Fruit of Capsicum annuum L. (capsicum or pepper) are one of the major sources of red food colourant and pungency for spice production. In the spice production industry, fruit are mechanically harvested at different ripeness stages and fruit colour needs to be synchronised before being processed. However, even though capsicum ripens normally on the plant it often fails to ripen fully and turn red once harvested at the green stage. Attempts to promote ripening of harvested fruits have had limited success and the reason for this has been unclear. This project, therefore, investigated ripening behaviour on and off the plant of capsicum fruit grown in Australia and examined effects of pre- and postharvest applications on ripening of green harvested fruit. To examine ripening behaviour on and off the plant, capsicum fruit from three different cultivars (a mild paprika type cv. “Papri Queen”, a cayenne chilli cv. “Caysan”, and a sweet type bell pepper cv. “Aries”) were either allowed to ripen naturally on the plant or harvested at three different maturity stages: light green, deep green and breaker. Harvested fruit were stored individually at room temperature and several ripening characteristics including internal ethylene (C2H4) and carbon dioxide (CO2) concentration, extractable colour, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and oxidase activity, and total soluble solid content (TSSC) were studied during storage. There was very limited involvement of C2H4 during ripening of capsicum and the change in ACC synthase and ACC oxidase (two enzymes in C2H4 biosynthesis pathway) activity was not closely related to that of C2H4. However, it appeared that colour development in cv. “Papri Queen” was closely associated with what C2H4 production did occur while a climacteric-like peak of C2H4 could be observed in all fruit from cv. “Caysan”. For all three cultivars, the level of internal CO2 concentration, extractable colour and TSSC were greater in fruit ripened on the plant followed by fruit harvested at the breaker, deep green and light green stage, respectively. Fruit harvested at the light green stage failed to change colour properly and had very low levels of internal CO2 concentration and TSSC while fruit harvested from the breaker stage onwards ripened normally and developed sufficient colour for spice processing. This may suggest a role of external carbon-supply during ripening. To study the effect of the external-carbon supply during ripening, the stem of fruit were cinctured when fruit reached the light green stage and fruit were left to ripen on the plant. Cincturing delayed colour development of fruit by approximately five days but cinctured fruit were still able to turn red and develop extractable colour higher than the acceptable level of 140 ASTA units. Cincturing did not significantly alter other ripening behaviour such as CO2 concentration or TSSC. The lack of external carbon-supply is, therefore, unlikely to play a major role in the failure of green harvested fruit to ripen. To study the effect of application of plant growth regulators (both pre- and postharvest), an effective method of solution application utilising cincturing was firstly developed. Different plant growth regulator solutions including ethephon, naphthalene acetic acid, abscisic acid, jasmonic acid, sucrose, and different combinations of these were applied to fruit at the light green stage to study preharvest effects on ripening parameters during storage. Only treatment with high concentrations of ethephon increased the extractable colour higher than the acceptable level of 140 ASTA units and induced the complete degradation of chlorophyll. To study effects of postharvest application, 10 µL of various plant growth regulators was dropped into the hole created on the stem of harvested fruit for ten consecutive days. Treatment with ethephon significantly increased extractable colour and degraded chlorophyll content of fruit. Pre- and postharvest ethephon treatment strongly up-regulated Capsanthin-capsorubin synthase (Ccs) gene expression in a manner similar to the up-regulation of Ccs observed in fruit ripened on the plant. This explains the effect of C2H4 on colour development and also indicates the possible reason for the failure of green harvested fruit to ripen. However, the Ccs gene expression and chlorophyll degradation induced by ethephon was not visible until 14 days after harvest which indicated it may not be a direct effect and other signal transduction factors may be involved. When fruit are ripened on the plant, colour development may, therefore, be induced by ripening-related factors (other than C2H4) which is possibly inhibited or inactivated when fruit are harvested at the green stage. C2H4 application to fruit at this stage may help to reactivate or recover these factors which in turn induce colour development. Thus, although capsicum fruit show typical non-climacteric behaviour, C2H4 appears to be involved in some aspects of the ripening process. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294648 / Thesis(Ph.D.)-- School of Agriculture, Food and Wine, 2007

