Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Producing fruit of the appropriate size and high quality is of the upmost importance to realize a profit in the fruit industry. This can be achieved through bloom or fruitlet thinning to reduce the number of fruit left on the tree. The cost of production is rising and labour cost forms a large part of the total production cost. Thinning of stone fruit is labour intensive and expensive, so an alternative to hand thinning needs to be found. Two alternatives are chemical and mechanical thinning. Chemical thinners are not routinely used in stone fruit as it is in pome fruit production and gibberellins were evaluated in this study. The Darwin 300TM was evaluated as a mechanical alternative to hand thinning. It thins flowers during bloom, before fruitlet thinning by hand is performed. In our trials on nectarines and Japanese plums the objective of reducing the time required for hand thinning was achieved, with the Darwin 300TM reducing the time required by up to 50%. When the time required to thin was reduced too much it also reduced the yield, but this could be overcome by lowering the rotor speed or using different strategies during supplementary hand thinning at the fruitlet stage. The bloom thinning and reduction in yield led to an increase in the fruit size. Care should be taken when using the Darwin 300TM as the earlier thinning could increase pit splitting and/or fruit cracking, especially in cultivars that are sensitive to these defects. The optimal rate of thinning needs to be determined for each cultivar individually. The application of gibberellic acid (GA3) and gibberellin A4+7 (GA4+7) at the pit hardening stage in the previous season could decrease the number of flowers for the following growing season. There was no effect on the yield at harvest or fruit size in the season of GA3 and GA4+7 applications, but the fruit firmness was increased. This effect was more pronounced for the GA4+7 applications. Our objective of reducing the time required for thinning was achieved in some but not all cultivars. The yield was not significantly reduced, with the fruit maturity only delayed in ‘African Rose’ plum. Again no increase in fruit size was found, but the fruit firmness was again increased. The GA-applications therefore were not satisfactory in their reduction of the time required for hand thinning. A positive effect is the increase in fruit firmness, which could possibly increase the storage potential of the fruit without having negative effects on the other aspects of fruit quality but this needs further evaluation. / AFRIKAANSE OPSOMMING: Produksie van vrugte met die verlangde vruggrootte en hoë vrug kwaliteit is baie belangrik vir die realisering van ‘n wins in die vrugte-industrie. Met hierdie mikpunt in gedagte, is blom- en vruguitdunning baie belangrik om die aantal vrugte per boom te verminder. Die kostes geassosieer met vrugte produksie is besig om te styg en arbeidskoste vorm ‘n groot deel van die totale produksiekostes. Uitdunning van steenvrugte is arbeidsintensief en baie duur, dus moet ‘n alternatief vir handuitdunning gevind word. Daar is twee alternatiewe naamlik chemiese en meganiese uitdunning. Chemiese uitdunmiddels word algemeen in kernvrugproduksie gebruik, maar daar is tans geen chemiese middels vir steenvrugte nie. In hierdie studie was gibberelliene ge-evalueer as potensiële uitdunmiddel. Die Darwin 300TM is ge-evalueer gedurende blomtyd as ‘n meganiese alternatief vir handuitdunning. Die masjien verwyder blomme en verminder so die vruguitdunning benodig. In ons eksperimente op nektarien- en Japanese pruimkultivars het ons gevind dat die tyd benodig vir handuitdunning met tot 50% verminder is deur die Darwin 300TM. Dit het ook daartoe gelei dat die totale oes per boom verlaag is. Hierdie effek kan vermy word deur die rotor spoed te verminder of die strategie vir aanvullende handuitdunning aan te pas. Die feit dat die grootste deel van die uitdunproses in blomtyd uitgevoer is en ook die feit dat die totale oes per boom verlaag is, het daartoe gelei dat die vrugte groter was. Die vroeër uitdunning met die Darwin 300TM kan egter lei tot ‘n verhoging in vrugkrake en gesplete pitte. Dit moet veral in gedagte gehou word by kultivars wat geneig is tot hierdie afwykings/defekte. Die optimum tempo van uitdunning moet vir elke kultivar individueel bepaal word. Wanneer gibberelliensuur (GA3) of gibberelien A4+7 (GA4+7) by pitverharding toegedien word in die vorige groeiseisoen, kan dit lei tot die vermindering van die hoeveelheid vrugte in die volgende seisoen. Daar was geen effek op die totale oes per boom en die vruggrootte tydens oes in die seisoen van aanwending nie, maar die vrugfermheid is verhoog. Die effek was hoër na die GA4+7 as na die GA3 aanwending. Die mikpunt om die tyd benodig vir handuitdunning te verminder, is in sommige kultivars bereik. Die oes per boom in die opvolgseisoen is weer eens nie verlaag nie, maar die vrug rypheid van ‘African Rose’ pruime is vertraag. Geen effek is op die vruggrootte opgemerk nie, maar die vrugfermheid was weer eens verhoog. Die GA-toedienings het dus nie bevredigend die tyd benodig vir handuitdunning verminder nie. ‘n Positiewe effek is die verhoging van die vrugfermheid, wat moontlik kan lei tot die verhoging van die opbergingspotensiaal van die vrugte sonder enige ander negatiewe effekte, maar hierdie aspek benodig verdere navorsing.

