Departamento de Botânica, ICB, Universidade Federal de Minas Gerais, Caixa Postal 486, Belo Horizonte, MG, 31270-901, Brazil.
Department of Biosciences, Plant Ecology, University of Salzburg, Hellbrunnerstr. 34, 5020, Salzburg, Austria.
Protoplasma. 2019 Jul;256(4):971-981. doi: 10.1007/s00709-019-01356-4. Epub 2019 Feb 22.
Caryocar brasiliense is a flagship species of the Brazilian Cerrado. It produces flowers with a strong peculiar scent, which are pollinated by bats and occasionally moths with short mouthparts. However, the cues responsible for attracting these nocturnal pollinators remain unknown. We aimed to identify osmophores of C. brasiliense, describe the ultrastructure of the cells involved in the synthesis and release of floral odour, and identify the constituents of the floral bouquet. We performed field observations and histochemical and ultrastructural analyses of flowers focusing on the androecium. Gas chromatography-mass spectrometry was used to analyse the scents emitted. Filament epidermal cells were found to possess an unusual shape and be responsible for the main production and release of odour. These cells, called foraminous cells, are elongate and possess pores where their cell walls are abruptly thin. The cuticle is practically absent over the pores, which facilitates odour emission. The foraminous cells have conspicuous nuclei and organelle-rich cytoplasm where oil droplets can be seen prior to anthesis. The features of these cells remain similar during anthesis, but many vesicles fuse with the plasma membrane and the number of oil droplets in the cytosol decreases. Twenty-nine components were found in the scent, especially fatty acid derivatives and N- and S-bearing compounds. Our analyses revealed that the androecium of C. brasiliense has a particular structure that acts as an osmophore. The scent from the androecium resembles that of the entire flower, which is an unprecedented finding for a plant with single flowers as the pollination unit.
巴西栗是巴西塞拉多的旗舰物种。它开出的花具有强烈的特殊气味，由蝙蝠和偶尔具有短口器的蛾类传粉。然而，吸引这些夜间传粉者的线索仍然未知。我们的目的是鉴定巴西栗的气味挥发物，描述参与花香合成和释放的细胞的超微结构，并鉴定花束的成分。我们对花朵（重点是雄蕊）进行了野外观察和组织化学及超微结构分析。使用气相色谱-质谱联用技术分析了释放的气味。发现花丝表皮细胞具有不寻常的形状，是主要产生和释放气味的部位。这些细胞被称为多孔细胞，呈长形，并且具有细胞壁突然变薄的孔。孔上的角质层几乎不存在，这有利于气味的释放。多孔细胞具有明显的核和富含细胞器的细胞质，可以在开花前看到油滴。这些细胞的特征在开花期间保持相似，但许多小泡与质膜融合，细胞质中的油滴数量减少。在气味中发现了 29 种成分，特别是脂肪酸衍生物和含 N 和 S 的化合物。我们的分析表明，巴西栗的雄蕊具有特殊的结构，充当气味挥发物。雄蕊的气味类似于整个花朵的气味，这对于以单个花朵作为授粉单位的植物来说是一个前所未有的发现。
