THE EFFECT OF THE GASEOUS STATE ON BUD INDUCTION AND SHOOT MULTIPLICATION IN-VITRO IN EASTERN WHITE CEDAR

The effect of vessel type and the gaseous phase on the morphogenic res ponse of Thuja occidentalis L. explants in vitro was studied. Explants were cultured in container types that varied in their degree of gas e xchange. Traps for ethylene and CO2 were employed. During shoot bud in duction from embryonic explants, the number and elongation of shoot bu ds improved significantly when gastight, serum-capped flasks were used compared to the foam bung-capped flasks or the regularly used Petri d ishes. Elimination of the two gases from the headspace of the flasks e ither singly or together reduced shoot bud induction and especially el ongation of shoots. A similar response was seen during axillary bud de velopment from cultured shoots. Ethylene and CO2 accumulation promoted development and elongation of axillary shoots. An increase in the zea tin concentration in the medium produced a greater number of axillary shoots and higher levels of ethylene in the culture vessels. Removal o f CO2 caused gradual death of the shoots, while removal of ethylene al one reduced axillary shoot lengths significantly. Inclusion of aminoet hoxyvinylglycine in the medium combined with ethylene traps produced a n effect similar to the use of ethylene traps alone.