Separation of the outer bract enclosing the flower bud and spike axis results in the stimulation of amylase synthesis in the petals of gladiolus. Light is implicated in this process. Amylase production is localised in the petal epidermis (which is free of starch) and not generalised in the ground parenchyma (which contains abundant starch). Depletion of starch in the petal is strictly basipetal. It is proposed that the reducing sugars released from hydrolysis of starch in the ground parenchyma cause osmotic water intake, leading to petal expansion and flower opening.

The percentage of buds opening and flower longevity as affected by the availability of water and sucrose to out spikes of gladiolus were studied. Uptake of sucrose solution and fresh weight changes in spikes were dependent on sucrose concentration. Marked reduction in uptake and fresh weight occurred when polyethylene glycol (peg) was used as the stressing agent. In comparison.peg failed to induce any significant change in the percentage of flower buds opening. Sucrose was essential for opening since the buds that failed to open in the control were caused to open in sucrose. Induced water stress did not curtail flower longevity at any given concentration of sucrose. Thus flower opening and longevity in gladiolus appear to be limited more by the availability of sucrose than water.

Flower growth and opening are commonplace events, but physiologically intricate and inadequately explained. In this review, we have brought together and evaluated information on this subject to focus attention on the dynamic facets of flower development. In particular, the physiological basis of flower bud dormancy, nature of cleistogamy, mechanism of flower bud growth and turgor maintenance and role of stamens in corolla growth have been examined. The regulation of flower movements and opening by temperature and light, and circadian rhythms in flower opening have been discussed, along with a consideration of the role of the petal epidermis in light perception.

It is emphasized that studies on flower physiology need to be intensified in view of the lacunae in our basic knowledge as well as to provide a sound basis for improving yields of both agricultural and horticultural crops.