What is stomatal bloom? And why do we care about it anyway?
|Bloom on grand fir and western hemlock|
|Rows of stomatal bloom on grand fir|
|Pacific silver fir and subalpine fir|
You can distinguish western white pine from sugar pine by looking at the stomatal bloom on their three-sided needles. Sugar pine has bloom on all three sides, while western white pine has bloom on just two.
|Western red cedar and Port Orford cedar|
Shade-tolerant conifers in the Pacific Northwest usually have bloom only on the lower surfaces of the needles. This is particularly noticeable in the firs and hemlocks. Natives with bloom on the lower and upper surfaces are generally more intolerant of shade, and often grow in the higher elevations. This seems reasonable. The bloom on the upper surfaces would block the sun. Shade-tolerant trees need to have clear upper surfaces to capture what sunlight they can under the forest canopy. On the other hand, the bloom on the upper surface of needles gives trees growing in direct sunlight protection from the sun’s ultra-violet rays, especially in higher elevations where sunlight is more intense. This may explain why you find subalpine firs growing in open meadows near the timberline, while Pacific silver firs compete better in shady woods.
These relationships between stomatal bloom and the distribution of conifers are bound to be complex. In any case, some familiarity of the differences in the presence of stomatal bloom on conifer needles can help us identify conifer species in the wild.
THE RELATIONSHIP OF CUTICLE STRUCTURE TO THE VISIBLE AND ULTRAVIOLET SPECTRAL PROPERTIES OF NEEDLES FROM FOUR CONIFEROUS SPECIES by JOHN B. CLARK AND GEOFFREY R. LISTER in Plant Physiol. Vol. 55, 1975, p. 307
Air Pollutants and the Leaf Cuticle edited by Kevin E. Percy,
, Richard Jagels, Caroline J. Simpson, p. 90. John Cape
Subalpine Fir in Silvics of North America
Thank you for an excellent overview.ReplyDelete
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