In South Africa, a shortage of litchi cultivars to expand the very short harvesting period has seriously threatened the viability of the local export orientated Litchi Industry. Only two cultivars have dominated commercial plantings for more than a century, namely ‘HLH Mauritius’ and ‘McLean’s Red’. The marketing period of litchis from South Africa coincides with large export volumes from competitor countries such as Madagascar, resulting in lower returns for local growers. To address this situation, the late season cultivar ‘Wai Chee’ was imported amongst others from Australia. ‘Wai Chee’ is harvested at a time in South Africa when there is a gap in worldwide litchi production, making the cultivar potentially very profitable. However, its potential and subsequent use in the industry is affected by small fruit size and questionable internal quality. As the South African Litchi Industry is export orientated and the qualities of ‘HLH Mauritius’ fruit currently dictate export requirements, solutions need to be found to improve fruit size and fruit quality in ‘Wai Chee’ litchi. In this study, a number of horticultural manipulation techniques were investigated with the aim of enhancing yield, fruit size and quality in ‘Wai Chee’ litchi. The use of chemical applications of foliar nutrients and plant growth regulators were found to improve certain fruit characteristics in ‘Wai Chee’. Foliar nutrient applications of nitrogen, potassium and calcium during the early stages of fruit set and -development improved fruit set and subsequently yield, and also increased fruit mass, fruit size and flesh mass. Treatments with potassium nitrate (KNOз), calcium nitrate (CaNOз) and calcium metalosate proved to be the most enhancing nutrient applications. Applications of synthetic auxins and auxin-like substances during the 2-3g stage of fruit development improved fruit size, fruit mass and flesh mass in ‘Wai Chee’. The combination treatment of Tipimon® (2,4,5-TP), applied at the 2-3g stage, followed by Maxim® (3,5,6-TPA) a week later, yielded the best results in this regard. With biological practices, pollination was found to have an influence on litchi tree- and fruit characteristics. Pollen source proved to have an influence on fruit set and fruit retention at harvest in ‘Wai Chee’. Initial fruit set was lower when using cross-pollination compared to the use of self-pollination in female flowers of ‘Wai Chee’, whereas final fruit retention was higher with the use of cross-pollinators when compared to retention of fruit with self-pollination. Although some beneficial effects with different pollen donors on fruit characteristics were observed, these effects were not significant, and would therefore necessitate further investigation. Pollen donor effect on quality parameters such as Titratable acid (TA)- and Total Soluble Solid (TSS) content of fruit was not significant. Cultivar differences regarding fruit characteristics and maturation rate were detected with the use of cultural practices such as bunch covering materials in ‘HLH Mauritius’ and ‘Wai Chee’. Beneficial effects on fruit size were obtained with thicker covering materials with nominal mass of 70 and 80 g/m² respectively on ‘HLH Mauritius’, while with ‘Wai Chee’, thinner covering materials (60 and 65 g/m²) showed enhancing effects. Maturation rate was significantly delayed only on ‘Wai Chee’ with the use of thicker covering materials (70 and 80 g/m²). Differences in colour were detected amongst different covering materials, but these should be verified with chromameter technology. Covering of fruit bunches for better fruit size and a later harvest date would, especially for ‘Wai Chee’ as a late season cultivar, be beneficial, since better prices are realised towards the end of the season. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Interest in planting Jatropha curcas L. for the production of biodiesel is growing exponentially. The properties of the crop and its oil have persuaded investors to consider J. curcas oil as a substitute for fossil fuels. However, this plant is still undomesticated, basic agronomic properties are not thoroughly understood and the environmental effects on growth have not been investigated. This thesis investigated different approaches that may contribute to improving the productivity of this plant. Seed germination and methods of propagation are usually the first consideration in any plant development programme. The effects of aerosol smoke, smoke water, potassium nitrate, naphthalene acetic acid and