No description available.

Thesis (Ph. D.)--University of California, Dec. 1927. / Description based on print version record. Bibliography: p. 127-133.

Fairway crested wheatgrass, which is identified taxonomically as Agropyron cristatum (L . ) Gaertn. (45 ), A. cristatiforme (38) , or A. pectiniforme Roem. and Schult (22), is an economically important range grass belonging to the "crested wheatgrass complex" (24, 38). The crested wheatgrass complex includes diploid, 2n = 14, tetraploid, 2n = 28, and hexaploid, 2n = 42, forms (1, 11, 22). The variety Fairway and Fairway-like derivatives are the only known diploid members of the species complex (24, 38). Meiotic chromosome behavior of Fairway diploids appears to be typical of other diploid species; however, the number of plants examined cytologically has been relatively small. Although Fairway crested wheatgrass is a good seed producer, interplant variation in fertility is high (13, 22, 25, 42). Irregular chromosome behavior is a common source of sterility and may be contributing to the variable seed set in diploid crested wheatgrass. No information is available concerning the relation of meiotic chromosome behavior to fertility in Fairway crested wheatgrass. Polyploid crested wheatgrasses are generally considered to be of autoploid origin, i.e., they are derived by duplication of the chromosome complement of a diploid prototype. Chromosome pairing in the polyploid species (31), in interspecific hybrids (12), and in polyhaploid plants (11) substantiate the autoploid derivation of polyploid crested wheatgrass. Diploid and tetraploid forms of crested wheatgrass have been hybridized by Knowles (24), and chromosome pairing in the hybrids suggest a close relation between the diploid and tetraploid genomes. Colchicine-induced tetraploids of Fairway crested wheatgrass have been produced by Knowles, 1 and these artificial tetraploids are currently being utilized in his crested wheatgrass breeding program. If the full breeding and cytogenetic potentials of diploid crested wheatgrass are to be realized, the meiotic chromosome behavior and the cytotaxonomic status of this species must be fully understood. The present investigation was designed to provide further information concerning the cytogenetic characteristics of Fairway crested wheatgrass and its autotetraploid derivatives. This investigation was established with the following objectives: 1. To examine meiotic chromosome behavior of Fairway crested wheatgrass. 2. To determine the relation of meiotic chromosome behavior to fertility in Fairway crested wheatgrass. 3. To evaluate the effectiveness of several colchicine treatments in doubling the chromosome complement of Fairway crested wheatgrass. 4. To determine the effect of induced polyploidy on plant morphology in colchicine-induced tetraploids of Fairway crested wheatgrass. 5. To determine the meiotic chromosome behavior and fertility of induced tetraploids of Fairway crested wheatgrass.

No description available.

In about half of the angiosperm species the gamete chromosome number is a multiple of that found in some related species. This and the fact that polyploidy has such a pronounced effect on plant physiology and growth, as pointed out by Noggle, serve only to emphasize the importance of understanding more about polyploid genetics.

Twenty selected Agropyron elongatum clones were evaluated in parent and progeny nurseries with each clone represented by 560 progenies. Agronomic characters evaluated on the progenies included degree of erectness, three height measurements, and green weight data. Correlations were calculated between the seed yields of the progenies and the forage yield of the parents. General combining ability was determined for the 20 clones. The clonal source of variation for erectness was high. More variation existed within clones for green weight than for any other character studied. Two specific clones exhibited better over-all general combining ability than the others. Successive seed yields on the same nursery were highly correlated, whereas no correlation was found between progeny forage and parent seed yields.

A study was made of factors that influence production of different numbers of flower stalks of crested wheatgrass on grazed and ungrazed areas. Both laboratory and field studies were made. Greatest response in flower stalk production resulted from application of nitrogen in the field, amounting to an increase of from 5 to 10 times the numbers of flower stalks on untreated areas. Responses of plants in the greenhouse supported these results. Plants grown in the dark indicated that higher carbohydrate reserves existed in ungrazed than in grazed plants. It was concluded that a high carbohydrate-low nitrogen balance was the primary factor in low production of flower stalks on ungrazed range. Removing photosynthetic tissue by grazing reduced the amount of root growth and amount of carbohydrates stored as reserves. On grazed range some stored carbohydrates are used in production of regrowth and new tillers giving a more favorable carbohydrate-nitrogen balance for production of flower stalks. Whether nitrogen is a primary or secondary factor in production of flower stalks depends upon the stage of plant development in which it is the limiting factor. Leachate from old growth showed no effect on production of flower stalks. Treatment with gibberellic acid suppressed flower stalk production on plants transferred to the greenhouse prior to beginning spring growth, and to a lesser extent on plants transferred after beginning spring growth. The effect was attributed primarily to the stimulation of rapid, increased growth and depletion of reserves required for differentiation and production of flower stalks. Plants produced increased numbers of flower stalks with exposure to outside cold temperatures at least up to 10 weeks' duration, which was the maximum period tested. Under field conditions, grazed plants would be subject to more rigorous temperatures than ungrazed plants, but this was believed to be a minor factor contributing to the greater numbers of flower stalks on grazed plants compared to carbohydrate-nitrogen relationships. Reduced light was shown to be a factor contributing to reduced numbers of flower stalks in the greenhouse and in an outside lath house. Reduced light was believed to be a minor factor, however, in contributing to the low numbers of flower stalks on ungrazed areas. Results of the present study indicate that the carbohydrate-nitrogen balance in plants is a better criterion for intensive management of range lands than carbohydrate reserves alone.

