This study of some common turf weeds of the Vancouver area considers some aspects of biology and control. Seed production observations indicated that seeds ranging from 300 to over 260,000 per plant were produced each season by different species. Seeds of Senecio vulgaris L., Sonchus oleraceus L. and Hypochaeris radicata L. germinated immediately after harvest while others required several months. H. radicata showed good germination in light while Cerastium vulgatum L. and Lamium amplexicaule L. germinated best in a shaded or dark environment. Two germination peaks in spring and fall occur in this group of turf weeds. However Stellaria media (L.) Cyrill produced flowers and seed for most of the year. Rumex acetosella L. also had a long flowering period as did Plantago lanceolata L. and P. major L. The three latter species were found to require a long time to mature in the flower head and so were not shedding seed over the considerable period of time characteristic of S. media. Leaf area development did not appear to be associated with root development in the seedling weeds examined, and variations in the relative leaf areas of the different species occurred with time. Marked differences in flowering period and characteristics were apparent in observations on the various weeds made over a 17 month period. Apomictic seeds of Taraxacum officinale L. were found to have a germination rate significantly lower than those produced by artificial pollination. Inhibitory materials present in leaves and stems of weeds were shown to delay germination of bent grass nearly three weeks and to definitely reduce the percentage germination. The species showing the greatest inhibitory properties were Matricaria matricarioides (Less.) Porter, S. media and P. lanceolata in that order. Four turf grasses were shown to differ in their responses to proprietory mixtures of the phenoxy type herbicides, and weed species similarly differed in their responses to the newer herbicides which included Banvel D (dicamba), Tordon, phenoxypropionic materials and mixtures containing two and three chemicals. / Land and Food Systems, Faculty of / Graduate

The effects of temperature and sulphur nutrition on the growth, yield and mineral composition (N, NO₃-N, S and SO₄-S) of Hordeum vulgare L. cv Olli, Pisum sativum L. cv Dark Skin Perfection and Brassica campestris L. cv Arlo, were investigated in controlled environments. The net CO₂ exchange rates and compensation points were also determined at two S levels (0 and 64 ppm) under various temperature regimes. When barley and rape plants were grown at 0 ppm S, deficiency symptoms developed in about two weeks, whereas pea plants at the same level developed deficiency symptoms in about three weeks. Plants at the lowest S level and the highest temperature took the shortest time to develop S deficiency symptoms. Fresh and dry weights, shoot length, number of nodes and number of fertile fruit increased with increasing S levels. Shoot growth in all three species was more depressed by S deficiency than root growth. Optimum growing temperature regimes for barley and peas were found to be 24/16 at the vegetative stage and 18/10°C at the mature stage as evident from increased weights, maximum fruit set and mineral uptake. Optimum temperature for rape plants was 29/21°C at both stages of growth. Detrimental effects of cotyledon or endosperm removal tended to mask the effects of temperature and S levels. This method was thus found to be unsatisfactory for the study of S nutrition in plants. Higher mineral concentration was observed at the vegetative stage than at the mature stage in peas and rape plants, while in barley the mineral concentration remained constant at both stages of growth. With increase in S supply there was an increase in uptake of both total S and SO₄-S. Uptake also increased with increasing temperatures. This increase was largely due to "concentration effects". Hence the use of SO₄-S level as a criterion for diagnosis of S deficiency may be unsatisfactory, unless plants are grown at optimum temperatures. S deficient plants had increased total N and NO₃-N concentrations in all three species. NO₃-N concentration also increased with an increase in temperature. The total N concentration did not increase appreciably with temperature. Consequently, at low S level (0 and 8 ppm) total N:total S ratios (N:S) tended to increase or decrease depending on low or high growing temperatures respectively. These changes in ratios were independent of actual size of the plants. Furthermore the ratios for all S levels at the vegetative stage were lower than those at the mature stage. Therefore both temperature and stage of growth are important factors to be considered in interpreting S deficiency from N:S ratios in plants. The net C0₂ exchange rates were generally higher at 20 days than at 30 days. At 0 ppm S level and at high temperature, the decline in net C0₂ exchange rate with age was greater. Maximum CO₂ exchange rates were observed at the optimum growing temperatures for both S levels. Increasing the measuring temperature above the growing temperature caused no further stimulation in CO₂ uptake, and at high temperatures there was a decrease in uptake. When CO₂ exchange rates were measured at two 5.5°C intervals above and below the growing temperatures the maximum rates were recorded at or below growing temperatures in all the species at both S levels. The CO₂ compensation values were higher with lower S level in the leaf tissue than at higher S levels. Increase in growing temperatures also caused larger CO₂ compensation values than at lower temperatures. Negative correlations between CO₂ compensation point and leaf tissue S level and positive correlations between CO₂ compensation point and temperature were observed in barley and peas. / Land and Food Systems, Faculty of / Graduate

