Plants are crucial to the survival of us all. Without them there would be no life on earth. So how do these guys stay alive themselves? Ecological relationships between plants, microbes, insects, humans and other wildlife conspire to keep the world spinning around. Plant biology explains how these green friends function and what biological mechanisms contribute to their existence. One of the most important elements of the plant make-up is the vacuole. Vacuoles are found both in animal and plant cells but they are much larger in plant cells than animal cells. In the course an Introduction to Biology learn more about the plant and animal biology basics.
Vacuoles (pronounced vak-q-ols) are fundamental components to the survival of a plant. They are, by definition, membrane bound organelles which are present in all plant and fungal cells. Vacuoles are formed by the fusion of vesicles, so in essence, they are larger and more effective versions of a vesicle. They act as miniature storage bins for plants and hold food and nutrients that are vital to the plant’s health. Vacuoles have many functions and are important players in the survivability of a plant. The structure of a vacuole consists of a membrane that encompasses a mass of fluid. The fluid is what contains the aforementioned nutrients or waste products. In the Biotech Basics course learn more in-depth about cell structure and functions.
Sometimes these storage sacs even hold waste as a measure of self-protection from contaminants. After a while these contaminants will be eliminated from the plant altogether. Additionally, vacuoles will export other unwanted substances from the cell in a timely manner.
If you’ve ever seen a dead or dying plant you’ll notice they look a little limp and weepy. This is due to the lack of fluid in the vacuoles. Plant cells are surrounded by cell walls that help provide support and protection for the individual cells. Cell sizes can increase or decrease depending on the amount of water present in the cell. It’s the job of the vacuole to store this water and thus increase the cell size which adds to the overall stability of the plant. The cell walls provide the skeleton of the plant so if there is a serious lack of water the plant won’t just disappear…it will retain its structure however will appear shriveled up. Vacuoles typically only hold fluid however sometimes they may engulf solid material. Read about the plant growth cycle in How do Plants Grow.
Hydrostatic pressure is a principle of fluid mechanics. It’s essentially the force that fluid molecules put on each other because of gravity. Or, the pressure of a fluid at rest because of the pressure of the fluid molecule above it. Cells are tightly packed little things and they often sit on top of one another. If hydrostatic pressure isn’t maintained, the cells could crush each other because the fluid in one shifts, a nearby cell’s pressure will also shift, and the nearby cell of that one… and so on. Maintaining hydrostatic pressure is a function of vacuoles as they are fluid storage sacs and internal mechanisms allow them to keep the pressure in balance. See turgor below for more information on these fluid mechanics.
One of the biggest functions of the vacuole is their role in autophagy. Autophagy is the degradation of unnecessary or dysfunctional cells. Lysosomes act as disintegrating agents, eating away or recycling the no longer needed cell components during nutrient starvation, infection or for repair. A mechanism of autophagy is programmed cell death which is a process that target non-essential cells to be eliminated. All of these mechanisms help aid the essential cells to stay alive which ultimately keeps the entity (in this case the plant) alive and healthier. Vacuoles maintain a balance between biogenesis (creation) and degradation (removal). Autophagy occurs in human cells to for the same purposes as plants. Interested in exotic plants? Check out the course on Southwest Mountain Plants in China.
The transport of protons from the cytosol to the vacuole maintains stability in the cytoplasmic pH. A stable cytoplasmic environment is more acidic than the typically preferred acid-base balance. A more acidic vacuole means a more proton force which helps the cell to transport nutrients in and out of the cell. Lysosomes, the agents that help eat away unwanted cells, also require a highly acidic environment. The higher a pH number the less acidic it is. The lower the number the more acidic it is.
As mentioned before, vacuoles are important in maintaining the structure of the plant. Without them, there wouldn’t be enough pressure to push against the wall to maintain the flow of water in and out of the vacuole. Because of osmosis, water diffuses into the vacuole which puts pressure on the cell wall and this keeps the structure of the cell full and not withered. Essentially, turgor pressure is the key to keeping a plant in the upright position.
There are many functions for vacuoles in plants, and it’s easy to see that without vacuoles plants (and animals) wouldn’t be able to survive. In fact, vacuoles store the proteins needed for the germination of seeds which makes them important for the start and continuance of plant life. If you are preparing a biology paper on the functions of vacuoles, or any other biology topic check out this course: A+ Research Paper in Biology.