Articles
EFFECTS OF LIGHT AND GROWTH RETARDANTS ON DORMANCY IN GREENHOUSE AZALEAS
High light intensity and short days promoted bud formation.
On the other hand, low light intensity during bud formation reduced the need for cooling.
During the cooling period, low light intensity had a somewhat lesser effect, but led to an earlier break of dormancy, as did full darkness.
Development from the end of the cooling to flowering was promoted by high light intensity, especially in plants which were cooled minimally.
A short period of high temperature applied during the cooling period seemed to reverse the breaking of dormancy.
This suggests that the effect of shading may partly be that the shading reduces the natural temperature fluctuations.
However, reduced light intensity obviously has a specific effect on dormancy in azalea.
Even at temperatures below the optimum for breaking of dormancy a marked effect of reduced light and darkness was observed.
A comparison between the effects of short days and growth retardants showed that CCC and B-9 hastened the bud formation and reduced shoot growth in much the same way as did short days.
However, growth retardants delayed flowering.
This delay was eliminated by a prolongation of the cooling period.
B-9 and CCC thus seemed to increase the dormancy in comparison with short days and consequently to increase the cooling requirement.