Transpiration and Transport in Plants
Water pulled up the xylem replaces what evaporates from the leaves, while phloem carries dissolved sugar to where it is used or stored. Covers stomata, guard cells, and what changes the transpiration rate.
What a learner can do afterwards
- Says what xylem carries and what phloem carries, and in which direction each one moves it.
- Predicts the effect of higher temperature, wind or humidity on transpiration rate.
- Explains why closing the stomata saves water and costs photosynthesis.
1 · Read
Roots absorb water, xylem pipes it upward, and leaves evaporate it away. Losing water on top tugs the whole column higher, and dissolved minerals ride along free. Sugar made in leaves travels separately: phloem carries it down to roots and fruits.
Leaves trade water for food through pores called stomata. Open pores admit carbon dioxide but leak vapour, and guard cells swell them shut in drought. Waxy skins and needle shapes ration loss further. Closing saves water but starves photosynthesis.
Heat, wind and dry air speed transpiration, while humidity and still air slow it. Roots play their part too: hairs balloon the surface area, thin walls ease entry, and vessels collect the flow.
Every opening is a deal: food in, water out. Compare species by counting stomata under a microscope. The hungrier the leaf, the thirstier it must be.
Xylem lifts water to the deal, stomata open it, and guards close it when the price in water runs too high.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.