Abstract:
The effect of temperature on in vitro germination and germ tube growth of urediniospores of Tranzschelia discolor was studied over time under constant temperature conditions. Studies were carried out on 1% water agar in the dark at 3�_C, 5�_C, 8�_C, 10�_C, 15�_C, 20�_C, 25�_C, 28�_C, 30�_C and 32�_C. Germination was observed at all temperatures between 5 and 30'C, and occurred rapidly over most of this range. At 2 h, germination exceeded 80% at temperatures between 10 and 28�_C, and this level was reached at 3 h at 8�_C. Germination at 5 and 30�_C was much reduced and at 7 h reached only 44% and 38% respectively. Germ tube growth occurred most vigorously at 15 and 20�_C, reaching lengths in excess of 500 8m at 9 h. The optimum range was narrower than that for germination, and growth was reduced or poor at 8�_C, 10�_C, 25�_C and 28�_C, which were favourable temperatures for germination. Average germ tube lengths at 9 h at these temperatures were 55, 245, 273 and 62 8m, respectively. Three-dimensional models were derived relating germination and germ tube growth to time and temperature.