150
I.S. Pereira
the partial pressure of CO2 in the air, Pa (Farquhar et al. 1989, see also
Chap. 19, this Vol.). The use of the discrimination for 13C in plant tissues to
study the relation between photosynthesis and growth has been limited.
Masle and Farquhar (1988) found in wheat plants with different growth rates
a strong negative correlation between p and the value of 13C discrimination
in leaf tissues. For a given increase in discrimination, the decrease in p was
proportionally larger than the decrease in assimilation rate so that relative
growth rate was positively correlated to 13C discrimination. We also found
that 13C discrimination was negatively relate to p and positively related with
growth and the quotient biomass production: solar radiation intercepted
(Osorio and Pereira, unpubl.). More work needs to be done in this area
(see Chap. 19, this Vol.).
8.3 Photosynthesis and Growth Rates
One obvious case of differences in growth being ascribed to differences
in metabolic rates is given by the generally higher rates of growth and pho35~------~--------------------~
CI) 30
N
E 25
o
E
::120
CI)
.~ 15
..c +oJ
c
>10 CI)
o
+oJ
• Eucalyptus sp .
• Carex sp.
• Salix sp.
A Geum & Cirsium
... Atriplex sp.
•
...
...
•
...
A
•
0 .
•
•
o •
•
•
o 5
..c
•
OL-~·----------~-------------L----~
(l.
0.05
0.15
0.25
Relative growth rate, g g -1 day -1
Fig. 8.1. Relation between Rw and leaf photosynthetic rates of woody and herbaceous
species, Eucalyptus spp. (Mooney et al. 1978; Pereira et al. 1992a), Carex spp. (Konings
1989), Salix aquatica grown at different irradiances (Waring et al. 1985), and Geum
urbanum and Cirsiumpalustre (Pons 1977). The regression line is Rw = 2.65 + 87.13* A(rZ =
0.25, n.s.)