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Agradecemos a compreensão. on 2016-10-18T17:50:01Z (GMT) / Submitted by MARIANA SILVEIRA BATISTA null (mariana.silveira.batista@hotmail.com) on 2016-10-24T03:16:28Z No. of bitstreams: 1 dissertação Mariana-corrigida20-07.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-10-24T18:26:21Z (GMT) No. of bitstreams: 1 batista_ms_me_ilha.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) / Made available in DSpace on 2016-10-24T18:26:21Z (GMT). No. of bitstreams: 1 batista_ms_me_ilha.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) Previous issue date: 2016-03-30 / A planta daninha está entre as espécies de maior importância nos campos de diversas culturas. Por se tratar de uma espécie que apresenta alto poder de produzir milhares de sementes que tem se adaptado ao uso de herbicidas, seu estudo se torna de grande importância para amenizar os danos causados às culturas. O trabalho foi desenvolvido com o objetivo de estudar as características morfofisiológicas da espécie Conyza canadensis (L.) Cronquist quanto à resistência ao herbicida do grupo químico das glicinas substituídas em plantas com histórico de resistência. O experimento foi instalado e conduzido durante o segundo semestre de 2014 em condição de campo na área da Universidade Federal do Mato Grosso do Sul – Campus Chapadão do Sul. O delineamento experimental foi blocos casualizados, com 4 repetições, os tratamentos em esquema fatorial 5x5, totalizando 25 tratamentos. O fator A correspondeu ao estádio de desenvolvimento: Tamanho I – plantas com 5 cm de altura; Tamanho II - 10 cm de altura; Tamanho III – 15 cm de altura; Tamanho IV – 20 cm de altura; Tamanho V – 25 cm de altura. O fator B foram as doses do glyphosate: Dose I (sem aplicação) - Testemunha; Dose II (1200 g i.a ha-1); Dose III (2400 g i.a ha-1); Dose IV (3600 g i.a ha-1) e Dose V (4800 g i.a ha-1). Foram realizadas análises de crescimento das plantas: altura de plantas e diâmetro do caule, aos 0, 14 e 28 dias após a aplicação dos tratamentos e uma avaliação de altura de plantas remanescentes ou rebrota realizada aos 100 dias após a aplicação. Para a análise de perdas de transpiração de folhas destacadas e hidratadas as plantas estavam em fase vegetativa e coletadas no terço-médio das plantas aos 0, 4 e 8 DAA. Os dados foram submetidos à análise de variância e as medias dos tratamentos comparadas pelo Teste de Scott Knott a 5% de probabilidade. Concluiu-se que tanto o tamanho das plantas como as doses do glyphosate influenciaram na altura de plantas, no diâmetro da haste e nas perdas de transpiração da espécie Conyza canadensis (L.) Cronquist. A porcentagem de redução da altura das plantas de tamanho menor foi maior conforme as doses de glyphosate aumentaram em todos os períodos das avaliações. Plantas de tamanho menor transpiram mais do que plantas de tamanho maior sem a aplicação de herbicida. Para as perdas de transpiração, as plantas de menor tamanho que receberam a aplicação do glyphosate em doses maiores, transpiraram menos. As plantas de tamanhos maiores transpiraram mais quando submetidas a doses medianas do glyphosate quando comparadas as doses maiores. / The weed is among the species of greatest importance in the fields of different cultures. Because it is a species that has a high power to produce thousands of seeds that have adapted to the use of herbicides, their study becomes very important to mitigate the damage to crops. The work was to study the morphological and physiological characteristics of species Conyza canadensis (L.) Cronquist for resistance to the herbicide chemical group of glycines substituted in plants with a history of resistance. The experiment was installed and conducted during the second half of 2014 under field conditions at the Universidade Federal do Mato Grosso do Sul-Campus Chapadão do Sul. The experimental design was blocks randomized with four repetitions, the treatments in a factorial 5x5, totaling 25 treatments. The factor A corresponded to the stage of development: Size I - plants with 5 cm; Size II - 10 cm; Size III - 15 cm; Size IV - 20 cm; Size V - 25 cm. The factor B were the glyphosate doses: Dose I (without application) - witness; Dose II (1200 g a.i. ha-1); Dose III (2400 g a.i. ha-1); Dose IV (3600 g a.i. ha-1) and Dose V (4800 g a.i ha-1). Plant growth analysis were performed: plant height and stem diameter at 0, 14 and 28 days after application of treatments and an assessment height of remaining plants or regrowth held at 100 days after application. For the analysis of transpiration losses highlighted and hydrated leaves the plants were in vegetative stage and collected the third-medium plants at 0, 4:08 DAA. The data were submitted to analysis of variance and the averages of the treatments compared by Scott Knott test at 5% probability. It was concluded that both the size of the plants as glyphosate doses influence on plant height, stem diameter and the losses in perspiration of species Conyza canadensis (L.) Cronquist. The percentage reduction of the height of the smaller plants was higher as the glyphosate rates increased in all periods of evaluations. smaller plants transpire more than plants of large size without the application of herbicide. For transpiration losses, smaller plants that received the application of glyphosate in larger doses, transpired less. The larger size plants transpired more when subjected to glyphosate median doses when compared to higher doses.

