Kristina F. Connor

Growth and intraspecific competitive abilities of the dioecious Lindera melissifolia (Lauraceae) in varied flooding regimes.

Abstract The contribution of sexual dimorphism to male-biased colony ratios observed in field populations of the federally endangered Lindera melissifolia was investigated. Growth characteristics and intraspecific relative competitive abilities were determined for first-year male and female L. melissifolia plants grown at varied densities and receiving three flooding treatments. In the no-flooding and 30-day-flooding treatments, stem height, stem diameter, and total leaf area for male plants were significantly greater than that of higher density male plantings and of female plants without respect to density. In both male and female plants, stem growth ceased and leaves were abscised in response to flooding. Although density effects in combination with hydrologic regime influenced intersexual competition, male-bias from competitive exclusion was not indicated. Growth characteristics for male plants grown alone suggest potential for greater interspecific competitive abilities than that of female plants. Therefore, male plants may be better adapted for colonizing suitable habitat, thus contributing to male-biased colony ratios observed in naturally occurring populations.

Temperature changes in lipid and protein structure measured by fourier transform infrared spectrophotometry in intact pollen grains

Abstract Fourier Transform infrared (FTIR) spectroscopy was used to monitor structural changes in lipids and proteins in four species of pollen grains at different temperatures. Spectral data were used to determine membrane phase transition temperature (Tm) in pollen at two hydration levels. Imbibition was conducted at temperatures above and below the determined Tm values to correlate damage to the presence of gel phase. For three species of pollen, hydration overcame imbibitional damage at low temperature. However, dry pecan pollen, which had a high lipid content, was injured during imbibition at temperatures above and below the Tm. Changes in protein structure were not related to imbibitional damage. FTIR spectroscopy is a useful tool in examining biochemical properties of intact pollen grains and has potential for evaluating cryopreservation protocols.

Lindera melissifolia responses to flood durations and light regimes suggest strategies for recovery and conservation

Passive management to preserve endangered plant species involves measures to avoid anthropogenic disturbance of natural populations, but this approach may not sustain plants that require disturbance-maintained habitats. Active management is often necessary to maintain existing habitats or provide new habitats for endangered species recovery. Our objective was to examine the effects of two disturbances in floodplain forests, soil flooding and light availability, on survival, stem length, stem diameter and ramet production of endangered Lindera melissifolia (Walt.) Blume. We used a water impoundment facility to control the timing and duration of flooding (0, 45 or 90xa0days) and shade houses to vary light availability (70, 63 or 5xa0% ambient light). Hydroperiod had little direct effect on steckling survival, stem length growth and stem diameter growth, supporting indications that soil flooding may be important for reduction of interspecific competition in L. melissifolia habitat. Greater ramet production by stecklings receiving no soil flooding likely resulted from longer periods of favorable soil conditions during each growing season. Positive stem length growth and stem diameter growth under all light levels demonstrates the plasticity of this species to acclimate to a range of light environments, though, greatest survival and stem length growth occurred when L. melissifolia received 37xa0% light, and stem diameter growth was greatest beneath 70xa0% light. Further, female clones produced more ramets as light availability increased. These results indicate that passive management absent natural disturbance could jeopardize sustainability of extant L. melissifolia populations, and this species would respond favorably to active management practices that create canopy openings to increase understory light availability.