Studies on the Glasshouse Carnation: Effects of Temperature and Growth Substances on Petal Number

A low temperature (5 ?C) given either continuously or at nightpromoted the formation of secondary growing centres within theflower of carnation. Additional petals were produced from thesecentres and hence the total petal number was markedly increased.The formation of secondary growing centres and additional petalscould also be promoted by application of GA₃or IAA to the shoottip during flower initiation. Increases in the number of petalsarising directly from the receptacle were produced by a localizedhigh temperature treatment of the shoot tip or by applicationof kinetin. Effects of temperature on petal number were exertedin the early stages of flower development before the flowerbud became visible between the leaves.