• Korean Journal Plant Pathology
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• v.2 no.1
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• pp.22-30
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• 1986

The effect of powdery mildew infection on the $^{14}CO_2$ assimilation and metabolism of $^{14}C-$assimilates was studied with spring barley cultivars, susceptible Peruvian and adult-plant resistant Asse at the four-leaf stage. No consistent differences between Peruvian and Asse were revealed in $^{14}CO_2$ assimilation and metabolism of $^{14}C-$assimilates in healthy whole plants. In the two cultivars, $^{14}CO_2$ assimilation and translocation of assimilates decreased as the number of infected leaves increased. Despite the same infection intensity, $^{14}CO_2$ assimilation was less inhibited in Asse than Peruvian. Infection reduced the fixation of $^{14}CO_2$ in noninfected fourth leaves of Peruvian more severely than that of Asse. Infection of the lower 3 leaves also inhibited the incorporation of 14 C into carbohydrates such as fructose and glucose in noninfected fourth leaves and their translocation into leaf sheathes, the inhibitions being greater in Peruvian than Asse. In the infected third leaves, there was a reduction of 14 C-activity in carbohydrates, more $^{14}C-$labeled fructose and glucose being retained in Peruvian. The stimulation of $^{14}C-$organic acid synthesis in all plant organs was more pronounced in Peruvian than Asse. Powdery mildew markedly increased the incorporation of $^{14}C$ into amino acids in infected third and noninfected fourth leaves, but reduced their translocation to the leaf sheathes. A greater rise of $^{14}C-$ activity in some amino acids in the two leaves was found in Peruvian than Asse.