Excretory tissue

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Example of glandular hair on the epidermis

The term excretory tissue refers to a cell structure in the plant that is responsible for the exchange of substances. The types of material exchange are divided into excretion and secretion. Their functions can be different, for example as food poison, defense against infection or to attract animals.

excretion

The excreta are excreted from the cells that form and belong to the secondary plant substances . These substances are not required for the “energy” or “building metabolism”.

Gland cells on the epidermis

Glandular hairs or glandular scales store the excreta between the excretory cells and the cuticle (skin). They can be distinguished by their secretion products in the mucous glands, resin glands, salt glands, oil glands, nectaries and digestive glands. In the pharmaceutical or perfume industry, lipophilic (oily) substances are often used, such as essential oils . By destroying the cuticle, the excrement is released and can be processed further. An example of this would be the peppermint plant. The microscopy of the different types of glandular hair is used in botany as a typical distinguishing feature of the plant species.

  • Glandular hair type A (scalp hair) is mainly found in the daisy family . It is round in plan view and has two secreting (secreting) rows of cells (bread-like appearance).
  • Type B glandular hair (glandular flakes) is mostly found on the leaves of the mint family . It is also round in plan view, but has four to twelve secreting cells that are arranged radially.

Elimination rooms

The inner excretory tissue is located in the parenchyma (base tissue) or other types of tissue and is either schizogenic or rhexigenous. Schizogenic means that the intercellular spaces (spaces) are formed by moving apart. The intermediate walls (middle lamellae) are dissolved by enzymes and the surrounding cells remain intact. Rhexigen, on the other hand, means that the cells tear through internal growth tensions and the oil container is formed, whereby surrounding cells are destroyed.

  • Excretory ducts transport and store the substances formed. One type of this is the resin canals. They are schizogenic and surrounded by glandular cells that release the resins into the ducts. If the plant is injured, the resins leak and close the wound. In addition, the resins also have a disinfectant effect.
  • Excrement containers are lysed (by dissolving the cells) or schizogenic and can contain oils that protect the plant or attract animals, which by eating the fruit contribute to the spread of the plant seeds.

Gland cells for excreting water

They are also called hydathodes or "water crevices". Their function is to eliminate excess water (guttation).

secretion

The secretions are released into the vacuoles of the plant. In contrast to the classification of animals, it cannot be precisely determined here whether the secretions are still needed by the plants or not.

Idioblasts

Idioblasts differ in their appearance and function from the surrounding cells. The secretion-containing cells can be connected to one another in long branched or compact systems. The idioblasts during secretion are divided into rows of crystal cells, milk tubes and lysigenic oil containers.

Rows of crystal cells

Fibers or fiber sheaths containing calcium oxalate can often be seen around the vascular bundles (vascular vessels) . These are called crystal cell rows.

Milk tubes

When emulsions ( milk juices ) are formed by the secretions and the transverse walls between the secretion cells dissolve, a kind of "duct" is formed (milk tube).

Lysigene oil container

They are secretory cells that lie close together and whose cell walls dissolve. This process creates the so-called lysigenic oil reservoirs. An example of this would be the filled with essential oil oil tank of bitter orange .

Special shape

Transfer cells

They are also called "transition cells" and have an intensive exchange of substances, such as salt or nectar. Their functions are different. For example, it could be haustoria, salt glands, nectaries, or similar cells.

Individual evidence

  1. Ray F. Evert, Rosemarie Langenfeld-Heyser, Susan E. Eichhorn: Glandular hairs that secrete lipophilic substances . In: Rosemarie Langenfeld-Heyser (Hrsg.): Esaus Pflanzenanatomie. Meristems, cells and tissues of plants - their structure, function and development . Walter de Gruyter , 2009, ISBN 978-3-11-020592-3 , p. 424 ( entry in Google book search).
  2. a b Biostudies: Table of Contents. biostudies.de, November 2008, accessed on January 15, 2011 .
  3. a b Wolfram Braune, Alfred Leman, Hans Taubert : Plant anatomical internship I: For an introduction to the anatomy of the vegetation organs of the seed plants . In: Volume 1 of Plant Anatomical Practical Training . Spektrum Akademischer Verlag , 2009, ISBN 3-8274-2289-2 , p. 368 ( entry in Google book search).