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 close them 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.
More to read
30.5 Transport of Water and Solutes in Plants
Plants drink without mouths. Roots absorb water, xylem pipes it upward, leaves evaporate it away. Evaporation tugs the whole column: lose water on top and more rises below. Dissolved minerals ride along free. Sugar made in leaves travels separately down phloem to roots and fruits.
30.4 Leaves
Leaves trade water for food. Stomata pores admit carbon dioxide for photosynthesis but leak vapour. Guard cells close in drought and open when wet. Waxy skins, sunken pores, and needle shapes all ration loss. Count stomata under microscopes to compare species.
30.3 Roots
Roots mine water silently. Hairs balloon surface area hundreds of times, thin walls ease entry, and vessels collect the flow. Growing tips push through soil first, branching wherever moisture hides. Mycorrhizal fungi extend the net for sugar payment. Dig up a seedling gently to see the hidden half.
2 · Watch
En anglaisTake it off screen
Where it sits
Learn first
Nothing; this is a starting point.
This opens up
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.