
Effects of Exogenous Nitric Oxide on Wheat Exposed to Enhanced Ultraviolet-B Radiation 1289
Enhanced ultraviolet-B caused reduction of chlorophyll
content and resulted in adaptive changes on photosynthetic
apparatus such as thylakoid membrane, PSII system [4,
12]. In the present study, we found not only chlorophyll
but also carotenoid content decreased under UV-B radia-
tion. Carotenoid plays a vital role in the photosynthetic
reaction centre where, it provides a mechanism for photo
protection against auto-oxidation and they also participate
in the energy-transfer process. The loss of carotenoid
might negatively influence the photosynthesis. Measure-
ment of the maximum efficiency of PSII photochemistry
(Fv/Fm) revealed that it decreased under UV-B radiation.
The ATP synthase of chloroplasts is an anabolic enzyme
which is the prime producer of ATP, using the proton
gradient generated by photosynthesis. ATP synthase
activity of chloroplasts was significantly inhibited under
UV-B radiation compared to that of the control, which
implied that the ATP generation might be hampered
accordingly. At the presence of SNP, the values of
Fv/Fm were higher than that of UV-B treatment alone, so
were the contents of chlorophyll and carotenoid, as well
as ATPase activity. We attribute those favorable effects
of SNP to following: NO, an important signaling molecule,
involved in UV-B transduction pathway and plants may
use exogenous NO as a protection strategy against ele-
vated doses of UV-B. NO may fulfill this function by
inducing more antioxidant to absorb UV-B. Decreased
UV-B irradiation and peroxidant damage on photosyn-
thetic apparatus as PSII and ATPase partially alleviated
the inhibition on them caused by UV-B. We also con-
clude ATPases of root cell membrane was less sensitive
to UV-B, but their activity was declined too, SNP alone
showed a more favorable effects compared to the control.
5. Acknowledgements
This research project was supported by the Shanxi Scho-
larship Council of the People’s Republic of China (2011-
061) and the National Nature Science Foundation of
Shanxi Normal University (SMYKZ-18).
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