Buds and leaves in pomegranate (Punica granatum L.): Phenology in relation to structure and development

• Phenological analysis is performed in relation to shoot anatomical changes.
• Two morphologically distinct dormant buds go through different developmental fate.
• Bud dimorphism results in the appearance of four shoot types.
• Variations in leaf morphology are related to their ontogenetic pathway.
• Leaf histogenesis starts within the dormant winter buds, not affected by shape.

Phenological analysis provides a useful tool in the study of fruit trees in various aspects, and is mostly based only on morphological characters. In this two years study, morpho-anatomical analyses of vegetative organs were conducted using light and scanning electron microscopy during pomegranate annual cycle. Punica granatum L. cv. Rabbab-e-Neyriz was investigated at six ontogenetic stages. Two types of ecodormant scaly buds developed either only into vegetative shoots or went through vegetative and/or reproductive phase, with a predictable fate in winter. Bud dimorphism resulted in the appearance of four branch types in spring. Pomegranate is heterophyllous, with two types of leaves, already distinguishable in dormant buds on the basis of shape and especially the apex. Both leaf types revealed the same anatomical features, but differed in their developmental aspect leading to obcordate and lanceolate final shape. An accelerated rhythm of leaf growth was noticed and histodifferentiation initiated within the dormant buds. The functional significance and eventual consequences of heterophylly in pomegranate are discussed.