indole-3-butyric acid on germination and seedling growth of J. curcas were investigated. Seed coat removal accelerated water imbibition and germination occurred within 48 h. Seeds exposed to aerosol smoke failed to germinate over the whole study period of three months. There were no significant differences in total germination between the treatments and the untreated control (intactand shelled-seed). However, shelled-seeds had a shorter mean germination time. The seedlings were subsequently sown in trays under shade house conditions and different seedling growth traits measured after three months. Smoke water, potassium nitrate and naphthalene acetic acid produced significantly heavier seedlings with longer stems and roots, wider stems and a higher vigour index compared to the control treatments. Smoke water, potassium nitrate and naphthalene acetic acid stimulated seedling growth and vigour of J. curcas. This opens the possibility of applying these treatments to produce quality seedlings for large scale planting and accelerated plant establishment in production orchards. Effective pollination is a prerequisite for many crops to increase seed-set and fruit production. Experiments were conducted to determine factors that could influence seed production in this potential biofuel seed crop. Controlled pollination experiments showed that plants required pollinator visits for seed production and were genetically selfx compatible. Pollen-supplementation did not lead to increased fruit set, suggesting that seed production in the study population was not pollen-limited. Both male and female flowers produced nectar and were highly attractive to honeybees. These insects were effective pollinators of J. curcas, as shown by experiments in which flowers exposed to single or multiple visits by honeybees set significantly more fruit than those from which visits were precluded. Pollinator-mediated self-pollination led to marginally lower levels of seed production relative to cross-pollination. Progeny from selfed plants had significantly shorter roots than progeny of outcrossed plants. However, in general, there was little evidence of inbreeding depression. The present results provide empirical evidence that honeybees are effective pollinators of J. curcas. Fruit arising from selfpollination were almost as numerous and as large as those arising from crosspollination, suggesting that promotion of cross-pollination does not have to be a priority in orchard management for fruit yield. Manipulation of pollen development and function is of vital importance for crop development and improvement. Experiments were conducted to investigate pollen viability, in vitro pollen germination and in vivo pollen tube growth in J. curcas. Light and fluorescence microscopy were employed to examine the different developmental stages. It was possible to determine pollen viability and distinguish between fresh and dead pollen using 2,3,5-triphenyltetrazolium chloride (TTC). Pollen germination was significantly higher in an agar-based medium composed of sucrose, boric acid and calcium nitrate compared with the control treatment (distilled water). Supplementation of IAA to the different media significantly increased pollen germination and pollen length compared with the control treatment. Pollen from hermaphrodite flowers had a lower viability, lower germination rates and shorter pollen tubes, with abnormal shapes, compared to the pollen from male flowers. Pollen tubes from both self- and crosspollinated flowers entered the ovary within 8 hours after pollination (HAP). However, at 6 HAP, the pollen tube length and growth rate were significantly higher in crosscompared to self-pollinated pollen. Our results suggest that TTC is a reliable test for pollen viability; boric acid, calcium nitrate, sucrose and addition of IAA are essential and beneficial for pollen germination in this plant. Pollen germination and pollen tube growth were not inhibited, nor interfered with, as a result of self-pollination treatments. During, both types of pollination, fertility is maintained as evidenced by ovule penetration by pollen tubes. This suggests that type of pollination has no influence on the success of fertilization in J. curcas. Manual pruning is one of the major management practices in commercial plantations of J. curcas, resulting in production of more branches and thus increased potential for more inflorescences leading to a higher seed yield. Experiments were conducted to determine the response of J. curcas plants to manual pruning under summer and winter conditions. The results showed that manual pruning under both conditions significantly increased the number of branches per plant. However, there were no significant differences in number of branches between winter and summer manual pruning. Winter pruning, however, had a