Page 150 - FRUTAS DEL TRÓPICO

150 Frutas del trópico

Internal CO concentration (substomatal CO concentration; internal partial pressure of
2 2
CO ) is the amount of CO in the small stomatal cavity waiting to be fixed during photosynthe-
2 2
sis. By plotting net CO assimilation over Ci (called an A/Ci curve) it can be determined if the
2
limitation to carbon fixation is due to stomatal or biochemical factors (Farquhar and Sharkey,

1982). The initial linear portion of the regression line slope represents the non-stomatal limi-

tation to photosynthesis. For example, Figure 3 shows A/Ci curves for mango trees growing

in the field where there was no root restriction and in pots where there was root restrictions

that resulted in an inhibition of photosynthesis.

Figura. 3. A/Ci curves of ‘Kensington’ mango plants in containers with and without root restriction
(from Schaffer et al., 1997).

40
A (µmol CO 2 m -2 s -1 ) 30

20

10
Field-grown (non-root restricted)

0 Container-grown (root restricted)
0 200 400 600 800 1000 1200 1400 1600
-1
Ci (mmol CO mol )
2

There was no difference in the initial slope of the A/Ci curve between root-restricted and

non-root-restricted plants, indicating that the reductions in net CO assimilation as a result of
2
root restriction was not related to biochemical causes such as a reduction in Rudp-carboxylase/

Universidad Autónoma de Chiapas