Inangiosperms, ahypanthium orfloral cup[1][2][3] is a structure where basal portions of thecalyx, thecorolla, and thestamens form a cup-shaped tube. It is sometimes called afloral tube, a term that is also used forcorolla tube andcalyx tube.[4]It often contains thenectaries of the plant. It is present in many plant families, although varies in structural dimensions and appearance.[5] This differentiation between the hypanthium in particular species is useful foridentification. Somegeometric forms areobconic shapes, as intoyon (Heteromeles), whereas some are saucer-shaped, as inMitella caulescens.
Its presence is diagnostic of manyfamilies, including theRosaceae,Grossulariaceae, andFabaceae. In some cases, it can be so deep, with such a narrow top, that the flower can appear to have aninferiorovary – the ovary is below the other attached floral parts. The hypanthium is known by different common names in differing species. In theeucalypts, it is referred to as thegum nut; in roses it is called thehip.
Inmyrtles, the hypanthium can either surround the ovary loosely or tightly; in some cases, it can be fused to the walls of the ovary. It can vary in length. The rims around the outside of the hypanthium contain the calyx lobes or free sepals,petals and either the stamen or multiple stamen that are attached at one or two points.
The flowers of therose family (Rosaceae) always have some type of hypanthium or at least a floral cup from which the sepals, petals and stamens all arise, which is lined with tissue known asnectaries, which producenectar, asweet substance that attracts to the flower birds and bees, which receivepollen from the lining of the hypanthium, subsequently transferring it to the next flower they visit, usually a neighbouring plant, facilitatingpollination.[6]
The stamens borne on the hypanthium are the pollen-producingreproductive organs of the flower. The hypanthium helps in many ways with the reproduction pathways of most plants. It provides weather protection and a medium to sustain the lost pollen, increasing the probability of fertility and cross-pollination.[7] The retained pollen can then attach topollinators such as birds, bees, moths, beetles, bats, butterflies and other animals. Wind can act as an instigator forfertilisation. The hypanthium is also an adaptive feature for structural support. It helps thestem fuse with the flower, in turn strengthening the bond and overall stability and integrity.[8]
{{citation}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)Foster, Tony."Botany Word of the Day".Phytography. Retrieved27 November 2014.
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