significantly wider crown diameter compared to the control and summer pruning. Both treatments produced significantly less fruits/per plant in the subsequent season compared to the un-pruned control. This study revealed that winter and summer manual pruning may be suitable practice to promote branching. Manual pruning, however, is time consuming, labour intensive and expensive. A study was conducted to determine the potential of different plant growth regulators (PGRs) to increase the number of lateral branches of J. curcas plants. A single foliar application of BA (benzyladenine) at 12 mmol l-1 significantly increased branches in both the pot (4) and field (13.2) trials compared to manual pruning (MP) (1.8 and 5.7 respectively) and control (no new branches) plants. In the field, treatment with TIBA (2,3,5-triiodobenzoic acid) (1 mmol l-1) significantly increased the number of branches (15.9) after seven months from application. Of all the PGRs examined, DK (Dikegulac) (2,3:4,6-di-Oisopropylidene- 2-keto-L-gulonic acid) at 2 mmol l-1 produced the maximum number of branches (18) in the field seven months after application. Concentrations of 2 and 3 mmol I-1 of MH (Maleic hydrazide) (1,2-dihydro-3,6-pyridazinedione, coline salt) significantly increased the number of branches, four and seven months after spraying in both the pot trial in the shade house and field respectively. Under field conditions J. curcas plants responded better to all the PGRs (DK < TIBA < BA < MH) when treated once, with insignificant variations of other growth parameters. This study indicates that a single foliar application of PGRs under field conditions can be an alternative method to MP for increasing the number of lateral branches of J. curcas plants. The field chemical pruning experiment was continued to determine the potential subsequent effects of the different PGRs on seed production. In the subsequent year following the single foliar application, the parameters of flowering, fruit set, fruit characteristics, total oil content and free fatty acid (FFA) content were evaluated. Number of flowers per plant and number of fruits per bunch were significantly affected by the different treatments. However, there were no variations in the degree of fruit set. A single foliar application of BA (6-benzylaminopurine) produced more flowers per plant, more fruits per bunch, heavier and bigger fruits and seeds with more oil compared to MP (manual pruning). TIBA (2,3,5-Triiodobenzoic acid) produced significantly more flowers per plant and heavier fruits compared to the control and MP treatments. However, it produced significantly bigger fruits with more seeds and a higher oil content than MP. DK (Dikegulac) (2,3:4,6-di-O-isopropylidene-2-keto-Lgulonic acid) produced more flowers per plant and seeds with high oil content compared to the control and MP. However, it produced more fruit per bunch and more seeds per fruit compared to MP. MH (Maleic hydrazide) produced more flowers per plant, heavier and bigger fruits with numerous, heavier and oil rich seeds compared to the control and MP. This study indicates that foliar application of PGRs can be used in J. curcas to increase seed production and improve fruit quality. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Made available in DSpace on 2014-06-11T19:32:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-29Bitstream added on 2014-06-13T19:43:45Z : No. of bitstreams: 1 meneghin_sp_dr_rcla.pdf: 500401 bytes, checksum: 1dbb48df89774c8c8a05446c822888e1 (MD5) / Universidade Estadual Paulista (UNESP) / Nas usinas, no início da safra, a obtenção de matéria-prima de boa qualidade é maximizada com a aplicação de fitorreguladores, os quais aumentam o teor de sacarose da cana-de-açúcar. Em áreas onde eles são aplicados, tem se observado melhor desenvolvimento e perfilhamento das plantas. Avaliou-se aqui o efeito da aplicação dos fitorreguladores Ethrel e Moddus sobre o crescimento da cana-de-açúcar, de forma direta e indiretamente, através da modificação da microbiota rizosférica. Além disso, objetivou-se também avaliar o uso de rizobactérias, isoladas dos experimentos com fitorreguladores, para o biocontrole de doenças e seus possíveis mecanismos de ação. Os efeitos dos fitorreguladores sobre os microrganismos do solo foram avaliados em meios de cultura acrescidos de Ethrel e Moddus em concentrações de 0 a 1000 ppm. Estes fitorreguladores foram aplicados via foliar e via solo para análise do desenvolvimento da cana-de-açúcar (variedades RB72454, RB835486 e RB855156) em casa-de-vegetação, utilizando-se solo sem tratamento e tratado com brometo de metila. Após dez meses, foram avaliadas a brotação, altura e matéria seca da parte aérea e das raízes das plantas cultivadas. Rizobactérias foram isoladas dos solos contidos nos vasos e avaliadas in vitro quanto à capacidade