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On t.p.: Systematics and Biodiversity Science. / Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Pollen grains of the southern African genus Heliophila L. (Brassicaceae), were examined using light microscopy (77 taxa), scanning electron microscopy (82 taxa) and transmission electron microscopy (IOtaxa). The present study emanates from a pilot study by Kose (200 I) in which palynology was identified as one of the taxonomically informative data sources that can be used in the classification and subdivision of the genus Heliophila. The aim of this study was to assess the taxonomic significance of palynological data in the genus Heliophila. All pollen grains of Heliophila taxa are prolate in shape and tricolpate. The exine surface sculpture varies and two main groups are identified. In the majority of the taxa the sculpture is psilate or psilate micro-perforate with suprateetal spinules (Pollen Type A), whereas in the remaining taxa the sculpture is micro-reticulate to reticulate with or without suprateetal spinules (Pollen Type B). Pollen Type B may be divided further into three subgroups based on the shape of the lumina and the position of the suprateetal spinules. TEM results also confirm the two main groups as proposed by the SEM. The structural and sculptural features of the exine proved important in the demarcation of the pollen grains into two distinctively different pollen types and the other pollen morphological data such as pollen grain sizes, pollen grain shape are discussed in relation to the groups/subgroups of pollen types. The sculpturing types are discussed with regard to their evolution and pollination discussed with regard to plant habit and pollen size. Cluster analysis, based on vegetative and reproductive characters, excluding palynological characters, was performed only after the pollen types were identified. These groups were well supported by plant habit, life form, leaf type, presence or absence of appendages on the filaments, indumentum of filaments and presence of the stipe on the ovary and divided the genus Heliophila into two main clades. It was observed that this division followed a sim ilar pattern as the species arrangement in the classification by Marais (1970). AIthough the two main pollen types occur in both clusters proposed by the morphological analysis, the specific pollen types are restricted to distinct subclusters. In conclusion, pollen data reveals that Heliophila is a heterogeneous genus. The present study also reveals that it is difficult to subdivide the Heliophila taxa into infrageneric units on the basis of palynological evidence alone. In conjunction with other data sources, it does, however appear to have systematic significance. Therefore, the results of the present palynological study can be used as an additional source of evidence to support the subdivision of the Heliophila taxa into infrageneric units in the near future if a better understandinz and classification of the zenus is to b b be achieved. / AFRIKAANSE OPSOMMING: Stuifmeelkorrels van die suider Afrikaanse genus Heliophila L. (Brassicaceae) is met behulp van ligmikroskopie (77 taksons), skandeerelektronmikroskopie (82 taksons) en transmissie-elektronmikroskopie (IOtaksons) bestudeer. Die huidige studie is 'n uitvloeisel van 'n lootsprojek deur Kose (200 I) waarin palinologie geïdentifiseer is as een van die taksonomies-belangrike data-bronne wat in die klassifikasie en subdivisie van die genus Heliophila gebruik kan word. Die doel van die studie was om die taksonomiese waarde van palinologiese data van die genus Hettophila te bepaal. Alle stuifmeelkorrels van Heliophila taksons is prolaat in vorm en trikolpaat. Die oppervlak-skulptuur van die eksien varieer en twee hoofgroepe word onderskei. In die meerderheid van die taksons is die skulptuur psilaat of psilaat-mikroperforaat met supratektale uitsteeksels (stuifmeeltipe A), terwyl die skulptuur in die oorblywende taksons rnikro-retikulaat tot retikulaat met of sonder supratektale uitsteeksels (stuifmeeltipe B) is. Stuifmeeltipe B kan verder in drie subgroepe, gebaseer op die vorm van die lumens en die posisie van die supratektale uitsteeksels, verdeel word. Resultate verkry vanaf die TEM bevestig die twee hoofgroepe soos voorgestel deur die SEM-studies. Die strukturele en skulpturele kenmerke van die eksien blyk belangrik te wees in die verdeling van die stuifmeelstruktuur in twee duidelike stuifmeeltipes