Download Photosynthesis/Guard Cell Images CWEGO: CO2 + H2O and Sun`s

Photosynthesis/Guard Cell Images
CWEGO: CO2 + H2O and Sun’s energy C6H12O6 + O2
carbon dioxide + water + energy Glucose and Oxygen
(occurs in the chloroplast of the plant cell)
The guard cells are specialized dermal cells that regulate the size
of the openings or stomata(singular stoma or stomate) in the
epidermis of the leaf. Each stoma is surrounded by two guard
cells that either take up or release water to the surround cells.
Note the location of the green chloroplasts and
the large vacuole which stores water. See how the
cytoplasm and nucleus are shrunk to the outer
edges since the vacuole is so large. Notice where
the guard cells are located.
When the guard cells release water to the surrounding epidermal
cells, the guard cells become flaccid which causes the two cells
to close off the stoma. This prevents water loss from the leaf.
Conversely, when the guard cells take up water from the
surrounding cells, the guard cells swell(become turgid) which
causes then to bow out, opening the stoma. This allows gas
exchange and an increase in water loss from the leaf,
transpiration.
Water is not directly pumped into our out of the guard cells.
Instead, the guard cells actively transport potassium ions and the
water follows by osmosis. When the guard cells close their
stomata, this conserves water, something which is important
when water is in short supply, but this also means that carbon
dioxide cannot be taken up by the leaf for photosynthesis and
excess oxygen produced by photosynthesis removed.
Source: http://staff.jccc.net/pdecell/plants/guard.html