This study examined the effects of lung expansion and changes in temperature on fluid movement by the lungs in the initial period after birth. In addition, experiments with amiloride support the belief that fluid reabsorption acts via a sodium transport mechanism. Lungs from fetal guinea pigs (56-67 days of gestation) were supported in vitro for three hours, and lung liquid production rates were measured using a dye dilution technique. The average production rate in the first hour of untreated preparations was 1.30 ±0.22 ml/kg body weight per hour, and this did not change significantly during the remainder of the experiment (n=30). This rate is comparable to secretion rates previously reported from chronically catheterized sheep. In 36 further preparations, the lungs were transferred from 37°C to fresh Krebs-Hanseleit saline at one of the following temperatures, for one hour (an ABA design): (a) 29°C; (b) 32°C; (c) 34°C; (d) 35°C; (e) 36°C; (f) 39°C. In all cases, the temperature change resulted in an immediate and significant fall in secretion. All lungs showed a tendency towards recovery when returned to starting conditions, except those subjected to a temperature increase. Reductions of 2-3°C, those normally seen in the delivery room, had the greatest effect and caused not only a decrease in secretion, but promoted fluid reabsorption. Amiloride at 10⁻⁶M had no effect on control preparations, but completely blocked the reabsorption stimulated by a temperature drop of 2°C. Expansion of the lungs, which occurs naturally as a newborn attempts to take its first breaths, was also examined. Thirty fetal lungs were expanded by one of the following amounts: (a) 18%; (b) 31%; (c) 43%; (d) 50%; (e) 72%. All expansions resulted in a significant fall in secretion rate, with the effect being proportional to the degree of expansion. Amiloride at 10⁻⁶M again blocked the strong reabsorption occurring with 70% expansion. Further studies investigated the possibility that expansion causes reabsorption via the local release of a substance occurring in the lungs. When one set of lungs was expanded in the presence of a second, unexpanded set, both showed a significant decrease in secretion, suggesting that the expanded lung had released some factor which affected the otherwise untreated lung. However, studies with α- and β- adrenergic blockers showed that it is unlikely the expanded lung was liberating either adrenaline or nor-adrenaline. The results of this study show that two changes which are likely to occur in the period immediately after birth, namely a 2-3°C decrease in core temperature, and lung expansion, may be important in promoting the vital reabsorption of fluid. They suggest that expansion may release substances locally in the lungs which stimulate this reabsorption, and that the fluid is removed from the potential air spaces via sodium transport mechanisms. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Methylmercury (MeHg) bioaccumulation in freshwater aquatic systems is impacted by anthropogenic stressors, including climate change and excess nutrients. The goal of this study was to determine how warmer water temperatures and excess nutrients would impact zooplankton communities and phytoplankton concentrations, and in turn increase or decrease MeHg concentrations in freshwater zooplankton. I used a 2x2 factorial design to determine if the interaction of temperature and nutrients would impact plankton metrics and zooplankton MeHg concentrations. Mesocosms were filled with Hg-contaminated water and plankton from Cottage Grove Reservoir, Oregon, a waterbody that has experienced decades of elevated MeHg concentrations and corresponding fish consumption advisories due to run-off from Black Butte Mine tailings, located within the watershed. Treatment combinations of warmer temperature (increased by 0.5°C) and nutrient addition (a single pulse of excess nitrogen and phosphorous), control, and a combination of temperature and nutrients were applied to mesocosms. While plankton did respond to treatments, zooplankton biomass and phytoplankton concentrations did not have significant relationships to MeHg concentrations. However, a significant interactive effect of nutrients and temperature was present: nutrients appeared to buffer against increased MeHg concentrations when temperature was elevated. The mechanisms for this interaction appear to be related to a shift to larger body size and an increase in abundance of Daphnia over copepods. Findings suggest that community composition and species-specific differences in both zooplankton and phytoplankton could play a role in MeHg transfer to higher trophic levels.

