Ventilation of culture vessels. II. Increased water movement rather than reduced concentrations of ethylene and CO2 is responsible for improved growth and development of Delphinium in vitro

Delphinium plantlets were cultured during Stage III in vessels modified to give different gas exchange rates. Modifications were achieved by the fitti ng of a covered aperture, or by the sealing of the lids. The concentrations of CO2 and ethylene were measured in conjunction with measurements of rela tive humidity, water loss, the uptake of mineral nutrients and growth. Both CO2 and ethylene concentrations were low in intact vessels, and significan tly higher in vessels sealed with parafilm. Water loss was similar in intac t and in sealed vessels, indicating that the vessel lid acted as a good bar rier to water but allowed high rates of gas exchange. Plant growth rate was not affected by the level of ventilation of the vessels although leaf area was greater in vessels having lower gas exchange rates. After one week of culture, tissue concentrations of calcium and magnesium were highest in the vessels having the highest gas exchange rates. Relative humidity within th e culture vessels was not affected by the level of ventilation. Improved st omatal performance, growth and survival of Delphinium from ventilated vesse ls appears to be due to an increased flow of water, and not to amelioration of the gaseous environment.