Orientador: Fernando Tadeu de Carvalho / Resumo: A planta daninha está entre as espécies de maior importância nos campos de diversas culturas. Por se tratar de uma espécie que apresenta alto poder de produzir milhares de sementes que tem se adaptado ao uso de herbicidas, seu estudo se torna de grande importância para amenizar os danos causados às culturas. O trabalho foi desenvolvido com o objetivo de estudar as características morfofisiológicas da espécie Conyza canadensis (L.) Cronquist quanto à resistência ao herbicida do grupo químico das glicinas substituídas em plantas com histórico de resistência. O experimento foi instalado e conduzido durante o segundo semestre de 2014 em condição de campo na área da Universidade Federal do Mato Grosso do Sul – Campus Chapadão do Sul. O delineamento experimental foi blocos casualizados, com 4 repetições, os tratamentos em esquema fatorial 5x5, totalizando 25 tratamentos. O fator A correspondeu ao estádio de desenvolvimento: Tamanho I – plantas com 5 cm de altura; Tamanho II - 10 cm de altura; Tamanho III – 15 cm de altura; Tamanho IV – 20 cm de altura; Tamanho V – 25 cm de altura. O fator B foram as doses do glyphosate: Dose I (sem aplicação) - Testemunha; Dose II (1200 g i.a ha-1); Dose III (2400 g i.a ha-1); Dose IV (3600 g i.a ha-1) e Dose V (4800 g i.a ha-1). Foram realizadas análises de crescimento das plantas: altura de plantas e diâmetro do caule, aos 0, 14 e 28 dias após a aplicação dos tratamentos e uma avaliação de altura de plantas remanescentes ou rebrota realizada aos ... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Interest and research on herbicide-resistant cropping systems has increased dramatically since the introduction of glyphosate-resistant crops in 1996. New advances in herbicide-resistant cropping systems, such as dicambaresistant soybean and cotton, provide opportunities to help alleviate selection pressure currently applied by glyphosate-only systems. While there is no doubt dicamba-resistant genetics will have a huge impact on production practice, there are questions that must be answered about possible interactions with dicamba and glyphosate tank mixtures. The primary objectives of this research were to evaluate the effect of glyphosate/dicamba combinations on common Mississippi weed species, as well as determine effects of these combinations on absorption and translocation of dicamba. Four monocots: johnsongrass, barnyardgrass, large crabgrass, and broadleaf signalgrass; and four dicots: sicklepod, hemp sesbania, prickly sida, and pitted morningglory, were chosen to represent troublesome weed species. Plants were sprayed at the 4±1 leaf stage with glyphosate, dicamba, and combinations of the two herbicides. Rates were chosen with the goal of achieving 40 to 70% control in order to determine synergistic/antagonistic responses. Antagonism was observed in each species tested. Increasing rates of both herbicides alleviated the antagonism in most weeds. A synergistic response was observed in all graminaceous species and pitted morningglory when herbicide rates increased. Barnyardgrass and sicklepod were selected to quantify absorption and translocation of 14C-dicamba in order to account for interactions observed from tank-mix combinations. Rates for dicamba and glyphosate were selected based on results from the interaction study. Dicamba, glyphosate, and tank-mix combinations were applied to sicklepod and barnyardgrass before treatment with 14C-dicamba. Plants were harvested 4, 12, 24, and 72 h after treatment. The addition of glyphosate to dicamba resulted in reduced translocation of 14C-dicamba in both species. While the data did indicate a translocation interaction, glyphosate and dicamba combinations effectively overcame antagonism effects when higher rates were applied on sicklepod and barnyardgrass.

