Forced Ventilation

The concepts of forced ventilation developed for plant micropropagation are only a decade old. Forced ventilation is the process of mechanically moving air from outside to inside a culture vessel and vice versa. In this process a particular gas mixture is flushed directly through the culture vessel by applying pressurized force. Forced ventilation is one of the most effective methods of ventilation and the basic principle behind this method of ventilation is to create a positive pressure inside the vessel. With this system, the gaseous composition (CO2, water vapour or any other necessary gases) of the incoming air and forced ventilation rate and/or air current speed in the culture vessel can be controlled relatively precisely by using a needle valve, mass flow controller and an air pump with an inverter (Kozai et al., 1999).

Figure 2. T50 measurements for the removal of injected ethylene from a 120 ml glass vessel capped in various ways. a) airtight system: sealed with silicone rubber bung; b) polypropylene disc; c) cotton bung; d) one adhesive microporous filter discs (filter pore diameter 0.45 ^m; Millipore Corporation, USA) on the hole (8 mm) of the lid; e) Suncap closer (Sigma, USA) and f) aluminium foil functioning diffusively.

Figure 2. T50 measurements for the removal of injected ethylene from a 120 ml glass vessel capped in various ways. a) airtight system: sealed with silicone rubber bung; b) polypropylene disc; c) cotton bung; d) one adhesive microporous filter discs (filter pore diameter 0.45 ^m; Millipore Corporation, USA) on the hole (8 mm) of the lid; e) Suncap closer (Sigma, USA) and f) aluminium foil functioning diffusively.

Table 1. Summarized results of the impact of ventilation on plant micropropagation.

Species names

Types of ventilation

Numbers of air exchange (NAE) or Flow rate (FR)

Major findings

References

Ananas mangium

Annona squamosa L.

Annona squamosa L. and

Annona muricata L.

Coconut

Natural ventilation; microporous filter membrane (Milli-Seal, Nihon Millipore Ltd., Yonezawa, Japan)

Natural and forced ventilation; Suba-seal rubber puncture cap, Cling film (PVC), polypropylene discs, through-flow (forced) ventilation apparatus

Forced ventilation; non-mechanized humidity induced pressurized forced flow system compared with natural ventilation (polypropylene disc) and airtight vessel

Natural and Forced ventilation; suba-seal rubber puncture cap, Cling film (PVC), Polypropylene discs, through-flow (forced) ventilation apparatus

NAE = 6.7 h"1 (photoautotrophy) and 0.6 (photomixotrophy)

Î50 = 5587 min (suba-seal rubber), 1313 min (cling film), 94 min (ventilation apparatus)

FR = 5 ml min"1; NAE = 0.1 (airtight), 1.5 h polypropylene and 5 h1 in forced ventilation system t50 = 5587 min (suba-seal rubber), 1313 (cling film), 94 (ventilation apparatus)

Ermayanti et al., 1999

Armstrong et al., 1997

Higher growth, root development, net photosynthesis in ventilated plants grown photoautotrophically

Leaf production was greatly increased and ethylene-induced leaf fall considerably delayed under forced flow system

Leaf and flower bud Zobayed et al., abscission was prevented and 2002 growth and multiplication enhanced under forced ventilation

In forced flow system calloid was more convoluted than under diffusive aeration and had a smooth distinct epidermal surface, clearly defined sub-epidermal meristematic nodules and resembled freshly initiated calloid from which regeneration of plantlets via somatic embryogenesis can be obtained

Armstrong et al., 1997

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