NOTES-chap 37

NOTES-chap 37 - Mineral nutrients. essential chemical...

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Mineral nutrients- . essential chemical elements absorbed from the soil in the form of inorganic icons. Ex : plants need nitrogen, which they acquire from the soil mainly in the form of nitrate ions. . 80% of herbaceous plant is water, and plants grow mainly by accumulating water in the central vacuoles . water is considered a nutrient because it supplies hydrogen atoms and some oxygen atoms that are incorporated into organic compounds by photosynthesis more than 90% of the water absorbed is lost by transpiration most of the water retained by the plant functions as a solvent, provides most of the mass for cell elongation helps maintain the form off the soft tissue by keeping the cells turgid . CO2 from the atmosphere is the main component of the bulk of organic material Water content can be measured by comparing the weight of the plant material before and after it is dried. The chemical composition of the residue can be analyzed. . organic substances account for 95% of the dry weight . inorganic substances making up 5% . carbon, oxygen, hydrogen (carbohydrates) are most abundant elements in dry weight of the plant . some organic molecules contain nitrogen, sulfur, or phosphorus essential nutrient: it is required for a plant to grow from a seed and complete the lifecycle . hydroponic culture helps determine which of the minerals are essential nutrients Macronutrients: nine macronutrients in total that plants need in large sums. The six major ingredients of organic compounds: carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus. The other three are potassium, calcium, and magnesium Micronutrients: iron, chlorine, copper, manganese, zing, molybdenum, boron, nickel. these function mainly as cofactors of enzymatic reactions. Ex: iron is a metallic component of cytochromes (ETC) because micronutrients only play catalytic roles, they are only needed in small amounts, however deficiencies may weaken or kill the plant. Mineral deficiencies depend not only on the role of the nutrient, but also its mobility within the plant. . young, growing tissues have ‘drawing power’ than old tissues for nutrients, and thus deficiencies show up first in the older organs preferential routing is the source-to-sink translocation in phloem . a deficiency of a nutrient that is relatively immobile within a plant will affect young parts of the plant first. . older tissues may have adequate supply of the mineral, which they are able to retain during periods of short supply Ex: iron does not move freely within a plant, and a deficiency of iron will cause yellowing of young leaves before any effect on older leaves is visible. .shortages of micronutrients are less common and tend to be geographically localzed because of differences in soile composition
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Ex: a zing deficiency in fruit trees can be cured by putting nails into the trunk .hydroponic farming can be precisely regulated and thus ensures optimal nutrition The texture and chemical composition of soil are major factors determining what kind of
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NOTES-chap 37 - Mineral nutrients. essential chemical...

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