Changes in Photosynthesis of Wheat Plants Infected with Wheat Stem Rust (Puccinia graminis f.sp. tritici)
1985
Berghaus, R. | Reisener, H.J.
Seven wheat cultivars of infection types 0, 1, 2 and 4 were inoculated with wheat stem rust, Puccinia graminis f.sp. tritici race 32. Net photosynthesis activity was measured polarographically with an oxygen sensor during the first ten days of pathogenesis. With the exception of highly resistant cultivars, which showed only small changes in assimilation activity, oxygen evolution in infected plants declined 4—5 days after inoculation as compared to healthy ones. The decrease was more pronounced in resistant plants belonging to infection type 1—2 than in susceptible cultivars, which, even though they were heavily inoculated maintained a part of their photosynthetic activity. Some cultivars showed an increase in assimilation activity during the first few days. This phenomenon proved to be independent of infection type. Chlorophyll content decreased in all interactions, and was most marked in infection type 1—2. Our results suggest that in moderately‐resistant cultivars the decline in the rate of net photosynthesis is due to a drop in chlorophyll content but that in susceptible cultivars additional factors are responsible for the decrease in O₂ evolution. The possibility is discussed of the reduction in photosynthesis and chlorophyll content alone acting as a resistance factor which is quite distinct from the hypersensitive reaction (HR).
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