The temperature-dependent development of pupae and adults of strawberry root weevil (SRW) Otiorhynchus ovatus (L.) was studied in strawberry (Fragaria x ananassa Duch. var. 'Totem'). The development of pupae and adults was investigated at constant temperatures from 3-33��C at 3��C intervals. Major emphasis was on the development of a weighted linear temperature-based pupal prediction model. The predictive ability of this weighted model was compared to a traditional non-weighted linear degree-day model by relating predictions to the observed occurrence of SRW lifestages determined by field sampling. The upper thermal lethal limit for SRW pupae was between 30 and 33��C. Pupae did not eclose below 6��C. Mean pupal duration was 127 d at 6��C and 7 d at 30��C. Rate of development (1/days) was greatest at 30��C. The weighted linear pupal prediction model produced a developmental threshold of 4.3��C and a degree-day requirement of 227.3. The non-weighted linear pupal prediction model produced a developmental threshold of 6.2��C and a degree-day requirement of 163.9. Adults fed at all temperatures from 3-33��C and oviposited at temperatures between 18 and 30��C . The longest preoviposition period (32.8 d) and the least total number of eggs (2.2) were observed at 18��C. The shortest preoviposition period (15.1 d) and the greatest total number of eggs (282.5) were observed at 27��C. A temperature range of 21 to 27��C appeared to be optimum for oviposition; i.e. relative to other temperatures, preoviposition time was short, mortality was low, and total number of eggs laid was high. / Graduation date: 2000

Graduation date: 1997

This research was conducted to determine the effects of temperature and competition on seedling root and shoot growth of cheatgrass (Bromus tectorum L.) and 5 collections of Idaho fescue (Festuca idahoensis. Elmer). For the temperature study, seedlings were grown in environmental chambers with 16 hours day/8 hours night, at temperatures of 5, 10 and l5°C. Root depth was weekly recorded during 9 weeks growth period. Seedlings were destructively harvested after 63 days and evaluated for root and shoot characteristics. At all temperatures, cheatgrass exhibited greater above and below-ground biomass, root depth, total root length, daily root depth rate and shoot height than Idaho fescue. Seedlings of the 5 Idaho fescue collections produced fewer roots and grew slower than seedlings of cheatgrass. As a group, the Idaho fescue collections showed similar root and shoot growth and produced more tillers than cheatgrass, except at 5°C. As temperature increased from 10 to 15 °C, shoot growth of Idaho fescue increased while that of cheatgrass was similar. For the competition study, seedlings were grown in pots in a greenhouse with planting ratios of Idaho fescue to cheatgrass of 1:0, 1:5 and 1:10, and under 2 watering regimes. Seedlings of Idaho fescue were established from transplants grown two months ahead of cheatgrass. Shoot height, tiller and leaf number were weekly recorded. Seedlings were harvested after 49 days and evaluated for aboveground dry weight. Competition from cheatgrass depleted soil moisture and reduced growth of Idaho fescue. Cheatgrass had greater aboveground dry weight and shoot height than Idaho fescue. However, Idaho fescue had greater tiller and leaf number than cheatgrass. In addition, when competing with cheatgrass, remnant Idaho fescue plants were less adversely affected in aboveground dry weight and shoot height than Idaho fescue plants from pristine areas. These results indicated that remnant Idaho fescue plants may be a different ecotype occurring in response to competition and may better tolerate the effect of the interference from cheatgrass. This information may serve as a basis for reestablishment of Idaho fescue in Central Oregon rangelands. / Graduation date: 1993

