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A sequential relaxation model for the susceptibility of site-diluted Ising systems is described. It is shown that the model, which yields an excellent fit to experimental results for the real part of the ac susceptibility of the site-diluted two-dimensional Ising spin glass, Fe0.4Mg0.6Cl2, predicts a change in susceptibility with time during aging that is confirmed by experiments on other spin glasses and the orientational glass KBr0.5CN0.5.

Callus was induced from pieces of immature inflorescence of a sterile F1 hybrid (2n = 4x = 28) between Elymus canadensis and E. trachycaulus on MS medium supplemented with 2 mg/L of 2,4-D. Calli were of two types: compact or soft. Regeneration occurred predominantly from the compact callus. Although some plantlets were obtained on the callus initiation medium, the frequency of regeneration increased considerably when the callus was transferred to an auxin-free MS medium. Deliberate aging of callus induced cytological instability and variation in chromosome number of the regenerants. Five of the 43 regenerated plants had deviant chromosome numbers, including an octoploid (2n = 8x = 56). Chromosome pairing in the octoploid plant suggests that it originated through chromosome doubling.Key words: callus culture, variation, chromosome number.

In spite of regular chromosome pairing, hybrids between Elymus canadensis (Linnaeus) and E. trachycaulus (Link) Gould ex Shinners at the tetraploid level are sterile owing to structural differences between the donor genomes. However, the hybrids between these species at the octaploid level (obtained through chromosome doubling of the tetraploid hybrid and also from a cross between the octaploids of E. canadensis and E. trachycaulus) exhibited a predominance of bivalents in meiosis in spite of the autotetraploid nature of their constituent S and H genomes. The colchicine-induced amphiploids showed varying degrees of fertility. Comparison of chromosome pairing in the hybrid octaploids with that in the parental octaploids and hexaploids revealed that random bivalent formation is promoted when the S and (or) H genomes are at the tetraploid level, but not when they are in the triploid state. A bivalentizing mechanism under polygenic control is suggested to explain the predominance of bivalents in the tetraploid S and H genomes.Key words: Elymus, S genome, H genome, octaploids, bivalents, bivalentization.

A tissue culture induced octoploid of Elymus canadensis was crossed with two accessions ("Canada" and "Montana") of the same tetraploid species to produce hexaploids. Hexaploid (2n = 42) and near-hexaploid progeny (2n = 43 or 40) obtained from the crosses were morphologically vigorous but either partially or completely sterile. Mean frequencies of univalents and trivalents in the hexaploid pollen mother cells at metaphase I were 3 or 4 and 2 to 4 per cell, respectively. In view of the genomic constitution of the parents, the hexaploids were expected to be genomically double triploids. Nevertheless, bivalents, averaging 14–17 per cell, predominated. This might be due to the failure of chiasma formation and chiasma terminalization. One hexaploid plant was backcrossed to the tetraploid. The progeny consisted of one pentaploid and five aneuploids including one tetrasomic and two trisomics. All of the progeny from the backcrosses were less vigorous than aneuploids at the near-hexaploid level. Tetrasomics and trisomics had stainable pollen and a 17–19% seed set. Two trisomic plants were morphologically indistinguishable from each other and predominantly showed chromosome pairing of 14 II + 1 I. This indicates failure of chiasma formation and chiasma terminalization between homologous chromosomes.Key words: Elymus canadensis, hexaploids, tetrasomics, trisomics, meiosis.

Reciprocal hybrids between Elymus trachycaulus (2n = 4x = 28) and Elymus canadensis (2n = 4x = 28) were generated through emasculation and hand-pollination. All the F1 hybrid plants were tetraploids (2n = 28). The F1 hybrids were readily produced (9 plants from 150 pollinated florets; 6% success) in crosses where E. canadensis was used as the pistillate parent and the hybrid plants were produced directly from the apparently normal hybrid seeds. The percentage of hybrid plants produced was lower (7 plants from 400 pollinated florets; 1.7% success) in crosses where E. trachycaulus was used as the pistillate parent, and embryo culture procedures were necessary to recover plants from the shriveled seeds produced. Distinct morphological as well as cytological differences between the reciprocal hybrids were observed. All the F1 plants from each reciprocal cross more closely resembled their pistillate parent, indicating a strong maternal influence. Chromosome pairing at metaphase I showed a very high frequency of cells with a hexavalent configuration (69–81%) and a low frequency of cells with univalents (15–23%) in hybrids produced from crosses with E. canadensis as the pistillate parent. In all hybrids produced from crosses with E. trachycaulus as the pistillate parent, chromosome pairing showed a relatively low frequency of cells with a hexavalent (12–22%), while the frequency of cells with univalents was high (78–81%). Cytology of these hybrids indicates substantial control by cytoplasmic genes on chromosome pairing behavior. Reciprocal hybridization betwen octaploid E. trachycaulus (8x) and tetraploid E. canadensis (4x) plants yielded three 2n = 42, one 2n = 41, and one 2n = 39 hybrid plants. All plants were weak and sterile and more closely resembled the octaploid parent, although some intermediate characters were apparent.Key words: Elymus, reciprocal hybrids, maternal influence, cytoplasmic genes, chromosome pairing.