During the past decade much attention has been attracted to the great range lands of the West. The inherently low productivity of these arid lands coupled with abnormal drought and constantly heavy use by livestock because of lack of grazing control, have caused these lands to become greatly depleated over most of the West. That the vegetation on most range land in the intermountain states is depleted appreciably is evident to the careful observer. Undoubtedly the vegetation of much of the range has decreased in quantity, but more serious in many cases is the decrease in quality. Valuable forage species have been replaced by less valuable or even worthless ones. This situation has been recognized by students of range ecology, and, therefore, management plans have been formulated to preserve or improve the forage cover. These plans have undergone changes and are still being modified as basic facts concerning the growth habits of range plants are brought to light. Grazing plans in the past were, of necessity, based upon superficial study and general impressions; plans of the future will be based upon scientific facts supplemented by experience. The studies herein reported were made during the summer of 1938 in southern Cache Valley, Utah. The range under observation is roughly comparable to the northern intermountain grasslands. The observed range occupies the benches and foothills above the more moist valley floor.

This study evaluated the early establishment phase of various monocultures and mixed species plantings of Agropyron desertorum (AGDE), Medicago sativa (MESA), and Atriplex canescens (ATCA). The study was conducted under both greenhouse and field conditions. In the green-house, the experimental design was a split-plot, randomized-block design in time, using transplanted seedlings. The treatments were exposed to three water levels to determine species response to varying moisture availability. Plastic pots of 15.4 cm (diameter) by 17.9 cm (depth) were filled with 2,800 g of sandy-loam soil and brought to field capacity. The pots were weighted twice weekly and the water lost to evapotranspiration was replaced. The plants were measured for plant height on six occasions at two week intervals. On the last measurement date, plants were harvested for above-and-below ground biomass. The field used the species treatment as in the greenhouse study and these were hand sown in 1 m2 plots. Using a line-source sprinkler system, species responses at four water levels were examined. Soil water content in the various field plots was determined at various depths via access tubes and a neutron soil moisture probe. The experimental design was a split-plot design in time. Seedling emergence was recorded daily for the first 35 days after seeding. Plant height was measured six times during the growing season. All the species were clipped, oven-dried, and weighed at the end of the experimental period in 1982. In the greenhouse, AGDE was the dominant species, yet produced more in the MESA combination. MESA exhibited a marked decrease in production when grown with AGDE. ATCA showed a remarkable ability to survive under high water stress. Variable soil water content created in the field resulted in significant differences in germination, emergence, and establishment among planting treatments. MESA germinated and emerged faster than AGDE and ATCA, allowing it to utilize water and nutrient resources earlier than the competing species. The greatest shoot production occurred when MESA grew alone. In the AGDE-MESA combination, shading apparently reduced AGDE growth and shoot production at the two most favorable water levels. ATCA exhibited poor germination and emergence in treatments with low soil water availability.

Dynamics of soil water use by two cool-season Agropyron bunchgrasses during the warm season depletion of soil water reserves were monitored for two years in experimental plots in the field. Agropyron desertorum, an introduced, competitive species from Eurasia, extracted more water from the deeper ( > 50 cm) soil layers than the native, less competitive Agropyron spicatum. Agropyron desertorum both extracts this water earlier and to lower soil water potentials than Agropyron spicatum. From the water extraction dynamics of the grasses in monocultures and in their two-way (50:50) mixtures with a shrub they commonly co-occur with, Artemisia tridentata, partitioning of the soil water resource between the grasses and the shrub was inferred. This indicated that Artemisia tridentata and Agropyron desertorum partitioned the soil water resource fairly evenly, while considerable quantities of water in the deeper soil layers under Agropyron spicatum seemed to be available to the shrub without direct competition. The implications of this difference in water resource partitioning for competition of the grasses with Artemisia tridentata are discussed. Predawn and midday xylem pressure potentials were not different between the two grasses in spite of different fluxes through the plants. Agropyron desertorum initiated new adventitious roots in fall and early spring while Agropyron spicatum did so only during spring. Observations from a root observation chamber indicated essentially parallel pattern of lateral root elongation during the depletion phase through top 200 cm of the profile. In both species the number of active tips, and the rate of elongation of active tips, decreased as the soil dried out. Root tips at all depths were inactive by the middle of September. Agropyron desertorum maintained root elongation at 50-110 cm for two weeks longer than A. spicatum.