Distribution of the Products of Photosynthesis between Powdery Mildew and Barley

The photosynthetic assimilation of ¹⁴CO₂ has been studied in healthy and mildew-infected barley. The parasite was separated from the host by removing the mycelium with a camel's hair brush. The ethanol soluble metabolites of the parasite, infected host and healthy host were extracted, separated by paper chromatography and individually identified. From this work it appears that there is a rapid movement of label from host to parasite mainly in the form of sucrose which is then quickly metabolized into many compounds. The majority is converted into mannitol, and lesser amounts are converted into trehalose, arabitol, aspartic acid, and glutamic acid. In conidia the major carbon reserve is arabitol instead of mannitol, with lesser amounts of trehalose and mannitol.

Photosynthetic uptake of ¹⁴CO₂ by the complex decreases steadily after inoculation as compared with healthy leaves. However, the ethanol soluble metabolites of the infected host tissue differ only slightly from those of healthy host tissue. The major differences are a slight decrease in the amount of sucrose and increases in malic acid and serine.