Partially fertile synthetic amphiploids (2n = 8x = 56) of Canada wildrye × slender wheatgrass F1 hybrid were crossed to slender wheatgrass and tetraploid lines resembling slender wheatgrass were recovered after four backcrosses. The BC1 progeny was hexaploid, while the BC2 and BC3 progenies were aneuploids with chromosome numbers ranging from 31 to 38. Tetraploid lines were recovered in the BC4 generation along with 29- and 30-chromosome types. Multivalents (mostly trivalents) resulting from intergenomic pairing were fequently encountered in BC1 and BC2 plants. The multivalent frequencies declined with each succeeding backcross. Pairing in the 28-chromosome BC4 plants was completely regular with 14 bivalents. Intergenomic pairing in the backcross progeny promoted introgression from Canada wildrye to slender wheatgrass.Key words: Elymus, intergenomic pairing, trivalents, recombination.

The three cereal crops oats (Avena sativa L.), barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) were tested for forage yields alone and in combinations with each other as well as in combinations with peas (Pisum sativum L.), soybeans (Glycine max. L.) and rape (Brassica napus L.) at three sites and in 3 yr. A range of seeding rates and crop combinations was used. While high yields of forage were obtained from these annual crops, the most favorable yields would not justify the additional expense of cultivation and establishment when compared with perennial forage yields over the same 3-yr period. Oats gave the best yields where seasons were longer and rainfall higher whereas barley gave the highest yields in areas with a drier, shorter season. Higher seeding rates improved yields and reduced fibre contents for all crops over the range tested. This increase was not, however, substantial and with the possible exception of oats, high seed rates would not be economical. The presence of a non-cereal in the mixture always reduced yield, but peas in a mixture with oats gave an increased yield of crude protein per hectare. Where a mixture of a cereal with a non-cereal was used, peas with oats yielded more than rape with oats, while rape with barley yielded more than peas with barley. Seeding the cereal and the non-cereal in alternate rows reduced yields for all the crop combinations tested. Yields were increased by delaying the harvest date beyond the time when the grain was in the dough stage.

The parents and progenies of a 7 × 7 diallel cross of smooth bromegrass (Bromus inermis Leyss.) were evaluated for the genetic variability of some morphological characters and their associations with yield, at four locations in Alberta in 1976 and 1977. Locations, years and their interactions were highly significant for all characters and were subsequently treated as eight environments. The partition of the genotypic variance into general combining ability (GCA) and specific combining ability (SCA) showed that for all morphological characters, GCA was more important than SCA, indicating the importance of additive genetic effects. The genotype × environment (GE) interactions were highly significant. Variation accounted for by GCA was generally higher than the interaction effects of GCA and SCA with environments. Phenotypic and genotypic correlation coefficients revealed that both tiller density and height were significantly correlated with yields. Path coefficient analysis also showed that tiller density, followed by leaf area and tiller dry weight, exerted the greatest direct influence on yield. Selection for large leaf area and more and heavier tillers per unit area would simultaneously increase bromegrass productivity. Furthermore, selection should be based on multi-year and multi-location tests.

Stomatal length and frequency were studied using a 7 × 7 diallel cross of smooth bromegrass (Bromus inermis Leyss.) clones and compared with data from an earlier study of the agronomic traits of the crosses. Silicon rubber impressions taken on different parts of a leaf, as well as on different leaves, showed that though variation was small for stomatal size, it was present for stomatal frequency. General combining ability was highly significant for both stomatal characters. Differences among the seven clones were marked. Both stepwise multiple regression and factor analysis were used to investigate the dependence structure that existed for stomatal and agronomic characters. Partial regression coefficients showed that stomatal frequency was related to yield. Factor analysis showed that the two stomatal characters accounted for 20% of the total variation in the dependence structure, whereas characters such as date of head emergence and plant height only accounted for 15%. These results reflect the importance of stomatal size and frequency in a breeding program in relation to agronomic practices.

