On two sites in south Mississippi, growth and survival of two oak species, Shumard oak (Quercus shumardii) and swamp chestnut oak (Quercus michauxii), and three planting stocks: 1-0 bareroot, conventional containerized, and EKOgrown® seedlings, were compared and evaluated for two years. Survival was assessed monthly during the first growing season and at the end of each growing season. Height and groundline diameter were assessed initially after planting and at the end of each growing season. After two growing seasons, Shumard oak exhibited superior performance generally when compared to swamp chestnut oak. EKOgrown® seedlings had poor survival likely caused by negative influences of competing vegetation. Bareroot seedlings performed better than other planting stocks, additionally, the cost efficacy of these seedlings justifies why bareroot planting stocks are superior in most cases of artificial regeneration of hardwoods.

Intact dark- and light-grown mung bean (Vigna mungo L.), black bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) cowpea (Vigna unguicul a ta (L.) Wa lp.) and squash (Cucurbita pepo L.) seedlings on hydroponic medium were osmotically stressed by exposing their roots to PEG 8000 of various concentrations (-0.2 to -0.6 MPa) to determine stress effects on growth and tissue water status. Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress, and resumes within 10 to 45 min. Growth of all other seedlings were measured usually after 3 to 24 h stress, and in 3 h, elongation is inhibited in dark-grown and is stopped in light-grown tissues. In dark-grown mung bean, black bean and squash hypocotyls and pea epicotyls, growth rates after 24 h stress were found to be proportional to the Ψ of the medium. In mung bean hypocotyls, growth stopped before any change in Ψ or Ψ(π) occurred in the growing region. In this tissue and also in dark-grown squash hypocotyls, pea epicotyls, and in lightgrown cowpea hypocotyls, equivalent reductions in Ψ and Ψ(π) were evident in the growing region after 3 h, so turgor remained constant. In other species, osmotic adjustment with turgor maintenance was evident after 24 h in both the growing and expanded regions. The results with mung bean hypocotyls provided the first demonstration that stress causes an almost instantaneous stress-caused cessation of elongation in dicots. Since data from all plants showed that stress causes growth rate inhibition or cessation without a concomittant decrease in Ψ(p), it is concluded that turgor is not the factor regulating growth. More likely, stress-caused growth and water status changes are responses to an earlier signal, such as a stress-caused reduction in the apoplastic Ψ.

Field and greenhouse studies were conducted in 1986 and 1987 to determine the impact of disturbance of microphytic soil crust on emergence of two warm season grass species. In the greenhouse, emergence of seedlings sown on the top of undisturbed crust, under the crust, on disturbed crust, and on bare soil was studied. The mean number of seedlings of "Cochise" lovegrass (Eragrostis lehmanniana x Eragrostis tricophora) and Kleingrass (Panicum coloratum) was higher on disturbed field plots than undisturbed plots. Disturbance reduced the microphytic crust cover, and the crust did not recover throughout the growing season. Presence of seedlings in samples of litter washed off the plots and observation on ants showed that all the seeds sown did not remain on the plots during the growing season. In greenhouse flats the emergence of seedlings of both species was greater on disturbed microphytic crust and bare soil than when seeded on top of or under an intact crust. Undisturbed crust restricted penetration of roots and shoots when seeds were placed on or under the crust.

Competition from non-crop vegetation decreases the productivity of conifer plantations across Canada. The objectives of this research were: (1) to develop reliable indices of perennial, interspecific competition; (2) to compare the responses of black spruce and jack pine seedlings to tree and brush competition in northern Ontario; and (3) to identify the silvicultural implications of the responses. An examination of potential components of a competition index considered measures based on hemispherical photographs, fractal geometry, stand maps, and mensurational data from 360 seedling-centred plots for each of the two crop species. Reliable competition indices should be simple formulations which include horizontal and vertical dimensions and which express the amount of competition relative to the size of the seedling. The optimum index was found to be the area of competing canopy on hemispherical photographs, relative to the seedling leaf area. An alternate index, requiring no elaborate equipment, was the sum of the competing stem volumes (relative to the seedling stem volume) of the largest competitor in each quadrant surrounding the seedling. Comparisons of crop tree responses were made using functional growth analysis, replacing the conventional time axis with a competition axis. The relationship between growth and competition was adequately modelled with a power exponential composite function. Jack pine and bare root stock of both species maintained superior growth despite greater sensitivities to competition, compared to black spruce and container stock, respectively. Thus, jack pine or bare root stock of black spruce would outperform the alternatives if tending were delayed, but competition should be removed in all cases to capture the maximum growth potential. The rate of growth decline in response to competition was consistently greatest at the lowest competition levels, indicating that no beneficial effect on growth was provided by a light cover of non-crop vegetation. Allometric analyses indicated that black spruce had a greater morphological plasticity than jack pine. At high competition levels black spruce allocated more biomass to branches and foliage, at the expense of stem and roots. Jack pine demonstrated no such adjustment in allocation pattern, but followed a strategy of stress avoidance through sustained high growth rates. / Forestry, Faculty of / Graduate

