Video Transcript
Parenchyma cells are involved in the metabolic functions of a plant. Which of the following is not a major function associated with parenchyma tissue? Thermoregulation, photosynthesis, storing water, or storing nutrients.
Let’s address this question by first looking at parenchyma tissue in a little bit more detail and addressing and defining some key terms along the way. A tissue is a group of cells which are specialized for specific functions, and parenchyma cells are found in simple parenchyma tissues. A simple tissue is one where most of the cells within it are the same or at least very similar, and parenchyma is an example of this. If we took a cross section inside this plant stem and then magnified it, we might be able to see parenchyma tissues, looking something like this.
Parenchyma tissues make up most of the fleshier parts of plant stems, leaves, and roots, and they have a wide range of metabolic functions. Remember, the word metabolic refers to all the reactions which happen within cells. Parenchyma cells have a thin cellulose cell wall, which does not contain any lignin, so water can pass into the cells easily. Lignin is a molecule found in the cell walls of some plant cells, and it makes those cells impermeable to water.
Waterproofing is really useful for some cells, like those which make up xylem vessels like the one pictured here. Their function is to transport water. The lignin found in the walls of xylem vessels increases their efficiency as it means they’re able to transport more water without as much leaking. But it also usually kills the cells. As parenchyma cells are alive, the plant must get water into them. This is partly because one of the major functions of parenchyma tissues is storing water and also because another one of the major functions is photosynthesis, which requires water.
Photosynthesis is the conversion of light energy into chemical energy in the form of glucose. Photosynthesis requires light, carbon dioxide, and water. So the cells must be able to access water in order to carry out photosynthesis to make their own food and so survive. Parenchyma cells tend to contain many chloroplasts, as these organelles are the site of photosynthesis. Another major function of parenchyma tissues is storing nutrients such as the carbohydrates, which are synthesized in photosynthesis. This is usually glucose, which is going to be stored in the form of starch so that it is easily available to be broken down for other processes, such as respiration.
Parenchyma cells also have various other roles which are more minor functions, such as gas exchange. Thermoregulation is the act of keeping a constant internal temperature of an organism. Plants are able to cool themselves down by losing water and with it heat, just like we humans do when we sweat. Plants cannot, however, warm themselves up when they’re too cold. So thermoregulation would not be a major function associated with parenchyma tissue. Photosynthesis and water and nutrients storage are major functions carried out by pretty much all parenchyma cells. So none of these options can be our correct answer. Thermoregulation, however, is not a major function of parenchyma tissue, so this must be our answer.
