USING GROWTH CHAMBERS TO SIMULATE ANCIENT CLIMATES AND MEASURE FUNCTIONAL LEAF TRAIT RESPONSE IN NON-WOODY FLOWERING PLANTS

Flowering plants experienced and persisted through severe environmental and climatic changes over the last 100 million years. Leaf functional traits offer insight on how important plant traits adapt to shifts in climate variables like [CO₂] and temperature. These leaf traits are useful to make inferences about how fossil leaf functional traits responded to past climates, and to forecast how living plants will be impacted by anthropogenic climate change. In this study, we grew ginger plants (Zingiberaceae) in growth chambers to measure trait response from elevated climate conditions.The ginger species Kaempferia angustifolia and Burbidgea scheizocheila were chosen for this study because their mature size is small enough to fit many specimens within a growth chamber, studying these two species provided interesting comparisons between temperate and tropical growth-forms, and Burbidgea belongs to the Alpinioideae subfamily, which is the group to which most fossil gingers belong. Plants were grown under six different sets of conditions of ambient and increased temperature (22^oC & 27^oC) and [CO₂] (500ppm, 750ppm, & 1200ppm). Stomatal conductance was measured in situ while the other following functional traits were measured after leaves were collected: vein length per area (VLA), leaf mass area (LMA), specific leaf area (SLA), and stomatal index. LMA and SLA had opposite trends, with LMA increasing under higher temperature and [CO₂], while SLA decreased; both were more greatly impacted by temperature. Stomatal index was independent of both temperature and [CO₂], but stomatal conductance largely decreased as [CO₂] increased. All VLA increased with higher temperature. Our results demonstrate consistency with other leaf functional trait studies. These experiments provide estimates of how fossil relatives of gingers may have responded to local climate shifts, and offer an outlook on how anthropogenic climate change will impact living gingers and other similar plants.