Friday, August 6, 2010: 8:00 AM
336, David L Lawrence Convention Center
Background/Question/Methods
Galax urceolata (Poir.) Brummitt (Diapensiaceae) is a common evergreen herb of southern Appalachian forests. During fall and winter, leaves of plants exposed to high light produce substantial amounts of anthocyanins, which attenuate excess blue-green light and prevent photoinhibition and photo-oxidative damage to the spongy mesophyll cells. Interestingly, this species also produce anthocyanins belowground in its rhizome, the functional benefit of which is currently unknown. For this observational study, we wanted to determine if there was a light-dependent relationship between above and belowground anthocyanin production for Galax plants in the field. We sampled ramets spaced more than 1 m apart from three populations over two different seasons in the mountains of northwestern North Carolina (Mount Jefferson State Natural Area in fall 2007 and Grandfather Mountain in fall/winter 2008-2009). Ramets were selected from habitats that were later classified as sunny or shady, as determined by periodically measuring photosynthetically active radiation over the season as the canopy senesced. Sampling started prior to leaf fall in September when all Galax leaves were green, and continued through the winter into March, by which time those leaves in a priori determined high light habitats had turned red. Those in shaded habitats remained green. Leaves and rhizomes from high and low light locations were sampled for chlorophyll and anthocyanin content, while carbohydrate amounts (various soluble sugars and starch) were determined on a subsample of the rhizomes from the 2008-2009 season. Results/Conclusions
There were significant (p < 0.05), positive correlations between leaf and rhizome anthocyanin contents in both green and red plants, but those in high light habitats produced significantly more anthocyanins (in both leaves and rhizomes) than those in low light habitats (p < 0.05). Interestingly, there were no differences in carbohydrate contents (p > 0.05) between sun and shade rhizomes, although for both groups starch significantly decreased through time while soluble sugars increased. These results contradict the paradigm that anthocyanins in plant tissues are produced only in the light. Furthermore, the relationship between leaf and rhizome anthocyanins is suggestive of some form of communication between leaves and rhizomes with respect to anthocyanin content, although the nature of that signal is not known. The adaptive significance of belowground anthocyanins in Galax remains unresolved at this time.
Galax urceolata (Poir.) Brummitt (Diapensiaceae) is a common evergreen herb of southern Appalachian forests. During fall and winter, leaves of plants exposed to high light produce substantial amounts of anthocyanins, which attenuate excess blue-green light and prevent photoinhibition and photo-oxidative damage to the spongy mesophyll cells. Interestingly, this species also produce anthocyanins belowground in its rhizome, the functional benefit of which is currently unknown. For this observational study, we wanted to determine if there was a light-dependent relationship between above and belowground anthocyanin production for Galax plants in the field. We sampled ramets spaced more than 1 m apart from three populations over two different seasons in the mountains of northwestern North Carolina (Mount Jefferson State Natural Area in fall 2007 and Grandfather Mountain in fall/winter 2008-2009). Ramets were selected from habitats that were later classified as sunny or shady, as determined by periodically measuring photosynthetically active radiation over the season as the canopy senesced. Sampling started prior to leaf fall in September when all Galax leaves were green, and continued through the winter into March, by which time those leaves in a priori determined high light habitats had turned red. Those in shaded habitats remained green. Leaves and rhizomes from high and low light locations were sampled for chlorophyll and anthocyanin content, while carbohydrate amounts (various soluble sugars and starch) were determined on a subsample of the rhizomes from the 2008-2009 season. Results/Conclusions
There were significant (p < 0.05), positive correlations between leaf and rhizome anthocyanin contents in both green and red plants, but those in high light habitats produced significantly more anthocyanins (in both leaves and rhizomes) than those in low light habitats (p < 0.05). Interestingly, there were no differences in carbohydrate contents (p > 0.05) between sun and shade rhizomes, although for both groups starch significantly decreased through time while soluble sugars increased. These results contradict the paradigm that anthocyanins in plant tissues are produced only in the light. Furthermore, the relationship between leaf and rhizome anthocyanins is suggestive of some form of communication between leaves and rhizomes with respect to anthocyanin content, although the nature of that signal is not known. The adaptive significance of belowground anthocyanins in Galax remains unresolved at this time.