STARR, GREGORY1,2* and STEVEN F. OBERBAUER2. 1School of Forest Resources and Conservation, University of Florida, Gainesville, FL 32611.; 21- Department of Biological Sciences, Florida International University, Miami FL 33199.. - The role of anthocyanins in photosynthesis of arctic evergreens during spring snow melt.
In arctic ecosystems, snow cover persists into the spring long after
air temperatures and light levels may be suitable for vascular plant
photosynthesis. However, the general assumption is that vascular
plants under the snow show little if any photosynthetic activity. We
have found that significant photosynthetic activity occurs in arctic
evergreens in late spring prior to snowmelt, which in turn has
implications in the ecosystem’s carbon balance. This photosynthetic
activity is quite variable and appears to be linked to
microtopographic characteristics that affect photosynthetic photon
flux densities (PPFD) reaching the plants. To protect their
photosynthetic apparatus against the effects of high PPFD during
spring melt, three arctic evergreens, Ledum palustre L.,
Vaccinium vitis-idaea L., and Cassiope tetragona L.,
were shown to produce significant concentrations of anthocyanins. The
concentrations of anthocyanins were dependent on leaf positioning on
individual plants and the position of individual plants within the
microtopography. Plants that faced directly south tended to produce
higher concentrations of anthocyanins than plants in shaded settings
or northern orientations. We also demonstrate that snow load and
anthocyanin concentrations are inversely correlated; as snow depth
decreases and PPFD increase at the ground surface, concentrations of
anthocyanins increase until moderate growing season conditions
persist. These findings add additional support to the light screen
hypothesis that suggests that anthocyanins protect photosynthetic
tissues from photoinhibition when high light is coupled with low
temperatures. This reduction in photoinhibition allows the species to
increase their physiological activity prior to emerging from snow
cover and allows them to reach maximum photosynthetic capacity within
days of becoming snow free. This strategy is an important aspect of
the acquisition of carbon reserves for these species during the short
growing season.
Key words: anthocyanins, arctic evergreens, spring snow melt