Agriculture Reference
In-Depth Information
photosynthesis, rather than adaptation developed as a result
of temperature. The wavy, compact mesophyll absorb and
consume heat better during seedling stage. Structurally, the
japonica plants are more thermodynamically adapted to low
temperature at seedling stage.
The four leaf stage seedlings of two rice varieties were
grown in combinations of 5 levels of nitrogen (N) (from 5 to 80
ppm) and three temperature regimes (day/night temperature of
22/17, 27/22 and 32/27ºC). It was found that the photosynthetic
rate was best expressed as leaf area basis. With this unit the
photosynthetic rate of single leaf was closely related with
chlorophyll content. There was linear relation between total N
content (and protein) and chlorophyll content, indicating that
photosynthesis per unit leaf area was closely correlated with
nitrogen assimilation in leaves of the rice plants. Temperature
and N level both affected photosynthesis of the rice leaves.
In a tiller, the photosynthetic rate of leaves at different node
positions was infl uenced by temperature and N level. At low
temperature (22/17ºC) there was no signifi cant difference of
photosynthesis among leaves at different node positions under
different N-treatments. However, when plants grew at higher
temperatures, lower photosynthetic rate was found at lower
positioned leaves under low level of N, but not under high
level of N. The results indicate that photosynthesis is under
the control of N uptake and metabolism of rice plants.
Total soluble protein and amino-N increased with the
increase in N concentration. There was higher N-content (both
soluble protein and amino nitrogen) in the plants grown at
lower temperature as compared with plants grown at higher
temperature, particularly with plants grown at higher level of
N, indicating the dilution effect of N by plant growth. Ribulose
bisphosphate carboxylase and cytochrome C-oxidase activities
