Isotopic Investigation of Mycoheterotrophy in the Southern Blue Thread(Burmannia capitata)
The Burmanniaceae contain several lineages of achlorophyllous mycoheterotrophic plants that may associate with arbuscular mycorrhizal fungi (AMF). Here we investigate the isotopic profile of a green and potentially mycoheterotrophic wetland plant in situ, Burmannia capitata, the Southern Blue Thread, and associated vegetation. We generated δ 13C and δ 15N stable isotope profiles of a population of B. capitata from the Sand Hills Game Lands in Scotland County, North Carolina. The shoots of B. capitata areindistinguishable from other C3 reference vegetation but did show significant depletion in δ 13C relative to C4 reference vegetation. The highest δ 15N values were observed in the B. capitata shoot. The δ 13C signal of B. capitata root fraction was significantly enriched relative to the root fraction, suggesting a signal from mycorrhizal associates. Within the genus Burmannia transitions to full mycoheterotrophy have occurred numerous times suggesting that some green Burmannia species are likely partially mycoheterotrophic. Further investigations of mycorrhizal associate using isotopic, molecular and microscopic methods are planned.
1 Dept of Biology, Catawba College, Salisbury, NC; 2 Dept of Animal and Plant Sciences, Sheffield, UK
P191 • William Wright, Maria B. Davenport, Stacey Hettes
Lateral Hypothalamic Glutamate Receptors Mediate Predation of Crickets by Sprague-Dawley Rats
Recent studies linking the periaquaductal gray and superior colliculus to the lateral hypothalamus (LH) have shown all three regions contribute to regulation of predatory hunting. These findings suggest a possible role for LH neurons in regulating hunting behavior in addition to their well-established role in regulating feeding behavior. Our lab has demonstrated that inactivation of LH glutamate receptors with the NMDA receptor selective antagonist D-AP5 disrupts eating and foraging for rat chow. The current study examined whether bilaterally injecting 300nl volumes of the D-AP5 (50 or 10nmol) or artificaial cerebrospinal fluid (aCSF) into the LH of food deprived rats (n=12) would disrupt hunting and consuming crickets. Rats’ behavior was continuously recorded upon placement in a 33 x 16 x 12 plastic tank with crickets. Both 10nmol and 50nmol doses of D-AP5 significantly reduced percent time spent hunting to 5% and 6% respectively compared to the aCSF control of 17% (p<0.001, by RM ANOVA and Student Newman Keuls). Percent time eating was also reduced for both 10nmol and 50nmol doses of D-AP5 to 14% and 9% respectively compared to the aCSF control of 25% (p<0.05). The average number of crickets eaten was also reduced for both 10nmol and 50nmol doses of D-AP5 to 12 and 10 respectively compared to the aCSF control of 25 (p<0.05). These results suggest the activation of NMDA receptors in the LH plays a critical role in the neural circuitry involved in regulating both eating and hunting.
Dept of Biology, Wofford College, Spartanburg, SC
P192 • W. Scott Fravel1, Nicole M. Hughes1, William K. Smith2
Thermogenic Effects of Anthocyanin Pigments in Evergreen Leaves
One of the earliest proposed functional hypotheses of leaf reddening was that (red) anthocyanin pigments increase absorption of visible radiation by leaves, thereby increasing leaf temperature. Studies testing thermogenic effects of red pigments on leaves have thus far failed to demonstrate any measurable difference in temperature between anthocyanic and acyanic tissues. However, most reported measurements of leaf temperature have been made without controlling for variables known by biophysical ecologists to ameliorate elevated leaf temperature (TLeaf) effects, such as wind, solar irradiance, and transpirational water loss, and none have examined leaves under cold winter conditions (when thermal conductivity of air is lowest). Here, we use a published model for leaf temperature to predict the environmental conditions under which a difference in leaf temperature between red and green leaves could occur, and use field observations to test our predictions. Environmental sensors paired with data loggers were used to simultaneously record the following variables: TLeaf, TAir, wind speed, and solar incidence of similarly sized red and green evergreen leaves of Galax urceolata during winter 2013. In all experiments, petroleum jelly was applied to the abaxial leaf surfaces to inhibit transpirational effects. We demonstrate that red leaves can exhibit significant (i.e. 1-7oC) increases in TLeaf relative to green leaves of comparable sizes under bright, cold, low wind conditions. These results suggest that anthocyanin pigments in evergreen leaves could function to elevate leaf temperatures, which would provide a substantial physiological advantage during cold winter months.
