The Translocation of 14C-Labelled Assimilates in Dwarf Bean Plants Infected with Xanthomonas phaseoli (E.F.Sm.) Dowson

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Abstract
The distribution of 14C-labelled assimilates in dwarf beans infected on one unifoliate with Xanthomonas phaseoli or systemically infected with the pathogen was compared with the distribution in plants subjected to water stress. Unifoliates on systemically-infected and water-stressed plants retained a much greater proportion of assimilated 14CO2 than equivalent leaves on healthy plants, but unifoliates directly inoculated with X. phaseoli (local infection) retained only a slightly larger proportion than control plants. Local infection had little influence on the distribution of exported radiocarbon but systemic infection produced marked effects and there were similar changes in water-stressed plants. These changes seem to be related mainly to changes in growth patterns, particularly to the reduced development of trifoliate leaves. The main causes of the altered assimilate distribution appear to be modified source-sink relationships, but the nature of the vascular system of dwarf bean and interference with vascular function by X. phaseoli seem to be more significant factors than in other diseases where assimilate distribution has been studied.