Thesis (PhD(Agric) (Horticulture))--Stellenbosch University, 2008. / Lack of winter chilling is a major problem in producing temperate-zone fruit in warm climates. Delayed foliation and protracted bud burst and flowering are the main problems necessitating artificial means to break dormancy. In South Africa (SA), most apple production areas receive insufficient winter chilling, and an annual application of rest breaking (RB) agents is included as standard practice. The most used RB agent in SA was dinitro-o-cresol (DNOC) but its use was discontinued. Hydrogen cyanamide (HC) became the replacement. It has been effective in apple, but variable effects on fruit set, blossom, yield and fruit quality have been reported. Thidiazuron (TDZ) has also shown the ability to break dormancy in apples. Another important practice in apple production is chemical thinning (CT). However, results are highly influenced by the type of chemical, weather conditions, cultivar and blossom pattern. With the increasing efficacy of RB and by identifying its effects on vegetative and reproductive development, it will be possible to determine more effective chemical thinning treatments. The objective of this study was to determine appropriate RB treatments for apple trees in a warm winter climate, identifying their effect on vegetative and reproductive development and the influence on CT efficacy. The research was performed in the Elgin area (34°S, 300 m) SA, over a period of three years, on ‘Golden Delicious’ and ‘Royal Gala’. In evaluating the effect of different HC concentrations and oil, no synergistic or antagonistic effects were observed on budburst and yield. Mineral oil at 4% plus 1 to 2% Dormex® combined were sufficient to break dormancy. Dormex® at 4% (2.08% HC) reduced fruit set and yield. In general, the rest breaking treatments (DNOC, HC and TDZ) enhanced the final vegetative bud burst compared to the control, while reproductive bud burst in 2002 and 2003 was not significantly influenced. The treatments compressed and advanced flowering periods, but this effect was not always evident when the spring was warm. The treatments synchronised flowering on the tree and between the two cultivars. The mixture of 0.245% HC and 4% oil was less effective in terms of increasing bud burst in ‘Royal Gala’ compared to other rest-breaking treatments. The mixture of 0.49% HC and 4% oil effectively compressed and synchronised flowering in ‘Golden Delicious’. TDZ-oil used at the lower rates also increased bud burst and concentrated flowering. However, it appears that after a cooler winter, higher rates could result in an exacerbated bud burst effect with excessive vegetative growth. The rate and timing of TDZ-oil application influenced the reproductive development of apples and therefore fruit quality. In ‘Golden Delicious’ increased fruit set, number of seeds, and reduced fruit russeting appear as beneficial results of TDZ-oil, whereas fruit set and russeting was not affected in ‘Granny Smith’. TDZ-oil, when applied late and at increasing rates, led to an increase in the malformation of calyx cavities, especially when chemical thinning was performed using the cytokinin-like compound benzyladenine. The effect seemed to be cultivar specific, with ‘Golden Delicious’ being the most severely affected. Increased return bloom in response to late TDZ application in ‘Golden Delicious’ and ‘Royal Gala’ appeared to be beneficial.

10 pp. / Pruning recommendations for shrubs commonly planted in the low and mid-elevation desert in Arizona are given based on the intended use and individual plant growth characteristics.

The purpose of this series of studies was to evaluate the effects of schedule thinning and delay-to-reinforcement following intervention for individuals diagnosed with intellectual and developmental disabilities. Study one was a systematic review of the available literature on schedule thinning, and study two evaluated the effects of a novel approach to delay-to-reinforcement following functional communication training. Results of both studies found that schedule thinning and delay-to-reinforcement are efficacious procedures for continued reductions in challenging behavior following intervention.

