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| Deficiency Symptoms Of Elements |
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| The absence or deficiency (not present in the required amount) of any of the essential elements leads to deficiency symptoms. The symptoms develop as hunger signs in the plants and can be studied by hydroponics or water culture or soil-less culture. |
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| In hydroponics, large volume of nutrient solution is used to grow the plants. Concentration and pH of the nutrient medium is adjusted regularly. Air is also supplied to the culture to provide enough oxygen to the root system. |
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| A Set-up of Hydroponics |
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| Potassium, nitrogen and magnesium are highly mobile. Their deficiency symptoms appear first in the older leaves. |
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| Sulphur, iron, boron, manganese and calcium are not mobile. Their deficiency symptoms appear first in young leaves. |
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| The absorption and conduction of mineral nutrients is called translocation. Soil serves as a main source of mineral salts in which clay crystals with a central nucleus is called micelle. The micelles are negatively charged. To maintain the balance, they hold positively charged ions on their surface. |
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| Mechanism of absorption of elements |
| The movement of ions is termed as flux. The movement of ions into the cell is called influx and the movement of ions from the cell to outside is known as efflux. |
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| Usually the uptake of mineral ions by the plant cells or tissues involve two main phases. |
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| In the first phase, tissues kept in mineral solution, show rapid uptake of ions into the 'free space' or 'outer space' of the cells. The outer space includes the intercellular space and cell wall. The entry of ions in to the outer space, mostly does not require the expenditure of metabolic energy. The ions exist in a freely exchangeable from in the outer space. |
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| In the second phase, the uptake of ions by the tissues is slow and the ions move into the 'inner space' of the cells. The inner space refers to the cytoplasm and the vacuole. Entry or exit of the ions from the inner space usually requires the expenditure of metabolic energy. The ions in the inners space are not in a freely exchangeable from. |
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| Theories of translocation of solution |
| Various theories have been proposed to explain the mechanism of mineral salt absorption and can be placed under the following two categories: |
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| 1. Passive absorption |
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| 2. Active absorption. |
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