Thesis (M. A. Agricultural Management (Plant Production)) -- University of Limpopo, 2020 / Although potato seed priming in water is not allowed for quality-related reasons in tubers of the produced crop, it was viewed as necessary to use the technique as a carrier of active ingredients of phytonematicides, with the hope that should the technique work, then other solutions could be used for priming of potato tuber seeds. The objectives of this study were to investigate the feasibility of using potato seed tubers as carriers of cucurbitacin A, cucurbitacin B and momordin from triterpenoid- containing phytonematicides to improve management of nematode population densities in potato plants under greenhouse, microplot and field conditions, respectively. In single treatments (A1B0M0, A0B1M0 and A0M0B1), potato seed tubers were without any phytotoxicity in 3% solutions, in any two permutations (A1B1M0, A1B0M1 and A0M1B1) at 1.5% each and at three permutations (A1B1M1) at 1% each, for 7 h and then dried under shade for 2 h prior to planting. Twenty-cm-diameter plastic pots were filled with 2 700 ml growing medium under greenhouse conditions and placed on benches at 0.3 m × 0.2 m spacing. Under microplot 30-cm-diameter plastic pots were used and pots were then inserted into 20-cm-deep holes at 0. 5 m × 0.5 m spacing and under field conditions potato seed tubers were set at 30-cm-depth with a 0.6 m × 0.6 m spacing. A 2 × 2 × 2 factorial experiment was laid out in a randomised complete block design, with the eight treatments replicated 7 times. Nemarioc-AL (A), Nemafric-BL (B) and Mormodica (M) phytonematicides served as first, second and third factors, respectively. At 56 days after applying treatments, the A1B1M1 interactions were not significant on all plant variables under greenhouse and field conditions however under microplot the interaction was significant (P ≤ 0.05) on fresh tuber mass, fresh root mass and dry root mass, contributing 28, 26 and 26% in Total treatment variation (TTV) of the respective variables. In contrast, the A1B1M1 xxviii interactions were highly significant (P ≤ 0.01) on chlorophyll content, contributing 43 and 40% in TTV. Generally, relative to untreated control, the second and first order interactions, along with individual treatments, significantly increased fresh tuber mass by 31% relative to the untreated control, except for Nemarioc-AL × Mormodica and Nemafric-BL × Mormodica interactions which were not different to the untreated. The A0B1M1 interaction was highly significant on plant height, stem diameter, chlorophyll content, dry shoot mass, dry root mass and fresh tuber mass, contributing 45, 36, 37, 35, 60 and 35% in TTV of the respective variables under greenhouse conditions similar to the microplot experiment, the interaction relative to the untreated control, also did not have any effect on plant variables. However, under field conditions the first order interaction, A0B1M1, was highly significant on dry root mass, contributing 60% in TTV on the variable. Relative to untreated control, the interaction reduced dry root mass by 14%, which was not different to the effect of Mormodica phytonematicide at 13%, but was significantly different to that of Nemafric-BL phytonematicide. A1B0M1 interaction had significant effects on fresh tuber mass, contributing 33% in TTV on the variable. Relative to the untreated control, the interaction increased fresh tuber mass (yield) by 32%, which was not different to that of Nemarioc-AL phytonematicide at 40%, but significantly different to that of Mormodica phytonematicide at 16%. Nemafric-BL and Mormodica phytonematicides under greenhouse conditions, each reduced dry shoot mass by 18 and 22%, respectively, whereas their interaction effects on the variable did not differ significantly from the untreated control. Similarly, under microplot conditions Mormodica phytonematicide alone significantly reduced plant height by 12%, although this was not different from the effects of Nemafric-BL phytonematicide. Also, the effects of Nemafric-BL phytonematicide on plant height was not different to that of the untreated control. However, Mormodica phytonematicide increased FSM, xxix DSM and FTM by 31, 33 and 19%, respectively. Mormodica phytonematicide effect on the variables was significantly different to the untreated control. The phytonematicide also reduced FRM and DRM by 17% and the effect on the two variable which significantly differed from the untreated control. The second order interaction were not significant on nematode variable under greenhouse and field conditions, but the interaction was significant only on total nematodes in roots, reproductive potential (RP) and final population (Pf) of Meloidogyne species on roots of potato plants and in the soil under microplot conditions, contributing 11, 13 and 10% in TTV on the variables, respectively. Relative to untreated control Nemarioc-AL × Nemafric-BL × Mormodica phytonematicide interaction reduced total nematode, RP and PF by 18, 64 and 18%, respectively, whereas their effects on the variables differed significantly from untreated control. Generally, Nemafric-BL × Mormodica interaction consistently in all three experiment reduced all nematodes variables. Nemarioc-AL × Nemafric-BL × Mormodica interactions were only significant on Na, contributing 7% in TTV o the variable. Relative to untreated control the interaction reduced Na by 33% and effects on the variable was significantly different to those of untreated control also Nemarioc-AL, Nemafric-BL and Mormodica alone. However, the second order interactions were not significant in greenhouse and field conditions. The A0B1M1 first order interaction although the interactive effects, contributed highly in TTV on Na and Zn in potato tuber tissues, relative to untreated control, the effects were rather negligent at 2 and 4%, respectively. In all different conditions of the study validating that potato seed tubers could be used as carriers of active ingredients of phytonematicides when used through the priming technology. The Nemafric-BL and Mormodica phytonematicide interactions consistently reduced population densities of the Meloidogyne species and increased yield under microplot and field experiments.

