LIGHT INHIBITION OF UREDOSPORE GERMINATION IN PUCCINIA RECONDITA
ARMY BIOLOGICAL LABS FREDERICK MD
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Nonhydrated, hydrated, and hydrated-redried uredospores of Puccinia recondita were germinated on one per cent water agar at 10 degrees and 20 degrees C under several light intensities. Intensities above 165 foot-candles inhibited shortperiod two-hour germination of hydrated and hydrated-redried spores. As in other species of Puccinia studied previously, this was not a permanent inhibition, but only a depression of the initial germination rate, since per cent germination for longer incubation periods six to eight hours was virtually the same for spores germinating in light and in darkness. Light inhibition is temperature-sensitive, though not so markedly as in P. graminis var. tritici. At the lower intensities investigated, inhibition was greater at 10 degrees than at 20 degrees C. Higher intensities 450 f. c. almost completely inhibited two-hour germination at both 10 degrees and 20 degrees C. Inhibition was never observed in nonhydrated spores but only in hydrated and hydrated-redried spores, suggesting that the uptake of water sensitizes them to light, the sensitivity remaining even after spores have been dried to a low moisture level following hydration.