Variety-specific response of wheat (Triticum aestivum L.) leaf mitochondria to drought stress
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The main objective of the present work was to examine leaf respiratory responses to dehydration and subsequent recovery in three varieties of winter wheat (Triticum aestivum L.) known to differ in their level of drought tolerance. Under dehydration, both total respiration and salicylhydroxamic acid (SHAM)-resistant cytochrome (Cyt) pathway respiration by leaf segments decreased significantly compared with well-watered plants. This decrease was more pronounced in the drought-sensitive Sadovo and Prelom genotypes. In contrast, the KCN-resistant SHAM-sensitive alternative (Alt) pathway became increasingly engaged, and accounted for about 80% of the total respiration. In the drought-tolerant Katya variety, increased contribution of the Alt pathway was accompanied by a slight decrease in Cyt pathway activity. Respiration of isolated leaf mitochondria also showed a variety-specific drought response. Mitochondria from drought-sensitive genotypes had low oxidative phosphorylation efficiency after dehydration and rewatering, whereas the drought-tolerant Katya mitochondria showed higher phosphorylation rates. Morphometric analysis of leaf ultrastructure revealed that mitochondria occupied approximately 7% of the cell area in control plants. Under dehydration, in the drought-sensitive varieties this area was reduced to about 2.0%, whereas in Katya it was around 6.0%. The results are discussed in terms of possible mechanisms underlying variety-specific mitochondrial responses to dehydration.
KeywordsDrought stress Leaf ultrastructure Plant mitochondria Wheat variety
Ratio of the amount of phosphorylated ADP to oxygen consumed
- Alt pathway
- Cyt pathway
Reactive oxygen species
This study was supported by grants from the Swiss National Science Foundation, SCOPES (project IZ73AO-111142, DILPA) and from the Ministry of Education and Science of Republic Bulgaria (projects CC 1503 and PISA-INI14). The authors are grateful to A. Kostadinova and B. Juperlieva-Mateeva for their excellent technical assistance, and to Marleen De Keukelaere for her help and support. We apologize to all colleagues whose relevant work could not be cited due to space limitations.
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