Can a stench be beautiful? – Osmophores in stem-succulent stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae-Stapeliinae)

Carrion flower stapeliads are examples of olfactory mimicry, forming sapromyiophilous flowers, which mimic food sources or oviposition sites to attract fly pollinators. The aim of this work was to investigate the ultrastructure of osmophores involved in the release of the carrion odor of Orbea variegata and Boucerosia indica flowers. In spite of their similar architecture (epidermal epithelium+subepidermal secretory layers), the osmophores of stapeliads feature some differences in morphology and ultrastructure. The epidermal epithelial cells of O. variegata and B. indica differ in shape, but both are extremely rich in endoplasmic reticulum and flocculent material in the vacuole. Unlike the Orbea, Boucerosia has starchless leucoplasts in the epidermal epithelium. Orbea features a cuticle with microchannels, while Boucerosia has a different mechanism for the pathway of scent substances to the cell exterior. They are released by rupturing of the outer layer of cuticle at the apex of the papillae. The epidermal cells of the adaxial corolla differ even between parts of the corolla, the corolla lobes and the annulus in the flower. This diversity may be connected with an odor gradient. The morphological and anatomical features of stapeliad (subtribe Stapeliinae) osmophores are generally similar to osmophores of members of subtribe Ceropegiinae (Ceropegia), thus, we suggest that this model of osmophores evolved before early diversification of Ceropegieae. The ultrastructural features of stapeliad osmophores are generally similar to those of Araceae, Orchidaceae and Passifloraceae.     

长萼兰花蕉(Orchidantha chinensis var.longisepala)气味腺结构探究

兰花蕉科(Lowiaceae)植物开花时,位于唇瓣的特殊腺体结构——气味腺(osmophores)能够产生和释放类似粪便的腐臭气味吸引传粉者。本研究以该科植物长萼兰花蕉(Orchidantha chinensis var.longisepala)为材料,采用中性红染色法初步确定气味腺的位置,然后用扫描电镜观察气味腺表皮细胞形态、透射电镜观察分泌细胞的超微结构。结果显示,散发腐臭气味的气味腺位于长萼兰花蕉唇瓣上端近轴面;气味腺由多样性的表皮细胞及表皮下1~2层分泌细胞构成,腺体细胞具有细胞核大、细胞质浓、线粒体和内质网丰富等特点;长萼兰花蕉花气味的释放主要依靠角质小泡的破裂完成,推测挥发性的小分子有助于花气味的释放。本研究结果有助于揭示兰花蕉科植物与传粉者之间的互作关系,了解植物的传粉过程。     

植物气味腺研究进展

气味腺是花器官上能够产生和释放花气味的特殊腺体结构,在传粉过程中与其他花部性状结合能够吸引传粉者访花,气味腺的研究有助于揭示动物与植物之间的协同进化机制,此外,气味腺外部形态特征及细胞微形态可作为分类依据之一。对气味腺的结构、类型和检测方法,及其在植物科属中的分布情况进行了归纳总结,并对气味腺在传粉过程中和分类学上的意义进行了分析。最后提出只有结合分子实验技术手段,全面综合考虑繁殖生物学和植物化学的分析方法,才能深入理解气味腺的多样性与演化。