re: HYB: anthocyanin pigments

I ran across this today - a link to global environmental issues.  Note
the last couple of sentences.

<http://www.sbs.auckland.ac.nz/research/plantscience/gould/>

<Anthocyanin function in leaves
 Leaves are bathed daily in potentially lethal doses of visible and
ultraviolet radiation. That plants can thrive in this apparently hostile

 environment has been ascribed to the presence of natural suncreens,
flavonoid compounds found in the vacuoles of leaf cells. Most
 conspicuous of all the flavonoids are the anthocyanins, a small class
of pigments that provide colours ranging from red to purple in the
 leaves of plants as diverse as Blechnum ferns and rimu trees.
Anthocyanin production is stimulated by both visible and ultraviolet
light, and
 certain Northern Hemisphere plants that are deficient in the genes for
anthocyanin biosynthesis are damaged greatly by prolonged
 exposure to UV-B radiation. The protective role of anthocyanins in
plants has become a tenet accepted by scientists worldwide.

 New Zealand's trees appear to be different. Our preliminary
investigations argue against wholesale applicability of this
photoprotection
 hypothesis. In a survey of leaves from 25 native species in the
Waitakere Ranges, only three were pigmented in the upper epidermis, the
 tissue best suited to screen subjacent cells from harmful radiation.
The majority had red cells in discrete regions of the lower layers.
 Moreover, pigment distribution varied dramatically across species and
often changed over the course of leaf development. The functional
 significance of the various localised distributions of anthocyanins has
never been addressed; nor is it known how the patterns arise, why
 one cell is pigmented but an adjacent othewise identical cell is
colourless. Neither the photoprotection hypothesis, nor classical
theories
 explain the pigment's variation in time and space.>

--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
photos archives: <http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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