Could someone familiar with the pressure- flow hypothesis of sugar movement thro
ID: 10574 • Letter: C
Question
Could someone familiar with the pressure- flow hypothesis of sugar movement through phleom in plants- explain the process and how sugars moves via, what my professor calls " source sink?" I have an idea- it reminds me of movement of water through cells by the differences in concentrations of salts and homeostasis.Sugars move up to plants by increasing the concentration of water towards the roots. (i.e., sugar needs to move up to leaves because spring has arrived). So what I remember is because of the increasing water molecules moving into the phleom via osmosis through cells and the xylem; this increases the sugars ability to move from a high concentration (e.g, roots ) to a low concentration (e.g., leaves) up through the phloem- and then water molecules diffuse back into the xylem.
please correct me if I am wrong! I have a test tomorrow on this stuff and I would rate highly! Thanks!
Explanation / Answer
Its been a while since I've take plant bio but from what I remember the flow of water and sugars goes up the plant because of the reasons you mentioned but also from the capillary action due to the properties of water and from the evaporation of H2O from the leaves.
The cohesion properties of H2O make it stick together easily, with the H bonds of one water molecule able to bind to other O from other water molecules, and the adhesion of H2O to stick to other surfaces thus facilitating the capillary action. This is partly what helps pull water upwards from the roots towards the top of the plant.
As air passes across the leaves of the top of the tree evaporation occurs from the stoma on the leaves. This evaporation causes a pull of water from the rest of the plant, pulling water upwards from the more water dense lower parts.
These and what you had mentioned help mechanically pull water from the water rich root "source" to the areas that have less water "sink" and thus in turn help facilitate the transport of sugars as well.
Hope this helps.