In field efficacy trials most glyphosate/surfactant combinations tested control barnyardgrass as well as preormulated glyphosate products 21 days after treatment (DAT). Preormulated glyphosate products controlled barnyardgrass quicker than combination treatments, most likely due to improved glyphosate formulations with improved surfactant systems. In greenhouse trials, preormulated glyphosate products exhibited greater fresh weight reductions across all species tested, including barnyardgrass, broadleaf signalgrass, hemp sesbania, johnsongrass, large crabgrass, pitted morningglory, prickly sida, sicklepod, yellow foxtail and Palmer amaranth. Nonionic tallow amine treatments exhibited variable control among species. A shikimate analysis was developed using non-glyphosate-tolerant soybean to estimate efficacy of surfactants; data were then correlated to the visual efficacy data on barnyardgrass in the field. However, there was not sufficient variability in barnyardgrass control to use the shikimate analysis as a predictor.

Master of Science / Department of Agronomy / Kassim Al-Khatib / Kochia (Kochia scoparia (L.) Schrad) is a troublesome weed throughout the western United States and Great Plains. It is an aggressive warm season annual dicot plant that exhibits protogynous flowering and facultative open pollination. The aggressive growth habit and prolific seed production enable kochia to spread and compete well for light, moisture, and nutrients. Kochia is ranked as one of the most problematic weeds in cultivated fields including corn, sorghum, wheat, soybean, and sugarbeet. Kochia has been found to lower yields as well as hinder mechanical harvest. Glyphosate is a nonselective herbicide that is widely used in controlling kochia in no-till cropping systems. With rapid adoption of no-till systems where glyphosate is used for weed burndown treatment before planting and extensive use of glyphosate resistant crops, it is common that glyphosate is frequently applied on the same field during the growing season. In 2007, poor control of kochia was observed in three fields in Western Kansas. Greenhouse experiments were conducted with 10 kochia populations to determine the efficacy of glyphosate on kochia when applied at 10 different rates and at 3 plant heights. Herbicide rates included 0, 0.0625, 0.125, 0.25, 0.50, 1, 1.5, 2, 4 and 6 times a typical use rate of 870 g ae/ha. Resistance to glyphosate was identified in three kochia populations. The glyphosate resistant populations from Ingalls, Norton, and Moscow Kansas were 4.6, 3.3, and 2.8 times more resistant to glyphosate than a susceptible population, respectively, based on the rate required for 50% control. Glyphosate injury symptoms included stunting, and chlorosis, followed by some necrotic tissue but resistant plants generally recovered from injury, or were slow to show symptoms. In general, the level of resistance is greater in more developed plants compared to younger plants. Experiments also were conducted on the different kochia biotypes to evaluate glyphosate absorption and translocation, and any differences in mineral content of the plants that might be detrimental to glyphosate activity. Differences in glyphosate absorption and translocation and kochia mineral content were not sufficient to explain the resistance to glyphosate.

Master of Science / Department of Agronomy / Nathan O. Nelson / Glyphosate-resistant (GR) soybean cultivars are widely accepted in the United States. Glyphosate-resistance provides many benefits to production agriculture, yet GR soybeans may require some additional management practices. The objectives of this research are to (a) determine response of GR and conventional (CV) soybean near isoline to manganese fertilization, (b) determine nutrient concentration and uptake in GR and CV soybean, (c) determine differences in yield of GR and CV soybean varieties, (d) quantifying Mn uptake when glyphosate is and is not applied to glyphosate-resistant soybean, and (e) determine glyphosate effect on soybean response to Mn treatments. A field study was conducted at 5 locations in Kansas from 2006 through 2007. Manganese soil test levels ranged from 4 to 52 mg Mn/kg. Soybean (near isoline) varieties were planted at each location in a split-block design with 4 replications. Manganese treatments consisted of soil-applied MnSO[subscript]4 at 0, 2.8, 5.6, and 8.4 kg Mn/ha and foliar applied Mn at 0.22 and 0.45 kg Mn/ha. Leaf tissue and whole plant samples were taken at approximately R1, R3, and R6 growth stages and analyzed for N, P, K, Mn, and other nutrient concentrations. Few significant differences were found between varieties for concentration of any nutrient. Overall nutrient uptake under optimal growth conditions was greater in GR soybean than CV soybean varieties. There were no yield differences between GR and CV soybean varieties at low yielding locations (< 3.3 Mg/ha). In high yielding environments, CV soybean yield was greater than GR soybean yield for the 0 kg Mn/ha rate. However, granular Mn additions increased yield of GR soybean but did not affect CV soybean yield while foliar Mn treatments at high yielding locations increased yields in GR and CV soybean. In addition, a greenhouse study was conducted with a completely randomized block design having 5 blocks. Manganese treatments in the greenhouse study consisted of soil-applied MnSO[subscript]4 at 0, 8.5, 17, and 25.5 mg Mn/pot and foliar applications of 0.66 and 1.33 mg Mn/pot. Treatments were with and without glyphosate applications. Glyphosate applications did not alter Mn concentrations or total Mn uptake in the soybean biomass.

Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Glyphosate remains an important herbicide in weed control. This is due to several positive attributes it has including sytemicity, wide spectrum of weed control and environmental friendliness. Its efficacy and lack of residual activity are therefore important to ensure adequate weed control without imposing hazards to the environment. Despite these favourable attributes for weed control glyphosate has its shortcomings. Evolution of resistance to glyphosate has been a major concern from 1996. However, there are other factors that reduce the maximum potential of glyphosate. Any factors that reduce glyphosate efficacy may result in the target plant being subjected to non-lethal concentrations of glyphosate. This in turn may predispose the plants to developing herbicide resistance. Some factors that may influence efficacy of glyphosate, and therefore be possibly selecting for resistance were investigated in this study. Although glyphosate is a postemergence herbicide, its efficacy is not exempt from the effect of soil and nutrients in which the weeds occur. The possibility of this occurring was investigated in a greenhouse study on ryegrass (Lolium spp.) In this study ryegrass was grown in three soils: pure sand (SS), soil from pasture paddock (PS) and soil from crop field (CS). The soils varied in nutrient composition and, although all were classified as sand, they had varying proportions of sand, loam and clay. This investigation consisted of four experiments. The first experiment was investigating the effect of growing a susceptible commercial ryegrass cultivar on PS, CS and SS soils on the efficacy of glyphosate (360 g a.i. L-1 formulation) applied at five glyphosate application rates (GAR). The GARs were 0 (0x), 67.5 (1/8x), 135 (1/4x), 270 (1/2x) and 540 (1x) g a.i. ha-1. The second experiment investigated the effect of growing a susceptible commercial ryegrass cultivar and a glyphosate resistant ryegrass biotype on PS and CS soils on the efficacy of glyphosate. The application rates were 0 (0x), 270 (1/2x), 540 (1x), 1080 (2x) and 2160 (4x) g a.i. ha-1. The third and the fourth experiments were similar to the first experiment except: The latter investigated the role of nutrient content of irrigation water (pure water or balanced nutrient solution) and; the former investigated the effect of soil activity (by covering the soil surface with cotton at the time of spraying) of glyphosate with regard to the role it plays on efficacy of glyphosate. Our findings showed that: i) soil affects the efficacy of glyphosate with more control (19% survivors) found in the PS soil compared to 50% and 62% survivors in CS and SS soils respectively, this effect may be dependent upon the species resistance as; ii) the effect in the resistant ryegrass biotype was reversed with about 95% of survivors in the PS soil compared to about 78% in CS soil; iii) efficacy of glyphosate is influenced by the soil nutrient status and the nutrient content of the irrigation water. This was shown by decrease in the control of ryegrass (100% survivors) grown in SS soil when fed with pure water compared to 45% when nutrient fed. In PS soil there was no significant effect. This was probably due to inherently higher nutrient content of the PS soil; and iv) glyphosate efficacy is influenced by the amount of glyphosate reaching the soil (absorbed through the roots). This was shown in PS soil where 1/8x GAR resulted in 93.3% survivors in covered soil compared to 60% in uncovered soil. A similar trend was also observed at 1/4x GAR. An opposite effect was shown in SS soil with 0% and 40% survival at 1/4x GAR in the covered and uncovered soil respectively. Glyphosate has been hailed as an environmentally friendly herbicide as it rapidly degrades in soil and it sorbs on metals embedded in soil matrix. However, reports in the literature have showed reduction in crop yield due to soil glyphosate residues. In these studies, glyphosate phytotoxicity was found to be dependent on certain soil characteristics and nutrient content. Following this, a greenhouse study was conducted to assess the phytotoxic activity of glyphosate on a susceptible commercial ryegrass cultivar grown in PS, CS and SS soils. Glyphosate was applied at 0 (G1), 540 (G2) and 3240 (G3) g a.i. ha-1. Ryegrass seedlings of comparable size were transplanted into the soil at intervals of two hours, three weeks and four