UNIT 6: NUTRITION AFFECTS PLANT GROWTH I. Reading comprehension Plants, like all other living things, need food for their growth and development. Plant require 16 essential elements. Carbon, hydrogen, and oxygen are derived from the atmosphere nd soil water. The remaining 13 essential elements (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, boron, molybdenum, and AM chlorine) are supplied either from soil minerals and soil organic matter or by organic 0 inorganic fertilizers. For plants to utilize these nutrients efficiently, light, heat, and water must be adequately supplied. Cultural practices and control of diseases and insects also play important roles in crop production. Each type of plant is unique and has an optimum nutrient range as well as a minimum requirement level. Below this minimum level, plants start to show nutrient deficiency symptoms. Excessive nutrient uptake can also cause poor growth because of toxicity. Therefore, the proper amount of application and the placement o. nutrients is important. Soil and plant tissue tests have been developed to assess the nutrient content of both the soil and plants. By analyzing this information, plant scientists can determine the nutrient need of a given plant in a given soil. In addition to the levels of plan available nutrients in soils, the soil pH plays an important role in nutrient availability and elemental toxicity. Adequate water and oxygen must be available in the soil. Water is required for nutrient movement into and throughout the roots. Oxygen is required in the soil for respiration to occur to produce energy for growth and the movement of mineral ions into the root cells across; their membranes. This is an active absorption process utilizing energy from respiration. Oxygen is not transported to roots from the shoot. Without adequate oxygen from the soil environment there is no energy produced for nutrient absorption. This also stops active absorption in which water flows into the cell due to the higher concentration of nutrients that were actively absorbed. Anything that lowers or prevents the production of sugars in the leaves can lower nutrient absorption. If the plant is under stress due to low light or extremes in temperature, nutrient deficiency problems may develop. The stage of growth or how actively the plant is growing may also affect the amount of nutrients absorbed. Many plants go into a rest period or dormancy during part of the year. During dormancy few nutrients are absorbed. Plants may also absorb different nutrients just as flower buds begin to develop.
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