en ander morfologiese kenmerke, byvoorbeeld die grootte en vorm van die stuifmeelkorrels word bespreek in hul verhouding tot die groepe / subgroepe van die stuifmeeltipes. Die tipes stuifmeel-skulptuur word bespreek ten opsigte van hul evolusie en bestuiwing word bespreek ten opsigte van groeiwyse en stuifmeelgroottes. Groepanalise, gebaseer op vegetatiewe en reproduktiewe kenmerke, uitsluitend palinologiese kenmerke, is saamgestel nadat die stuifmeeltipes geïdentifiseer is. Die groepe word gevorm op grond van groeiwyse, groeivorm, blaartipe, aan- of afwesigheid van aanhangsels aan die helmdrade, die indumentum van die helmdrade en die aanwesigheid van 'n stipe op die vrugbeginsel en verdeel die genus Heliophila in twee hoofgroepe. Daar is waargeneem dat hierdie analise 'n soortgelyke patroon volg as die spesie-rangskikking in die klassifikasie van Marais (1970). Alhoewel die twee stuifmeeltipes in beide die morfologiese hoofgroepe aanwesig is, stem die stuifmeeltipes duidelike ooreen met die sub-groepe wat deur die morfologiese analise gevorm is. Ten slotte, stuifmeeldata dui daarop dat Heliophila 'n heterogene genus is. Die huidige studie dui ook daarop dat' n onderverdeling van Heliophila in infrageneriese eenhede op grond van palinologiese kenmerke alleen ook baie moeilik is, maar saam met ander kenmerke kan stuifmeeldata wel van taksonomiese waarde wees. Dus, die resultate van hierdie studie kan as 'n aanvullende bron van data gebruik word om 'n onderverdeling van die genus te steun en 'n klassifikasie van die genus daar te stel.

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Differences in plant structure and host abundance, distribution and density within and between plants may affect host finding success of searching parasitoids. The main objective of this research consisted in developing and validating a model that can predict parasitism by Trichogramma evanescens on various plant structures. Also, we evaluated the effect of both artificial and natural plant structures on host encountering success and on searching behavior of two species of Trichogramma. / Size (S), heterogeneity (H) and connectivity (C) define plant structure. The development of the model of parasitism was based on laboratory experiments using three dimensional artificial plants of different combinations of S, H and C. The model was then validated with experiments, within greenhouse, using natural cruciferous plants of different structures. Significant regressions of observed values of parasitism as a function of those predicted by the model were obtained. / The effect of plant structure on two species of Trichogramma was studied by using three species of Lepidoptera and three structurally different but closely related crucifers. Also the distribution pattern of parasitized eggs according to leaf side and plant height was characterized. A repeated measure ANOVA in time where plant ages defined the repeated measures showed that all three main effects (plant, host, parasitoid) had significant effect on parasitism and only the parasitoid x plant structure interaction was significant. Mean percent of parasitism was higher on cabbage, intermediate on broccoli and lower on Brussels sprouts whereas cabbage appeared to be intermediate in plant structure, broccoli appeared to be the most simple and Brussels sprouts the most complex plant structure. On simple plant structure, both wasp species performed well on the three varieties of plant but T. evanescens outperformed T. pretiosum more often on the various plant structures. A doubly repeated measures ANOVA in space revealed significant effects of leaf side and plant height on parasitism, being greatest under leaf surface and at the base of the plant. The interaction between those two variables was not significant. / The effect of plant structure on searching behavior of T. evanescens was determined by direct observation of individual females searching on simple and complex plant structures during 1 hour. Time, frequence and sequence associated to activities and plant parts explored were obtained and analyzed. Plant structure had significant effect on time budget associated to activities (walking, resting, flying) and plant parts explored. / This study demonstrates that plant structure mediates ecological interactions by affecting host finding success and this may have important implications in population dynamics, evolution of hosts and parasitoids but also in biological control programs.

