R. Ferris et al., CONTRASTING CO2 AND TEMPERATURE EFFECTS ON LEAF GROWTH OF PERENNIAL RYEGRASS IN SPRING AND SUMMER, Journal of Experimental Botany, 47(301), 1996, pp. 1033-1043
The effects of increased atmospheric carbon dioxide (CO2) of 700 mu mo
l mol(-1) and increased air temperature of +4 degrees C were examined
in Lolium perenne L. cv. Vigor, growing in semi-controlled greenhouses
, Leaf growth, segmental elongation rates (SER), water relations, cell
wall (tensiometric) extensibility (%P) and epidermal cell lengths (EC
L) were measured in expanding leaves in spring and summer. In elevated
CO2, shoot dry weight (SDW) increased in mid-summer, In both seasons,
SDW decreased in elevated air temperatures with this reduction being
greater in summer as compared to spring, Specific leaf area (SLA) decr
eased in elevated CO2 and in CO2 x temperature in both seasons, In spr
ing, increased leaf extension and SER in elevated CO2 were linked with
increased ECL, %P and final leaf size whilst in summer all were reduc
ed, In high temperature, leaf extension, SER, %P and final leaf size w
ere reduced in both seasons. In elevated CO2 x temperature, leaf exten
sion, SER, %P, and ECL increased in spring, but final leaf size remain
ed unaltered, whilst in summer all decreased. Mid-morning water potent
ial did not differ with CO2 or temperature treatments. Leaf turgor pre
ssure increased in elevated CO2 in spring and remained similar to the
control in summer whilst solute potential decreased in spring and incr
eased in summer, Contrasting seasonal growth responses of L. perenne i
n response to elevated CO2 and temperature suggests pasture management
may change in the future, The grazing season may be prolonged, but wh
ole season productivity may become more variable than today.