In response to commercial propagators’ inquiries regarding potential phytotoxicity of alcohol used in root-promoting solutions for cutting propagation, three experiments were conducted using stem cuttings of seven herbaceous and woody plant taxa. Solutions were prepared with three rates of isopropyl alcohol (0%, 25%, or 50%) in combination with three rates of indole-3-butyric acid (IBA): 0, 1000, or 2000 ppm (Expt. 1); 0, 100, and 200 ppm (Expt. 2); or a mixture of IBA and 1-naphthalene acetic acid (NAA): 0+0, 500+250, or 1000+500 ppm IBA+NAA, respectively (Expt. 3) and applied to cuttings using the basal quick-dip method (Expts. 1 and 3) or total immersion method (Expt. 2). No stem or leaf burn occurred using the basal quick-dip method (except for lantana), whereas foliar and stem burn occurred on cuttings of African wormwood, lantana, and garden geranium using the total immersion method with solutions containing alcohol (regardless of IBA rate).

With the development of transgenic crops resistant to auxin herbicides will come an increase in the use of these herbicides for weed control. This new technology will greatly aid growers that have glyphosate-resistant weeds such as Palmer amaranth (Amaranthus palmeri S. Wats) in their fields. A challenge will be with farmers that choose not to use this new technology and have susceptible crops on their farm or adjoining farms. Auxin herbicides such as 2, 4-D and dicamba are well-documented as being very injurious to susceptible crops, even at low doses. It is for this reason that research is being conducted to compare the differences in the amount of particle drift with hooded boom sprayers compared to open boom sprayers. Along with this research, various droplet sizes will also be analyzed and compared between the two sprayers.

The present investigation was undertaken as a preliminary study to learn the response of Escherichia coli cells grown under identical experimental conditions to various concentrations of indoleacetic acid, gibberellic acid, and kinetin alone, and in combination with one another.

