Agriculture Reference
In-Depth Information
In rice, stomatal aperture as well as conductance is strongly
correlated with leaf photosynthesis where as photosynthesis
by rice leaves is also infl uenced by other factors, such as leaf
nitrogen and content of the enzyme ribulose-1, 5- bisphosphate
carboxylase/oxygenase; stomatal conductance is codominantly
correlated with the rate of leaf photosynthesis (Makino et al.
1987).
Temperature range of 10 to 15ºC has been reported to
signifi cantly reduce chlorophyll content, and below 10ºC, the
chlorophyll content reduction is more pronounced due to the
fact that membrane bound chlorophyll is destroyed by the free
radicals of oxygen despite the protective action of carotenoids
(Smillie et al. 1987).
Photosynthesis, a key determinant of the rate of plant
growth, is infl uenced by both CO
2
concentration and is also
related parabolically to leaf temperature. These responses
are described mechanistically by the biochemical model of
photosynthesis. The model has two major parameters: the
potential rate of electron transport (Jmax) and the maximum
rate of RuBP (ribulose 1,5 bisphosphate) carboxylation (Vc
max). Photosynthesis often shows down regulation under a
long term increase in CO
2
concentration. In many species, a
long term increase in temperature leads to all increase in the
optimal temperature of maximal photosynthetic rate. There
was both an increase in the absolute value of the ligh saturated
photosynthetic rate at growth CO
2
(P growth) and an increase in
Topt for P growth caused by elevated CO
2
in FACE conditions.
Seasonal decrease in P growth was associated with a decrease
in nitrogen content per unit leaf area (N area) and they in the
maximum rate of electron transport (Jmax) and the maximum
rate of RuBP Carboxylation (Vc max). At ambient CO
2
, Topt.
