plants

• plants have evolved adaptations to minimise water loss without reducing gas exchange
• plants have a waterproof, waxy cuticle to prevent water loss by evaporation
• plants' stomata are usually kept open during the day to allow gas exchange
• 1. K+ ions move into the guard cell by active transport, lowering the water potential in the cell
• 2. water moves by osmosis into the guard cells, making them turgid, which opens the stomata
• 3. if too much water has been lost from the plant, the guard cells lose water and become flaccid, which closes the stomata, preventing water loss
• xerophytic plants grow slower due to the stomata closing, so there's less carbon dioxide uptake, so less photosynthesis