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Accumulation of assimilates in stem-rust-infected wheat leaves Using wheat plants (cv. 'Prelude'), the effects of stem-rust infection on photosynthesis and assimilate partitioning were studied with the aid of the short-lived carbon isotope 11C. Photosynthesis of strongly infected leaf parts declined by about 30 % within 1 day. This rapid inhibition was caused by the formation of appressoria and the growth of infection tubes into the stomata, leading to a reduction in gas exchange. Further decline of photosynthesis to 5-10 % was accompanied by the degradation of chlorophyll. Nevertheless, during sporulation, the dry weight of the infected leaf area increased by about 50 %. With the use of 11C, the reduced export of photosynthate from the infected leaf part and the capture of labelled compounds from the apical leaf section were quantified. The enhanced storage of assimilates in stem-rust-infected leaves can be attributed to the increase in invertase activity. [ABSTRACT FROM AUTHOR]

By means of gas-exchange measurements (minicuvette system and porometer), photosynthesis and its light dependence was investigated on attached leaves of different varieties of faba beans. The results showed no relevant difference in photosynthetic capacity for the varieties. This is true also for parameters calculated from light dependence, i.e. light compensation point, light saturation, and quantum yield. Generally, the light compensation point lay under 50 µE PAR/m²/s and light saturation was reached at about 1400 µE PAR/m²/s. Photosynthesis was strongly dependent on leaf age and difference in photosynthetic capacity due to different varieties could be excluded as an essential reason for different rates of flowers dropping and pod dropping in faba beans. [ABSTRACT FROM AUTHOR]