Thursday, October 2, 2008
Continuation of 36.2
The inner wall of each guard cell is thick and elastic when turgor develops within the two guard cells flanking each stomata the thin outer walls bulge out and force the inner walls into a crescent shape. This opens the stoma. When the guard cells lose turgor, the elastic inner walls regain their original shape and the stoma closes.
Translocation of Phloem Sap
Phloem transports organic products of photosynthesis from the leaves throughout the plant.
Sieve tubes carry food from a sugar source (a plant organ where sugar is being produced) to a sugar sink (an organ that consumes sugar).
Figure 2: Strawberrys are filled with glucose.
Flow through the phloem occurs mainly as a result of bulk flow-loading of sugar into cells creates a high solute concentration at the source end of the sieve tube and this lowers the water potential and causes the water to flow in the tube.