Adaptations, Guttation and Bleeding

Challenges to clear

• Fill the Guttation bin correctly.
• Sort every item.
• Fill the Bleeding box — sap forced out of a cut stem, not lost as vapour.

The task

Sort each item into what it actually is.

What this lesson covers

• An adaptation that reduces water loss: Stomata sunk into pits, as in Nerium (A pocket of still, humid air sits over the pore and slows evaporation.); Stomata covered by hairs (Same principle — they trap a layer of moist air.); Leaves reduced to spines, as in cacti (Almost no leaf surface left to lose water from.); Leaves rolled or folded (It encloses the stomata-bearing surface.)
• Transpiration: Water lost as vapour, mainly through stomata (Vapour, not liquid — this is the key contrast with guttation.); Happens mostly during the day (Stomata are open in light.)
• Guttation: Water forced out as liquid drops through hydathodes (Liquid water containing dissolved salts, so it leaves a mark on drying.); Happens at night or early morning in humid conditions (Absorption continues while transpiration has almost stopped, so the pressure must be relieved.); Drops appear at leaf margins and tips (That is where the hydathodes are — unlike dew, which settles everywhere.)
• Bleeding: Sap oozing from a cut or injured stem (Caused by root pressure pushing sap out of the wound.)

Hint

The clean test: transpiration releases VAPOUR from stomata, guttation pushes out LIQUID from hydathodes, and bleeding is sap escaping from an injury. All three are driven by different things.