Physiological changes during flower bud opening in rose (Rosa hybrida L.)

The present study was undertaken to understand the physiological basis of flower bud opening in rose (Rosa Hybrida L.). Flower stems of two cultivars of rose ‘Grandgala’ and ‘First Red’ were harvested at six developmental stages (stage 1 to stage 6). The flower stems were kept in water contained in plugged water bottles and water uptake by stems was recorded after 72 hrs. Petals were separated from seven different petal whorls in flowers (outermost to innermost) of both the cultivars at all developmental stages and their fresh weight, turgid weight, RWC & dry weight determined. It was observed that during the opening of flower bud in vase, water uptake was found to be maximum at stage 4 and thereafter, a significant decline was observed with the visible sign of petal rolling and flower wilting. A striking behavior of petal RWC was noticed throughout the flower bud opening. After a peak at stage 4 petal RWC decreased with time and reached to a lowest level (55%) at stage 6. Water potential of flower head followed a parallel increase with flower bud opening. A general increase in fresh weight of petals was recorded during first three phases of flower bud opening followed by a declining trend at later stages. The initial development of flower bud was accompanied by the substantial increase in the dry matter of petals up to stage 3, when the flower bud was attached to the plant. During further opening in vase, the dry matter of the petals tended to fall with the expansion of petals in different whorls.