Date of Award


Degree Name

MS in Biological Sciences


Biological Sciences


Charles Knight


  • Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T25)and photosynthetic recovery (RT25) were quantified in 27 species. We also studied the relationships between T25, RT25 and leaf mass per area (LMA). Leaf temperature was also monitored in the field.
  • Leaves used in this study were collected from two distinct environments representing desert and montane plant assemblages. T25 and RT25 were measured using a chlorophyll fluorescence protocol incorporating sub-saturating light and short duration heat stress.
  • Mean T25and LMA were significantly different between environments. Mean RT25 was not significantly different between environments. There was a positive relationship between T25 and LMA in both environments.
  • The ability to recover from heat stress does not differ between two biomes that experience vastly different mean maximum temperatures during the summer months. LMA is a predictive leaf trait for thermal tolerance.