Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
Department of Environmental Biology, Botany section, University of Siena, Siena, Italy.
Plant Biol (Stuttg). 2019 Sep;21(5):920-926. doi: 10.1111/plb.12998. Epub 2019 May 30.
The composition of pollenkitt and its role in the progamic phase of reproduction are poorly understood. With the aim of extending knowledge on these topics, we chose to study two monocotyledons rich in pollenkitt, with bi-celled and long-lived pollen and dry-type stigma: Crocus vernus Hill subsp. vernus and Narcissus poeticus L. Fatty acids of pollenkitt were assayed with gas chromatography. Germination tests were performed in vivo by pollinating the stigmas with a beard hair under a stereomicroscope, and in vitro in liquid culture medium using pollen, either treated or not, with carbon disulphide to remove pollenkitt. The pollen tube percentages were evaluated using fluorescence microscopy techniques. Scanning electron microscopy was used to examine pollen and to follow the early post-pollination stages. Pollenkitt forms bridges between pollen grains but not between grains and stigma papillae. It consists of a mixture of 25 fatty acids, most with long and unsaturated chains, among which are some omega acids. The same acids with different percentages persist on the peritapetal membrane. After its removal, the pollen loses adhesiveness and dries quickly, but retains full capacity for germination on the papillae and can even trigger germination in contiguous pollen grains that do not touch the papillae. The results, while confirming the key role of pollenkitt in protecting pollen and favouring pollination, suggest secondary roles in the progamic phase, and highlight the interactive ability of the pollen regardless of lipid shell. The predominance of fatty acids with 18:3 and 16:0, as already noted in Brassica napus pollenkitt, suggests their hierarchy independent of plant species.
花粉内壁的组成及其在有性生殖阶段的作用还不太清楚。为了扩展对这些课题的认识，我们选择了两种富含花粉内壁的单子叶植物进行研究，它们的花粉具有二细胞型和长寿命，柱头为干燥型：番红花（Crocus vernus Hill subsp. vernus）和水仙（Narcissus poeticus L.）。用气相色谱法分析了花粉内壁的脂肪酸。在体内，通过在立体显微镜下用胡须毛给柱头授粉进行发芽试验，在体外的液体培养基中用花粉进行发芽试验，花粉可以用二硫化碳处理或不处理以去除花粉内壁。用荧光显微镜技术评估花粉管的百分率。扫描电子显微镜用于检查花粉并跟踪授粉后的早期阶段。花粉内壁在花粉粒之间形成桥梁，但不在花粉粒和柱头乳突之间形成桥梁。它由 25 种脂肪酸组成，其中大多数具有长而不饱和的链，包括一些 ω 酸。具有不同百分比的相同酸在周壁膜上保持不变。去除花粉内壁后，花粉失去粘性并迅速变干，但在乳突上仍保持完全发芽能力，甚至可以在不接触乳突的相邻花粉粒中引发发芽。这些结果证实了花粉内壁在保护花粉和促进授粉方面的关键作用，同时也表明了它在有性生殖阶段的次要作用，并强调了花粉无论脂质外壳如何都具有相互作用的能力。与 Brassica napus 花粉内壁中已经观察到的情况一样，18:3 和 16:0 脂肪酸的优势地位表明它们的层次与植物物种无关。
