THE DEVELOPMENT AND CAUSES OF PETAL BLACKENING AND MALFORMATION OF BACCARA ROSE FLOWERS
Since these phenomena occured only in winter, it could have been caused by each of the following environmental factors: short days, low light intensity and low temperatures. All these possibilities were examined. Reducing light intensity in the summer and extending day length in the winter have had no significant effect either on blackening or on malformation. The only factor left was, therefore, the drop in temperatures. The controlled experiments reported here confirm this assumption.
A survey of various fields and greenhouses proved that although under outdoor winter conditions both blackening of petals and malformation occur at one and the same time, this is not the case in greenhouse flowers. Therefore, it was decided to investigate each phenomenon separately.