Responses of Lotus corniculatus to environmental change .1. Effects of elevated CO2, temperature and drought on growth and plant development

Five clonal plants of three genotypes of Lotus corniculatus were grown in each of eight controlled environments under combinations of two temperature regimes (18/10 degrees C and 25/15 degrees C), two CO2 concentrations (ambient and 700 ppmv) and two water applications (ad libitum or 60% droughted). Plants were harvested at full flower and measurements made of plant growth and development. Of the three environmental variables studied, higher growth temperatures resulted in the largest number of significant changes to the measured variables. Reproductive capacity, growth rate, shoot biomass, water use efficiency and chlorophyll content were all enhanced by raising the growth temperature from 18 to 25 degrees C. Doubling the CO2 concentration enhanced the growth rate, shoot biomass and water use efficiency and ameliorated some of the effects of drought, including reproductive capacity, and biomass production, but reduced flowering lime, specific leaf area, and chlorophyll content of both droughted and undroughted plants. Drought alone reduced reproductive capacity, growth rate and above ground biomass but significantly increased root biomass in all environments. The agronomic effects resulting from a combined increase in growth temperature, doubled CO2 concentration and mild drought in this experiment were a shorter vegetative period and an increase in biomass, but a fall in reproductive capacity.