Protective Tissue - Study Notes

Protective Tissue Plants need protection from all external influences that are detrimental to their growth, for example lack of water, mechanical damage, air temperatures that are too high or low, loss of nutrients, as well as protection against disease and pest attacks.Protective tissue in plants is epidermal tissue and cork tissue. 1) Epidermal tissue Epidermis tissue is the outermost tissue of plants that originates from protoderma tissue and covers the entire plant body.Epidermal tissue usually consists of one layer of living cells and is located on the outer surface of plant organs. The cells have various shapes and are tightly arranged so that there are no non-intercellular spaces. The large vacuole is in the middle, filled with colored cell fluid (anthocyanin) or it can also be colorless.Apart from functioning as a protective tissue, epidermal tissue also functions as a place for exchange of substances. The epidermis is found in stems, roots and leaves.The epidermis on the surface of leaves and stems is usually covered with a kind of fatty substance called cuticle, for example on jackfruit leaves. Meanwhile, in banana leaves and taro leaves, the epidermis forms a waterproof wax layer. Some epidermal cells can develop into other additional organs called epidermal derivatives, for example stomata and trichomata. a) Stomata (Leaf Mouth) Stomata are derivatives of epidermal tissue in leaves. Stomata are in the form of holes, each of which is lined by guard cells, namely epidermal cells that have undergone changes in shape and function.  Guard Cell Guard cells are also called guard cells. Guard cells consist of a pair of cells that appear symmetrical and generally have the shape of a kidney. Guard cells are active (living) cells. In the guard cells there are chloroplasts.  Gap (Aperture = porus)Between the two guard cells there is a gap (porus) in the form of a small hole. Guard cells can regulate the closing or opening of pores based on changes in osmosis.  Neighboring Cell (Subsidiary Cell) Neighboring cells are cells that are adjacent to or around the guard cells. Neighboring cells can consist of two or more that specifically carry out their functions in association with guard cells.  Inner Air Chamber (Substomata Chamber) The air space is a large intercellular space and has a dual function in photosynthesis, transpiration and respiration.The state of these four parts is different when the stomata are open and closed. Based on the location of the guard cells, stomata candivided into two types as follows.  Phanerophore stomata, namely stomata whose covering cells are located on the surface of the leaf (protrude) making it easier to release water, for example in hydrophyte plants.  Cryptophore stomata, namely stomata whose covering cells are far below the surface of the leaf (hidden), whose function is to reduce excessive evaporation. For example in xerophytic plants. b) Trichomata Trichomata are derivatives of the epidermis that form various structures such as hair, scales, glandular hairs, protrusions, etc. Trichomata are found in almost all plant organs.Sometimes trichomes are short in shape which appear in the form of protrusions (like small hills) on the surface of the epidermis. Trichomata like these are called papillae.Papilla is a secretion tool that secretes a kind of mucus. Papillae that do not secrete any kind of mucus, but only secrete water are called papullae. Trichomata have the following functions.  Enlarge the function of the epidermis as a protective tissue, especially preventing excessive evaporation. For example, trichomes on leaves, leaf veins and stems.  As a means of sucking water and saltssoil, for example root hairs.  Helps spread seeds and allows them to grow.  Protect plants from external disturbances. For example, stinging hairs (pneumatocysts).  As a means of transmitting stimuli coming from outside. For example, trichomes on pottery leaves.  As a means of secretion. Based on the presence or absence of a secretory function, trichomes can be divided into two as follows. (1) Trichomata that do not produce secretions (nonglandular trichomes). Several types of nonglandular trichomes are as follows.    Hair is single-celled or multi-celled and not flat, for example in Lauraceae and Moraceae. Scale hairs that are flat and have many cells, for example on durian leaves (Durio zibetinus). Branched and multicelled hairs, for example on hibiscus leaves (Hibiscus tiliaceus). (2) Trichomata that produce secretions (glandular trichomes). Trichomata on tobacco leaves (Nicotiana tabacum) are simple glandular trichomes, having stalks with singlecelled or multi-celled heads. In plants, various types of glandular trichomata are often found, namely as follows.    Trichomata hydatodes, consist of stalk cells and several head a solution.For example, in the taro family (Araceae). Salt glands, consisting of a large glandular cell with a example in mangrove plants. Honey glands, in the form of one or more celled hairs with capable of secreting honey onto the cell surface, for example cells and secrete short stalk, for thick plasma and in banana plants.  Itchy hair, in the form of a single cell with a sac-shaped base and a pointed tip.The contents of the cells cause itching. For example, in the hair, the sting of kemaduh (Laportea stimulans).