Fruit ripening is a highly coordinated process involving numerous structural, biochemical and physiological changes, many of which are influenced by both endogenous and environmental stimuli. Light signaling and plant hormones such as ethylene and auxins have been identified as important regulators of tomato fruit ripening. However, it is still not fully understood how light and hormonal signaling cascades interact to control the development and physiology of fleshy fruits. By applying a mutant-based approach, this study investigated the potential interconnection among light, auxin and ethylene signaling cascades during tomato fruit ripening and carotenogenesis. Analysis of ethylene and auxin metabolism and signaling in ripening fruits of the light-hyperresponsive high-pigment 2 (hp2) mutant revealed that the loss of HP2 function promotes the transcription of genes encoding key regulators of fruit ripening and increases ethylene signaling along with the increments in carotenoid synthesis and accumulation typically found in this mutant. Compared to the wild type (WT), significant changes in fruit auxin signaling were also observed in the hp2 mutant, including significantly higher activation of the auxin-responsive promoter DR5, severe down-regulation of all AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) genes more closely associated with fruit ripening as well as disturbed transcript abundance of genes encoding AUXIN RESPONSE FACTOR (ARF) transcription factors. Evidence of increased tissue responsivity to ethylene and auxins in hp2 ripening fruits is also provided. Moreover, comparing the auxin and ethylene metabolism and signaling in fruits of the phytochrome chromophore-deficient mutant aurea (au) in relation to the WT genotype provided new insights into the phytochrome-hormonal signaling crosstalk regulating the timing of fruit ripening. Compared to the WT, fruits of the au mutant exhibited a delayed-ripening phenotype, which was associated with the late induction of genes encoding master controllers of ripening, delayed ethylene climacteric production as well as coordinated changes in the expression of auxin signaling-related genes. Besides the temporal changes in hormonal signaling associated with ripening, the deficiency in functional phytochromes also seems to repress the cyclization of lycopene, leading to reduced levels of ?-carotene and lutein in the fruit tissues. Although the exact molecular mechanisms behind the altered hormonal responses in tomato fruits triggered by changes in light signaling remain to be further elucidated, the data obtained in this study provide clear evidence that an intricate crosstalk among light, ethylene and auxin signaling may be involved in controlling tomato fruit ripening and carotenogenesis. Therefore, these findings open up a window of opportunity for further improvement in the regulation of ripening-associated processes through the combined manipulation of hormonal and light signaling-related genes / O amadurecimento de frutos é um processo altamente regulado que envolve várias mudanças estruturais, bioquímicas e fisiológicas, muitas das quais são influenciadas tanto por fatores endógenos quanto ambientais. O sinal luminoso, bem como os hormônios vegetais etileno e auxina têm se revelado importantes reguladores do amadurecimento de frutos. Porém, ainda não está totalmente esclarecido como as cascatas de sinalização luminosa e hormonal interagem a fim de controlar o desenvolvimento e a fisiologia dos frutos carnosos. O presente estudo teve como objetivo analisar as interações entre as cascatas de sinalização da luz, do etileno e das auxinas durante o amadurecimento e carotenogênese em frutos de tomateiro por meio do uso de mutantes fotomorfogênicos dessa espécie. As análises do metabolismo e sinalização do etileno e das auxinas em frutos do mutante high-pigment 2 (hp2), o qual apresenta respostas exageradas à luz, revelaram que a perda da função do gene HP2 resultou no aumento dos níveis de transcritos de genes que codificam os reguladores-chaves do processo de amadurecimento bem como um incremento na sinalização do etileno, sendo que essas mudanças estiveram atreladas ao maior acúmulo de carotenoides tipicamente encontrados neste mutante. Comparado ao genótipo selvagem, frutos do mutante hp2 também apresentaram uma elevação considerável na sinalização das auxinas, incluindo incrementos na ativação do promotor DR5, regulação negativa da maioria dos genes AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) envolvidos no amadurecimento do tomate, bem como alterações na abundância de transcritos dos genes que codificam os fatores de transcrição AUXIN RESPONSE FACTOR (ARF). Indícios obtidos também sugerem uma maior responsividade dos frutos de hp2 aos hormônios etileno e auxinas. Além disso, as análises do metabolismo e a sinalização das auxinas e do etileno realizadas em frutos do mutante aurea (au), deficiente na síntese do cromóforo dos fitocromos, indicaram que a interação entre esses fotorreceptores e fitormônios influencia o início do amadurecimento dos frutos de tomateiro. Os frutos deste mutante, quando comparados ao selvagem, exibiram um atraso no amadurecimento, o qual se mostrou temporalmente relacionado à indução tardia dos genes que controlam esse processo, ao atraso na produção climatérica do etileno, bem como associado a alterações nos níveis de transcritos de genes-chaves relacionados com a sinalização das auxinas. Além das mudanças temporais na sinalização hormonal associadas ao amadurecimento, os dados obtidos também sugerem que a deficiência em fitocromos funcionais reprime a ciclização do licopeno, levando a níveis reduzidos de ?-caroteno e luteína nos tecidos dos frutos. Embora os mecanismos moleculares responsáveis pelas alterações nas respostas hormonais desencadeadas pela luz ainda precisem ser melhor elucidados em frutos de tomateiro, os dados obtidos neste estudo forneceram evidências de que uma complexa interação entre a sinalização luminosa, do etileno e das auxinas estaria envolvida no controle do amadurecimento e carotenogênese nessa espécie. Portanto, estas descobertas trazem consigo oportunidades de melhoria na regulação de eventos relacionados ao processo de amadurecimento por meio da manipulação combinada de genes relacionados à sinalização luminosa e hormonal

