Tuesday, November 22, 2011

albino phenotype in Sequoia sempervirens

albinistic mutations are often recorded in Redwood (Sequoia sempervirens).  Popular literature indicates these mutations are 'very rare' in S. sempervirens: Discover Magazine has “25 of these trees are known to exist around the world, eight of which are at Henry Cowell State Park in California”, while “Field Notes by Barry Evans”, The Journal, Humboldt County “Only about 50 are known to exist”.  Exactly how frequent these mutations occur is uncertain.  

Insofar as I find in literature, there is no certainty as to the type of mutation that results in albinsitic crown sprouts in S. sempervirens.  In general, the albino phenotype in vascular plants results from mutations in either nuclear genes that code precursors for plastid biogenesis, or in chloroplast genes, and at least in grasses, plants with nuclear mutations often have plastids with only carotenoid pigments present, producing a faint yellow in the affected leaves.   The color of the mutant S. sempervirens below suggests no mature carotenoid pigments form, as there is no hint of yellow pigment.

This albino S. sempervirens occurs near Nisene Marks State Park, Santa Cruz, County.  This particular clump has been essentially this size, about 2 meters tall, for nearly 2 decades now, although individual stem axes die and are replaced.    The principal factor seemingly associated with the state of this particular clump is that it gets ‘smothered’ by litterfall, which has broken or bent down individual stem axes over the years. 

The albino phenotype of S. sempervirens was reported upon by George J. Peirce in Proceedings California Academy of Sciences, Third Series, Botany, Volume 2, p. 83-107 (1900-1904), and reading his article it seems these albino trees were known from throughout the Bay Area early on.  Peirce termed them  “not an especially rare peculiarity” and “I have entirely failed to detect even rudiments of plastids” on plants from near La Honda, while albino mutants from near Redwood Retreat (vicinity of Gilroy) he states “contained chromatophores which ranged in size from those about half as large as the average chloroplastids in the normal green leaves down to indistinguishable rudiments.”  His observations might therefore suggest that these albino forms can result from a mutations either in nuclear or chloroplast genes.  

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