Definition
Root hairs greatly increase the root's surface area for absorption. Water moves into root cells by osmosis; salts (ions) are absorbed by active transport, which can move them even against a concentration gradient (using energy).
Definition
Transpiration is the loss of water vapour from a plant, mainly through stomata on the leaf surface. The resulting transpirational pull helps draw water (and dissolved minerals) up the xylem from the roots.
Rule
Transpiration increases with higher temperature, lower humidity, and more wind (each removes water vapour from around the leaf faster, steepening the diffusion gradient that drives water loss).
Remember
Transpiration isn't purely wasteful: alongside the water lost, it also drives the upward transport of water and minerals through the plant and provides some cooling — so it isn't simply harmful, even though it does cost the plant water.
Definition
Stomata open and close by changes in guard cell turgor, controlled largely by potassium () ion movement — when flows into guard cells, water follows by osmosis, they swell, and the stoma opens.
Definition
Food (mainly as sucrose) is loaded into phloem at a "source" (e.g. a leaf), raising pressure there; it is unloaded at a "sink" (e.g. a root or growing fruit) where pressure is lower — this pressure difference drives the flow, in either direction depending on where the source and sink currently are.
Definition
Macronutrients (needed in large amounts): e.g. nitrogen (for proteins, chlorophyll), magnesium (chlorophyll's central atom).
Micronutrients (needed in tiny amounts): e.g. iron, zinc — essential, but only in trace quantities.
Plants excrete wastes differently from animals: excess water and salts leave via transpiration and guttation; some plants (like rubber and keekar trees) store waste products as resins or gums, isolating them in tissues that no longer function actively.
Quick Recap
- ●Root hairs increase absorption area; water enters by osmosis, salts by active transport
- ●Transpiration: water vapour loss through stomata, pulls water up the xylem; rises with heat, wind, and low humidity
- ●Stomata open/close via guard cell turgor, driven by K movement
- ●Pressure flow mechanism: food moves from a high-pressure source to a low-pressure sink in the phloem
- ●Macronutrients (large amounts, e.g. N, Mg) vs micronutrients (trace amounts, e.g. Fe, Zn)
