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Trichomes
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| Trichomes |
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| ‹ Plant Anatomy › |
| What's up with the three different cell types? |
| Parenchyma |
| The most common cell type in plants. A good way to remember this is: They are relatively unspecialized, thin walled, and carry out most of the plant’s metabolic functions. So, they seem “cheap” to make (energy-wise, anyway), since they are thin walled, and they are also VERY important to the plant. So why would any other type of cell be the most common? It just wouldn’t make sense! |
| Collenchyma |
| These are a lot like parenchyma cells, except with uneven cell walls (that is a great way to remember them). Collenchyma cells normally provide support to parts of the plant that are still growing. These cells can often be found in a cylinder shape just below the surface of the stems (the “strings” of celery, for example). These sometimes taste good with ranch dressing or peanut butter. |
| Sclerenchyma |
| You can think of these cells as the “tough” ones. They sometimes contain lignin to strengthen their already thick cell walls, and are even willing to make the ultimate sacrifice—some give up their protoplasts in order to be more specialized for support, which results in their own death. However, unlike most dead things, these types of cells even serve a function to the plant after death, by continuing to provide support to the plant by its rigid walls. |
| What about the tissues? |
| Dermal Tissue (epidermis) |
| Like our own epidermis (skin), a plant’s epidermis covers the entire plant body. Some are specialized for protection and the regulation of gas movement inside the plant. |
| Xylem |
| These function in the transport of water and minerals, and providing support. The water conducting elements in the xylem are elongated cells called tracheids and vessel elements. Both types of cells are DEAD at maturity, and act like a tube or straw for the water to travel through. Elements in the xylem called fibers provide support. |
| Phloem |
| This important tissue transports the products of photosynthesis (sucrose and some other organic compounds) throughout the plant. In contrast to cells of the xylem, phloem cells are ALIVE at functional maturity. |
| How about the tissue systems? |
| Dermal tissue system |
| This forms a protective layer that covers the plant—the “skin” (Note the word “dermal”). This contains the epidermis and a waxy layer called the cuticle, to prevent water loss. |
| Ground tissue system |
| This makes up the bulk of a young plant, since it occupies the space between the dermal and vascular systems. It is mostly parenchyma, but collenchyma and sclerenchyma are sometimes found. This functions in photosynthesis, storage and support. |
| Vascular tissue system |
| This functions in transport and support. It is made up of xylem, phloem, and vascular bundles (clusters of xylem and phloem). |
| A great way to remember this is to relate this to a human—the dermal tissue system is like the skin, the vascular tissue system is like the circulatory system and the ground tissue system is “everything else”, including muscles and organs. |
| Major functions of various plant structures: |
| Stems |
| Support leaves, conduct water and other inorganic substances |
| Roots |
| Anchorage of the plant, absorption of water and minerals from the soil, conduction of water and minerals to the base of stem, starch storage |
| Leaves |
| Photosynthesis (uptake of carbon dioxide, absorption of light), through stomata |
| An interesting fact about stomata—many plants, especially those that reside in hot and dry climates, have the majority of their stomata on the bottom on their leaves, and only open up the stomata at night. This is because every time the stomata open to get carbon dioxide from the environment, a small amount of water is lost. Water loss is detrimental to the plant, especially when rainfall is uncommon and evaporation occurs rapidly because of the heat. So… where do you think native southern Nevadan plants’ stomata are? |
| Are trichomes (leaf hairs) and root hairs the same thing? |
| No! They may look somewhat similar under the microscope, but they are NOT the same! |
| Trichomes |
| Hair-like outgrowths from the epidermis of the plant’s leaves. Although many purposes can be hypothesized, it is probably true that trichomes provide a first line of defense against insects, pathogens and herbivores. They can also help protect the plant from water loss via evaporation. |
| Root Hairs |
| Hair-like outgrowths near the root tips of the plant. These tiny projections increase the surface area of the roots dramatically, enabling the plant to absorb a lot more water than it would without them. What a great adaptation! |
updated 3-12-06