant pathogenic virus [1] in the family Bromoviridae. [2] This virus has a worldwide distribution and a very wide host range, [3] having the reputation of the widest host range of any known plant virus. [4] It can be transmitted from plant to plant both mechanically by sap and by aphids in a stylet-borne fashion.
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. [1] Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are: [citation needed]
Necrosis of the phloem tissue particularly in the haulm is observed after onset of symptoms. Plants infected with PLRV experience stunted growth and produce smaller tubers. Infected tubers retain normal shape but experience necrosis of the vascular tissue. Necrosis of the tuber may not be apparent at harvest and can develop in storage.