de controle de fungos fitopatogênicos (Thielaviopsis paradoxa, Fusarium spp. e Hendersonina sacchari), e in vivo, quanto à capacidade de promoção de crescimento de plântulas de cana-de-açúcar. Alguns mecanismos de ação das rizobactérias foram também estudados, como produção de ácido indol acético, ácido cianídrico, sideróforos e solubilização de fosfato inorgânico. Constatou-se que as populações de fungos foram mais sensíveis à adição dos fitorreguladores do que outros grupos de microrganismos, com redução... / For sugar and alcohol industries, at the start of harvesting, to obtain good quality raw material is potentially possible with the application of plant regulators, which have a role in natural sugar cane maturation, increasing sucrose content. In areas where they have been applied, better plant development and shooting have been observed. The aim here was to evaluate the application of plant regulators Ethrel and Moddus on sugar cane growth, not only in a direct way, but also indirectly, through the modification of rhizosphere microorganisms. Besides, this work also aimed the evaluation of rhizobacteria isolated from the experiments using plant regulators upon the disease biocontrol and their action mechanisms in this respect. The effects of plant regulators upon the soil microorganisms were verified in culture media where Ethrel and Moddus were added in concentrations ranging from 0 to 1000 ppm, while the effects of these substances (applied in leaves and in soil) upon the sugar cane development (varieties RB72454, RB835486 and RB855156) were surveyed in greenhouse, using soil without treatment and treated with methyl bromide. After a ten-month period, the experiments were finished, and sprouting, height and aerial part and root dry matter were analyzed. Soil samples were taken from the pots for rhizobacteria isolation, which were evaluated initially in vitro regarding their ability to control plant pathogenic fungi (Thielaviopsis paradoxa, Fusarium spp. and Hendersonina sacchari), and in vivo, regarding their ability to promote sugar cane growth. Some action mechanisms were also studied, as indol acetic acid, cyanide acid and siderophore production and inorganic phosphate solubilization. It was verified that the fungi populations were more sensitive to the addition of plant regulators than other microorganisms, reducing their colony-forming unit (CFU)...(Complete abstract, click electronic access below)

Made available in DSpace on 2014-06-11T19:32:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-03-16Bitstream added on 2014-06-13T19:43:14Z : No. of bitstreams: 1 santos_mhlc_dr_botfca.pdf: 1509424 bytes, checksum: 0e38e7b79ee2e60018b38f884c2d8420 (MD5) / Beehive ginger inflorescences have yellow bracts when they are young, which are ornamental and are specially used in gardening projects and as cut flowers. However, there are crop management and postharvest factors that affect the expansion of the species. So, the objective of this work was to study some physiological postharvest aspect of beehive ginger inflorescences grown in the lower middle São Francisco river basin. Flower stems just harvested were submitted to different treatments (distilled water; 75 mg L-1 of silver nitrate - AgNO3; 1000 mg L-1 of cobalt chloride - CoCl2; 5 mg L-1 de GA3 - Progibb® and 10 mg L-1 of 6-benzylamino purine - BAP), in an environment with controlled temperature and humidity, for 15 days. The longevity was monitored from non-destructive analysis (grading scale, fresh weight, consumption and pH of the preservative solution) as well as destructive ones (peroxidase and polyphenol oxidase activity, total soluble and reducing carbohydrates, phenols, putrescine, spermine and spermidine content). The non-destructive analysis showed that the beehive ginger stems treated with gibberelin and silver nitrate presented a better visual aspect according to the grading scale, the ones treated with AgNO3 absorbed a greater volume of the solution during the experimental period, while the ones treated with silver nitrate and BAP had a greater fresh weight. The smallest variation of the preservative solution pH took place with the treatments containing the plant regulators. The destructive analysis revealed that the inflorescences maintained in preservative solutions with gibberelin and distilled water kept their stocks of total soluble sugars for 3 days longer than the stems submitted to the other treatments. The contents of reducing sugars increased 7 considerably in inflorescences treated with cytokinin. The BAP promoted alterations in the activity of the... (Complete abstract click electronic access below)