Investigation of the host-parasite relationship between oilseed rape, Heterodera cruciferae and H. schachtii has shown that the rate of hatching, development and reproduction is strongly influenced by temperature, two possible generations occurring on an autumn-sown crop. H.schachtii preferred warmer temperatures, hatched and reproduced more than H. cruciferae. Comparisons between newly-formed eggs in cysts and egg sacs showed that their different hatching responses were related to their physiology; cyst-bound eggs hatched poorly whereas juveniles hatched readily from egg sacs and facilitated the early establishment of a second generation. Multiplication of both species varied greatly between cultivars and differences in hatching and multiplication were attributed to the effects of plant growth and intrinsic differences between cultivars. Plant age influenced the hatching activity of root diffusates and nematode development. Multiplication rates of single and mixed species populations declined with increaSing initial population density indicating that intraspecific competition and root damage limited population growth. Nematodes multiplied synergistically in concomitant infestations suggesting that interspecific competition was less important. In a damage assessment test, root and shoot growth of nematodeinfested plants was reduced and the increased accumulation of calcium in their shoots indicated that they used water less efficiently than uninfested plants. These effects were density-dependent and H.schachtii was more damaging than H.cruciferae. Tolerance to nematode attack was attributed to good root establishment. The rate of decline of H.cruciferae populations varied with time, soil depth and between populations; low soil moisture and temperature favouring nematode survival. The role of weeds as ~maintainer hosts' of H.cruciferae was assessed but considered negligible. Nematode population dynamics were simulated using a computer model. Population densities fluctuated considerably under typical crop rotations but large populations had generally declined to less damaging levels before a host was cropped again. It was indicated that a long run of non-hosts or nematicide use would achieve better control of H.schachtii than H.cruciferae.

Studies were undertaken to identify the basis of differences in seed coat pigmentation between selected yellow- and brown-seeded Brassicaceae, and near-isogenic yellow- and brown-seeded lines of </i>Brassica carinata</i> (PGRC/E 21164). Histochemical analyses of dissected seed coats from six genera of the Brassicaceae revealed condensed tannin (proanthocyanidin) and phlobaphene pigments in dark-seeded species and in scattered spots in most yellow-seeded species. Anthoeyanins were not detected in any seed coat tissue of these species. In leaf tissue, anthocyanin content was lower in yellow-seeded 'B. carinata' at the three- to four-leaf stage grown at 20 to 25°C, compared to similarly grown brown-seeded plants. At 15 to 18°C, both yellow- and brown-seeded lines produced similar amounts of anthocyanin in the seedling leaves. In TLC and HPLC analyses, 't'-cinnamic acid, dihydromyricetin [trace amounts], dihydroquercetin, dihydrokaempferol and flavonols (quercetin, kaempferol) were more abundant in extracts from seed coats of yellow-seeded ' B. carinata' than in extracts from seed coats of brown-seeded ' B. carinata'. Myricetin was not detected in any seed coat extracts. Mass spectra were determined for phenylpropanoid and flavonoid aglycones from the seed coat extracts and for authentic standards. Dihydroflavanol reductase ('DFR') transcripts from developing seed were absent or less abundant at 5, 10, 20 and 30 days after pollination in the yellow-seeded line compared to the brown-seeded line of 'B. carinata'. 'DFR' transcripts in seedling leaves from the yellow-seeded line grown in warm, bright conditions were less abundant compared to similarly grown brown-seeded material. Seedlings grown at 15 to 18°C produced greater amounts of 'DFR' transcript in both yellow- and brown-seeded lines of 'B. carinata' compared to warm-grown plants. Data from these experiments suggest that seed coat pigmentation in the Brassicaceae is due to condensed tannin and phlobaphene accumulation, not anthocyanins, and that seed coat pigment biosynthesis is down-regulated at dihydroflavonol reductase. The regulatory factor controlling 'DFR' expression in developing seed may be temperature sensitive and also affect anthocyanin biosynthesis in seedlings and in related metabolic pathways: thioglycolic lignin concentration was significantly lower in the yellow-seeded Brassicaccae and in the seed coat tissue of yellow-seeded 'B. carinata' compared to dark-seeded samples.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Restricted until October 2003. Includes bibliographical references.

