Title page for ETD etd-42398-124213

Type of Document Master's Thesis
Author Youlin, Tang M.S.
Author's Email Address yotang@vt.edu
URN etd-42398-124213
Title Response of Leaf Protein to Ozone in Two White Clover Clones
Degree Master of Science
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
Chevone, Boris I. Committee Chair
Chevone, Boris I. Committee Member
Hess, John L. Committee Member
Moore, Laurence D. Committee Member
  • White Clover
  • Ozone-Responsive Protein
Date of Defense 1998-05-07
Availability restricted
Response of Leaf Protein to Ozone in White Clover Clones

Youlin Tang


A white clover ( Trifolium repens ) system, based on one

ozone-sensitive (NC-S) and one ozone-resistant (NC-R) clone,

has been developed as an indicator to estimate the effects

of tropospheric ozone on plant biomass production. A

reduction in the vegetative biomass ratio (NC-S/NC-R) of the

clones was correlated with increasing concentrations of ozone

during a 28-day exposure period. However, the mechanism of

ozone sensitivity or tolerance at the biochemical or

molecular level is not known. Superoxide dismutase isozyme

activities in the two clones did not respond differently to

ozone treatment. However, catalase activity increased

somewhat more in the leaf tissue of NC-R, compared to NC-S,

after ozone treatment. Two-dimensional polyacrylamide gel

electrophoresis (PAGE) showed the presence of two proteins

(Ozone-Response-Proteins, ORPs) that were more responsive to

ozone in the tolerant genotype than in the sensitive one.

After ozone treatment for three days, the ORPs were four-fold

higher in leaf tissue of NC-R compared to NC-S. Also,

the amount of the ORPs was twenty-fold higher in leaf tissue

of ozone-treated NC-R than in that of control NC-R. These

proteins have apparent molecular weights of 21.5 kD and

23 kD and isoelectric points of 4.1-4.4 on SDS-PAGE gels.

The filtrate of a 100 kD concentrator showed that the native

molecular weights of the ORPs were less than 100 kD.

The results obtained from a study of field samples

demonstrated that protein content in leaf tissue of both

NC-R and NC-S was positively correlated with ORP content.

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