PARENT SESSION
Contributed Oral Session 47: Invasive Species: Environmental and Habitat Factors
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal
Effects of variable ambient light on the photosynthetic physiology, growth and reproduction of the invasive C4 grass Pennisetum setaceum in Hawaiian dry forests.
Cervin, Nichole*,1, Sandquist, Darren1, 1 California State University, Fullerton, Fullerton, CA, USA
ABSTRACT- Fountaingrass (Pennisetum setaceum) is an invasive C4 African grass that produces unmanageable amounts of biomass in the understory of Hawaiian Dry Forests. C4 grasses generally require high irradiance to achieve maximum productivity. When grown in reduced light C4 species typically exhibit decreased amounts of phosphoenolpyruvate carboxylase (PEP-C) and increased chlorophyll concentrations. These changes are correlated with a decrease in maximum photosynthetic rates, reduced respiration rates and increased quantum yields; possibly leading to diminished growth rates, biomass and reproductive output. The photosynthetic light responses, growth rates and reproductive capabilities of P. setaceum grown under variable light conditions were assessed by cultivating the grass in treatments of 100, 60, 40 and 20% ambient light. Maximum photosynthetic rates, quantum yields and respiration rates under different light levels were identified based on photosynthetic light response curves. Growth rates and total biomass were calculated from leaf-length measurements and inflorescence produced per plant. Few distinctions in gas exchange characteristics were observed, except for maximum photosynthesis rates in cooler months, which were greatest for plants in 100% sunlight. There were no significant differences in total productivity among grasses in the 100%, 60% and 40% light levels, but total growth at 20% sunlight differed significantly from that in 100% sunlight. Plants cultivated in 100% and 60% treatments produced a significantly higher numbers of flowers than those at 20% ambient light. While reduced irradiance had little apparent influence on the photosynthetic physiology of this species, differences in growth and reproductive output were observed between the highest and lowest light treatments.
Key words: Pennisetum setaceum, Hawaii, invasion, C4 productivity