weeks after glyphosate application referred to as TAS1, TAS2 and TAS3 respectively. Evidence of soil glyphosate activity was shown by the decrease in percentage survival with the application of glyphosate. This was significant in the SS soil where about 60% and 48% survival in G1 and G2 GAR respectively was observed compared to about 100% in the untreated control when transplanted three weeks after glyphosate application. The decrease in percentage survival was time mediated with significant effect of G2 GAR shown at TAS 1 whereas at G3 GAR the effect was significant at TAS1 and TAS 2. At TAS 3 there was no effect at all GARs. Similar trends were observed with dry mass and shoot length. Trace metals required for normal plant growth have been implicated in the reduction of glyphosate efficacy. This follows glyphosate’s original development as a metal chelator. Glyphosate-trace metal antagonism has recently sparked interest following co-application in glyphosate resistant soybeans. Molybdenum (Mo), an anion, may play a role at the physiological level on the antagonism of glyphosate. A greenhouse assay was carried out where seedlings grown from seeds (of susceptible commercial ryegrass cultivar (S biotype) and glyphosate resistant biotype (R biotype)) were grown with nutrient solutions containing 0x, 1x and 2x molybdenum (Mo) concentrations where 1x is 0.05 mg L-1 Mo. Glyphosate was applied at 0 (0x), 135 (1/4x), 270 (1/2x), 540 (1x) and 1040 (2x) g a.i. ha-1 rates. In the R biotype applying 2x Mo resulted in 0% survival in the R biotype at 1x GAR compared to 50% and 90% survival at the same GAR with 0x and 1x Mo. In terms of dry mass and shoot length the results did not show any conclusive trends. / AFRIKAANSE OPSOMMING: Glifosaat is ‘n baie belangrike onkruiddoder wat in verskeie onkruidbeheerstelsels gebruik word. Dit is as gevolg van verskeie positiewe eienskappe waaroor dit besit onder andere sistemiese werking, wye spektrum van onkruidbeheer en omgewingsvriendelike werking. Die onkruiddoder se effektiwiteit en gebrek aan residuele aktiwiteit is dus belangrik om bevredigende onkruidbeheer te bewerkstellig sonder om skade aan die omgewing te veroorsaak. Ten spyte van hierdie voordelige eienskappe het glifosaat ook tekortkominge. Vanaf 1996 is ontwikkeling van weerstand teen glifosaat in onkruide ‘n groot bron van kommer. Daar is egter ook ander faktore wat die maksimum potensiaal van glifosaat strem. Enige faktore wat die effektiwiteit van glifosaat strem mag veroorsaak dat die teikenplant aan subletale dosisse van glifosaat blootgestel word. Dit mag weer daartoe lei dat sulke plante blootgestel word aan die ontwikkeling van weerstand. Sommige faktore wat die effektiwiteit van glifosaat mag strem en dus moontlik kan lei tot seleksie vir weerstand is in hierdie studie ondersoek. Alhoewel glifosaat ‘n na-opkoms middel is kan die effektiwiteit moontlik beïnvloed word deur grondfaktore en nutriënte. Hierdie moontlikheid is ondersoek in ‘n glashuisstudie waarin raaigras (Lolium spp.) gebruik is. In hierdie studie is raaigras geplant in drie verskillende grondsoorte nl. suiwer sand (SS), grond vanaf ‘n weidingskamp (PS) en grond vanaf ‘n gewasland (CS). Die gronde het gevarieer in terme van nutriëntinhoud en alhoewel al drie gronde as sand geklassifiseer is, was daar tog verskille in fisiese eienskappe. Hierdie afdeling het uit vier eksperimente bestaan. In die eerste eksperiment is die invloed van verskillende gronde (PS, CS en SS) waarin die kommersiële raaigras kultivar geplant was op die effektiwiteit van glifosaat (360 g a.b. L-1 formulasie) teen vyf verskillende dosisse (GAR) ondersoek. Die dosisse was 0 (0x), 67.5 (1/8x), 135 (1/4x), 270 (1/2x) and 540 (1x) g a.b. ha-1. Die tweede eksperiment het die invloed van twee grondsoorte (PS en CS) waarin ‘n vatbare kommersiële raaigras kultivar en ‘n glifosaat weerstandbiedende raaigras biotipe geplant is, se invloed op die effektiwiteit van glifosaat ondersoek. Die dosisse was 0 (0x), 270 (1/2x), 540 (1x), 1080 (2x) and 2160 (4x) g a.b. ha-1. Die derde en vierde eksperimente was soortgelyk aan die eerste eksperiment behalwe dat die derde eksperiment die invloed van voeding (suiwer gedistileerde water teenoor ‘n gebalanseerde voedingsoplossing) saam met besproeiing ondersoek het. In die vierde eksperiment is die grondwerking van glifosaat wat as blaarbespuiting toegedien is ondersoek deurdat sommige potte wat gespuit is se oppervlakte met ‘n laag watte bedek is tydens die spuitproses en dadelik na spuit verwyder is teenoor die ander behandeling waar die grondoppervlakte nie bedek is nie. Die resultate het getoon dat i) grondtipe die effektiwiteit van glifosaat beïnvloed met beter beheer (19% oorlewing) in die PS grond vergeleke met 50% en 62% oorlewing in die CS en SS grondtipes respektiewelik. Hierdie effek kan moontlik beïnvloed word deur die weerstandsvlak van spesies omdat ii) die effek in die weerstandbiedende biotipe omgekeer is met ongeveer 95% oorlewing in the PS grondtipe vergeleke met 78% in die CS grondtipe; iii) effektiwiteit van glifosaat is beïnvloed deur die voedingstatus van die grond en die besproeiingswater. Dit word aangedui deur die afname in beheer van raaigras (100% oorlewing) wat in SS grond gegroei het en met suiwer gedistilleerde water besproei is vergeleke met 45% oorlewing in dieselfde grond wanneer met ‘n gebalanseerde voedingsoplossing besproei is. Plante wat in PS grond gegroei het het geen betekenisvolle verskille tussen die besproeiingsbehandelings getoon in hulle reaksie op glifosaattoediening nie, waarskynlik as gevolg van die inherente hoër nutriëntinhoud van die grond en iv) glifosaat effektiwiteit word beïnvloed deur die hoeveelheid glifosaat wat die grond bereik en deur die wortels opgeneem word. Dit is bewys in plante wat in PS grond gegroei het waar 93.3% plante oorleef het waar die grondoppervlakte bedek was teenoor 60% oorlewendes waar die grondoppervlakte nie bedek was nie indien glifosaat teen 1/8x toegedien is. ‘n Soortgelyke tendens is by die 1/4x dosis waargeneem. ‘n Teenoorgestelde effek is in SS grond waargeneem waar die oorlewingspersentasie in bedekte en onbedekte grond by 1/4x glifosaatdosis 0% en 40% onderskeidelik was. Glifosaat is aanvanklik aangeprys as ‘n omgewingsvriendelike onkruiddoder omdat dit vinnig in grond afgebreek word en omdat dit geadsorbeer word aan metale in die grondmatriks. In teenstelling hiermee is daar egter verslae in die literatuur wat dui daarop dat glifosaatresidue in die grond gewasopbrengste kan verlaag. In die gemelde studies is gevind dat fitotoksisiteit van glifosaat residue afhang van grondeienskappe en grondvrugbaarheid. Na aanleiding hiervan is ‘n glashuisstudie uitgevoer waarin die fitotoksisiteit van residuele glifosaat op ‘n kommersiële raaigraskultivar wat in PS, CS en SS gronde groei, ondersoek is. Glifosaat is op die grond in potte toegedien teen 0 (G1), 540 (G2) and 3240 (G3) g a.b. ha-1. Raaigras saailinge is daarna in die potte ingeplant twee ure, drie weke en vier weke nadat die glifosaat toegedien is. Bewys van grondaktiwiteit van glifosaat is gelewer deur die vermindering in persentasie oorlewing van die saailinge met toediening van glifosaat. Die vermindering in oorlewing was betekenisvol in die SS grond waar ongeveer 60% en 48% oorlewing van saailinge was by G2 en G3 dosisse onderskeidelik teenoor 100% oorlewing in die onbehandelde kontrole. Die afname in persentasie oorlewing is deur tyd beïnvloed deurdat die G2 dosis slegs by die twee ure behandeling betekenisvolle verlaging in oorlewing veroorsaak het terwyl die G3 dosis by die twee ure sowel as die drie weke behandeling betekenisvolle verlagings veroorsaak het. Vier weke na toediening was daar geen effek van glifosaat op die saailinge in enige van die gronde gewees nie. Soortgelyke tendense is waargeneem by die droëmassa en lengte data. Spoorelemente wat noodsaaklik is vir normale plantgroeiprosesse is al geïmpliseer in verlaging van glifosaat effektiwiteit. Dit is waarskynlik omdat glifosaat oorspronklik ontwikkel is as ‘n metaal cheleerder. Glifosaat-spoorelement antagonisme was onlangs in die nuus nadat glifosaat saam met sulke elemente toegedien is op glifosaat weerstandbiedende sojabone. Molibdeen (Mo), ’n anioon, mag ’n rol op fisiologiese vlak speel in doie effektiwiteit van glifosaat. ‘n Glashuisstudie is uitgevoer waarin saailinge van ‘n glifosaat vatbare kommersiële raaigras kultivar en ‘n glifosaat weerstandbiedende raaigras biotipe besproei is met voedingsmengsels wat 0x, 1x en 2x Mo bevat waar 1x 0.05 mg L-1 Mo is. Glifosaat is op die plante toegedien teen 0 (0x), 135 (1/4x), 270 (1/2x), 540 (1x) and 1040 (2x) g a.b. ha-1 dosisse. Die 2x Mo toediening het gelei tot 0% oorlewing in die R biotipe by 1x GAR vergeleke met 50% en 90% oorlewing by dieselfde GAR met 0x en 1x Mo. In terme van droëmateriaal en lengtegroei was daar geen konkrete tendense nie.

