Antioxidative Defense System, Pigment Composition, and
Photosynthetic Efficiency in Two Wheat Cultivars
Subjected to
Drought1
Barbara Loggini,
Andrea Scartazza,
Enrico Brugnoli, and
Flavia Navari-Izzo*
Dipartimento di Chimica e Biotecnologie Agrarie, Università
degli Studi di Pisa, 56124 Pisa, Italy (B.L., F.N.-I.); and Consiglio
Nazionale delle Ricerche, Istituto per l'Agroselvicoltura, 05010 Porano (TR), Italy (A.S., E.B.)
We analyzed antioxidative defenses,
photosynthesis, and pigments (especially xanthophyll-cycle components)
in two wheat (Triticum durum Desf.) cultivars, Adamello
and Ofanto, during dehydration and rehydration to determine the
difference in their sensitivities to drought and to elucidate the role
of different protective mechanisms against oxidative stress. Drought
caused a more pronounced inhibition in growth and photosynthetic rates
in the more sensitive cv Adamello compared with the relatively tolerant
cv Ofanto. During dehydration the glutathione content decreased in both
wheat cultivars, but only cv Adamello showed a significant increase in
glutathione reductase and hydrogen peroxide-glutathione peroxidase
activities. The activation states of two sulfhydryl-containing
chloroplast enzymes, NADP+-dependent
glyceraldehyde-3-phosphate dehydrogenase and
fructose-1,6-bisphosphatase, were maintained at control levels during
dehydration and rehydration in both cultivars. This indicates that the
defense systems involved are efficient in the protection of sulfhydryl
groups against oxidation. Drought did not cause significant effects on
lipid peroxidation. Upon dehydration, a decline in chlorophyll
a, lutein, neoxanthin, and 
-carotene contents, and an
increase in the pool of de-epoxidized xanthophyll-cycle components
(i.e. zeaxanthin and antheraxanthin), were evident only in cv Adamello.
Accordingly, after exposure to drought, cv Adamello showed a larger
reduction in the actual photosystem II photochemical efficiency and a
higher increase in nonradiative energy dissipation than cv Ofanto.
Although differences in zeaxanthin content were not sufficient to
explain the difference in drought tolerance between the two cultivars,
zeaxanthin formation may be relevant in avoiding irreversible damage to
photosystem II in the more sensitive cultivar.
1
This study was funded in part by Consiglio
Nazionale delle Ricerche (no. 97.01525 CT06) and in part by
Università di Pisa (Fondi di Ateneo, 1997).
*
Corresponding author, e-mail fnavari{at}agr.unipi.it; fax
39-50-598614.
Plant Physiol. (1999) 119: 1091-1100
Copyright Clearance Center: 0032-0889/99/119//10
© 1999 American Society of Plant Physiologists
