Uptake and transport of nutrients
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Plants take up CO2 from the air, and minerals and H2O from soil water; most of their mass comes from the CO2. -
Soil water uptake is controlled by a selective barrier (Casparian strip) and the plasma membranes of root cells. -
Water and minerals are moved up the plant through xylem primarily by transpiration, which is controlled by guard cells at the leaf pores (stomata) opening and closing via ion pumps regulating turgor. Root pressure only contributes a minor amount to water transport. -
Photosynthetic products are transported through phloem through an osmotic pressure flow mechanism, where sugar molecules flow from sources to sinks.
A plant must obtain essential elements to complete its life cycle.
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Macroneutrients (C, O, H, N, S, P, Ca, K, Mg) are the building blocks of organic compounds or are needed for physiological regulation. -
Micronutrients (Fe, Cl, Cu, Mn, Zn, Mb) function as cofactors in enzymes. -
Topsoil provides nutrients through breakdown of rock and humus, and nutrient availability is regulated through cation exchange. -
Mycorrhizae help plants absorb nutrients by increasing surface area for absorption, and bacteria provide soluble nitrogen through fixation in root nodules. -
Some plants supplement nutrient intake (especially N) through predation or parasitism.
Science is currently changing agriculture in at least two major ways.
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Organic farming is small but the fastest growing segment of the US agricultural market, and must meet certain standards -
Two major goals of current agricultural biotech research include maximizing protein content of crops, and genetic engineering to increase yields.
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