Orientador: Samia Maria Tauk-Tornisielo / Banca: Sandra Regina Ceccato Antonini / Banca: Regina Teresa Rosim Monteiro / Banca: Antonio Ismael Bassinelo / Banca: Carlos Renato Corso / Resumo: Nas usinas, no início da safra, a obtenção de matéria-prima de boa qualidade é maximizada com a aplicação de fitorreguladores, os quais aumentam o teor de sacarose da cana-de-açúcar. Em áreas onde eles são aplicados, tem se observado melhor desenvolvimento e perfilhamento das plantas. Avaliou-se aqui o efeito da aplicação dos fitorreguladores Ethrel e Moddus sobre o crescimento da cana-de-açúcar, de forma direta e indiretamente, através da modificação da microbiota rizosférica. Além disso, objetivou-se também avaliar o uso de rizobactérias, isoladas dos experimentos com fitorreguladores, para o biocontrole de doenças e seus possíveis mecanismos de ação. Os efeitos dos fitorreguladores sobre os microrganismos do solo foram avaliados em meios de cultura acrescidos de Ethrel e Moddus em concentrações de 0 a 1000 ppm. Estes fitorreguladores foram aplicados via foliar e via solo para análise do desenvolvimento da cana-de-açúcar (variedades RB72454, RB835486 e RB855156) em casa-de-vegetação, utilizando-se solo sem tratamento e tratado com brometo de metila. Após dez meses, foram avaliadas a brotação, altura e matéria seca da parte aérea e das raízes das plantas cultivadas. Rizobactérias foram isoladas dos solos contidos nos vasos e avaliadas in vitro quanto à capacidade de controle de fungos fitopatogênicos (Thielaviopsis paradoxa, Fusarium spp. e Hendersonina sacchari), e in vivo, quanto à capacidade de promoção de crescimento de plântulas de cana-de-açúcar. Alguns mecanismos de ação das rizobactérias foram também estudados, como produção de ácido indol acético, ácido cianídrico, sideróforos e solubilização de fosfato inorgânico. Constatou-se que as populações de fungos foram mais sensíveis à adição dos fitorreguladores do que outros grupos de microrganismos, com redução...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: For sugar and alcohol industries, at the start of harvesting, to obtain good quality raw material is potentially possible with the application of plant regulators, which have a role in natural sugar cane maturation, increasing sucrose content. In areas where they have been applied, better plant development and shooting have been observed. The aim here was to evaluate the application of plant regulators Ethrel and Moddus on sugar cane growth, not only in a direct way, but also indirectly, through the modification of rhizosphere microorganisms. Besides, this work also aimed the evaluation of rhizobacteria isolated from the experiments using plant regulators upon the disease biocontrol and their action mechanisms in this respect. The effects of plant regulators upon the soil microorganisms were verified in culture media where Ethrel and Moddus were added in concentrations ranging from 0 to 1000 ppm, while the effects of these substances (applied in leaves and in soil) upon the sugar cane development (varieties RB72454, RB835486 and RB855156) were surveyed in greenhouse, using soil without treatment and treated with methyl bromide. After a ten-month period, the experiments were finished, and sprouting, height and aerial part and root dry matter were analyzed. Soil samples were taken from the pots for rhizobacteria isolation, which were evaluated initially in vitro regarding their ability to control plant pathogenic fungi (Thielaviopsis paradoxa, Fusarium spp. and Hendersonina sacchari), and in vivo, regarding their ability to promote sugar cane growth. Some action mechanisms were also studied, as indol acetic acid, cyanide acid and siderophore production and inorganic phosphate solubilization. It was verified that the fungi populations were more sensitive to the addition of plant regulators than other microorganisms, reducing their colony-forming unit (CFU)...(Complete abstract, click electronic access below) / Doutor

O objetivo deste trabalho foi avaliar os efeitos do biorregulador MBTA [cloridrato de N,N-dietil-2-(4-metilbenziloxi) etilamina] aplicado em diferentes épocas e concentrações sobre a produtividade e qualidade dos frutos das laranjeiras &#39;Hamlin&#39;, &#39;Valência&#39; e &#39;Pêra&#39; e em características fisiológicas da laranjeira &#39;Hamlin&#39;. Em duas safras consecutivas, o MBTA foi aplicado em três diferentes concentrações (8; 16 e 32 mg L-1) e em duas diferentes fases fenológicas (25% e 100% de flores abertas) em árvores cítricas adultas, utilizando um volume de 7 litros de solução por planta acompanhada do adjuvante Silwett L-77 0,05%. Foram amostrados 20 frutos por planta em quatro diferentes épocas para cada cultivar estudado para determinar o teor de sólidos solúveis totais; acidez; quantidade de sólidos solúveis totais em caixa industrial de 40,8 kg; pH; rendimento de suco; cor do suco, massa média e diâmetro médio dos frutos. Os efeitos do MBTA variaram de acordo com o cultivar, concentração aplicada e com a fase