Paul N. Walker, C.W. Heuser, P.H. Heinemann
Two studies have been completed to help determine the optimum ventilation for micropropagation vessels. Other studies are underway. In the first study, Rhododendron 'P.J.M.' cuttings were grown using standard Stage II micropropagation techniques except that the vessels were ventilated. The ventilation treatments were filtered atmospheric air and bottled nitrogen and oxygen mixtures with 0, 300, and 1000 ppm carbon dioxide. The results showed that plant fresh weight and number of shoots in the nonventilated vessels were significantly higher than in the ventilated vessels and that there was no significant difference between any of the ventilated treatments. Apparently the ventilation diluted the concentration of some beneficial gaseous material produced inside the vessels.

In the second study, short vertical dividers were added inside unventilated micropropagation vessels to separate the agar medium in two halves. The medium in each half was identical except for the concentration of growth hormones. All possible combinations of hormone levels of 0, 0.1 and 1.0 times the normal level were used. Rhododendron cuttings grown in the vessel halves with zero or low hormone levels had higher plant weights and number of shoots if the other half of the vessel had a normal hormone level than if the other half of the vessel had a zero or low hormone level. It was concluded that the vessel halves with the normal level of hormone were producing a beneficial gaseous material. Another study is underway to help determine if that material is ethylene.

Walker, Paul N., Heuser, C.W. and Heinemann, P.H. (1988). MICROPROPAGATION: STUDIES OF GASEOUS ENVIRONMENTS. Acta Hortic. 230, 145-152
DOI: 10.17660/ActaHortic.1988.230.15

Acta Horticulturae