| Summary: | 碩士 === 國立臺灣大學 === 農藝學系 === 85 === AbstractSeveral crop plants have been found to have the ability
to absorb ozone, and have the potential on reducing ozone
pollution. The objective of this study was to explore the
relationships between rice growth and ozone in troposphere. The
concentration of ozone in the air beside the Kee-Long Road along
the field of The Experimental Farm Station of National Taiwan
University, and control and rice field was detected. Ozone
absorption rate of seedlings of selected rice cultivers were
measured and compared. Ozone treatment was carried out on
several rice varieties by using continuously stirred tank
reactors, the tolerance, physiological responses to ozone and
activities of enzymes involved in scavenge of free radical were
studied. The result1. There was no difference between the ozone
concentration detected in side way of Kee-Long Road along The
Experimental Farm Station of National Taiwan University or
measured at Ku-Ting Station of Environment Protection
Administration. Ozone concentration in rice-growing field was
reduced by 1 to 3 ppb from the seedling stage to the maturing
stage. Ozone was absorbed mostly on the flowering stage with a
amount of 9 %, suggesting that ozone in the air could be reduced
by rice field. Absorption ability of ind2. Under ozone exposure,
leaves of rice seedlings showed brown spots. Leaf tips became
dehydration and etiolating when the rice were treated with smell
gas for 24 hours. 24 rice varieties treated with ozone could be
graded into five classes with respect to the injury symptom.
Japonica varieties were more tolerant to ozone than indica
varieties. Injury symptom in japonica varieties appeared until
the ozone concentration reached 800 ppb, while the symptom in
indica varieties already showed when the concentrat3.
Chlorophyll and protein contents of indica rice were higher than
those of japonica rice. The contents in indica rice decreased
significantly by ozone treatment, and there was a negative
correlation between the chlorophyll or protein content and the
injury grade. Chlorophyll and protein contents in japonica
varieties remained constant under ozone treatments. The leakage
conductivity values of indica varieties were higher than those
of japonica varieties. Indica rice showed significant injury
under concent4. There were no statistical difference on leaf H2
O2 content among tested varieties. Even H2O2 content was not
related with chlorophyll content, but tested varieties had high
H2O2 contents under a heavier injury status. Thus, reduce the H2
O2 content in rice plant might reduce the injury caused by
ozone.5. Enzyme activities of antioxidase, such as peroxidase
and catalase, especially peroxidase were higher in japonica
varieties. This might be correlated with the results that H2O2
content of japonica rice were much lower than that of indica
rice, i.e., peroxidase within japonica could scavenge injury-
produced peroxide. Although superoxide dismuctase is suggested
to be one of key enzymes that could clear the peroxide free
radicals in plant, but in this work, its activity decreased
after ozone treatment. AscorThe results of the present research
showed that japonica varieties were more tolerant to ozone than
did the indica rice. This might be due to that japonica
varieties have a more efficient peroxidase enzyme system, and
have a lower ozone absorption ability. Rice cultivated in Taiwan
are mostly japonica varieties, it is worthy of further
evaluation whether there is a reduction effect of ozone at the
troposphere by the whole rice field in Taiwan.
|
|---|