fenológica de aplicação. Na laranjeira &#39;Hamlin&#39;, o MBTA na concentração de 16 mg L-1 aplicado com 25% de flores abertas incrementou o teor de sólidos solúveis totais, o rendimento de suco e a quantidade de sólidos solúveis totais por caixa de 40,8 kg. Este mesmo tratamento também reduziu a massa média dos frutos e não alterou a acidez, o &#34;ratio&#34;, a cor do suco, o diâmetro médio dos frutos e a produtividade final da laranjeira &#39;Hamlin&#39;. O incremento médio foi de 0,45 a 0,56% na concentração de sólidos solúveis totais e de 0,16 a 0,18 kg na quantidade de sólidos solúveis por caixa padrão de 40,8 kg. Na laranjeira &#39;Pêra&#39;, o MBTA na concentração de 8 mg L-1 aplicado com 25% de flores abertas incrementou o teor de sólidos solúveis totais, a acidez, a quantidade de sólidos solúveis totais por caixa de 40,8 kg e a produtividade. Este mesmo tratamento também reduziu a massa média dos frutos e não alterou o rendimento de suco, o ratio, a cor do suco e o diâmetro médio dos frutos. O incremento médio foi de 0,49 a 0,65% na concentração de sólidos solúveis totais, de 0,11 a 0,13 kg na quantidade de sólidos solúveis totais por caixa padrão de 40,8 kg e de 20,4 kg/planta na produtividade. Na laranjeira &#39;Valência&#39;, o MBTA na concentração de 16 mg L-1 aplicado com 25% ou 100% de flores abertas incrementou a quantidade de sólidos solúveis totais por caixa de 40,8 kg. Estes tratamentos não promoveram alterações consistentes sobre o teor de sólidos solúveis totais, o rendimento de suco, a acidez, o ratio, a massa média dos frutos, o diâmetro médio dos frutos, a cor dos frutos e a produtividade. O incremento médio foi de 0,11 a 0,14 kg na quantidade de sólidos solúveis totais por caixa industrial padrão de 40,8 kg. Aumentos na assimilação de CO2 e uma diminuição no conteúdo foliar de carboidratos foram observados nas folhas tratadas com MBTA na concentração de 16 mg L-1. Os efeitos do MBTA sobre a produtividade e a qualidade dos frutos estão possivelmente relacionados com a fotossíntese a com relações fonte-dreno. / The purpose of this research was to evaluate effects of MBTA [N,N-diethyl-2-(4- metylbenzyloxy) ethylamine hydrochloride] bioregulator applied on different times and concentrations on the yield and fruit quality of &#39;Hamlin&#39;, &#39;Pera&#39; and &#39;Valencia&#39; sweet orange and on physiological characteristics of &#39;Hamlin&#39; sweet orange. In two consecutive harvest seasons, the MBTA was sprayed in three different concentrations (8; 16 and 32 mg L-1) and in two different phenological phases (25% and 100% open flowers) in citrus mature trees, using 7 L of spray per tree added with Silwett L-77 adjuvant at 0.05%. For each cultivar, twenty fruits per tree were sampled in four different times to determine the total soluble solids concentration, acidity, quantity of total soluble solids in 40.8 kg box, pH, juice concentration, juice color, fruit weight and diameter. The effects of MBTA varied according to the cultivar, concentration and phenological phase of application. In &#39;Hamlin&#39; sweet orange, the MBTA at 16 mg L-1 concentration sprayed with 25% open flowers increased the total soluble solids concentration, juice concentration and the quantity of total soluble solids per 40,8 kg box. This same treatment decreased the fruit weight and didn´t affect the acidity, ratio, juice color, fruit diameter and yield. The average increase was from 0.45 to 0.56% on total soluble solids concentration and from 0.16 to 0.18 kg on the quantity of total soluble solids per 40.8 kg box. In &#39;Pera&#39; sweet orange, the MBTA at 8 mg L-1 concentration sprayed with 25% open flowers increased the total soluble solids concentration, acidity, the quantity of total soluble solids per 40.8 kg box and the yield. This same treatment decreased the fruit weight and didn´t affect the juice concentration, ratio, juice color and fruit diameter. The average increase was from 0.49 to 0.65% on total soluble solids concentration, from 0.11 to 0.13 kg on the quantity of total soluble solids per 40.8 kg box and 20.4 kg/tree on yield. In &#39;Valencia&#39; sweet orange, the MBTA at 16 mg L-1 concentration sprayed with 25% or 100% open flowers increased the quantity of total soluble solids per 40.8 kg box. These treatments didn&#39;t cause consistent changes in the total soluble solids concentration, acidity, fruit diameter, fruit weight, juice concentration, ratio, juice color and the yield. The average increase was from 0.11 to 0.14 kg on the quantity of total soluble solids per 40.8 kg box. An increase on the CO2 assimilation and a decrease on foliar carbohydrate content were observed in the leaves sprayed with MBTA at 16 mg L-1 concentration. The MBTA effects on the yield and fruit quality are possibly related to the photosynthesis and source-sink relations.