An autoallooctaploid (2n = 56) form of Elymus trachycaulus (Link) Gould ex Shinners (previously Agropyron trachycaulum (Link) Malte ex H. F. Lewis) was induced by treating allotetraploid shoots with 0.2% colchicine. Successive backcrossing to tetraploid pollen parents was successful and yielded five hexaploid (2n = 42), one pentaploid (2n = 35), and three hyperploid (2n = 31, 32, 33) plants. Metaphase I of the tetraploids was normal and 14 II chromosomes were observed, almost all of which were ring bivalents. Chromosome pairing in one octaploid, four hexploids, and one pentaploid were 4.38 IV + 0.65 III + 17.84 II + 0.85 I, 13.16 III + 0.84 II + 0.84 I, and 5.82 III + 8.18 II + 1.18 I, respectively. Efficiency of chromsome pairing (chiasmata per chromsome) was highest in tetraploids (1.29), lowest in hexaploids (0.75), and intermediate in both octaploid (0.95) and pentaploid (0.93) plants. The octaploid produced longer and broader leaves than the tetraploid, although the total dry matter produced was 14.3% lower. Total dry matter yield of the hexaploid was on an average 30.04% higher than the tetraploid and the leaves were significantly larger. The hexaploid plants were taller than both the tetraploid and the octaploid plants. Metaphase I pairing in hyperploid 1 (2n = 33) was 4.34 III + 9.66 II + 0.66 I, hyperploid 2 (2n = 32) was 2.98 III 11.03 II + 1.00 I; hyperploid 3 (2n = 30 + 1 t) was 1.97 III + 12.05 II + 0.66 I + 0.33 t. The pattern of chromosome pairing in these hyperploids suggest that they are a quintupal trisomic, a quadrupal trisomic, and a triple trisomic respectively. Backcrossing these hyperploids to euploid pollen parents was successful. Backosses and their progeny should result in a series of primary trisomiclines and some monosomic plants, which would be useful for gene mapping. Key words: octaploid, hexaploid (double triploid), pentaploid, tetraploid, hyperploid, trisomic monosomic, Agropyron.

Electrical and mechanical properties of the distal canine lower esophageal sphincter were studied in vitro to investigate possible means of inducing pacemaker activity. Both direct excitation and block of potassium conductance were investigated. The acetylcholine analog, carbachol, induced tissue depolarization and increase in tone but no electrical slow waves. Tetra-ethylammonium (TEA) chloride induced depolarization and evoked continuous spiking activity and increase in tone. BaCl did not depolarize the tissue but low amplitude spiking activity developed and increased tone. The putative potassium channel blocker, aminacrine at 2 × 10−4 M, induced electrical slow wave activity in the distal lower esophageal sphincter, with or without superimposed spikes, accompanied by phasic contractile activity. This activity closely resembled the spontaneous pacemaker activity observed previously in the proximal lower esophageal sphincter. The aminacrine-induced activity was abolished by calcium influx blockers. Aminacrine, but not TEA or BaCl, abolished the nonadrenergic nerve-mediated inhibitory junction potentials. In conclusion, block of inhibitory innervation, and induction of electrical slow waves as a control mechanism for phasic contractile activity, seems to require blockade of an aminacrine- but not TEA-sensitive potassium conductance.Key words: smooth muscle, potassium conductance, slow waves, aminacrine, lower esophageal sphincter.

Seven clones of smooth bromegrass (Bromus inermis Leyss.), five of which were resistant to diseases caused by Pyrenophora bromi (Dred.) and Selenophoma bromigena (Sacc.), were crossed in all combinations forming a 7 × 7 diallel. Plants of both the F1 and its reciprocal cross, as well as the parents, were grown in the field at Edmonton and were measured for dry matter production, plant diameter, days to head emergence and plant height during their 2nd yr. Highly significant variation due to general and specific combining ability were recorded for all the traits. Four of the disease-resistant clones were low yielding and small in plant diameter. On the basis of general combining ability effects these same clones showed little promise as parents. However, one of the disease-resistant clones, B42, was found to perform relatively well and should be of value as a breeding stock.

A multipassed Fabry–Perot interferometer has been used to determine phonon linewidths. The line-shapes may also be obtained using a Bayesian deconvolution technique. Results on amorphous silica and CN− doped KCl are presented as illustrations.