Two dormancy induction trials were conducted in a private container nursery in Saanichton, British Columbia. The first study examined the effects of photoperiod induced dormancy on morphology, root growth and field performance of fall planted western hemlock (Tsuga heterophyl_1ji (Raf.)Sarg.) and Douglas-fir (Pseudotsuga menzi_esv[ (Mirb.) Franco) seedlings. Various periods of eight hour days, ranging from two to eight weeks, were applied throughout July and August 1983. Outplanting was done in late September. Survival and growth were assessed one year later. The second project investigated the effectiveness of short days, varying levels of moisture stress and a combination of both as dormancy induction techniques for Douglas-fir seedlings. The short day treatment was four weeks of eight hour days. Four levels of predawn moisture stress were: -5, -10, -15 and -25 bars. These classes respectively corresponded to control, light, medium and severe moisture stress levels. Short days and moisture stress were also combined whereby the four week period of short days followed the moisture stress treatments. These induction treatments were applied in July and August 1984. All seedlings were lifted in January 1985 and placed into cold storage for five weeks until March 1985. Morphology, root growth capacity, frost hardiness and dormancy intensity were assessed in January. Root growth capacity and dormancy intensity were again measured in March. In Study I, short days quickly initiated homogeneous budset in both species in approximately three weeks. The average height increment after treatment initiation was 3.7 cm in Douglas-fir and 4.2 cm in western hemlock. Short days reduced shoot dry weight and height. Caliper and root dry weight were unaffected. In September a surge in root growth occurred in hemlock seedlings treated with six or eight weeks of short days. The importance of early budset to allow increased root growth prior to a fall lift was demonstrated. Root growth capacity was similar among all treatments for both species. The planting survival of western hemlock seedlings increased with increasing weeks of short days. Control plants had 76% survival while the eight week regime had 91%. Survival was similar for all treated Douglas-fir seedlings. It ranged from 89% in the two week interval to 98% in the four week regime. One year height increment was significantly greater in the six and eight week short day treatments for both species. For hemlock, it ranged from 6.1 cm in the control plants to 10.4 cm in the six week trees. Douglas-fir height increment ranged from 6.4 cm for the control interval to 8.6 cm in the eight week regime. The six and eight week photoregimes produced the best quality hemlock seedlings for this study. Four weeks of short days appeared adequate for Douglas-fir. In Study II short days effectively initiated and maintained budset in Douglas-fir seedlings in four weeks. After six weeks from treatment initiation, a light to severe moisture stress was as effective in controlling height growth. A natural photoperiod with no moisture stress was least effective. In a comparison of all treatment combinations, only the control plants under a natural photoperiod were significantly larger in all morphological properties. Short days, moisture stress or a combination of both had similar effects on reducing height, caliper, shoot dry weight and root dry weight. Unstressed seedlings in a natural daylength had the highest value of root growth capacity. All other treatment combinations had significantly lower root growth capacity. Only the severe stress under a natural photoperiod significantly reduced root growth capacity compared to any other treatment. Short days accelerated bud burst in the January and March dormancy intensity tests. Frost hardiness was similar among all treatments. Selection of a regime which controlled height growth while maintaining seedling quality was not clearcut. A short photoperiod with no moisture stress was most effective in initiating budset. However, few morphological and physiological differences were evident between short day plants and light and medium stressed seedlings. / Forestry, Faculty of / Graduate

The purpose of this study is to determine the relationship of light wave length to tissue differentiation in sunflower seedlings.

LD2668 .T4 1962 O73

Soybean seeds are known to contain high levels of lipoxygenase activity, especially during early stages of germination. Crude mitochondrial fractions from germinating soybeans also have been shown to exhibit high rates of cyanide-insensitive oxygen uptake. These results show the effects of successive discontinuous PercollR density gradients on mitochondrial fractions from 2 day old soybean seeds as judged by polarographic studies and Ouchterlony double diffusion. Axis mitochondria exhibited totally cyanide-sensitive oxygen uptake after two gradients and cotyledon mitochondria exhibited from none to 11% cyanide-insensitive oxygen uptake after three gradients. Mitochondrial fractions which were assayed for lipoxygenase with double diffusion exhibited positive results with fractions that showed cyanide-insensitive oxygen uptake and negative results with cyanide-sensitive mitochondria. These results suggest that lipoxygenase can loosely associate with the mitochondrial membrane and that gradient centrifugation can purify mitochondria free of both lipoxygenase and cyanide-insensitive oxygen uptake.

Extensive areas of potentially productive but depleted range land in the United States are occupied by a weed commonly known aa cluster tarweed (Madia glomerata). Moat attempts at seeding these areas to useful forage plants have resulted in failure. Many of these failures have been attributed to the vigorous competitive growth of tarweed plants. More recent observations of seedings in tarweed areas and laboratory work at the University of Utah indicate that tarweed is not only a strong competitor but may also produce substances which inhibit the germination and growth of other species of plants.

Thesis (M.S.)--Oregon State University, 1980. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.