Agriculture Reference
In-Depth Information
Some plants have the ability to maintain similar respiratory
rates when grown at different temperatures. This phenomenon
is referred to as respiratory homeostasis. Using rice cultivars
with different degrees of respiratory homeostasis, it was
demonstrated that high homeostasis cultivars maintain shoot
and root growth at low temperatures (Kurimoto et al. 2004).
Four indica and fi ve japonica varieties of rice (
Oryza sativa
L.) had been found with their differences in photosynthetic
activity and dark respiration rate infl uenced by leaf nitrogen
levels and temperatures. The photosynthetic rate of single leaf
showed correlation with total nitrogen and soluble protein
content When compared at the same level of leaf nitrogen
or soluble protein content, the four indica varieties and one
japonica variety, Tainung 67, which have some indica genes
derived from one of its parents, showed higher photosynthetic
rates than the remaining japonica varieties. When the leaf
temperature rose from 20 to 30ºC, the photosnthetic rates
increased by 18 to 41% whereas respiratory rates increased by
100 to 150%. These increasing rates in response to temperature
were higher in the japonica than in the indica varieties. In this
respect Tainung 67 showed the same behavior as of other four
japonica varieties (Weng and Chen 1987).
Tsunoda and Khan (1968) found differences in the
photosynthetic tissue of indica and japonica types. The
indica types have arranged chlorenchyma cells sparsely in
the mesophyll, the adaxial surface of the mesophyll is fl atter.
The japonica types have chlorenchyma cells more compactly
arranged and the adaxial surface of the mesophyll is very
wavy. However, these differences were found only at the
seedling stage and not at the later stage of growth. It can be
interpreted that since light is not limiting at the seedling stage,
these differences may be an adaptation directly concerned with
