Photosynthetic characteristics of Garrya ovata Benth. (Lindheimer's silktassle, Garryaceae) at ambient and elevated levels of light, CO2 and temperature

Garrya ovata Benth. (Lindheimer’s silktassle) is a shrub or small tree found in woodlands and savannas of the central Texas Edwards Plateau region. Plant communities where G. ovata occurs are mainly Juniperus ashei/Quercus virginiana woodlands or savannas with intercanopy grassland gaps or patches. These communities are found in stressful environments of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, G. ovata is a low density, woody understory species in these communities. Although G. ovata was only found in the understory, this study suggests it is more of a sun or edge species and not truly a shade or understory species. Maximum photosynthetic rate (Amax), dark respiration (Rd), intercellular CO2, light saturation (Lsp) and water use efficiency significantly increased when light levels and CO2 concentrations were elevated but not when temperatures were elevated. Stomatal conductance decreased when the CO2 concentration doubled but was little affected by elevated temperature. These findings suggest that G. ovata should be more common in central Texas Juniperus/Quercus woodlands or savannas as well as in associated gaps or grasslands today and imply that it will have a higher density in these communities in a future high CO2 environment. However, they do not explain why it has a low density in these communities today. Published on-line www.phytologia.org Phytologia 97(2): 103-119 (April 1, 2015). ISSN 030319430.