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°C and 25/15°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°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 time, 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.