Phosphorus-31 nmr data are reported for tri-n-butylphosphine selenide complexes of mercury(II) and cadmium halides and for some miscellaneous complexes of tertiary phosphine sulfides and selenides with the same metal halides. The ligands in the complexes are labile in solution at room temperature but the exchange can be "frozen out" in certain cases at reduced temperature. Selenium-77–phosphorus-31 coupling constants are less in the complexes than in the free ligands and 1JPSe decreases in each observable case with decreasing temperature. Two bond mercury-199–phosphorus-31 coupling is observed in some of the cooled solutions of the complexes.

Twenty-one progenies and the parents of a 7 × 7 half diallel cross of smooth bromegrass (Bromus inermis Leyss.) were evaluated at four locations in Alberta in each of two years, for genetic variation and genetic by environment interactions in the expression of their yield potentials. Years, locations and their interactions were highly significant in the combined analysis of variance. Combining ability analysis revealed that general combining ability (GCA) and specific combining ability (SCA) were both important in the expression of yield, including spring, fall and annual yield, whereas GCA was more important than SCA for yield per area. Although the genotype × environment interactions were all highly significant, variation accounted for by combining ability effects was generally higher than the interaction effects of GCA and SCA respectively, with environments. High average GCA effects for spring, fall and annual yield were demonstrated for the clones UA5, UA9 and B42. These together with the high average SCA effects suggested that the three clones could be included in a synthetic to develop high yielding cultivars. The results suggested that recurrent selections involving multi-location and multi-year testing seems necessary in breeding for high yielding bromegrass cultivars in Alberta.

Emasculated clones of tetraploid and octaploid Elymus trachycaulus crossed with Pseudoroegneria spicata yielded 69 triploids and 13 pentaploid hybrids. The triploid hybrids were morphologically intermediate between the parental species but the pentaploid hybrids resembled E. trachycaulus more closely than P. spicata. A very high degree of plant size variability (very weak to very vigorous) was observed among the 50 triploids that survived to maturity. The variability among the pentaploids, though apparent, was not high. Mean chromosome associations among the selected eight triploids varied from low multivalent formation at meiosis (7.60 I + 6.18 II + 0.24 III + 0.08 IV) to high multivalent-forming meiosis (7.28 I + 5.66 II + 0.32 III + 0.36 IV). The bivalent configurations in these triploids were attributed to homoeologous pairing between the S1 genome of P. spicata and S genomes of E. trachycaulus and the multivalents indicated intergenomal and intragenomal pairings. Mean chromosome associations of 5.22 I + 11.94 II + 1.97 III in 78.7% and 7 I + 14 II in 21.3% of the 150 cells were distributed among the three pentaploid hybrids. The low frequency of trivalents and the absence of multivalents higher than trivalent configurations suggest that homoeologous pairing was substantially reduced and there was no intergenomal and intragenomal pairing in these 2n = 35 x hybrids. Fourteen triploids and three pentaploid hybrids were produced from 4x and 8x forms of E. trachycaulus and P. spicata spp. inermis crosses. The triploids were intermediate between the parents but the pentaploids were more similar to E. trachycaulus. Mean chromosome associations in the triploids (6.020 I + 5.315 II + 0.554 III + 0.235 IV + 0.250 V + 0.048 VI + 0.03 VII) and in the pentaploids (3.50 I + 10.18 II + 3.54 III + 0.13 IV) indicated a very high degree of intergenomal and intragenomal pairing in the triploids; nevertheless, it was greatly reduced in the pentaploids. The Pseudoroegneria spicata ssp. inermis genome may have gene(s) that affect a high degree of intergenomal and intragenomal pairing in triploid hybrids with E. trachycaulus. However, in pentaploid hybrids (SS HH S2) the S and H genomes of E. trachycaulus in double dose seem to have restored its regular meiotic bahaviour, at least partially, and reduced homoeologous pairing as well as intergenomal and intragenomal pairing. Key words: Elymus trachycaulus, Pseudoroegneria spicata, regular meiotic behaviour, double dose, intergenomal pairing, intragenomal pairing.

For each of the three spring wheat cultivars, Pembina, Thatcher, and Manitou, the weight of approximately 900 seeds from 30 randomly selected heads was recorded. These seeds were grown to maturity in the field and mature plant characters associated with yield were recorded. Simple and partial correlation coefficients as well as multiple regression formulae were calculated for all traits. The size of the individual seeds planted was shown to account for 2.5 to 4.5% of the observed variations in yield and other mature plant characters, including the number of heads produced per plant. Head number was the most important component of yield.