Thesis (MScAgric)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Sunburn is a major problem in the apple industry worldwide. A kaolin product, M-97- 009 (100% kaolin), originally developed for insect control, was evaluated for its efficacy in controlling sunburn on pome fruit. Trials were conducted over two seasons in two different areas of the Western Cape, South Africa. During the first season, 'Royal Gala', 'Fuji' and 'Granny Smith' apples were evaluated in the Koue Bokkeveld. The kaolin was mixed with water and applied to the trees by means of a hand-gun regularly throughout the season. In addition to the effect on sunburn, effects on yield, colour development, snout beetle damage and other defects were determined. Sunburn was reduced on all the cultivars tested, although not significantly on 'Granny Smith'. Inconsistent effects on yield parameters were observed. The applications significantly reduced red colour on 'Fuji', but this problem was rectified by an improved application technique the following season. During the second season, additional apple cultivars and 'Rosemarie' pears were included in the trials. The apple trials were conducted in the Elgin area, and the 'Rosemarie' trial in the Koue Bokkeveld. Surround™ (95% kaolin) was applied to the trees by means of a commercial "blower". The effects on sunburn, yield, colour development and fruit maturity were determined. In contrast to the previous season, sunburn was not reduced on any of the cultivars examined. Yield parameters were not affected except in the case of 'Royal Gala' where the number of fruit was increased, and 'Cripps' Pink' where the number of fruit was reduced. Fruit colour was not affected in the apple cultivars, but chroma of 'Rosemarie' pears was reduced, indicating a less intense colour. The kaolin applications had a variable effect on fruit maturity. The effect of the foliar applications on photosynthetic photon flux density (PPFD), photosynthetic rate, stomatal conductance and transpiration rate was determined. In addition to these spot measurements, photosynthetic light response curves were determined. Measurements were taken on both the inner and outer canopies The applications significantly reduced photosynthetic rates in the inner canopy and reduced the apparent quantum efficiency of leaves on the outer canopy. No significant effect on PPFD was found. It appears that the white coating reflects light and allows less light to penetrate the leaf, thus reducing photosynthesis. Surround™ treatments could not counteract the damaging effects of the high temperatures experienced in the Western Cape during this season and was not effective as a control measure for sunburn. This does not appear to be a commercially viable solution for the sunburn problem and it would be worthwhile to investigate the use of alternative options, such as evaporative cooling. / AFRIKAANSE OPSOMMING: Sonbrand is een van die grootste probleme wat wêreldwyd in die appelbedryf ondervind word. 'n Nuwe produk, M-97-009 (100% kaolien), is oorspronklik ontwikkel vir insekbeheer in geïntegreerde plaagbeheer, maar daar is beweer dat dit moontlik sonbrand op kemvrugte kan verminder. Proewe is oor twee seisoene uitgevoer in die Koue Bokkeveld en ook in die Grabouw-omgewing in die Wes-Kaap. Tydens die eerste seisoen is die effek van M-97-009 op 'Royal Gala', 'Fuji' en 'Granny Smith' appels beoordeel. Die kaolien is met water gemeng en deur die loop van die seisoen met 'n handspuit op die bome gespuit. Die effek van die produk op sonbrand, oesgrootte, vruggrootte, kleurontwikkeling, kalanderskade en ander defekte is bepaal. Sonbrand is op alle kultivars verminder, alhoewel nie betekenisvolop 'Granny Smith' nie. Die effek van kaolien op oesparameters was rue konsekwent nie. kleurontwikkeling op 'Fuji' benadeel, heel moontlik Die toedienings het as gevolg van die toedieningstegniek. Met verbeterde toedieningsmetodes die volgende seisoen, is kleurontwikkeling van 'Fuji' nie benadeel nie. Tydens die tweede seisoen is die effek van kaolien op nog appelkultivars en 'Rosemarie' pere ge-evalueer. Die