The main nutrient involved in plant nutrition is thecarbon , extracted from the carbon dioxide from the air by plants autotrophic through the process of photosynthesis . Plants do not chlorophyll , called heterotrophs depend on autotrophs for nourishment charcoal.
Nutritional uses absorption processes gas and solutions minerals and directly into the water to the lower plants and aquatic plants , as in the case of vascular plants in the nutrient solution from the soilby the roots or in the air by leaves .
The roots, trunk and leaves are the organs of vascular plant nutrition: are the vegetative apparatus . Hairs by their roots (rootlets), the plant absorbs the soil solution, ie water and mineral salts , which are the raw sap (it happens that the roots are associated with fungi to better absorb the soil solution , one speaks of mycorrhiza ).
For the leaves, where it makes the photosynthesis , the plant receives amino acids and sugars that are the elaborated sap .
For the stem , the two types of circulating sap the raw sap the phloem sap and elaborated by the xylem .
The macronutrients
The macronutrients are characterized by concentrations above 0.1% of dry matter. Among them are the major nutrients needed for plant nutrition, which are the carbon , the hydrogen , the oxygen andnitrogen . These four components of the organic matter represent more than 90% of the average dry matter of the plant. To which are added the elements used as fertilizer and amendments that are thepotassium , the calcium , the magnesium , the phosphorus and the sulfur . The first three macronutrients are in the air and water. Nitrogen, although representing 78% of atmospheric air can not be used directly by plants that can not, except for some bacteria and algae , assimilate it only under a mineral, mainly in the form of ion nitrate (NO3). This explains the importance of "added nitrogen nutrition" in plant nutrition and its addition as fertilizer by farmers.
The trace elements are bioelements present in small amounts (less than 0.05%) in living organisms and therefore its absence as a concentration above its characteristic can be harmful to the body, becoming hepatotoxic. Apart from the four major elements that make up life on Earth: oxygen , hydrogen , carbon and nitrogen present in the molecular organizations, there are a variety of essential chemicals. Chemical additions require a primary erosion disintegrate. Bacteria play this role by being able to absorb from the primary mineral nutrients, which then will move up the food chain . Plants absorb minerals dissolved in the soil, which are thus collected by herbivores and minerals and are passed between living things. It is known that there are large organisms that consume soil ( geophagy) and visit mineral deposits of salt to complete their diet.
The use of soil for greenhouse production before the 1960s was common. Today a few growers still use soil in their mixes. The bulk of production is in soilless mixes. Soilless mixes must provide support, aeration, nutrient and moisture retention just as soils do, but the addition of fertilizers or nutrients are different. Many soilless mixes have calcium, magnesium, phosphorus, sulfur, nitrogen, potassium and some micronutrients incorporated as a pre-plant fertilizer. Nitrogen and potassium still must be applied to the crop during production. Difficulty in blending a homogenous mix using pre-plant fertilizers may often result in uneven crops and possible toxic or deficient levels of nutrients. Soilless mixes that require addition of micro and macronutrients applied as liquid throughout the growth of the crop, may actually give the grower more control of his crop. To achieve optimum production, the grower can adjust nutrient levels to compensate for other environmental factors during the growing season. The absorption of mineral ions is dependent on a number of factors in addition to weather conditions. These include the cation exchange capacity or CEC and the pH or relative amount of hydrogen (H+) or hydroxyl ions (OH-) of the growing medium, and the total alkalinity of the irrigation water.
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