Carbon and oxygen are obtained from the air the rest

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Unformatted text preview: small amounts. • Carbon and oxygen are obtained from the air. The rest of the required nutrients are from water and minerals dissolved in the water. • Microbes in the soil form symbiotic relationships with root cells which benefit plants by helping them acquire scarce nutrients. • Fungal mycorrhizae help plants absorb minerals, especially phosphorous. • Nitrogen-fixing bacteria convert nitrogen compounds into forms that plants can absorb. • Transpiration (water transport) involves three processes: absorption at the roots, capillary action in the xylem, and evaporation at the leaves. • Roots acquire dissolved minerals in a four-step process: • Active transport into the root hairs, which moves minerals against their concentration gradient. • Diffusion through the cortex cells and into the pericycle. • Active transport out of the pericycle cells and into the vascular cylinder. • Diffusion into the xylem. • Capillary action, which draws water up the xylem vessels. • Cohesion: water mo...
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