Integuments


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Integuments

 

the external tissues that protect plants from unfavorable influences and perform the functions of absorption and excretion. Gas exchange between the plant and the environment occurs through the integuments. Primary integuments—epidermis and epiblem—arise from the protoderm, which consists of cells of primary meristem of the growing point of a stem or root. Exodermis becomes differentiated from the basal meristem of the growing point.

The epidermis covers the shoot, parts of the flower, the fruit, and the seed. Usually the outer walls of the epidermal cells of leaf and stem are thickened and impregnated with wax and cutin which, upon emerging to the cell surface, form the cuticle. Gas exchange and evaporation are accomplished through the stoma-tal apertures in the epidermis. The epiblem is formed just below the root apex, which is covered by the root cap. The cells of the epiblem absorb water and dissolved mineral matter from the soil; they also effect gas exchange and the excretion of metabolic products. The cells form root hairs, which significantly increase soil contact. After atrophy of the epiblem, the external cells of the primary cortex—the exodermis—take on a protective function. The primary integument is often replaced by a secondary one, or cork, which is a component of the periderm. The protective properties of cork are increased by the deposition of a sub-erin lamella on the internal surface of the cell membranes. Cork contains areas of loosely arranged cells known as lenticels, through which gas exchange and evaporation occur.

M. A. GULENKOVA

References in periodicals archive ?
This is done in order to remove grains that are broken during hydration or have had their integument broken, and to remove foreign material that may have remained in the grain mass after the cleaning stage.
May 4 ~ May 7###Microspore tetrad stage###Inner and outer integument initiation to elongation
Extraction of Embryos from The Ovul: Open ovules at the end opposite to that of the micropyle were cut and embryos from the ovular integuments were carefully excised.
The seeds were in contact with water for varying periods: five minutes during decontamination in NaOCl, three fast washes in sterile water, and, for extracting embryo integuments (endotegmen and exotesta), they were placed over moistened sterile filter paper for several minutes.
One of the first defense systems that parasites encounter after successful penetration of the integuments of metazoans is the extracellular blood clotting system.
In the micropylar end of the seed, there are two separate membranous structures; the one closely adhering to the sclerotesta is the unvascularised part of the pleurotesta, derived from the inner layers of the integument whilst the other one represents the remains of the nucellus (perisperm), firmly attached to the female gametophyte and covering the archegonium chamber.
Chaetotaxy, the presence and arrangement of setae and other sensory structures on the integument of arthropods, has been widely used for systematic and taxonomic studies in a variety of groups, including insects (e.
In contrast, three types of ovules were observed in ovaries of vc genotypes: (i) normal megagametophyte except that the nucellus was exposed and frequently extruded from the integuments, (ii) normal megagametophyte except inner integuments and nucellus were shorter than normal, and (iii) no internal development of a megagametophyte.
The subversive move is to reveal within the very integuments of "whiteness" the agonistic elements that make it the unsettled, disturbed form of authority that it is - the incommensurable "differences" that it must surmount; the histories of trauma and terror that it must perpetrate and from which it must protect itself; the amnesia it imposes on itself; the violence it inflicts in the process of becoming a transparent and transcendent force of authority.
For people even to conceive of the state, or of its active intervention in altering the social distribution of wealth or property relations, they are required to share a cognitive map which includes a view of a wider world beyond locality, and of the integuments which hold it together.
The zygote was at dormancy stage during and after the development of the free nucleate endosperm whereas the inner integuments progressively degenerated (Fig.