appelproewe is in Elgin uitgevoer, terwyl die 'Rosemarie'-proefin die Koue Bokkeveld uitgelê is. Surround™ (95% kaolien) is met kommersiële spuitpompe toegedien. Weereens is die effek van die produk op sonbrand, oesgrootte, vruggrootte, kleurontwikkeling en vrugrypheid bepaal. Sonbrand is nie verminder nie. Vruglading tydens oes is nie betekenisvol beïnvloed nie, behalwe in die geval van 'Royal Gala' waar die vruglading verhoog is, en 'Cripps' Pink' waar daar minder vrugte op die gespuite bome was. Die Surround™ toedienings het geen uitwerking op kleur van appels gehad nie, maar het die chromawaarde van 'Rosemarie' pere verlaag, d.w.s die vrugkleur was minder intens. Die kaolienspuite het 'n uiteenlopende effek op vrugrypheid gehad. Fotosintetiese foton vloeddigtheid (FFV), fotosintesetempo, huidmondjieweerstand en transpirasietempo is gemeet en ligreponskurwes van beide die buitenste en binneste blaardak is bepaal. Die Surround™ toedienings het fotosintese van blare ill die binneste gedeelte van die blaardak verminder en die kwantumdoeltreffendheid van blare op die buitenste deel van die blaardak verminder. Geen betekenisvolle effek is op FFV gekry nie. Dit wil voorkom asof die wit laag kaolien op die bome lig weerkaats en veroorsaak dat minder lig na die blaar deurdring. Dit verminder dan die fotsintesetempo. Met die baie warm weer wat in die Wes-Kaap gedurende die tweede seisoen ervaar is, kon die SUITound™behandelings nie sonbrand verhoed nie. Dit wil voorkom asof Surround™ nie 'n baie doeltreffende oplossing in kommersiële boorde sal wees nie. Alternatiewe oplossings, soos byvoorbeeld evaporatiewe verkoeling, saloorweeg moet word.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Delayed foliation is commonly observed in apple and pear producing countries with warm and/or short winter climates, resulting in less synchronised budburst, of fewer buds and reduced yield. Applications of rest-breaking agents minimise the symptoms of delayed foliation. According to chilling models used in fruit producing areas of the world, the climate of South Africa is not suitable for deciduous fruit production, however fruit has been successfully produced here for a long time. This study aimed to quantify the effects of freezing temperatures, different chilling temperatures and the period of chilling, to obtain a better knowledge of bud dormancy release on apple and pear shoots. The chilling period was the most important factor influencing the progression of dormancy. While in some cases the chilling temperature and the freeze treatment effects were significant, the contribution to differences in the progression of dormancy was negligible. Our findings indicate that currently used chilling models should emphasise the time of exposure to low temperatures more than the difference in temperatures between I to ro-c. The South African apple and pear industry made good progress in moving towards high density plantings, but large variation in soil types, non-optimum growing conditions, replant situations and a lack experience with dwarfing rootstocks limited further development. However, there is sti II an urgency to obtain higher early yields of good quality fruit applying the most efficient production practices. We aimed to quantify the field performance of locally available apple and pear rootstocks, in particular from data outside of previously reported local trials, as well as early production of newly planted trials. Information obtained form the industry indicates that BPI and BP3 are the preferred pear rootstocks. From production records of 'Packham's Triumph' pears, it appeared that BP3 and OHxF97 produced the best yields compared to the other rootstocks. Production of 'Doyenne du Cornice' was the best on QA and BP3. In newly planted 'Rosemarie', 'Flamingo', and 'Forelle' trials, different rootstocks were evaluated. 'Rosemarie' showed indications 01 incompatibility with QA and QC5 I, but on BPI and QA with a 'Beurre Hardy' interstock produced good initial yields although BPI induced slightly larger trees. 