Open-field burning has been an effective, economical, and widespread method of post-harvest residue management in creeping red fescue seed production in the Willamette Valley since the late 1940s. However, the use of field burning has been legislatively restricted due to air quality and safety issues. The foliar-applied plant growth regulator trinexapac-ethyl (TE), commercialized in the USA as Palisade, has been accepted by producers as a yield enhancing agent and is considered here as an alternative to open-field burning over a four-year period. The effects of open-field burning versus mechanical removal (flailing) of post-harvest residue, and spring versus fall applications of TE on seed yield, dry matter partitioning, and seed yield components were evaluated in a split-plot design. The response to the different treatment combinations differed across years. The young stand responded with a seed yield increase to spring TE applications, regardless of residue management treatment. However, as the stand aged, field burning became critical for maintaining high yields and, in 2003 and 2004, only spring TE applications resulted in seed yield increases in burned plots. The higher potential seed yield achieved in burned plots over flailed plots, as a result of a higher number of panicles per unit area and spikelets per panicle, was critical for maintaining high seed yields as the stand aged. Spring applications of TE, further increased seed yield over the untreated check by increasing the number of florets per spikelet, reducing fertile tiller height and lodging and consequently, favoring pollination and fertilization of the florets. Late spring TE applications also increased 1000-seed weight in 2003 and 2004. Although spring applications of TE were a promising alternative to open-field burning early during the life of the stand, as the stand aged they did not increase seed yield on flailed plots. Fall TE applications did not have a consistent effect on seed yield, dry matter partitioning or seed yield components, and were found not to be a viable management practice. / Graduation date: 2005

Lodging poses a serious limitation to successful economic production of small grain cereals and can lead to extensive yield and quality losses. Plant growth regulators (PGR's) that reduce plant height and lodging have been employed in management systems in Europe and the United States, however, these compounds have not been evaluated on commercial cultivars of wheat, barley and oats in South Africa. Current recommendations to reduce lodging include limiting N inputs, seeding rates and critical irrigations, all of which may also limit yield potential and grain quality. The objectives of this study were to assess the effects of two common stem-elongation-inhibiting PGR's (chlormequat chloride and ethephon) on the growth, development, and agronomic characteristics of wheat, barley and oats. The aim of the study was to introduce an additional component of intensive cereal management in the form of PGR's, and to allow producers to implement intensive production practices without incurring losses due to lodging. Field trials were conducted with each of the three cereal crops in the 2003 and 2004 seasons at Vaalharts and Bethlehem. The PGR's were applied separately and in combination with each other to lodging-tolerant and -susceptible cultivars (wheat and oats) at different stages of development (tillering, elongation, flag leaf stage). The PGR's were also tested in combination with different levels of N (barley) applied at the haulm elongation stage, the flag leaf stage, or both. The PGR chlormequat produced negligible effects on plant height, lodging, yield, or quality components in all of the tested cultivars . Ethephon and the PGR combination successfully reduced plant height (by 120 to 150mm) and lodging (by 25 to 94%) when applied to the lodging susceptible cultivars of wheat and oats at the flag leaf stage or as a split application to the barley cultivar "Puma" (plant height and lodging reduced by 180 to 230mm and 83 to 92% respectively). Effects on grain yield were variable, ranging from occasional reductions (by 3 t ha(-1) and improvements (by 1 t ha(-1) with the barley, and no effects with the wheat and oats. Wheat quality parameters such as protein content and hectolitre mass were improved by 2 and 4% respectively. However, the nature of the responses was highly dependent on the times of application with later applications producing the greatest positive effects on quality, yield and lodging reductions. Additionally, ethephon and the PGR combination allowed higher levels of N to be employed without increases in lodging of barley. Generally, ethephon and the PGR combination applied at the flag leaf stage of growth are suitable anti-lodging tools for small grain cereal production and should be employed as an insurance measure against lodging in intensive management systems. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Natural plant growth regulators (phytohormones) are a group of organic compounds which, in very small amounts, act as regulators of physiological processes in plants.Methods were developed for the analysis of phytohormones in samples from Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris (L.) Karst»). Identification of abscisic acid, 3-indoleacetic acid, gibbe-rellin Ag and the conjugate N-(3-indoleacetyl)aspartic acid was performed by GC-MS as their methyl esters. A quantitative determination of abscisic acid was made by GC-ECD and this method was also applied to anther samples of Anemone canadensis. 3-Indole-acetic acid and N-(3-indoleacetyl)aspartic acid were quantified by reversed-phase HPLC and spectrofluorimetric detection. Dichlorophene, used as a growth regulator in containerized seedlings of pine and spruce, was analysed by GC-MID in peat and paper. / digitalisering@umu