Study On The Variation And Evolution Of Flower Organs Of Osmanthus Fragrans 'Tianxiang Taige'

Combining attractive colors, strong fragrance, and elegant shapes, Osmanthus fragrans is a famous aromatous plant of China with a long cultivation history. The O. fragrans flower is relatively conservative morphologically, but the petals do vary in number and shape. Using paraffin section and SEM techniques, we studied floral bud differentiation, pollen characteristics, and petal morphology of O. fragrans'Tianxiang Taige'and other 4 cultivars. The results are as follows:1. O. fragrans'Huangchuan Jingui','Ziyingui','Dangui', and'Sijigui'commence floral bud differentiation late in May. This 4-month process can be divided into 5 stages: Involucrum differentiation, Sigle flower primordia differentiation, Top flower perianth differentiation, Stamen differentiation, Pistil differentiation. All four cultivars show normal androecium development, yielding functional pollen sacs and ripe pollens. However they differ markedly in gynoecium development,'Huangchuan Jingui'and'Ziyingui'are fertile while'Dangui'and'Sijigui'are sterile. The pistil capel primordium of the fertile cultivars forms 2 protrusions that fuse into a normal pistial. The pistil carpel primordium of the sterile cultivars forms 2 protusions that do not close.'Tianxiang Taige'has 3 different types of flower buds: normal, special, and duplication. The normal and special buds both undergoes 5 differentiation stages: involucrum differentiation, sigle flower primordia differentiation, top flower perianth differentiation, stamen differentiation, and pistil differentiation. The entire process lasts for about 5 months. The duplication flower bud has an extra 1-month stage of duplication formation following pistil differentiation. All three flower buds cannot form normal pistils, the normal and special buds give rise to pistils that degenerate into leaf-like carpels, while the duplication flower bud forms pistils that degenerate into branches and leaflets.2. All cultivars have oblong, 3-labed (polar-view), rounded pollen particles of the N3P4C5 type according to the NPC classification system, with reticulate ornamentation. In rising sequence of P value, the cultivars are:'Sijigui','Tianxiang Taige','Huangchuan Jingui','Ziyingui', and'Dangui'.'Sijigui'has the smallest P and P/E values while'Dangui'has the largest. L/P is positively correlated with P/E.3. Using Environmental-SEM and Cryo-SEM, we observed petal surface ultra-structures of O. fragrans'Zijingui','Baijie','Shanghaidangui', and'Tian Xiang Taige'. The results show that the upper petal surfaces are composed of regular protruding ridges. Cultivars differ markedly in epidermal cell shape and ridge number. In cryo-SEM images, varying numbers of particles can be found on and between the ridges.