This work is aimed at elucidating the structures and spectroscopic properties of phosphine and b phosphonite complexes of Mn(III), Co(III) and Rh(III) porphyrins, a class of coordination compounds that has been little reported on in the literature to date. In this work, a range of novel bis(phosphine) and bis(phosphonite) complexes of the three aforementioned metals have been synthesized, crystalized and analysed by means of X-ray structure determination, 1H NMR, 13C NMR, 31P NMR as well as electronic and IR spectroscopy. [Mn(TPP)(PPh3)2](SbF6) crystallizes in the monoclinic space group P21/c and displays an extraordinarily long Mn-P bond length of 3.088(2) A. Moderate ruffling of the porphyrin ligand is observed. This complex is paramagnetic with fast proton relaxation times, and thus did not yield any useful 1H NMR data. In an attempt to crystallize [Mn(TPP){P(OPh)3}2](SbF6), a complex bearing an O-donor contamination product, [Mn(TPP){(O)PH(OPh)2} ](SbF6), was isolated and its solid state structure determined by X-ray diffraction methods. The structure of this complex has been included in this work as it displays interesting structural features and is the very first phosphonate complex of a metalloporphyrin. This compound crystallizes in the monoclinic space group P21/n and shows a significantly saddled conformation. The axial Mn-O bond length measures 2.122(3) A. The Mn-Nporph bond lengths are 1.998(6) and 2.002(3) A for the bis(phosphine) and phosphonate complexes, respectively. Since the diethyl phosphonate complex was an unintended reaction product, no further characterisation of it was undertaken. [Co(TPP)(depp)2](SbF6), where depp = diethylphenylphosphine, crystallizes in the monoclinic space group P21/c. This complex displays inversion symmetry at the metal center and the porphyrin core is effectively planar. However, [Co(TPP)(edpp)2](SbF6), where edpp = ethyldiphenylphosphine, crystallizes in the· monoclinic space group P21/n and shows a significantly ruffled conformation of the porphyrin core and displays no inversion symmetry. [Co(TPP)(deppt)2](SbF6), where deppt = diethylphenylphosphonite, also crystallizes in the monoclinic space group P21/n, but displays inversion symmetry through the central cobalt ion. As a result, this complex does not display any significant conformational deviations of the porphyrin core from planarity. The axial Co-P bond lengths are significantly shorter than that of . the equivalentbond in the manganese bis(triphenylphosphine) complex at 2.312(1) A, 2.323(10) A and 2.258(2) A for [Co(TPP)(depp)2](SbF6), [Co(TPP)(edpp)2](SbF6) and [Co(TPP)(deppt)2](SbF6), respectively. The Co-Nporph bond lengths average to 1.980(3) A, 1.972(7) A and 1.980(4) A for these three complexes, respectively. I03Rh NMR measurements of three rhodium bis(phosphine)/bis(phosphonite) porphyrins have been performed by the indirect probing of the rhodium metal center by means of the phosphorus nucleus of the coordinated axial ligand. The resulting I03Rh NMR shifts for [Rh(TPP)(edpp)2](SbF6), [Rh(TPP)(edppt)2](SbF6), where edppt = ethyldiphenylphosphonite, and [Rh(TPP)(deppt)2](SbF6) are 2558, 2413 and 2365 ppm, respectively. [Rh(TPP)(edpP)2](SbF6) crystallizes in the monoclinic space group P21/n and shows moderate ruffling of the porphyrin core. The axial Rh-P bond length is 2.401(2) A. [Rh(TPP)(edppt)2](SbF6) and [Rh(TPP)(deppt)2](SbF6) both crystallize in the monoclinic space group P21/c. The porphyrin core of [Rh(TPP)(edppt)2](SbF6) displays a moderate degree of ruffling, as observed in [Rh(TPP)(edpp)2](SbF6), yet the axial Rh-P bond length is substantially shorter at 2.361(9) A. [Rh(TPP)(deppt)2](SbF6) exhibits the shortest Rh-P bond length of the three complexes at 2.332(2) A. The porphyrin core is mostly planar. The Rh-Nporph distances average 2.034(1) A for the S4-ruffled complexes and 2.044(3) A for the planar complex, the shorter distance in the ruffled derivatives being consistent with a distortion-induced compression of the Rh(III) ion. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003

