Stomata ⇒ enclosed by bean shaped guard cells Guard Cells ⇒ only cells in epidermal tissue that contain chloroplasts → as they control opening and closing of stomata ⇒ thereby regulating passage of gasses into and out of the leaf.
- Guard Cells photosynthesis and manufacture glucose
- Increase in glucose concentration decreases the WP of the cell sap in the vacuole of guard cell
- Water potential in the guard cell becomes lower than that of its neighboring cells. Water from neighboring cells enter vacuole of Guard Cell by Osmosis.
- Guard Cells swell and become more turgid and curved.
- Cell wall around stomatal pore is much thicker compared to cell wall around other parts of the cell. hence cell curves around the stoma and the stoma opens.
Stomata generally open in light and close in dark ⇒ guard cells help to regulate passage of gasses between leaf and env. Example: Guard Cells can reduce amount of WV escaping from leaf.
Stomata can close to reduce water loss even when plant is in sunlight ⇒ such as extremely hot days in such situations ⇒ excess evaporation of water > causes guard cells to become flaccid ⇒ thus stomatal pore closes ⇒ preventing excessive water loss
