Monday, June 8, 2009

Cymose inflorescences: Euonymus and Tilia

If you already know what a cyme is you can stop paying attention, but if you don't, its sort of cool, sort of interesting, and easy to understand. There isn't a lot of thinking involved but in a couple of minutes you'll know something you didn't know before and that's good!

There are two basic inflorescences, or arrangements of flowers: racemose, or indeterminate and cymose or determinate. Imagine flowers grouped along an axis with the growing tip at the end; if the oldest (lowest) buds open first then there is the possibility for an infinite amount of new buds to be produced above them and flowering can go on ad infinitum. If, however, the end, the tip, the apical meristem, whatever you call it produces the bud that flowers first, then all the others have already formed and are waiting below it and so the number of flowers is determinate, there will be no more buds produced. Racemose inflorescences are indeterminate and cymose are determinate. There are lots of variations on these two basic themes.

All through school I was shown diagrams of cymes, or groups of buds with the largest in the middle; Today I just happened on two plants with very typical cymose inflorescences: Euonymus carnosus and Tilia sp..

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