Regeneration of forest stands is often complicated by the establishment and competition of brush on logged and burned-over areas. The encroachment of brush in the ponderosa pine type of Idaho, particularly Ceanothus velutinus, Dougl. presents a difficult problem to the forest manager. The brush competition severely reduces the growth rate of associated trees, thus extending the period necessary to grow a crop of trees. This situation may seriously limit the economic production of a wood crop of ponderosa pine. Any approach to the solution of brush problems should include a thorough understanding of brush ecology. Those phases of ecology dealing with reproduction and distribution of brush need special emphasis. It has been assumed that most of the brush on logged or burned-over areas originated from seed stored in the forest floor; yet little is known of the quantity or distribution of these seeds. This study was carried out to learn what kind, number and variability of seed is present in the forest floor, and to investigate the number of seed located in different forest conditions, aspects and soil layers. To achieve the above objectives, 48 square-foot, duff-soil samples were taken in the ponderosa pine type of the Boise Basin Experimental Forest in Idaho. Seeds were separated from the samples and major species identified, pretreated and germinated. Appropriate statistical techniques were employed to determine significant results among the different forest conditions, aspects and soil layers sampled.

I investigated how shrub-induced spatial heterogeneity influenced and was manifested by a representative ground-story plant species at a sagebrush-steppe site in southwestern Wyoming. The dispersion of cheatgrass (Bromus tectorum) reflected differences between undershrub (higher plant densities) and interspace (between shrubs, supporting lower densities) microenvironments, hence the population ecology of this annual species served as a biological probe of shrub-associated patch structure in this community. Since cheatgrass is an annual, factors affecting the seed portion of its life cycle were of special interest. First, attributes of the above- and below-ground seed pool were characterized. The environment-wide seed depositional pattern was assessed using seed traps of several designs, and the legacy of seed incorporation into the soil was examined by separating seeds from soil samples. For both components of the seed pool, annuals' seeds predominated. Seeds at the surface were subject to substantial redistribution, moving readilythrough interspace, and their deposition was related to both the interaction of wind and shrub canopies and the presence of litter. More annuals' seeds were encountered in undershrub than in interspace soils; seeds of cheatgrass were restricted to the soil surface. Second, a manipulative experiment tested effects of granivoryfherbivory and presence/absence of a replicate shrub's canopy upon success of cheatgrass plants arising from known numbers of seeds introduced into undershrub versus interspace microenvironments. While biomass of plants in treatments accessible to herbivores was less than that of protected plants, consumers did not affect plant densities, and herbivore effects were not microenvironment-specific . Shrub canopy removal had no effect on plant success, and, contrary to expectations based on the dispersion of indigenous plants, interspace plants fared better than undershrub counterparts. Finally, demographic fates of individually marked seeds were observed, to disentangle effects of microenvironment from effects of microenvironment-specific surface types on determining safe sites. Littered microsites were strongly associated with undershrub microenvironments, and on these surfaces, cheatgrass seeds were less likely to move and to suffer depredation, and more likely to become favorably positioned for subsequent germination and establishment, than on bare ground surfaces typifying interspace. \

The conversion of wetland systems to aquaculture provides alternate aquatic habitats for a variety of waterbirds. In response to the 2010 British Petroleum oil spill, the National Resource Conservation Service (NRCS) enacted the Migratory Bird Habitat Initiative (MBHI) through which NRCS partnered with landowners to provide additional wetlands and associated foraging habitat for migrating waterbirds. During winters 2011–2013, I estimated abundances of waterbirds, seeds, and invertebrates in six production and idled aquaculture facilities in the Mississippi Alluvial Valley. Wintering waterbirds exhibited similar densities on production (i.e., ~22 birds/ha) and idled (i.e., ~20 birds/ha) MBHI sites. My results suggest production and idled MBHI aquaculture impoundments produced suitable conditions for waterbirds in terms of food and habitat. I recommend future programs strive to enroll properties that promote an increased diversity of habitats in terms of vegetation structure, available forage, and varying water depth, with the aim of maximizing waterbird diversity.

