Different studies explains the importance of micro and macro nutrients, which is required for the biological as well as chemical functions of plants, without these a plant can not able to complete its cycle. Each nutrients have their own functions like carbon is required for the formation of bio molecules, hydrogen is necessary for building sugars, nitrogen helps in the formation of proteins, phosphorus is involved in the formation of structure of plant components, Zinc play a vital role in the DNA transcription, stabilization of different proteins present in plant and functioning of different enzymes etc. The deficiency of any nutrient can disturb the life cycle of plants. . In rice, Cu, Mo, Mn, Zn are considered an essential micro-nutrients. Zinc is necessary for the developing tissues like meristem and for reproductive organs of rice plant.
Rice is considered as the one of major staple food in all over the world, especially in Asia. it is the major source of proteins as well as carbohydrates. It provides energy as well as micronutrients. Therefore, high yielding varieties of rice is grown in most of the countries of the world for better production.
Zinc deficiency is mostly occurred in Asia on neutral to alkaline calcareous soil containing more than 1% organic matter. In rice, after the nitrogen, phosphorus, potassium, zinc deficiency is considered as the cause of low yielding. The deficiency of zinc causes the disorder of nitrogen metabolism in rice plants. It depressed the production of proteins in meristematic tissues and brought about the accumulation of free amino-acids and amides. The deficiency of zinc may stop the growth of a plant, leaf cannot attain its size, crop maturity period increased, decrease the production of tillers and ultimately causes the low yield.
Zinc plays an important role in the human body as it helps in the immune system as well as helps in cellular metabolic activities. It is present in nearly 300 enzymes in the human body. The deficiency of zinc in rice plants also lead to the risk of different diseases in human beings in developing countries. For terrestrial life, zinc is considered as the transition metal, which is required in low concentration. For adequate plant growth, the concentration 30 and 100 microgram zinc per gram DW are enough. If it is above 300, it causes the toxicity.
Therefore, different recommendation of fertilizers are used in field to overcome the deficiency of zinc in rice plant. Usually, the soil application of 5-17kg Zn/hac/y or 25-85 kg zinc sulphate heptahydrate/hac/y is preferred for rice crop. Now a days, ZEU(zinc enriched urea) is also available in Asia for better supply of zinc as well as nitrogen it may also used in wheat. OsHMA 2, a heavy metal, present in rice, helps in the preferential distribution of zinc in plants. If the three strains of bacteria like AX, BC,AB and foliar spray (ZnSO4.7H20) applied collectively in a field at different stages of crop development like flowering, milking, dough stage etc, the yield of crop increased because it helps to increase the height of plant, it increases the number of tillers, filled grains on each panicle etc. ZnSO4 and Zn EDTA are used as a foliar spray in the saline soil where zinc deficiency occurs. Bio fortification helps to improve the deficiency of zinc in rice. For zinc biofortification new genetic tools are developed which is obtained by the exploration of genetic diversity of rice.
Rice are the basic source of zinc which is required to human body for the performance of different functioning specially human metabolism. Therefore , there is need to improve the deficiency of zinc in rice crop.