Determination of floral development stages in ‘Cabernet Sauvignon’ (Vitis vinifera L. cv.): highlighting the manifestation of stamens and pistil primordia with new intermediate stages linking the phenological stages

Abstract

Despite relatively intensive work on the development of inflorescence primordia during grapevine growth in season one, some informational gaps are present in the flower and floral organ development in the season two. In addition, concurrents events of phenology and formation of flowers and floral parts has not been dealt with. With the aid of digital imaging, this research had three objectives; a) describe the developmental events that take place during and after bud break in the buds and in the individual flowers in terms of differentiation, b) match these events with phenological stages, and c) determine size-related growth of the floral organs. After careful dissecting and examination of the samples under microscopy, taken ever 5-10 days between March 20 and May 10 in 2016, the results indicated that highly esteemed works regarding the reproductive anatomy of grapevines needed some additional stages to fully describe events in the stamen and pistil primordia after the appearance of petal primordia. Five intermediate stages were added to the stages of “formation of flowers”. Differentiation of inflorescence and individual flowers occurred in the second season as the buds swelled in the spring. Stamens and pistil could be seen about 3 weeks later and completed their initial growth in another 3 weeks. Flower primordia was visible on April 1 and showed a more than 9-fold increase over the course of 5 to 6 weeks. flowers increased their width and their length more than 9- and 15-fold, respectively, between stage 8.1 (April 1) and 10.3 (May 10). At first, they were wider than they were longer, but at later stages they grew longitudinally. Reproductive organ primordia were visualized around the time of 2-4 leaves separated on the shoots. Signs of generative parts become apparent in late April. Anthers were the smallest in the flower. Filaments, on the other hand, elongated almost 7-fold in a period of 20 days. Gynoecium growth was the most impressive and total pistil length increased from 52.8 to 162 μm, ovary width from 40.4 to 99.8 μm, and stigma diameter from 9.96 to 44.9 μm in twenty days. By the time the pistil took its final shape, 6-8 leaves grew on the shoot during which inflorescence could also be seen.