No description available.

No description available.

This study was conducted on plots established by the Benson Institute in the Tamborada region of Cochabamba, Bolivia. The objective of the study was to evaluate the seed production of tall grasses that are tolerant to drought and salinity. A design of randomized blocks in divided plots with and without fertilizer was used. The results showed that the species with the greatest number of stems and inflorescence was Bromus inermis with 10.9 and 88.67 respectively. It was determined that fertilization has an effect on plant height. Furthermore, the species with the greatest seed yield was Festuca arundinacea with 30.4 kg/ha.

No description available.

Seed priming is a controlled hydration process, followed by dehydration, that allows pregerminative metabolic activity to proceed without germination. The objective of this research was to investigate the effects of priming on intrinsic characteristics of seed germination including temperature, water, and development, in order to understand how priming affects the germination of broccoli (<i>Brassica oleracea var. italica</i> Plenck) seeds. Priming of broccoli seeds consistently improved germination and emergence rate in the laboratory and field and was related to the accumulation of a specific level of hydropriming units expressed in MPa*h. Priming reduced the sensitivity of seed germination to temperature and increased the temperature range of germination but did not lower the minimum temperature for germination. Primed seeds leaked less electrolytes at supraoptimal temperatures (≥ 35°C) compared to nonprimed seeds. In the field, primed seeds produced a greater plant stand and yield under stressful emergence conditions. Under optimal conditions in the field for stand establishment, the advancement in emergence of primed seeds did not carry over to earlier, greater yields. Matric priming, using calcium silicate as the carrier in the ratio 1.0:0.8:1.8 (seed:carrier:water; by weight) for 7 d at 20°C, was superior to osmotic priming using polyethylene glycol (pEG 8000) at -1.2 :MPa in nearly all variables examined. This may be attributed to reduced respiration during priming of seeds in PEG or nutrient uptake by seeds in calcium silicate. The testa was observed to be a barrier to broccoli seed germination. Priming-induced changes to the physical characteristics of broccoli seeds included increased volume (32%) and an irreversibly expanded, and weakened testa with some minute cracking near the area where the radicle emerges. Primed seeds germinated faster, in part by maintaining a lower hydrotime constant, and thus exhibited a greater progression towards germination per unit water potential at a constant temperature compared with nonprimed seeds. It was hypothesized that, since the testa threshold was reduced after priming by expansion and formation of free spaces, the reversibly expanded embryo of primed seeds does not become immediately appressed to the testa upon rehydration. Thus the yield threshold component controlling the rate of germination of primed seeds is lower by the amount of the testa threshold. The priming effect is more than just reducing the yield threshold as indicated by a significant invigoration of seeds with split testae. Despite the increased volume as a result of the formation of free spaces, primed broccoli seeds did not imbibe more water or have a greater turgor at full hydration. Priming did not lower the minimum water potential allowing germination, and primed seeds did not plateau in water uptake but, instead, moved immediately from imbibition to expansive growth. Priming improved the germination rate of broccoli seeds at all stages of maturity with the most significant effects at stages before attainment of maximum dry weight. Dry storage of broccoli seeds at harvest able maturity (≥ 56 days after pollination) did not improve germination, indicating a lack of post harvest dormancy. / Ph. D.

The dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a variety of treatments, including after-ripening and stratification. This study was conducted to investigate and characterize more systematically factors affecting both after-ripening and stratification effectiveness, and the aging that can occur concomitantly with after-ripening. More than one year of after-ripening at ambient temperature and humidity was necessary for germination of newly harvested seeds to increase from as low as 5% to around 80%. After-ripening was not accelerated at temperatures above ambient for seeds stored in paper bags, which permitted the loss of seed moisture at the increased temperatures. Both after-ripening and aging accelerated with increases in temperature (5 to 60°C) and seed moisture content (50 to 130 g kg⁻¹), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60°C and 50 g kg⁻¹ seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30°C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N₂. After-ripening of switchgrass seemed not to be influenced by N₂ or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy. / Ph. D.