Thèse--Toulouse. / Bibliography: p. [17]-21.

Thèse--Toulouse. / Bibliography: p. [17]-21.

Dyers woad (Isatis tinctoria L.) is a noxious weed on northern Utah rangelands. Chemical and mechanical means of control are unsuitable for rangelands. A potential alternative, biological control, is difficult due to a lack of basic ecological information. To remedy this, some aspects of the population biology and autecolgy of dyers woad were studied. The feasibility of controlling dyers woad by early spring grazing was also investigated via clipping experiments. A population study followed the survivorship of experimentally established populations over two years. Fall germinating individuals (1984) overwintered as rosettes twice and all survivors reproduced successfully. Spring germinating individuals (1985) overwintered as rosettes only once and 87% seeded the subsequent spring. Thus, on a good condition {high seral) foothill rangeland, dyers woad behaved predominantly as a biennial. Peak mortality in both fall and spring populations coincided with summer drought. The population size of dyers woad was constricted at two stages: (i) germination and establishment, and (ii) young rosette. The risk of mortality mortality in young rosettes was 77%. Dyers woad should be targeted for biological control at this vulnerable stage of growth. The seed dispersal pattern of dyers woad was best described by a negative exponential model of the type logy= a+ bx; (r = .78, a= 1.92, and b = -0.02). Ninety-five percent of a11 fruits were deposited within 54cm of mother plants. The root system of dyers woad was predominantly a taproot with some lateral sin the upper 30cm of the soil. There was little difference between mapped taproot and total mapped root lengths of rosette and mature plants. Significant mortality and reduction in reproductive performance occurred only by clipping, on or after 23 May 1984, at 60% or 90% intensity. Clipping twice, at either intensity, before 23 May had no effect on dyers woad. Sheep utilization of dyers woad ceased after mid-May, and had no significant effect on its mortality, percent flowering, and fruit production. Sheep grazing on dyers woad did not occur when much impact on mortality or seed production could be expected. The stocking re qui red to restrict dyers woad will result in range deterioration. More host-specific biological control agents should be tried.

Northern Utah rangelands have become infested with dyers woad (Isatis tinctoria L.) and control is needed. Mechanical and chemical control on rangelands produce undesirable effects. A possible alternative is biological control, but information is not available on plant response to this control method. This autecological study and simulation of control methods examined dyers woad phenology, seed endurance and response to simulated grazing, hand rogueing and plowing. The phenology study documented dyers woad growth patterns from May 1982 to November 1983. During the first year, 65 percent of the seedlings died while the remaining 35 percent grew rosette leaves. During the following growing season, 50 percent of the remaining population flowered and died. The other 50 percent continued to grow rosette leaves. The seed endurance study showed seed viability remaining high and relatively stable, but germination decreased during the ten month study period. Methods used indicate future germination and viability studies should more closely simulate field conditions. The simulation of control methods involved clipping dyers woad once at three different heights to simulate grazing, hand rogueing and plowing on three different dates that correspond with the phenological stages of initial rosette growth, pre-bolting, and post-bolting. Simulated grazing stimulated plant survival and growth. Simulated plowing and hand rogueing reduced plant survival. Treatment at all three levels after initial rosette growth depressed flowering for one year. Treatment to simulate plowing and hand rogueing during initial rosette growth depressed flowering compared to the untreated controls. Treatment early in the growing season did not significantly affect plants receiving simulated grazing. Seed production was depressed by simulated plowing but was promoted by simulated hand rogueing when compared to untreated controls. The ability of plants to survive and/or flower after treatment could not be predicted from this study because a one time clipping of dyers woad did not produce significant population decreases. A more severe treatment in the form of more clippings per season is suggested for future study.

My thesis deals with dye plants and possibilities of their use. The first part contains classification of dye plants and history of their use. In the next part, there is a summary of dye plants and colors we can get from them. Methodology of coloring is also introduced. At the end, there are botanic parameters, environment needs and cultivation methods of eight selected dye plants. The thesis include database of dye plants in electronic form.