Saturday, March 3, 2012

Precocious flowering of ramets in Poa sierrae

Photos: top to bottom – two ramets before potting, after 130 days, respectively. Note that the ramet with a single axis is smaller than the ramet that started with three axes!!!

Poa Section Madropoa is mostly restricted to high mountains of western North America.  Poa sierrae is odd within the clade: it is characterized as being rhizomatous, dioecious and by the distinctive scaly ‘bulbils’ produced on the rhizomes.  These ramets doubtless propagate by fragmentation, so it is puzzling why P. sierrae is quite narrowly distributed.

On August 3, 2011, Poa sierrae was collected (my #21,134) at the type locality (‘Lewisia’ rock near Belden, Feather River Canyon, Plumas County, CA).  Genets were potted up quickly thereafter, and kept moist throughout the fall.  These ramets remained dormant until mid-November, when, perhaps induced by decreasing daylength, they began growth.  Growth continued modestly once the ramets responded.  After about 130 days of growth, inflorescences began to emerge. 

Precocious flowering has been reported in Poaceae: tissue-cultured bamboo can be induced to flower  (Nature Nature 344, 335 - 336, 22 March 1990).  In Arabidopsis, precocious flowering is controlled by a pair of antagonistic genes (Science Vol. 286:1960-1962. 1999).

Ordinarily, sensu Baker & Stebbins 'Genetics of Colonizing Species' one would conclude that a vegetatively spreading, precociously flowering species would be weedy.  For Poa sierra, exactly not.

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