The possibility of manipulating calcium (Ca2+) and potassium (K+) levels in seeds of Brassica rapa by altering parent plant nutrition and investigating the potential for increased salinity tolerance during germination, given that considerable amounts of literature imply that greater amounts of available exogenous Ca2+ and K+ can ameliorate the effects of salinity on both whole plant growth and germination, was evaluated. The investigation consisted of four growth trials. Two preliminary growth trials suggested that seed ion manipulation was possible without affecting the overall growth and vigour of the plant. After developing suitable high and low Ca2+ and K+ nutrient solutions for growth, a trial was carried out in a growth room and greenhouse, with various substrates and the seed of a certain size category was collected for subsequent ion and salinity tolerance analysis. Seed Ca2+ and K+ was significantly affected by growth substrate and nutrient solution and data showed that a significant negative regression relationship existed between seed Ca2+, K+ and Ca2+ + K+ levels and salinity tolerance. Further experimentation using hydroponic culture attempted to remove any possible effects of substrate and also to compare size categories of seed with a view to elucidating localisation of Ca2+ and K+. Seed Ca2+ was found to be significantly altered by nutrient solution in the two different sizes tested and higher Ca2+ nutrient solution was found to increase salinity tolerance in daughter seed. One significant negative regression correlation between salinity tolerance and seed K+ concentration existed in smaller seed, but disregarding seed size in a regression analysis of seed ion content and salinity tolerance, a significant negative relationship existed between seed Ca2+, K+ and Ca2++ K+. The results, especially in terms of Ca2+ nutrition, contradict much previous research that suggests increased salinity tolerance at germination can arise with the increased presence of Ca2+ and/or K+. Salinity tolerance was greater in seeds of larger size across all nutritional treatments and the smaller size range exhibited increased Ca2+ and K+ per μg seed. Ca2+ concentration in smaller seeds with greater surface area:volume ratios provided a clue to the potential localisation of Ca2+. Cross sectional staining showed that a greater proportion of seed Ca2+ may reside in the coat. This was confirmed by analysis which showed an approximate 50% split of total extractable seed Ca2+, regardless of size, between coat and embryo within a seed; the majority of which, per μg, resides in the coat. Further work looked at the relative solubility of the Ca2+ and K+ in these tissues and whole seed to look at the potential bioavailability of Ca2+ during germination from various parts of the seed. Most water soluble Ca2+ exists in the embryo and most insoluble Ca2+ exists in the coat, but coat Ca2+ was found to be ionically exchangeable and therefore bioavailable. K+ appeared mostly water soluble in embryo and coat. In line with previous whole plant research in this species, most Ca2+ is readily water soluble or ionically exchangeable in form and the possible negative effects of how increasing bioavailable Ca2+ may reduce salinity tolerance was discussed.

