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Unit 3: Plant Physiology and Regulation

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    Plant physiology focuses on the chemistry and physics of how plants function. Plants capture light energy and produce sugars through photosynthesis and break down these sugars through aerobic cellular respiration. They respond to a variety of environmental conditions through growth changes, life events like germination or flowering, and even, in special cases, through movement. Plants rely on soils for mineral nutrients and water, and biogeochemical cycles replenish soils with these nutrients. Once water and minerals are absorbed, they must be transported through the xylem, and this movement is driven by the loss of water vapor from leaves (transpiration) and the cohesive and adhesive properties of water. Likewise, sugar-rich assimilate must be moved, or translocated, through the phloem. Five main types of hormones in plants are responsible for relaying messages throughout the plant body. Throughout this unit are examples of how plants regulate their internal conditions whether it the concentration of carbon dioxide in the leaves; the positioning of stems, roots, and leaves; or the movement and retention of water (Figure \(\PageIndex{1}\)).

    Microscope image of an open stoma (top) and closed stoma (bottom). Both are surrounded by transparent, thick-walled guard cells.
    Figure \(\PageIndex{1}\): Plants balance water loss with their need for carbon dioxide through stomatal opening (top) and closure (bottom). Image by KuriPop (CC-BY-SA).


    Melissa Ha (CC-BY-SA)

    Thumbnail image: A normal Arabidopsis plant (left) and a mutant that does not respond properly to the hormone auxin. Image by William M. Gray (CC-BY).

    This page titled Unit 3: Plant Physiology and Regulation is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Melissa Ha, Maria Morrow, & Kammy Algiers (ASCCC Open Educational Resources Initiative) .

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