Absorption Tissues

Absorption Tissues

Poikilohydric plants do not save water and they can survive even complete des-iccation because their cells will hibernate. An example of a poikilohydric plants would be mosses. Homoiohydric plants (which are majority of plants2), how-ever, do save water. They try to support the water content and do not survive complete desiccation. An example of a homoiohydric plant would be any “typical” plant, saying, corn. Somehow similar traits are comparable in poikilother-mic animals, such as reptiles, and homoiothermic animals, such as birds and mammals, except in reference to body heat rather than water conservation.

Absorption tissues are always simple, primary tissues. Most important of them is rhizodermis (rhizoderm), or root hairs, which originates from protoderm (proto-epidermis), but its lifespan is much shorter than of epidermis. Thereare other absorption tissues, for example, velamen of orchids, which originates from the root cortex and consists of large, empty, easy to get wet dead cells.

Other Tissues

Secretory tissues spread across the plant body, concentrating in leaves and young stems. These tissues may secrete latex, volatile oils, mucus and other chemicals. Its functions can be attraction or dis-attraction, communication or defense, and many others.

In addition to tissues, plant body may contain idioblasts, cells which are quite dissimilar from surrounding cells. Idioblasts used for accumulation of unusual (and possibly dangerous) compounds like myrosinase, protein splitting glucosi-nolates into sugars and toxic isothiocyanate (mustard oil). We use mustard oil as a spice but for the plant, it works like a binary chemical weapon against insect herbivores: when myrosinase-containing idioblasts are damaged, mustard oil kills damaging insects. Among plants, the whole order Brassicales from rosids is capable to produce myrosinase, examples are different cabbages (Brassica spp.), papaya (Carica), horseradish tree (Moringa) and many others.