Student Number : 0115350V - MSc dissertation - School of Plant, Animal and Environmental Science - Faculty of Science / The effect of between-tree competition in separate even aged stands of a Eucalyptus grandis seedling and a single Eucalyptus grandis x Eucalyptus urophylla hybrid clone was assessed. This was done by comparing treatments within an experiment, that was designed to test the effect planting density and genotype had on timber production and stand dynamics through time. This experiment is located on an escarpment in the Summer rainfall region of South Africa, approximately 7 km North West of Albert Falls dam in the Kwa-Zulu Natal Midlands. The terrain is flat with deep apedal soils, and the site has an estimated mean annual precipitation of 1143 mm. The simplest method of evaluating competition effects in plantation stands is through the use of spacing trials. Spacing trials create stands/plots in which all silvicultural and climatic variables are constant. Differences between treatments can then be attributed to competition alone. The planting densities tested were 6667 stems.ha-1, 3333 stems.ha-1, 2222 stems.ha-1, 1587 stems.ha-1 and 1111 stems.ha-1 respectively. Competition was measured at three levels, namely; (i)individual tree, (ii)size-class and (iii)stand level. Vigour and its distribution within the population were used to explain competition processes. Basal area was chosen as the size variable for which vigour would be analysed. Relative Growth Rate (RGR) and Relative Production Rate (RPR) were chosen as the measures of vigour for analysis. Morphological changes in the trees as a result of competition were also used to understand the competitive mechanisms. It was found that resources are not shared amongst individuals in proportion to their size, but rather the larger individuals use disproportionately more of the resources than the smaller individuals, and therefore competition is asymmetrical. The dominant form of competition was found to be resource pre-emption where larger individuals passively prevent solar resources from reaching smaller competitors. Using RPR as the measure of vigour, competition was found to be one-sided, meaning that smaller individuals do not reduce the vigour of larger ones. If RGR is accepted as the measure of vigour then competition is two-sided meaning that the smaller individuals do reduce the vigour of the larger ones to a certain extent. There was no difference in the degree to which the smaller competitors in the clonal and seedling treatments reduced the growth of the larger individuals. The self-thinning rate in the seedling treatments was significantly higher than in the clonal treatments. Increases in mean tree size and production per hectare were accompanied by increases in mortality in the seedling treatments. In the clonal treatments it was found that even once the mean tree size approached the self thinning line, very few or no trees died, however there was also very little or no increase in mean tree size. When the relationship between number of live trees and production per hectare was analysed it was found that the clone could increase production per hectare without any change in survivorship, which is contrary to popular theory. As time progressed the skewness of the population progressed from negative to positive. This increase was the most pronounced in the higher planting density treatments, and the clonal treatments. The size variability in the population first decreased, then steadily increased. This increase was more pronounced in the high planting density treatments, and the clonal treatments. Clones and seedlings react in very different ways to competition. The large differences in population dynamics observed, indicate that we cannot just apply knowledge built up over the years regarding the management of Eucalyptus grandis and other plantation species to Eucalyptus hybrid clones.

Thesis (Ph. D.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 75-77). Also available on the World Wide Web.

Thesis--Gembloux, Belgium. / Abstract in English. Includes bibliographical references (p. 223-242).

This study evaluates the life history responses of yellow perch to mass removal and the potential for population recovery. We removed approximately 94% of a perch population from Nepawin Lake, a 35 hectare oligotrophic lake in Algonquin Provincial Park, Ontario, as part of a study designed to enhance the recruitment success of brook trout. Several response variables were examined both before and after mass removal: (1) condition, which includes growth, diet and overall condition responses, and (2) reproduction, which includes size at maturity and fecundity. We examine the question of whether compensatory life history responses in the yellow perch will overcome brook trout predation leading to a reestablishment of a high density perch population. Results showed that prior to the manipulation, perch exhibited a narrow size distribution, high dietary overlap, and low condition, typifying a stunted population. After mass removal, the perch population remained in a narrow size distribution, exhibited decreased growth rates for older age classes, showed increased mean condition and increased consumption of zooplankton in all size classes. Perch also exhibited increased size at maturity and decreased fecundity immediately following the mass removal. A time lag is expected before compensatory recruitment is possible in the population, but it is likely that the perch will recover from the mass removal because of strong age 0+ and 1+ cohorts. However, stunting and bottlenecking may still occur in the population. Continued monitoring and management is necessary to observe further changes to the perch population dynamics in Nepawin Lake.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 93-103). Also available via the Internet.