Orientador: Rogério Lopes Vieites / Banca: Angela Vacaro de Souza / Banca: Pricila Veiga dos Santos / Banca: Regina Marta Evangelista / Banca: Renata Saad Diniz de Castro / Resumo: A couve-folha ocupa 5,6 % da área de produção de hortaliças no Brasil, sendo a cultivar 'Manteiga' a que possui maior aceitabilidade de mercado. Em função da mudança do estilo de vida da população brasileira está mais frequente a procura por uma alimentação mais saudável, onde as frutas e hortaliças estão se sobressaindo nas vendas. Como alternativa o consumidor tem optado por produtos minimamente processados, que estão ganhando mercado devido a sua praticidade. A higienização é uma etapa de extrema importância no processamento mínimo, onde geralmente é utilizada solução clorada, mas a grande preocupação está sendo com os resíduos deixados pelo cloro. Devido a esses resíduos, outros agentes higienizantes estão sendo propostos em substituição ao cloro, como é o caso do ácido acético, ácido peracético, compostos quaternários de amônio e as biguanidas. Deste modo, o objetivo deste trabalho foi avaliar diferentes concentrações de higienizantes à base de biguanidas (comercialmente, o Frexus DC®) e oxicloreto de cálcio (comercialmente o Frexus CH®). O trabalho foi conduzido em duas etapas, no primeiro experimento a couve foi higienizada de acordo com os seguintes tratamentos: T1 (água); T2 (0,1 mL L-1 Higienizante 1), T3 (0,2 mL L-1 Higienizante 1), T4 (0,3 mL L-1 Higienizante 1), T5 (0,4 mL L-1 Higienizante 1), por 15 minutos, seguidas por enxágue em água corrente, e cortadas mecanicamente. Após o corte passaram por uma segunda higienização com o Higienizante 1 e enxágue, centrifu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Cauliflower occupies 5.6% of the vegetable production area in Brazil, being the cultivar "Butter" the one with the highest market acceptability. Due to the changing lifestyle of the Brazilian population, the search for a healthier diet is more frequent, where fruits and vegetables are excelling in sales. Alternatively the consumer has opted for minimally processed products, which are gaining market due to their practicality. Hygienization is an extremely important step in minimal processing, where chlorinated solution is generally used, but the major concern is with the residues left by chlorine. Due to these residues, other sanitizing agents are being proposed in place of chlorine, such as acetic acid, peracetic acid, quaternary ammonium compounds and biguanides. Thus, the objective of this work was to evaluate different concentrations of biguanide-based sanitizers (commercially Frexus DC®) and calcium oxychloride (commercially Frexus CH®). The work was conducted in two stages, in the first experiment the cabbage was sanitized according to the following treatments: T1 (water); T2 (0.1 mL L-1 Sanitizer 1), T3 (0.2 mL L-1 Sanitizer 1), T4 (0.3 mL L-1 Sanitizer 1), T5 (0.4 mL L-1 Sanitizer 1) for 15 minutes, followed by rinsing under running water, and mechanically cut. After cutting, they underwent a second sanitization with Sanitizer 1 and rinse, centrifugation for 5 minutes and packaging in expanded polystyrene trays with polyvinyl chloride (PVC) film (± 180 g each tray) and refrigerated in cold room (5 ± 1 ° C and 85 ± 5 % relative humidity). In the second experiment the cabbage was sanitized according to the following treatments: T1 (water); T2 (15 g L-1 Sanitizer 2), T3 (30 g L-1 Sanitizer 2), T4 (60 g L-1 Sanitizer 2), T5 (90 g L-1 Sanitizer 2) for 15 minutes, followed by rinse under running water, and cut into semi-industrial processor. After cutting, they underwent a second cleaning and ... / Doutor

This research investigated the phenology of the striped flea beetle (Phyllotreta striolata (Fabricius) (SFB) and crucifer flea beetle (Phyllotreta cruciferae (Goeze)) (CFB), and examined the efficacy and the persistence of biological activity of the reduced-risk insecticides cyantraniliprole, clothianidin, and thiamethoxam applied as seed treatments to spring canola. Yellow sticky cards were placed around field perimeters in order to assess if CFB and SFB have synchronous phenology. It was found that CFB and SFB have largely asynchronous populations in southern Ontario. In laboratory bioassays, while flea beetle control with cyantraniliprole was comparable to that provided by thiamethoxam or clothianidin at the cotyledon stage, control did not persist through the 1st and 2nd leaf stages. Thiamethoxam and clothianidin both provided moderate control of flea beetles in both 1st and 2nd leaves. Field studies suggested that cyantraniliprole may offer control of flea beetles comparable to that provided by thiamethoxam and clothianidin. / E.I. DuPont Canada Co.