Abstract:
Germinability in harvest-mature wheat grain showed a marked dependence on temperature. The optimum temperature for the complete germination of all grains ranged from 20�_C for the non-dormant variety, Timgalen, to 10�_C for the strongly dormant red wheat RL 4137, whereas the optimum in terms of the shortest lag period ranged from 25�_ to 15�_C for the same varieties. Germinability gradually increased during post-harvest storage and, for after-ripened grain, the optimum temperature for both complete germination and shortest lag period were greater than 30�_C. Germinability could also be increased by pre-treating imbibing grains at temperatures of 5�_, 10�_ or in some cases 15�_C. This treatment was only effective for grain at moisture contents >25% (dry weight) and the effect was not reversed by redesiccation. The pre-treatment temperature required for maximum germinability decreased with increasing levels of grain dormancy. Complete removal of dormancy required a pre-treatment period of c. 48 h; however, lesser periods gave the shortest lag period in the case of the dormant varieties. The implications of these results for the utilization of dormancy in the development of preharvest sprouting damage tolerant varieties and their subsequent use in practice are discussed.