Plant require various nutrients in different amount so that they may grow, reproduce and complete their life cycle. some mineral elements are essential and others beneficial. There are minerals that a plant cant complete its life cycle without and there are others that are not that essential thus the name beneficial.
2. Essential nutrients
• To be able to germinate, grow and reproduce plants must have specific
elements
• These are elements so critical that plants cannot complete their
lifecycle in their absence.
• They are 17: C, H, O, N, P, K, Mg, Ca, S, Zn, B, Mn, FE, Mo, Cu, Cl,
Ni.
• Macro nutrients- they are elements that are required in large amounts
like N, P, K, Mg, Ca, S.
• Micro nutrients- they are elements required in small quantities like
Zn, B, Mn, FE, Mo, Cu, Cl, Ni.
3. Criteria for essentiality of elements
Requirements for essentiality :
i. A plant cannot complete its life cycle in absence of the element
ii. The element’s function is not replaceable by another element
iii. The element in directly involved in metabolism
5. Beneficial elements
• These are mineral elements that only stimulate growth but
don’t satisfy criteria for essentiality
• They are: Aluminum, Cobalt, Sodium, Selenium, Silicon
• They are helpful in some plants only like Silicon for rice
• Not critical for all plants but may improve yield
6. Role of silicon
• Acts as a physical barrier and enhance plants resistance to toxic
elements
• Helps reduce salt damage in saline conditions
• Reduce drought stress by improving plant water status
• Improves rice yields
• Reduce susceptibility to insect damage and disease
7. Role of cobalt
• Required by Rhizobia for nitrogen fixation
• It’s the primary component of vitamin B12
• Its a component in some enzymes
• Some researchers suggest it plays vital role in production of ethylene
8. Role of selenium
• Selenate promotes germination in raddish, tomato
• Se in low concentration enhances growth of plants
• Reduces salt stress damage by enhancing detoxification system
• Has ability to regulate water status of plant in drought stress
9. Role of sodium
• Function is in the maintenance of osmotic relations of the cells
• It has beneficial effects on growth and water regulation in sugar beet
• Has been shown to be an essential element in CAM photosynthetic
pathway.