Hyperhydricity (previously known as vitrification) is a

physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

malformation that results in excessive hydration, low lignification, impaired stomatal function and reduced mechanical strength of tissue culture-generated plants. The consequence is poor regeneration of such plants without intensive

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...

acclimation for outdoor growth. Additionally, it may also lead to leaf-tip and bud

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

in some cases, which often leads to loss of apical dominance in the shoots. In general, the main symptom of hyperhydricity is translucent characteristics signified by a shortage of

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

and high water content. Specifically, the presence of a thin or absent cuticular layer, reduced number of

palisade cells A palisade, sometimes called a stakewall or a paling, is typically a fence or defensive wall made from iron or wooden stakes, or tree trunks, and used as a defensive structure or enclosure. Palisades can form a stockade. Etymology ''Palisade' ...

, irregular

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

, less developed

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...

and large intracellular spaces in the mesophyll cell layer have been described as some of the anatomic changes associated with hyperhydricity.

Causes

The main causes of hyperhydricity in plant tissue culture are those factors triggering oxidative stresses such as high salt concentration, high relative humidity, low light intensity, gas accumulation in the atmosphere of the jar, length of time intervals between

subculture A subculture is a group of people within a culture that differentiates itself from the parent culture to which it belongs, often maintaining some of its founding principles. Subcultures develop their own norms and values regarding cultural, poli ...

s; number of subcultures, concentration and type of gelling agent, the type of explants used, the concentrations of microelement and hormonal imbalances. Hyperhydricity is commonly apparent in

liquid culture A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagn ...

-grown plants or when there is low concentration of gelling agent. High

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...

concentration also contributes to hyperhydricity.

Control

Hyperhydricity can be monitored by modifying the atmosphere of the culture vessels. Adjusting the relative humidity in the vessel is one of the most important parameters to be controlled. Use of gas-permeable membranes may help in this regard as this allows increased exchange of water vapor and other gases such as ethylene with the surrounding environment. Using higher concentration of a gelling agent, on top of the use of a higher-strength gelling agent may reduce the risk from hyperhydricity. Hyperhydricity can also be controlled by bottom cooling, which allows water to condense on the medium, the use of cytokinin-meta-topolin (6-(3-Hydroxybenzylamino)purine), the combination of lower cytokinin and ammonium nitrate in the medium, use of

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

or glutamine as the sole nitrogen source and decreasing the ratio of NH4+:NO3- in the medium. In studies on calcium deficiency in tissue cultures of ''Lavandula angustifolia'', it was shown that an increase in calcium in the medium reduced hyperhydricity.

Notes and references

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External links

* http://users.ugent.be/~pdebergh/tro/tro3_d01.htm Cell culture Biotechnology Cell biology Plant physiology

Causes

Control

See also

Notes and references

External links