Tuesday, December 28, 2010

Branching in Camissonia seedlings

Branching in Camissonia lacustris begins at the cotyledonary node (at red arrow, the cotyledons at yellow arrows, 80 day old seedlings). At this age, the cotyledons are still fully functional and are, after post germination maturation, identical to the first formed foliage leaves. Precious branching is not uncommon throughout angiosperms, indicating that the feature is adaptive in specific environments, and can be selected out of a genome again and again. In Onagraceae, within Camissonia as delimited by Raven (1969), the differences in growth features between rosette annuals (now treated within Chylisma and Eremothera) and Camissonia sensu stricto are manifold, and support the dismemberment of the Raven genus concept. Done. Remember, Raven dismembered the Munz' genus Oenothera with the occasional raised eye-brow typical of the pre-DNA era of systematics. In thinking about the expression of branching control in Camissonia seedlings, the feature of flowers at basal nodes in Gayophytum, where G. diffusum, which branches distally and is very common, contrasts to G. decipiens and its basal branching and relative rarity comes to mind: perhaps the grazing lips of a herbivore ought to be brought into the mix: lateral gene transfer? {by that I mean that there is a distance above the ground surface which grazing influence does not penetrate, the lip-o-the-grazer distance. Branch below that distance, and survive.

Plants are cool!

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