Nectary structure and function in relation to angiosperm reproductive success: Developmental and evolutionary perspectives

蜜腺是分泌花蜜的植物腺体，花蜜是一种富含碳水化合物但也含有较低浓度其他溶质的溶液。尽管蜜腺小而神秘，但在加拿大和国际上，蜜腺对于促进植物和生物在其环境中的有益互动具有极其重要的生态学意义。花蜜腺通常位于关键位置，导致访客接触花药(产生花粉的器官)和柱头(授粉发生的接受花粉的地点)。因此，当蜜蜂和其他昆虫等访花动物从花蜜中收集花蜜作为重要的食物来源时，就会产生互利关系，最终导致种子和果实结实。我们日常饮食的主要部分可以直接归因于昆虫的授粉，因此也可以归因于蜜腺。一些花基甚至有刺，这是一种管状延伸，可以隐藏花蜜，只有舌头长度足够的动物才能获得它。对于一种极其有益的蜜蜂(意大利蜜蜂)来说，花蜜是加拿大和世界范围内一种非常有价值的商品-蜂蜜的前身。 蜜腺的研究需要显微镜。每个蜜腺通常有三个结构成分：一个表皮(一层覆盖细胞)，几层真皮下腺细胞，外加一个维管供应(管道)。我们将通过寻找细胞生长和发育的机制来研究这三个组成部分，从而在进化的背景下获得关于蜜腺形式和功能的新知识。我们将研究i)产生花蜜的花枝，其独特之处在于其顶端形成了一个分叉(如字母Y)。有趣的是，蜂鸟和某些昆虫的舌头是分叉的。使用光学显微镜、共聚焦显微镜和扫描电子显微镜，我们将在其发育过程中放大骨刺的细胞，以确定这些Y分支骨刺是如何发展的。此外，使用定期涂抹在相同活刺上的牙印材料，甚至可以让我们在表皮细胞分裂和伸长时追踪它们的个别档案；ii)被称为韧皮部的植物管道的糖导形式将在各种花蜜腺中进行检查，在这些蜜腺中，我们已经发现了伴生细胞的差异，这种特殊的细胞将到达的糖卸载出来，作为花蜜分泌到外部。此外，我们将调查一个非常大的科，菊科的花蜜腺，以扩大我们对形成在表皮中的韧皮部的发现，这在植物中是一种独特的现象；以及iii)来自几个物种的奇怪的不育花突变体，它们在花瓣和萼片中形成蜜腺--有时仍然具有功能。我们将比较这些突变植物和正常植物的蜜腺结构和蜜腺产量，以更多地了解在甚至无法授粉的情况下仍然存在的花蜜腺的起源。

Nectaries are plant glands that secrete nectar, a solution rich in carbohydrates but also containing other solutes at lower concentrations. Despite being small and cryptic, nectaries are extremely important ecologically for fostering beneficial interactions between plants and organisms in their environment, both in Canada and internationally. Floral nectaries typically reside in strategic locations leading to the visitor's contact of anthers (pollen-producing organs) and stigmas (pollen-receiving sites, where pollination occurs). Thus, mutualistic relationships occur when flower-visiting animals such as bees and other insects gather nectar as an important food source from floral nectaries, leading eventually to seed and fruit set. Major parts of our daily diets can be attributed directly to pollination by insects, and hence to nectaries. Some flower bases even possess spurs, tubular extensions that conceal nectar available only to animals with sufficient tongue length to attain it. And for an extremely beneficial species, the honey bee (Apis mellifera), nectar is the precursor of a highly valued commodity in Canada and worldwide - honey. The study of nectaries requires microscopy. Each nectary typically has three structural components: an epidermis (a layer of covering cells), several subepidermal layers of glandular cells, plus a vascular supply (plumbing). We shall investigate these three components by searching for mechanisms of cellular growth and development leading to new knowledge about nectary form and function, in an evolutionary context. We shall study I) nectar-yielding floral spurs which are unique by the formation of a bifurcation (like the letter Y) at their tip. Interestingly, hummingbirds and certain insects have bifurcated tongues. Using light, confocal, and scanning-electron microscopy, we shall magnify the cells of spurs throughout their development, to determine how these Y-branched spurs develop. Also, use of a dental impression material applied at regular intervals to the same, living spur will even allow us to trace individual files of epidermal cells as they divide and elongate; II) the sugar-conducting form of plant plumbing called phloem will be examined in a variety of floral nectaries in which we have already discovered differences in companion cells, special cells that unload arriving sugar to be secreted externally as nectar. Also, we shall survey floral nectaries of a very large family, the Asteraceae, to expand our discovery of phloem that forms in the epidermis, a unique occurrence in plants; and III) strange sterile flowers called "agamous type" mutants from several species which form nectaries - sometimes still functional - amidst their petals and sepals. We shall compare nectary structure and nectar production in these mutant and normal plants, to learn more about the origin of floral nectaries still present when pollination cannot even occur.