Glyphosate based herbicides are among the most widely used herbicides in the world. The purpose of this study was to determine developmental toxicity of glyphosate, the active ingredient in the common herbicide Roundup, on developing chicken embryos. Few studies have examined toxic effects of glyphosate alone versus the full compound formulations of Roundup, which include adjuvants and surfactants. Adjutants and surfactants are added to aid in solubility and absorption of glyphosate. In this study chicken embryos were exposed at the air cell on embryonic day 6 to 19.8 or 9.9 mg / Kg egg mass of glyphosate in Roundup or glyphosate only. Chickens treated with 19.8 and 9.9 mg / Kg glyphosate in Roundup showed significant reduction in survivability compared to glyphosate alone treatments and controls. On embryonic day 18, embryos were sacrificed for evaluation of developmental toxicity using wet embryo mass, dry embryo mass, and yolk mass as indicators. Morphology measurements were taken on liver mass, heart mass, tibiotarsus length and beak length. Embryos treated with 19.8 mg / Kg glyphosate and 9.9 mg / Kg glyphosate in Roundup showed significant reductions in wet and dry embryo mass and yolk mass. Tibiotarsus length in 9.9 mg / Kg glyphosate in Roundup treatments were significantly reduced compared to 9.9 mg / Kg glyphosate treatments. Beak length was significantly reduced in 9.9 mg /Kg glyphosate in Roundup treatments compared to all other groups.

Master of Science / Department of Agronomy / Mithila Jugulam / Extensive, often exclusive, use of glyphosate in crop production has resulted in evolved glyphosate resistance in several weed species globally. Kochia is a competitive summer annual weed, well adapted to the North American Great Plains and has recently evolved resistance to glyphosate by gene amplification of 5-enolpyruvyl shikimate 3-phosphate synthase (EPSPS), the target-site of glyphosate. The overall objective of this research was to investigate the genetic basis of glyphosate resistance in kochia, specifically to study 1) the inheritance of glyphosate resistance and 2) determine the chromosomal distribution of EPSPS gene copies. Homozygous resistant (R) and susceptible (S) parental lines of kochia were identified. Using these parents, reciprocal crosses were performed to produce F₁ progeny. As expected for a nuclear encoded EPSPS gene, F₁ plants from both crosses survived various doses of glyphosate application. However, F1 plants showed intermediate shikimate accumulation and EPSPS gene copies (relative to ALS reference gene) compared to parents. F₂ progeny were produced by selfing F₁ plants. In response to 870 g ae ha⁻¹ glyphosate, F₂ plants (n=115) segregated into 3:1 (R:S) implying a Mendelian monogenic segregation of glyphosate resistance in kochia. Additionally, relative EPSPS gene copies ranged from 1-10 in the F₂ progeny (n=51) with a genotypic segregation of 40:11 (plants with 3 or more EPSPS gene copies: plants with 1 EPSPS gene copy). In F₂ dose-response, a correlation between the level of resistance and relative EPSPS gene copies was observed. Genomic organization of the amplified copies using fluorescent in situ hybridization (FISH) displayed a single and larger hybridization site of the EPSPS gene on one pair of homologous chromosomes in R compared to a faint hybridization site in S samples of kochia. These results suggest possibility of amplification of EPSPS gene mediated via unequal recombination leading to the evolution of the glyphosate resistance in kochia.