'Flamingo' on QA and QC51 produced the best yields. 'Forelle' on BPI, BP3, and QA produced similar yields up to the 4th leaf. For apples M793 seems to be the preferred rootstock in the South African industry. From production records of 'Golden Delicious' and 'Granny Smith' apples, it appeared that M793 and MM 106 produced the best yields when compared to Seedling rootstock. In a 'Cripps' Pink' trial, MMI09, M793 and M25 were more vigorous than M7, MMlll and MMI06. MMI06 was cumulatively, over four years from planting, the most yield efficient, although no consistent trend regarding fruit quality was observed between the rootstocks evaluated. / AFRIKAANSE OPSOMMING: Vertraagde bot word algemeen opgemerk in appel en peer produserende lande met n' warm enlof kort winter klimaat, wat veroorsaak dat bot van minder knoppe, meer ongelyk plaasvind en gevolglik lei tot swakker opbrengste. Toediening van rus-breek middels beperk die simptome van vertraagde bot. Volgens koue modelle wat in vrugte produserende areas in die wereld gebruik word, is Suid Afrika se klimaat nie geskik vir die verbouing van sagtevrugte nie alhoewel sagtevrugte al vir n lang tyd met groot sukses hier verbou word. Hierdie studie is daarop gemik om die effek van vries temperature, verskillende koue temperature en die periode van koue op die vrystelling van dormansie op knoppe van appel en peer lote te kwantifiseer. Die peri ode van koue was die mees belangrikste faktor wat die ontwikkeling van dormansie beinvloed het. In sommige gevalle was die effek van die koue temperature betekenisvol, maar die bydrae tot die verskille in die ontwikkeling van dormansie was weglaatbaar klein. Ons bevindinge dui aan dat die huidige koue modelle wat gebruik word, meer klem moet le op die periode van blootstelling aan koue as aan die effek van verski llende temperature tussen 1 en 10°e. Die Suid Afrikaanse appel en peer bedryf het goeie vordering in die beweging na hoe digtheid aanplantings gemaak, maar groot verskille in grond tipes, sub-optimale groei toestande, herplant probleme en n' tekort aan ondervinding met dwergende onderstamme het verdere ontwikkeling beperk. Ten spyte hiervan is daar steeds n' dringendheid om hcer produksies, van goeie kwaliteit vrugte so vroeg as moontlik te kry deur die toepassing van die mees effektiewe produksie praktyke. Ons het gepoog om die prestasie van plaaslik beskikbare appel en peer onderstamme te kwantifiseer, in besonder deur data wat nog nie van tevore oor verslag gedoen is nie en ook deur te meld van vroee produksies op nuut aangeplante proewe. lnformasie uit die bedryf het aangedui dat BP 1 en BP3 die voorkeur peer onderstamme is. Deur na die produksie geskiedenis van 'Packham's Truimph' pere te kyk kom dit voor of BP3 en OHxF97 die beste produksies in vergelyking met die ander onderstamme gelewer het. Die produksie van 'Doyenne du Com ice' was die beste op QA en BP3. In nuut geplante 'Rosemarie', 'Flamingo', en 'Forelle' pro ev e was verskillende onderstammc gecvalueer. 'Rosemarie' het tekens van onverenigbaarheid getoon met QA en Q 51, maar op BP 1 en QA met n 'Beurre Hardy' tussenstam het 'Rosemarie' goeie aanvanklike opbrengste gel ewer, al was bome op BP 1 effens grater. 'Flamingo' op QA en QCS 1 het die beste opbrengste gelewer. 'Forelle' op BP 1, BP3, en QA het ongeveer ewe veel tot die 4dc blad geproduseer. By appels is M793 die voorkeur onderstam van die Suid-Afrikaanse appel bedryf. M793 en MM 106 gee beter opbrengste as Saailing onderstam wanner die produksie geskiedenis van 'Golden Delicious' en 'Granny Smith' appels evalueer word. In n' 'Cripps' Pink' proefwas MMI09, M793 en M2S meer groeikragtig as M7, MMlil en MMI06. MM I 06 het kumulatief meer geproduseer en was ook meer produsie doeltreffend tot en met die 4de blad na plant. Daar was egter geen konstante neiging rakende vrug kwaliteit tussen die verskillende onderstamme wat getoets is nie.