Ca. Berryman et al., STOMATAL RESPONSES TO A RANGE OF VARIABLES IN 2 TROPICAL TREE SPECIESGROWN WITH CO2, ENRICHMENT, Journal of Experimental Botany, 45(274), 1994, pp. 539-546
Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F.
Muell) were grown with or without CO2 enrichment (700 mu mol CO2 mol(
-1)). The response of stomatal conductance (g(s)) to leaf drying, exog
enous abscisic acid and calcium ions was investigated in M. corymbosa.
Reciprocal transfer experiments were also conducted whereby plants we
re grown in one treatment and then transferred to the other before g(s
) was measured. Stomatal conductance in M. corymbosa was more sensitiv
e (a greater percentage decline in g(s) per unit percentage decline in
leaf fresh weight) to leaf water status under conditions of CO2 enric
hment compared to ambient conditions. However, the rate of reduction o
f g(s) in response to exogenous abscisic acid was not influenced by CO
2 treatment. In contrast, the rate of reduction of g(s) in response to
exogenous CaCl2 was decreased under conditions of CO2 enrichment. Rec
iprocal transfer experiments showed that exposure to CO2 enrichment re
sults in a short-term, reversible decline in g(s) as a result of decre
ased stomatal aperture and a long-term, irreversible decline in g(s) a
s a result of a decreased stomatal density. Seedlings of E. tetrodonta
were used to investigate the response of g(s) to light flux density,
leaf-to-air vapour pressure difference (LAVPD), leaf internal CO2 conc
entration (C-i) and temperature. Reciprocal transfer experiments were
also conducted. CO2 enrichment did not influence the pattern or sensit
ivity of response of g(s) to LAVPD and C-i in E. tetrodonta. In contra
st, the slope of the response of g(s) to temperature decreased for tre
es grown under elevated [CO2](a) conditions and the equilibrium g(s) a
ttained at saturating light was also decreased for plants grown under
elevated [CO2](a) conditions.