Vitrification

Vitrification is also known as hyperhydricity, is a morphological and physiological disorder of plants vegetatively propagated in vitro. They have a glassy appearance. Their stems and leaves are often thick, rigid and easily breakable.

They are characterized by decreased protein and chlorophyll content, low phenolics, an increase water content and an altered ion composition. In many cases, vitrification leaves do not have palisade tissues, instead they have only a spongy and largely vacuolated mesophyll with large intercellular spaces.

Vitrification is dependent on water availability, micronutrient content and hormonal imbalance in the media. However, microenvironment of the culture vessel and ethylene composition inside the culture vessel were found to have a prolonged effect on vitrification.

Histochemical studies of guard cells from vitrification leaves revealed lower levels of lignins, cellulose, pectins and cutin, as well as deposits of callose.

Microscopic studies indicated that the pore surrounded by the guard cues in vitrification leaves is more rounded in contrast to the elliptical pore in normal leaves. Faulty orientation ans callose presence affected the stomatal apparatus movement in hyperhydric leaves. The availability of Ca2+ and other ions, known to affect callose formation may have affected cell wall thickening, microfibril orientation and callose formation in the walls. Callose instead of cellulose deposition under such conditions may have caused stomatal malfunction.



Taken From: Hazarika, BN. 2006. Morpho-physiological disorders in in vitro culture of plants. Scientia Horticulture. 108: 105-120.

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