meristem

(redirected from meristematic)
Also found in: Dictionary, Thesaurus, Medical.

meristem

(mĕr`istĕm'), a specialized section of plant tissue characterized by cell division and growth. Much of the mature plant's growth is provided by meristems. Apical meristems found at the tips of stems and roots increase the length of these sections. Stems and roots may also grow in thickness or in diameter through cell divisions in lateral, or secondary, meristems, found just under the surface along the length of the stem or root. Tissues derived from differentiated lateral meristem are known as secondary tissues. In one type of lateral meristem, called cambium, or vascular cambium, the cells divide and differentiate to form the conducting tissues of the plant, i.e., the woodwood,
botanically, the xylem tissue that forms the bulk of the stem of a woody plant. Xylem conducts sap upward from the roots to the leaves, stores food in the form of complex carbohydrates, and provides support; it is made up of various types of cells specialized for each of
..... Click the link for more information.
, or xylem, and the phloem (see barkbark,
outer covering of the stem of woody plants, composed of waterproof cork cells protecting a layer of food-conducting tissue—the phloem or inner bark (also called bast).
..... Click the link for more information.
; stemstem,
supporting structure of a plant, serving also to conduct and to store food materials. The stems of herbaceous and of woody plants differ: those of herbaceous plants are usually green and pliant and are covered by a thin epidermis instead of by the bark of woody plants.
..... Click the link for more information.
). The growth in diameter of tree trunks is wholly dependent on the division of cambium cells. Other meristematic tissues include corkcork,
protective, waterproof outer covering of the stems and roots of woody plants. Cork is a specialized secondary tissue produced by the cork cambium of the plant (see meristem, bark).
..... Click the link for more information.
 cambium, which divides to produce waterproofing and protective cork tissue at the surface of the stem and root; and intercalary meristems, modified apical meristems found in different positions than either apical or lateral meristems, e.g., in the stem nodes of grasses. See also differentiationdifferentiation,
in biology, series of changes that occur in cells and tissues during development, resulting in their specialization. This, in turn, permits a greater variety of organisms.
..... Click the link for more information.
, in biology.

Meristem

 

formative tissue, a plant tissue characterized by prolonged cell-division activity. Some cells of the meristem—the initiating cells—remain in the embryonic phase of development and, by dividing, provide uninterrupted growth of the plant body. Other cells of the meristem gradually become differentiated, forming various derivative tissues (integumentary, conducting, mechanical, basal).

Meristems originate from the protomeristem of the embryo, which develops into the apical and lateral meristems. The apical meristems—the growing points of shoots and roots—are formed very early in the embryo. The formation of the cotyledons and later of the leaf rudiments on the growing point of the shoot results in differentiation of the lateral meristems into the procambium and cambium. Meristematic tissue is partially preserved in some parts of the plant body during plant growth, for example, in the roots (Pericycle—rhizogenic meristem), the nodes of the shoot, and the medullary rays of the stem. Intercalary meristem is temporarily preserved in the buds, the inter-nodes of the shoot (Gramineae), and the bases of the petioles.

Because almost all living, mature tissues (except the sieve tubes) possess the capacity to divide, new, or secondary, meristems, such as Phellogen (forming cork tissue) and callus, may arise in the plant. Meristem cells differ from the cells of permanent tissues in that they are smaller, densely arranged, and almost cubical in shape (only cells of the procambium and cambium are elongated). They usually have a thin primary membrane and a dense protoplast, in which the nucleus and nucleolus occupy a central position. The endoplasmic network is poorly developed; there are many ribosomes. The mitochondria and dictyosomes are only slightly differentiated. The vacuoles are very small, and the plastids are in the form of protoplastids. Meristem cells are characterized by high metabolic activity.

REFERENCES

Esau, K. Anatomiia rastenii. Moscow, 1969. (Translated from English.) Lehrbuch der Botanik fur Hochschulen, 30th ed. Jena, 1971.
I. S. MIKHAILOVSKAIA

meristem

[′mer·ə‚stem]
(botany)
Formative plant tissue composed of undifferentiated cells capable of dividing and giving rise to other meristematic cells as well as to specialized cell types; found in growth areas.
References in periodicals archive ?
In aerial parts, galling Nematoda usually penetrate young leaves or stems, inducing the redifferentiation of meristematic cells, and necrotic regions are rarely observed (Goodey, 1939, 1948; Dropkin, 1969; Watson & Shorthouse, 1979; Skinner et al., 1980).
According to Smet e Beeckman (2011), the adventitious root initiations involves the meristematic cell niche formations (initial cells and/or target cells) which are dependent on external and internal factors.
Boron is involved in many biochemical and metabolic functions such as cell wall growth, respiration, formation of meristematic tissues, regulation of metabolic pathways, metabolization of carbohydrate, RNA; and indole acetic acid [5, 6, 7, 8, 3, 2].
These favourable influences resulted into greater meristematic activities and apical growth, thereby improving plant height, branches/plant and dry matter accumulation/plant at all the stages.
A stereomicroscope (Wild M3B Heerbrugy, Switzerland) was used to locate and magnify (10x by 16x) the meristematic region on the sterilized stem section.
A meristematic, more or less rectangular cell was developed in the apex of the prothalli (Fig.
The answer lies in the remarkable regenerative capacity of meristematic cells located in the tips of plant roots and shoots.
The primary bud is the largest meristematic tissue of the three and is in the middle of the compound bud.
Galling insects produce galls by inducing cellular hypertrophy and hyperplasia on plant meristematic tissues (Mani, 1964).
The site occupation in the meristematic zones was altered (p < 0.05) by the evaluation periods.
In higher plants, ethanol is making in the root tip meristematic tissue under aerobic conditions, alcohol dehydrogenase enzyme declined by zinc deficiency in plants, as a result root development reduced [15,16].