Nutrients213-page5

Nutrients213-page5 - as well as transmembrane passage and...

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Plant Nutrients and Soils - 5 Obtaining Water and Minerals from the Soil Water and most minerals are obtained from soil. Hence it is valuable to learn something about soil when discussing nutrient requirements of plants. Water moves into roots from the surrounding soil spaces by diffusion. Most minerals must be absorbed as water-soluble ions, which move into the root dissolved in water. Water from rainfall percolates through soil spaces and forms a film around soil particles. Soluble ions (minerals) dissolve into H 2 O from the surrounding soil There is a competition for minerals by root absorption versus minerals leaching through soil as water percolates past root region. Water and dissolved minerals move into root in the root hair region by diffusion and active transport From the root hairs, nutrients move through the cortex, along apoplastic (cell wall and intercellular spaces) and symplastic pathways (using plasmodesmata
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Unformatted text preview: as well as transmembrane passage) and into the stele via the endodermis. • From the stele, most minerals are moved along with water in xylem throughout the plant. Recall that mycorrhizae are very important in mineral absorption for many plants, and accumulate a higher mineral concentration for plants. Mycorrhizae "infection" is promoted by the secretion of strigolactones by roots that stimulate the growth of the fungal hyphae (cells)toward the root. Mycorrhizae significantly increase the area for absorption and actively absorb minerals that are naturally in low concentration in soil. Both ectomycorrhizae and endomycorrhizae are common. Recall, too, that nitrogen fixation by bacteria is also critical for nitrogen availability. (See later with mineral cycling and the Nitrogen cycle.)...
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