Tissue hydration is the process of absorbing and retaining

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

in biological tissues.

Plants

Land plants maintain adequate tissue hydration by means of an outer waterproof layer. In soft or green tissues, this is usually a waxy

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

over the outer

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

. In older,

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

y tissues, waterproofing chemicals are present in the secondary

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

that limit or inhibit the flow of water.

Vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s also possess an internal vascular system that distributes fluids throughout the plant. Some xerophytes, such as cacti and other desert plants, have mucilage in their tissues. This is a sticky substance that holds water within the plant, reducing the rate of dehydration. Some

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s and

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s remain dormant until adequate moisture is present, at which time the seed or spore begins to germinate.

Animals

Animals maintain adequate tissue hydration by means of (1) an outer

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

, or

; (2) a fluid-filled coelom cavity; and (3) a

circulatory system In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart ...

. Hydration of fat free tissues, ratio of total body water to fat free body mass, is stable at 0.73 in mammals. In humans, a significant drop in tissue hydration can lead to the medical condition of

dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

. This may result from loss of water itself, loss of electrolytes, or a loss of blood plasma. Administration of hydrational fluids as part of sound dehydration management is necessary to avoid severe complications, and in some cases, death. Some invertebrates are able to survive extreme

desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...

of their tissues by entering a state of cryptobiosis.

References

Plant physiology Animal physiology {{plant-physiology-stub

Plants

Animals

See also

References