The structural importance of the plant vacuole is related to its ability to control turgor pressure. Turgor pressure dictates the rigidity of the cell and is associated with the difference between the osmotic pressure inside and outside of the cell.
Osmotic pressure is the pressure required to prevent fluid diffusing through a semipermeable membrane separating two solutions containing different concentrations of solute molecules. The response of plant cells to water is a prime example of the significance of turgor pressure. When a plant receives adequate amounts of water, the central vacuoles of its cells swell as the liquid collects within them, creating a high level of turgor pressure, which helps maintain the structural integrity of the plant, along with the support from the cell wall.
In the absence of enough water, however, central vacuoles shrink and turgor pressure is reduced, compromising the plant's rigidity so that wilting takes place.
Plant vacuoles are also important for their role in molecular degradation and storage. Sometimes these functions are carried out by different vacuoles in the same cell, one serving as a compartment for breaking down materials similar to the lysosomes found in animal cells , and another storing nutrients, waste products, or other substances. Several of the materials commonly stored in plant vacuoles have been found to be useful for humans, such as opium, rubber, and garlic flavoring, and are frequently harvested.
Vacuoles also often store the pigments that give certain flowers their colors, which aid them in the attraction of bees and other pollinators, but also can release molecules that are poisonous, odoriferous, or unpalatable to various insects and animals, thus discouraging them from consuming the plant.
License Info. Image Use. Custom Photos. Site Info. Contact Us. In a way, they're specialized lysosomes. That is to say that their function is really to handle waste products, and by handle, mean take in waste products and also get rid of waste products.
Sometimes the waste product is water, and therefore a vacuole would have as its function to maintain the balance of water inside and outside a cell. Sometimes a vacuole's function is to get rid of harmful toxins or to clear the extracellular space of those harmful toxins by bringing them into the cell for conversion; for chemical conversion into more safe compounds.
The vacuoles are quite common in plants and animals, and humans have some of those vacuoles as well. In free living single celled animals and plants such as Amoeba or Euglena that inhabit fresh water, osmosis is a big problem. These cells constantly take up water across the semipermiable membrane and if this process went on indefinitely, the cell would burst. Instead, these cells collect the excess water into a contractile vacuole , which, as its name suggests, can contract.
When full of water the vacuole connects with the outside and pumps, forcing the water out of the cell. Vacuoles Mendel and others looking down their microscopes at plant cells could perhaps be forgiven for thinking the cells were empty.
0コメント