Question

Necrosis of tissue, particularly leaf tissue is due to deficiency of
(a)N, K, Mg, Fe, Mn, Zn, and Mo
(b)Ca, Mg, Cu, and K
(c)N, K, and S
(d)Mn, Zn, and Mo

Answer 1

Hint: It is not a disease, but rather a symptom of a disease or other distress the plant is experiencing which can lead to the death of the cell. The diseases caused by various factors or organisms may be a common cause of necrosis, but weather-related problems, water quality and availability, insect activity, and nutrient deficiency also may be factors.

Complete answer:
Necrosis term comes from an Ancient Greek word which means "death", it is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Factors, such as infection, or trauma external to the cell or tissue can cause necrosis which results in the unregulated digestion of cell components. Apoptosis is the programmed cell death of a cell which is often beneficial to the organism, but necrosis is almost always detrimental and can be fatal.
The critical concentration of elements in plants can be defined as the concentration of the essential element below which plant growth is retarded, where the element is said to be deficient when present below the critical concentration. When the limitation of any particular element occurs, plants start to show certain morphological changes since each element has one or more specific structural or functional roles in plants. Due to the absence or deficiency of essential mineral elements, some externally visible morphological changes are produced which are called deficiency symptoms and necrosis refers to the death of tissue, particularly leaf tissue mainly due to the deficiency of Ca, Mg, Cu, and K.

Additional Information: 1)The cell walls cannot be bonded if pectin cannot be synthesized due to the calcium deficiency and thus an impediment of the meristems which will lead to necrosis of stem and root tips and leaf edges.
2) A species of Dipterans called Drosophila mettleri has developed a p450 detoxification system, therefore cacti such as the Saguaro and Cardon in the Sonoran Desert experience necrotic patch formation regularly.
3) Throughout an entire plant or in just a portion, necrosis can inhibit normal growth (hypotrophy) or induce excessive abnormal growth (hypertrophy or hyperplasia) and these are some symptoms associated with necrosis: leaf spots, blight, scab, rots, damping-off, anthracnose, dieback, and canker.
So, the correct answer is, ‘Ca, Mg, Cu, and K’.

Note: Necrosis can’t be prevented but we can take some precautions to spread it less like if we have other plants in the area with one with some disease, separate the infected ones from the healthy ones as soon as possible. Again we can clip off the worst of the leaves which will make the problem easier to monitor and we can also get rid of some fungal spores should the problem be caused by fungi. Another precaution is to never get the foliage wet – don’t mist the plant or spray the leaves with water, no matter what causes the problem this can spread the disease or make it worse. And as medicinal care plants can be sprayed with a multi-purpose fungicide.