Plant Dermal Tissue – Stomata, Root Hairs and Trichomes

Plants like all complex life on earth are organisms, made up of organs.  Leaves, stems, roots and flowers and fruits are organs found in plant which are made up of tissues.  Tissues are just made up of a combination of cells working together.  The tissue types found in plants are ground tissue, dermal tissue and vascular tissue.    Ground tissue is where cells that do the basic plant metabolism are found. Vascular tissue is where cells form tubes to transport material around the plant, much like our veins, arteries and capillaries.  The dermal tissue is the outer layer of the plant.  Most plants have a waxy layer called a cuticle that protects the plant from UV damage, prevents dehydration and can help protect from predation.  Under the cuticle, in the epidermis we find some specialized cells.  Guard cells are specialized cells found in pairs.  The opening between the guard cells is called a stoma (stomata is plural).  The stomata are where plants take in CO2, and release H2O generated during photosynthesis.  Many plants have a lot of stomata under the leaf, and indoors without rain, you may find increased plant growth if you mist or apply foliar spray to the leaves to rinse the dust out of the stomata.  However, mold can also benefit from foliar sprays, if you are only growing plants indoors under a light, and they only live a few months, you might not need to clean out the stomata, but if you have plants indoors that are year’s old, maybe spring cleaning should include a shower for your plants.

Other outgrowths of the dermal tissue are trichomes and root hairs.  Root hairs occur below ground, and are very important to plants because the root hairs increase the surface area of the roots, increasing water and nutrient uptake.  Many beneficial bacteria and mycorrhiza fungi are actually smaller than root hairs, so they increase nutrient and water uptake.  Your roots should be white and‘fuzzy’ if your plants are healthy, the fuzzyness is the root hairs seeking water and nutrients for your plant. Root hairs usually only last for 2 to 3 weeks and then die off.  This means you will find healthy root hairs at the ends of your roots, which makes sense, since the plant may have used up nutrients around the old root hairs.  The take away message   is that you want to minimize damage when potting up, which is one reason I recommend using the starter plugs vs. just plain sol for seedlings.
Trichomes are a general term for outgrowths that occur on the stem and/or leaves.  I could write many posts about the different kinds of trichomes.   In many plants these little ‘hairs’ help plants regulate water and heat loss.  They can also help with predation with both small and even large herbivores.  In some plants substances are secretedseveral basic functions or advantages of having surface hairs can be listed.  Studies of trichomes on plants subjected to frost show the ‘hairs’ keep the frost away from the living surface cells.   Other studies show that dense coatings of “hairs” reflect solar radiation, protecting the more delicate tissues underneath
Good Growing,
 Dr. E.R. Myers

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