Agriculture Reference
In-Depth Information
in the response. Hungarian-1 showed least impairment in
photosynthesis with greater reduction in quantum yield under
chilling treatment.
Rice plants lose signifi cant amounts of volatile NH
3
from
their leaves; an increase in O
2
increased ammonia diffusion
rate in the two cultivars, accompanied by a decrease in
photosynthesis due to enhanced photo respiration, but did not
greatly infl uence transpiration rate and stomatal conductance.
There were signifi cant positive correlations between ammonia
emission rate and photorespiration in both cultivars.
Increasing light intensity increased AER, PG, Tr and
Gs in both cultivars, where as increasing leaf temperature
increased AER and Tr but slightly decreased PG and Gs. Thus,
photorespiration is strongly involved in NH
3
emission by rice
leaves and with differences in GS activity. It is also suggestive
that NH
3
emission in rice leaves is not directly controlled by
transpiration and stomatal conductance (Fig. 29).
Ammonia emission from rice leaves is in reaction to
photorespiration and genotypic differences in glutamine
synthetase activity (Kumagai et al. 2011).
Temperature acclimation for photosynthesis has been
related to leaf nitrogen economy, since more than half of the
leaf nitrogen is in photosynthetic apparatus and thus the
photosynthetic capacity is strongly related to the leaf nitrogen
content. Leaf nitrogen content on a leaf area basis is greater in
leaves grown at lower temperatures. This is considered as a
compensatory response to low temperature, which decreases
enzyme activity. As respiration rates are also related to leaf
nitrogen content, a similar response has also been observed
for the temperature acclimatization of respiration.
