Anatomy of the olive inflorescence axis at flowering and fruiting

In spite of the importance of the peduncle and pedicel in supporting and connecting flowers and fruits to the mother plant, these structures are little known in the olive, and more detailed information can be instrumental in studies of fruit development, ripening and abscission. The structure of pedicel and peduncle was studied at flowering and at fruit maturation for the Spanish olive cultivar “Picual”. Both organs have a stem-like structure. At flowering the pedicel is less developed as the transport requirements to individual flowers are minimal compared to that of the complete inflorescence, and the structure has high chances of being shed in the heavy flower abscission in this species. The peduncle is thicker, due to a ridged cortex, and has larger xylem vessel size. By fruit maturation in November, the overall diameter of both pedicel and peduncle increases, due to both conducting tissues and support tissues: in the pedicel the xylem increases 6-fold, in the peduncle 3-fold, while the phloem undergoes smaller increases. An important developmental feature of pedicel and peduncle is the increase in their capacity to mechanically support the growing fruit. To this end both organs, in addition to the increased thickness of the conducting tissues, produce a lignified sclerenchyma ring. Unlike the stem, however, which produces numerous sclereids, the sclerenchymatous ring only consists of fibres, which offer greater flexibility and make the structure less prone to breaking.

► Change of anatomical structure in olive inflorescence pedicel and peduncle during the growing season.
► Changes of xylem and phloem features.
► Starch grains: small in flower pedicels and large in other conditions.
► Lignification of pith cells.