{"id":261,"date":"2014-10-29T12:57:48","date_gmt":"2014-10-29T12:57:48","guid":{"rendered":"http:\/\/orbisec.com\/?page_id=261"},"modified":"2014-10-29T12:57:48","modified_gmt":"2014-10-29T12:57:48","slug":"milkweed-flower-morphology-and-terminology","status":"publish","type":"page","link":"https:\/\/orbisec.com\/index.php\/milkweed-flower-morphology-and-terminology\/","title":{"rendered":"Milkweed Flower Morphology and Terminology"},"content":{"rendered":"

YOUR DAILY DOSE OF BOTANY \u2013 FEBRUARY 2014<\/strong><\/h1>\n

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Milkweed Flower Morphology and Terminology<\/strong><\/h2>\n

Submitted by Scott Namestnik, snamestnik@orbisec.com<\/a><\/h2>\n

As evidenced by the number of posts about it on my blog, one my favorite genera, of showy plants at least, is the genus Asclepias<\/em> (see http:\/\/handlensandbinoculars.blogspot.com\/search\/label\/Asclepias<\/a>).\u00a0 There are plenty of reasons to be fond of this genus, not the least of which is the important role that the lower taxa play in the life cycles of over 450 different insect species.\u00a0 Another reason to like this genus is that at least one species of Asclepias<\/em> is known from 49 of the 50 states, so no matter where you travel around the country there is a good chance you can find a milkweed.\u00a0 Yet another reason is the unique floral morphology of plants in the genus Asclepias<\/em>.\"Milkweed<\/p>\n

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The flowers of plants in the genus Asclepias<\/em> are often in clusters, with all of the flower stalks originating from a single point (an umbel<\/strong>).\u00a0 The flowers are bisexual and actinomorphic (remember what that means from the Flower Symmetry<\/a> article in the\u00a0October 2012 issue of The Plant Press<\/em>?).\u00a0 Each individual flower has a five-parted calyx<\/strong> (sepals) and a five-parted corolla<\/strong> (petals).\u00a0 Pretty normal so far, but here\u2019s where the flowers get interesting.\u00a0 Each flower often has a corona<\/strong> (translated: crown) arising from the middle of the corolla.\u00a0 The corona can look different on different species, but it often has five upright hoods<\/strong> that can be mistaken for petals.\u00a0 Each hood often contains a pointed, incurved horn<\/strong>, also known as a crest<\/strong> or beak<\/strong>.\u00a0 Surrounded by the five hoods is the gynostegium<\/strong>, which is a compound structure that includes the fused column of the stamens<\/strong> (male reproductive parts) and the heads of the styles<\/strong> (part of the female reproductive parts).\u00a0 This is where the magic happens, folks.\u00a0 The anthers<\/strong> (pollen-bearing portion of the stamens) are split into two halves, and each tw\"Milkweed<\/a>o adjacent half-anthers are connected at the corpusculum<\/strong> (a gland that assists in transporting pollen).\u00a0 Unlike plants in most other genera, in which the pollen consists of individual grains or small groups of grains, the pollen in Asclepias<\/em> is grouped into waxy masses known as pollinia<\/strong> (pollen sacs).\u00a0 Crazy, I know.\u00a0 Here\u2019s where it gets good.\u00a0 When an insect visits a milkweed flower for nectar (contained within the hoods), its legs slip into the crevices created by two adjacent half-anthers.\u00a0 In the process, it unknowingly picks up a pair of pollinia that it takes to the next milkweed flower that it visits.\u00a0 As its leg again slips into the crevice, it can distribute the pollinia if that crevice is vacant.\u00a0 The pollinia need to be placed precisely into the crevice or pollination will not take place.\u00a0 Isn\u2019t it amazing how much is going on \u201cbehind closed doors\u201d about which we are not even remotely aware?<\/p>\n

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If you have a question about plant terminology or morphology that you would like answered in a future edition of this column, send me an email at snamestnik@orbisec.com<\/a>.\u00a0 I may not be able to address all requests given the space allotted for this column, but I will answer those that I can.<\/p>\n