i. Copper is a constituent of cytochrome oxidase and component of many enzymes like ascorbic acid oxidase, phenolase, lactase.
ii. It helps in oxidation-reduction process in plants.
iii. The compounds containing copper like plastoquinones and plastocyanins help in electron transport from chlorophyll to NADP and from water to chlorophyll during phosynthesis. Hence, it plays the role in photosynthesis.
iv. It promotes formation of vitamin A in plants.
i. The young growth develops chlorosis, withering and distortion of terminal leaves. Buds often die resulting into sprouting of auxiliary buds.
ii. Young leaves of the cereal crops show bleaching and withering at the tips. The emerging leaves fail to open and have needle like appearance. The tillers are poorly formed and fail to flower and fruit.
iii. In corn yellowing of upper or youngest leaves is noticed. Such leaf tips curl with ragged edges, and short internodes in stem is also noticed.
iv. In cruciferous plants the young leaves develop interveinal chlorotic mottling and marginal scorching. v. The citrus face with die back of new growth recognized as “exanthema”, gum pocket develops between the bark and the wood; the fruit shows brown excrescences.
i. Zinc regulates the auxin concentration in plants.
ii. It helps in synthesis of chlorophyll, portein, nucleic acid, carotein, IAA (indole acetic acid) etc.
iii. It participates in the metabolism of plants as an activator of several enzymes.
iv. It is also required for seed production, RNA synthesis and ribosome stability.
v. It helps in utilization of phosphorus and nitrogen in plants.
Interveinal chlorosis, reduction in the size of young leaves having bronze and purple, violet, reddish-brown or brown colouration of the foliage are the prominent deficiency symptoms. The deficiency diseases have following names:
i. Mottle leaf (little leaf type) or frenching of citrus: The young emerging leaves remain smaller, chlorotic and shoots die back.
ii. White bud of maize: The seedlings, soon after sprouting, develop interveinal yellowing followed by white necrotic spots and later the seedlings die.
iii. Leaf spot/bronzing of rice: Rice seedlings of 3-4 weeks of age develop reddish brown pigmentation starting from middle then it spreads over entire lamina. These spots become papery and necrotic resulting into collapse of entire mass of leaves and growth of plants is arrested.
iv. The absence of zinc also may have an adverse effect on the production of seeds in beans and peas and the development of fruit in citrus.
i. Molybdenum plays a role in the enzymes nitrite reductase, nitrate reductase and nitrogenase, where in it acts as an electron carrier between oxidized and reduced states.
ii. It helps in protein and amino acid synthesis.
iii. It accelerates nitrogen-fixing efficiency of aerobic (Azotobacter), anaerobic (Clostridium), blue green algae (BGA), Azolla and symbiotic bacteria.
iv. It regulates the carbohydrate metabolism in plants.
i. The deficient plants show chlorotic mottling between the veins in older and middle leaves. Under severe deficiency the leaves show scorching and withering which start from the margins and spreads over entire lamina except petiole. It gradually extends to young leaves, if the deficiency continues. The affected young leaves fail to expand, growing point becomes necrotic and growth of the plant is arrested. These symptoms are termed as “whip tail” in cauliflower and other Brassica spp.
ii. The tomato leaves show chlorotic mottling and inward curling of leaf margins. The older leaves of radish show interveinal yellowish green mottling, they become papery, bleached and have downward cupping. Similar symptoms appear in beans which is called as ‘scald’.
iii. In cereals the middle leaves becomes golden yellow at the tip during ear/head/panicle emergence stage. Affected leaves become dry and papery while younger leaves become spirally twisted.
iv. Similar symptoms appear in citrus and the deficiency disease is called as “yellow spot of citrus”.
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