The offspring from crosses of 'Cadet' by 'Cadet – Rescue 5A' and 'Winalta' by 'Winalta – Rescue 5A' were studied to obtain information on the inheritance of cold hardiness, winter–spring growth habit, rosette growth habit, height of cold-hardened plants, and length of leaves of hardened plants. The results indicate that a minimum of two loci on chromosome 5A are involved with cold hardening. One locus controls hardiness in part and is tightly linked to the one that controls in part the length of leaves of hardened plants. The other locus is, or it tightly linked to, Vrn1, a winter-spring growth habit locus. This locus may also control part of rosette growth habit. It is postulated that Vrn1 is involved in sensing temperature and in part triggering vernalization, cold hardening, and the development of the rosette growth habit. If so, Vrn1 could code for production of a temperature-sensitive protein, which undergoes conformational changes with changes in temperature.Key words: Triticum aestivum L., cold hardiness, vernalization, rosette growth habit, plant height, leaf length, temperature sensing.

No abstract

Megasphaera elsdenii, an anaerobic rumen bacterium, produced intracellular polysaccharide granules varying in size from 0.05 to 0.15 μm during growth in batch culture. This polysaccharide material was purified and was found to contain D-glucose as the only reducing sugar. The polyglucose polymer was highly opalescent in aqueous solution and formed a strong reddish-brown iodine complex with a maximum absorbance at 493 nm. Its infrared spectrum had characteristic absorption bands at 8.70, 9.25, and 9.75 μm and was identical with that of the glycogen of enteric bacteria and beef liver. When these polysaccharide granules were observed with an electron microscope, they resembled the glycogen granules produced by Arthrobacter globiformis and Escherichia coli. These properties indicate that the polysaccharide was a type of glycogen. The yield of crude glycogen was 16.82% of the dry weight of late log-phase cells (14-h).The lysis of cells of M. elsdenii and other rumen bacteria that store polysaccharide granules inside the cells, in the rumen of cows fed a feed of fine-particle size (344 μm, geometric mean particle size) and high-energy content, may contribute to the high-carbohydrate level and high viscosity of the cell-free rumen fluid of these cows. Cows fed a coarse feed (519 μm, geometric mean particle size) of the same composition have rumens that contain few bacteria with polysaccharide granules. The cell-free rumen fluid of these cows has low viscosity and low-carbohydrate content.

Experiments in which winter wheat plants were exposed to two different controlled hardening-temperature regimes (constant 3 °C, and 5.5 °C (day): 3.5 °C (night)) for long periods (up to 15 weeks) indicate that cold hardiness changes with time.The cold hardiness in plants grown from seed at 3 °C drops rapidly immediately after moistening and reaches a minimum 2–3 weeks later. Hardiness then begins to increase and reaches a maximum that lasts approximately from the 7th to the 11th week of growth after which it slowly declines.The patterns of change in cold hardiness during growth at 3 °C, and 5.5 °C:3.5 °C were almost synchronous if hardiness was plotted against duration of hardening, but were not synchronous if hardiness was plotted against stage of development as measured by the number of leaves produced. A somewhat similar result was obtained if plants grown for 3 weeks at 21 °C before hardening were compared with plants grown from dry seeds under the same hardening conditions. These experiments show that duration of hardening is more important in determining the level of cold resistance and the ability of wheat to retain its cold resistance than is stage of development, as measured by the number of leaves produced at the time cold resistance is measured.When plants seeded outdoors in mid-September were transferred at various dates (0–30 weeks after seeding) during the fall or winter to standardized hardening conditions in a growth cabinet for 0–15 weeks before freezing, their cold resistance changed in a way that suggests that plants in the field undergo the same pattern of changes in cold resistance as plants reared continuously in a growth chamber. This result suggests that the long exposure to hardening temperatures is one of the reasons why wheat in the field has less cold resistance in late winter than in autumn. Loss of carbohydrate reserves during winter may be an additional reason for this phenomenon.Under both growth cabinet and field conditions, increasing cold hardiness coincided with vernalization. Maximum cold hardiness was retained for several weeks after the completion of vernalization. These results suggest that the development of the maximum level of cold resistance may be related to the vernalization process.

The cold resistance of 18 varieties of winter wheat hardened in a growth chamber was studied at various stages of development and the tesults were compared with the field survival of these varieties.In the Ero',vth chamber two maxima of cold resistance vrere found, the first for the?ry or freshly moistened seed and the second rvhen plants had.approxi--mately 4 to 6 leaves. Varietal difercnces v'ere found in thc exact timing of this second maximum and in its duration. As a result, some varieties changed their rank for cold resistance as they developed.Partial asreement was observed betrveen the field survival of varieties sown at difierenidates and the changes in cold resistancc of these varieties as thcy developed in the growth chamber.