Photosynthesis
In photosynthesis, plants use light energy, absorbed by chlorophyll in chloroplasts, to make glucose from carbon dioxide and water, releasing oxygen: . Glucose is used for respiration or converted to starch (storage), cellulose (cell walls), sucrose (transport) and, with nitrate ions, amino acids. The rate is controlled by limiting factors: light intensity, carbon dioxide concentration and temperature; whichever is in shortest supply limits the rate.
≈ 45 minLeaf structure and mineral ions
Leaves are adapted for photosynthesis: broad and thin (large surface area, short diffusion distance), with a waxy cuticle, a transparent upper epidermis, a palisade mesophyll layer packed with chloroplasts, a spongy mesophyll with air spaces for gas exchange, stomata (opened and closed by guard cells) and vascular bundles (xylem brings water, phloem removes sugars). Plants also need nitrate ions to make amino acids (deficiency: stunted growth, yellow older leaves) and magnesium ions to make chlorophyll (deficiency: yellowing between veins).
≈ 30 min