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Endogenous isoprene protects Phragmites australis leaves against singlet oxygen
Author(s) -
Velikova Violeta,
Edreva Aglika,
Loreto Francesco
Publication year - 2004
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.0031-9317.2004.00392.x
Subject(s) - isoprene , photosynthesis , chemistry , singlet oxygen , rose bengal , phragmites , light intensity , oxygen , photochemistry , botany , biochemistry , biology , organic chemistry , ecology , wetland , physics , optics , copolymer , polymer
The possible protective role of endogenous isoprene against oxidative stress caused by singlet oxygen ( 1 O 2 ) was studied in the isoprene‐emitting plant Phragmites australis . Leaves emitting isoprene and leaves in which isoprene synthesis was inhibited by fosmidomycin were exposed to increasing concentrations of 1 O 2 generated by Rose Bengal (RB) sensitizer at different light intensities. In isoprene‐emitting leaves, photosynthesis and H 2 O 2 and malonyldialdehyde (MDA) contents were not affected by low to moderate 1 O 2 concentrations generated at light intensities of 800 and 1240 µmol m −2 s −1 , but symptoms of damage and reactive oxygen accumulation started to be observed when high levels of 1 O 2 were generated by very high light intensity (1810 µmol m −2 s −1 ). A dramatic decrease in photosynthetic performance and an increase in H 2 O 2 and MDA levels were measured in isoprene‐inhibited RB‐fed leaves, but photosynthesis was not significantly inhibited in leaves in which the isoprene leaf pool was reconstituted by fumigating exogenous isoprene. The inhibition of photosynthesis in isoprene‐inhibited leaves was linearly associated with the light intensity and with the consequently formed 1 O 2 . Hence, physiological levels of endogenous isoprene may supply protection against 1 O 2 . The protection mechanisms may involve a direct reaction of isoprene with 1 O 2 . Moreover, as it is a small lipophilic molecule, it may assist hydrophobic interactions in membranes, resulting in their stabilization. The isoprene‐conjugated double bond structure may also quench 1 O 2 by facilitating energy transfer and heat dissipation. This action is typical of other isoprenoids, but we speculate that isoprene may provide a more dynamic protection mechanism as it is synthesized promptly when high light intensity produces 1 O 2 .