Plant Physiol, February 2001, Vol. 125, pp. 738-751
Effect of Solar Ultraviolet-B Radiation during Springtime Ozone
Depletion on Photosynthesis and Biomass Production of Antarctic
Vascular Plants1
Fusheng S.
Xiong and
Thomas A.
Day*
Department of Plant Biology and The Photosynthesis Center, P.O. Box
871601, Arizona State University, Tempe, Arizona 85827-1601
We assessed the influence of springtime solar UV-B radiation that
was naturally enhanced during several days due to ozone depletion on
biomass production and photosynthesis of vascular plants along the
Antarctic Peninsula. Naturally growing plants of Colobanthus
quitensis (Kunth) Bartl. and Deschampsia
antarctica Desv. were potted and grown under filters that
absorbed or transmitted most solar UV-B. Plants exposed to solar UV-B
from mid-October to early January produced 11% to 22% less total, as
well as above ground biomass, and 24% to 31% less total leaf area.
These growth reductions did not appear to be associated with reductions
in photosynthesis per se: Although rates of photosynthetic
O2 evolution were reduced on a chlorophyll and a dry-mass
basis, on a leaf area basis they were not affected by UV-B exposure.
Leaves on plants exposed to UV-B were denser, probably thicker, and had higher concentrations of photosynthetic and UV-B absorbing pigments. We
suspect that the development of thicker leaves containing more photosynthetic and screening pigments allowed these plants to maintain
their photosynthetic rates per unit leaf area. Exposure to UV-B led to
reductions in quantum yield of photosystem II, based on fluorescence
measurements of adaxial leaf surfaces, and we suspect that UV-B
impaired photosynthesis in the upper mesophyll of leaves. Because the
ratio of variable to maximal fluorescence, as well as the initial slope
of the photosynthetic light response, were unaffected by UV-B exposure,
we suggest that impairments in photosynthesis in the upper mesophyll
were associated with light-independent enzymatic, rather than
photosystem II, limitations.
1
This work was supported by the National Science
Foundation (grant no. OPP-9615268). This is publication no. 443 from
The Photosynthesis Center at Arizona State University.
*
Corresponding author; e-mail tadday{at}asu.edu; fax
480-965-6899.
© 2001 American Society of Plant Physiologists
