Elevated CO2 and temperature: effects on plant canopy development [abstract]

An experiment was conducted in a suite of eight Solardome glasshouses program med to provide a factorial combination of two levels of CO, concentrations (ambient and ambient plus 340 ppm) and two levels of temperature (ambient and ambient +3°C) with two replicates for each C02 x temperature combination. Plants were grown in 0.11 m diameter pots made from 1.5m lengths of drainage pipes, filled with washed silica sand and supplied with full strength Long Ashton solution. Combined and independent increases in [CO,J and temperature promoted leaf extension and increased final leaf length, particularly during the early stages of the growing season (July) the absence of any CO, effect on leaf extension later in the season (August) in Dactylis glomerata was possibly due to its large canopy, with leaf extension more closely coupled to canopy microclimate than externally imposed treatments. Elevated C02 concentrations had no significant effect on leaf numbers.Elevated temperature significantly increased leaf production in Helianthemum nummularium (p<0.05), but only in combination with an increase in [CO,] in Plantago lanceolata (p<0.05).Elevated CO, promoted early leaf senescence (p<0.05) with the exception of Poa alpina which was more sensitive to a 3C increase in growth temperature (p<O.O I ). The greater sensitivity of P. alpina to elevated temperature than [CO,] may reflect its alpine habit. • Elevated [CO] increased leaf size but not leaf n umber and promoted early leaf senescence in most species. • There was little evidence of any interaction between elevated [CO2] and temperature on plant canopy development.