The literature provides three explanations of the way in which genetic homeostasis functions. An attempt was made to determine which of these was applicable to the changes which occurred when selection for geotaxis was relaxed in certain strains of Drosophila melonogaster. The strains, for which selection stopped, were divided into two parts and generations were advanced in two environments. One was the same as that in which selection had been made and the other was new. When selection was relaxed strains reverted to a mean geotactic score close to that of the populations from which they had been selected. This change was more rapid in the new environment. A series of diallel crosses compared strains for which selection was continued with those for which it was relaxed. An analysis of the components of genetic variation showed that the principle change that had taken place was in the additive component of genetic variation. It was concluded that genetic homeostasis resulted from the action of natural selection on additive genetic variance, a conclusion which is in agreement with one of the three current hypotheses.

A regression technique was used to analyze the behavior and adaptability of widely grown commercial strains of Canadian hard spring wheat. Yield advances achieved by plant breeding in the past 60 years were estimated. The analysis showed that the advantage derived from rust-resistant varieties has been to increase yields under high-productivity conditions. Manitou and Thatcher were shown to be the more widely adapted of the commercial strains considered. Park is adapted to high-productivity and Cypress to low-productivity conditions.The same method was used to analyze results from trials including strains from Mexico. Pitic 62 is a high-yielding variety shown to have low phenotypic stability. Of the strains tested, Carazinho is phenotypically the most stable but also has the lowest yield. This yield difference was particularly marked at the higher productivity levels.

Records from seven spring wheats in a diallel cross showed that flag-leaf lamina area, extrusion of the head from the leaf sheath, head length and yield were all controlled by minor genes. Additive gene action and general combining ability were shown to be important genetic factors for all characters studied. Partial dominance was present for yield, flag-leaf area and head length. There was evidence that over-dominance played a part in the inheritance of extrusion. The genetic factors which controlled the expression of small leaf size showed dominance over those for large leaves and appeared to be distributed over all chromosomes. Increased extrusion and large flag-leaf area were both shown to be associated with high yield.

Two methods of dividing the Prairie Provinces into regions, one based on soil type and the other on climate, were compared. Reasons were presented for grouping and considering trial sites by climatic regions rather than soil zones. A regression technique was used to study the yields of the more important commercial cultivars of wheat, durum, two- and six-row barley, oats, rape, and flax which have been tested in the Western Co-operative cultivar trials in the prairie provinces of Canada over the period 1953–68. The behavior of the commercial cultivars of the principle arable crops of the three provinces was considered and is discussed in relation to the main soil and climatic features of the area.

A diallel cross among eight spring wheat cultivars examined the inheritance of yield, its components, certain developmental stages and morphological characters above the flag leaf node. Additive genetic variance was important for all the characters studied. For yield, kernels per ear, ear volume and for the developmental stages considered dominance was also present. Results presented here agreed with the main conclusions drawn in four other diallels crosses which were reported previously.

A diallel cross between five spring wheat varieties showed that structures above the flag leaf node which contributed to the overall photosynthetic area of this region were highly heritable. For most of the characters studied additive genetic variance was significant while non-additive variance was not. The number of ears per plant and the yield per plant showed full dominance, while for the 1,000-kernel weight overdominance was present. Partial dominance was significant for peduncle length, the extrusion of the head from the leaf sheath and for the ear length.

The electrical impedance of alfalfa tissue was measured at a range of root depths and stem heights. The results showed that only for unhardened roots was position of the measuring device important. Partial correlation coefficients for the relation of both stem and root diameter with impedance were significant for cold-conditioned and untreated material. Stems had higher impedance values than roots. Higher impedances were also associated with lower relative water contents. Differences in impedance readings for individual cultivars were large below 60% relative water content. In their present form, none of the methods used would be of value in identifying fine differences in the segregating populations used in plant-breeding programs.

The impedance and conductivity of plant tissue were studied for four species of grasses before, after, and during cold-conditioning. Conditioned plants gave high impedance readings and untreated plants low readings. When introduced to low temperature conditions, all plants showed increasing impedances. A highly significant relation between conductivity percentage and log impedance was found in all four species. Although the impedance method was rapid and convenient, there were temporal fluctuations for both cold-conditioned and unconditioned plants of all species. Thus, neither impedance method nor the determination of conductivity would provide a satisfactory test for the evaluation of differences in the response to cold stress of grass populations used in plant-breeding programs.