Differential effects of elevated ozone on two hybrid aspen genotypes predisposed to chronic ozone fumigation. Role of ethylene and salicylic acid.
The role of ethylene (ET) signaling in the responses of two hybrid aspen (Populus tremula L. x P. tremuloides Michx.) clones to chronic ozone (O(3); 75 nL L(-1)) was investigated. The hormonal responses differed between the clones; the O(3)-sensitive clone 51 had higher ET evolution than the tolerant clone 200 during the exposure, whereas the free salicylic acid concentration in clone 200 was higher than in clone 51. The cellular redox status, measured as glutathione redox balance, did not differ between the clones suggesting that the O(3) lesions were not a result of deficient antioxidative capacity. The buildup of salicylic acid during chronic O(3) exposure might have prevented the up-regulation of ET biosynthesis in clone 200. Blocking of ET perception with 1-methylcyclopropene protected both clones from the decrease in net photosynthesis during chronic exposure to O(3). After a pretreatment with low O(3) for 9 d, an acute 1.5-fold O(3) elevation caused necrosis in the O(3)-sensitive clone 51, which increased substantially when ET perception was blocked. The results suggest that in hybrid aspen, ET signaling had a dual role depending on the severity of the stress. ET accelerated leaf senescence under low O(3), but under acute O(3) elevation, ET signaling seemed to be required for protection from necrotic cell death.
Institute of Biotechnology and Department of Biosciences, University of Helsinki, Viikinkaari 9, Finland.
Jorma
J
Vahala
Markku
M
Keinänen
Andres
A
Schützendübel
Andrea
A
Polle
Jaakko
J
Kangasjärvi
D000222:Adaptation, Physiological / Q000187:drug effects; D003517:Cyclopentanes / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D005838:Genotype; D006823:Hybrid Vigor / Q000187:drug effects / Q000235:genetics; D054883:Oxylipins; D010126:Ozone / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects / Q000235:genetics; D032107:Populus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; D010126:Ozone; C011006:jasmonic acid; C036216:ethylene; D020156:Salicylic Acid