Variation for winter hardiness generated by androgenesis from
Festuca pratensis × Lolium multiflorum amphidiploid cultivars with different winter susceptibility
Androgenic populations produced from three Festuca pratensis × Lolium multiflorum amphidiploid (2n = 4x = 28) cultivars show wide within population variation for winter hardiness. Populations comprising a total of 423 androgenic plants derived from 23 donor plants from 3 Polish F. pratensis × L. multiflorum cultivars Felopa, Sulino, and Rakopan were studied over 3 years (1999–2002) in a field experiment at Lopuszna, Poland (20∘08′E, 49∘28′N, altitude 568 m). The results indicate that despite differences in winter hardiness between the three amphidiploid cultivars, the mean winter hardiness of androgenic progeny from each cultivar was the same. Thus an androgenesis component in a plant breeding programme may provide an opportunity to recover winter hardy genotypes from high yielding cultivars that are themselves adapted poorly to stress conditions. Androgenesis also evoked variation in snow mould resistance. In this case, androgenic plants with the greatest snow mould resistance were recovered from the least winter hardy donor cultivars and plants. The results indicated the low importance of snow mould resistance as a component of winter hardiness under the field conditions used for these experiments.
Breeding winter hardy grasses
SummaryPerennial grasses are vital for Norwegian agricultural production. The nature and extent of winter damage on grasslands is highly dependent on climatic conditions, and determines both persistency and yield. Physical stresses such as frost and ice encasement predominate in coastal regions with an unstable winter climate, while biotic stresses such as low temperature fungi are more common in the inland regions. Development of hardening depends on plant adaptation and climatic conditions during autumn and winter. New winter-hardy cultivars should be bred for wide adaptation to winter stresses. The genetic background for the most important character, freezing tolerance, seems to be of polygenic nature with mainly additive gene action. Selection for increased freezing tolerance has been effective over generations in grasses, and in most grass species ample variation still exists to be exploited by breeding. However, in some species like perennial ryegrass, modern biotechnological methods should be used to improve freezing tolerance and winter hardiness.
Heat Transfer Characteristic for a New Plate Metal Hydride Reactor
The property of major metal hydride reactors in the world was analyzed and a new plate metal hydride reactor was designed.An experimental facility to test the metal hydride reactor was also designed correspondingly.The effective thermal conductivity of the plate metal hydride reactor was measured by varying the initial metal hydride packing fraction,the kind of filled gas and the pressure of the filled gas,cycle numbers.The test results show that the effective thermal conductivity of the reactor,has exceeded(7.5) W/(m·K) before activation,which is increased greatly.After alloy activation,the effective thermal conductivity of the reactor has a linear change trend with the hydrogen pressure during the interval 0.1~3.5 MPa.The effective thermal conductivity of the reactor just only decreases quickly at the beginning,but becomes stable after several cycles.