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Palmer amaranth (Amaranthus palmeri) and common ragweed (Ambrosia artemisiifolia) are two of the most troublesome weeds in soybean. Both weeds possess widespread resistance to glyphosate and acetolactate synthase (ALS) inhibiting herbicides resulting in the use of protoporphyrinogen oxidase- (PPO) inhibitors to control these biotypes, although PPO-resistant biotypes are increasing. New soybean herbicide-resistant trait technologies enable novel herbicide combinations. Combinations of two herbicide sites-of-action (SOA) improved control 19 to 25% and 14 to 19% of Palmer amaranth and common ragweed, respectively, versus using one SOA (mesotrione, dicamba, 2,4-D, or glufosinate alone). Seed production of 5 to 10 cm Palmer amaranth and common ragweed was reduced greater than 76% by fomesafen, auxin (dicamba and 2,4-D), or glufosinate containing treatments. Some weeds survived and set seed even when treated at the proper size. As weed size increased from 10 to 30 cm, control diminished and fecundity increased, underscoring the importance of proper herbicide application timing. Effective preemergence herbicides reduced the number of weeds present at the postemergence application compared to no treatment, reducing the likelihood of herbicide resistance development. Dicamba, 2,4-D, or glufosinate applied alone or auxin + glufosinate combinations reduced Palmer amaranth seed production greater than 95% when applied at first visible female inflorescence; this first report, in addition to previous reports on individual herbicides, indicates this application timing may be useful for soil seed bank management. This research informs mitigation of herbicide resistance spread and development. / Master of Science in Life Sciences / Over 30 million hectares of soybeans were harvested in 2019 in the United States, totaling over $31 billion in value. Two of the most troublesome weeds in soybean, Palmer amaranth (Amaranthus palmeri) and common ragweed (Ambrosia artemisiifolia) can cause even greater yield reductions in soybean, up to 79 to 95%, respectively. Frequent, exclusive, and repeated use of a single herbicide has led to multiple herbicide-resistance in both of these weeds. Co-applying two effective herbicides reduces the likelihood of resistance development. New soybean varieties have been genetically modified for resistance to herbicides that were previously unusable, allowing new herbicide combinations. Research was established to investigate these herbicide options to control and reduce seed production of Palmer amaranth and common ragweed with the overarching goal of mitigating herbicide resistance, particularly resistance to protoporphyrinogen oxidase (PPO) inhibiting herbicides, which are a critical part of herbicide options in soybean production. Preemergence herbicides are vital tools in herbicide programs, reducing the number of weeds present at a postemergence application and thereby reducing the risk of herbicide resistance development to the postemergence herbicide. PPO herbicides (flumioxazin, sulfentrazone, or fomesafen) applied preemergence reduced Palmer amaranth and common ragweed density at the postemergence application 82 to 89% and 53 to 94%, respectively. The preemergence herbicide used did not affect control four weeks after the postemergence herbicides were applied. Postemergence herbicides were applied targeting three weed heights: 5 to 10 cm (ideal), 10 to 20 cm, and 20 to 30 cm. Control decreased as weed height increased and larger weeds had greater biomass and seed production, underscoring the importance of proper herbicide application timing. The single site-of-action treatments dicamba, 2,4-D, glufosinate, or fomesafen resulted in greater than 85 and 92% morality of 5 to 10 cm Palmer amaranth and common ragweed, respectively. Palmer amaranth and common ragweed control improved by 19 to 25% and 14 to 19%, respectively, when using two herbicide sites-of-action increased versus using one SOA (mesotrione, dicamba, 2,4-D, or glufosinate alone). The use of two herbicide sites of action resulted in maximum biomass reductions, depending on weed height, of 57 to 96% and 73 to 85% for Palmer amaranth and common ragweed, respectively. Dicamba, 2,4-D, glufosinate alone and in combination with fomesafen reduced seed production (relative to the nontreated) of 5 to 10 cm Palmer amaranth and common ragweed greater than 98 and 76%, respectively. Dicamba, 2,4-D, and glufosinate applied alone or auxin (dicamba and 2,4-D) and glufosinate combinations reduced Palmer amaranth seed production greater than 95% when applied at first visible female inflorescence. This indicates that these herbicides may be useful in soil weed seed bank management. This research reinforces the utility of PPO herbicides for preemergence control and their efficacy postemergence when combined with another effective herbicide, a practice known to reduce herbicide resistance development. This research also reinforces the potential for dicamba, 2,4-D, or glufosinate to reduce weed seed production when applied at a delayed timing. Future research should investigate the progeny of these weeds treated with herbicides at a delayed timing to evaluate the potential for this practice to reduce herbicide resistance development.

Trichoderma species are soil-borne filamentous fungi widely utilized for their many plant health benefits, such as conferring improved growth, disease resistance and abiotic stress tolerance to their hosts. Many Trichoderma species are able to produce the auxin phytohormone indole-3-acetic acid (IAA), and its production has been suggested to promote root growth. Here we show that the production of IAA is strain dependent and diverse external stimuli are associated with its production. In in vitro assays, Arabidopsis primary root length was negatively affected by the interaction with some Trichoderma strains. In soil experiments, a continuum effect on plant growth was shown and this was also strain dependent. In plate assays, some strains of Trichoderma spp. inhibited the expression of the auxin reporter gene DR5 in Arabidopsis primary roots but not secondary roots. When Trichoderma spp. and A. thaliana were physically separated, enhancement of both shoot and root biomass, increased root production and chlorophyll content were observed, which strongly suggested that volatile production by the fungus influenced the parameters analyzed. Trichoderma strains T. virens Gv29.8, T. atroviride IMI206040, T. sp. "atroviride B" LU132, and T. asperellum LU1370 were demonstrated to promote plant growth through volatile production. However, contrasting differences were observed with LU1370 which had a negative effect on plant growth in soil but a positive effect in plate assays. Altogether our results suggest that the mechanisms and molecules involved in plant growth promotion by Trichoderma spp. are multivariable and are affected by the environmental conditions.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.