Plant physiology

Photosynthesis is an endothermic reaction using light energy to combine carbon dioxide and water into glucose and oxygen:

carbon dioxide + water → glucose + oxygen.

Its rate is controlled by limiting factors (temperature, light intensity and carbon dioxide concentration); whichever is in shortest supply limits the rate.

Two transport tissues:

• Xylem: lignified dead cells carrying water and mineral ions from the roots up to the stem and leaves.
• Phloem: living cells carrying dissolved sugars from the leaves to the rest of the plant (translocation).

Root hair cells are adapted (large surface area) to absorb water and minerals. Transpiration is water loss through the stomata; its rate rises with light intensity, air movement, temperature, and falls with humidity.

• Calling photosynthesis exothermic (it takes in energy, so it is endothermic).
• Mixing up xylem (water, upward, dead cells) and phloem (sugars, living cells).