Methyl bromide fumigation, a common method used to combat soil borne pathogens in commercial tomato cultivation, was to be limited by the Montreal Protocol due to concerns of ozone depletion. Alternative methods to protect tomatoes against diseases include grafting. However, short grafted transplants may expose the scion to the soil. To avoid scion exposure, hypocotyl elongation of two tomato rootstocks 'Maxifort' and 'Aloha' via end-of-day far-red (EOD-FR) was examined in terms of light quality (red to far-red ratio, or R/FR) and dose (product of far-red intensity and duration). In EOD-FR light quality experiments, 'Aloha' seedlings were exposed to unfiltered and filtered incandescent light with an R/FR of 0.5 and 0.05 respectively. The resulting hypocotyl elongation was higher in filtered light than either the unfiltered light or the untreated control. Hypocotyl elongation response to EOD-FR dose in 'Aloha' and 'Maxifort' was affected by both far-red intensity and treatment duration. A saturating response was also found within a far-red dose between 0–8 mmol•m⁻²•d⁻¹ and modeled using non-linear regression with a three parameter Michaelis-Menten equation to estimate the far-red dose required to obtain near-maximum hypocotyl elongation for 'Aloha' and 'Maxifort'. The far-red dose required was affected by cultivar and experimental period. None of the EOD-FR treatments affected plant mass or stem diameter. To conclude, for maximum hypocotyl elongation using EOD-FR, the lower R/FR would increase the effectiveness of the treatment. The far-red dose should preferably be at 4–8 mmol• m⁻²•d⁻¹.

The photosynthetic process has the unique ability to capture energy from sunlight and accumulate that energy in sugars and starch. This thesis deals with the light driven part of photosynthesis. The aim has been to investigate how the light-absorbing protein complexes Photosystem I (PS I) and Photosystem II (PS II), react upon illumination of light with lower energy (far-red light; 700-850 nm) than the absorption peak at respective primary donor, P700 and P680.  The results were unexpected. At 295 K, we showed that both PS I and PS II were able to perform photochemistry with light up to 130 nm above its respective primary donor absorption maxima. As such, it was found that the primary donors’ action spectra extended approximately 80 nm further out into the red-region of the spectrum than previously reported.  The ability to perform photochemistry with far-red light was conserved at cryogenic temperatures (< 77 K) in both photosystems. By performing EPR measurements on various photosystem preparations, under different illumination conditions the origin of the effect was localized to their respective reaction center. It is also likely that underlying mechanism is analogous for PS I and PS II, given the similarities in spatial coordination of the reaction center pigments. For PS II, the results obtained allowed us to suggest a model involving a previously unknown electron transfer pathway. This model is based upon the conclusion that the primary cation from primary charge separation induced by far-red light resides primarily on ChlD1 in P680. This is in contrast to the cation being located on PD1, as has been suggested as for visible light illumination. The property to drive photochemistry with far-red wavelengths implies a hither to unknown absorption band, probably originating from the pigments that compose P700 and P680. The results presented here might clarify how the pigments inside P680 are coupled and also how the complex charge separation processes within the first picoseconds that initiate photosynthetic reactions occur.

Interspecific competition is comprised of both resource dependant and resource independent processes. While many studies have focused on the role that resource dependant competition plays in reducing crop yields, few have investigated whether resource independent effects, such as light or hormonal signaling, may contribute to these yield losses. The focus of this thesis was to investigate the role of the shade avoidance response in determining the onset and outcome of crop-weed competition in maize (Zea mays L.). The results of greenhouse and field trials demonstrate that shade avoidance in maize can be induced shortly after seedling emergence and that the effects of this early response can be detected throughout the entire life cycle of the crop. Seedlings exposed to a weedy or low red to far-red light (R/FR) environment at emergence displayed an initial increase in plant height and a reduction in the root-to-shoot ratio. These effects were followed by a reduction in the rate of leaf appearance (RLA) and a linear decline in biomass and leaf area (LA) as the duration of time spent in a weedy environment increased. Conversely, seedlings emerging in a weed-free or ambient R/FR environment were unaffected regardless the duration of time spent in the weedy environment. These effects of early crop-weed competition are distinct from those of plant population density (i.e., intraspecific competition). Results of a field trial demonstrated that intraspecific competition at a conventional density of 8 plants m-2 did not negatively impact RLA or biomass accumulation until well after the defined critical period for weed control. Moreover, intraspecific competition at 16 plants m-2 was not detected until the 12th leaf tip stage, suggesting that the effects of crop density are more closely associated with canopy closure than an early shade avoidance response. At maturity, seedlings that expressed shade avoidance at early stages of development set fewer kernels and partitioned less biomass to the developing ear. Shade avoidance also doubled the plant-to-plant variability in yield parameters without affecting the mean or frequency distribution of shoot biomass at maturity. When taken together, the results of these studies indicate that shade avoidance destabilizes stand productivity by increasing plant-to-plant variability in reproductive effort prior to intra- or interspecific competition for resources.

Barley protoplasts were shown to be a suitable experimental system for studies on the relative maximum during the decay of luminescence observed in most photosynthetic systems after excitation with far red light and in the presence of O2. The far red induced relative luminescence maximum was shown to be a result of three coinciding events: *Randomization of the S-states of the water splitting system during illumination with far red light. *Extreme oxidation of the PSII acceptor side after excitation with far red light and in the presence of O2. *Reverse coupling, causing partial re-reduction of the PSII acceptor side in the dark after far red illumination. When the CO2 concentration in the air above an intact barley leaf was lowered in the dark, the primary PSII acceptor QA was partially reduced. The effect was obtained by changes in CO2 over a wide concentration range including that of saturated photosynthesis. It was thus concluded that the effect was not related to the role of CO2 as the terminal electron acceptor in photosynthesis. White light induced relative maxima during the decay of luminescence frqm low CO2 adapted green algae were shown to be the result of either one or two interacting mechanisms: *Relaxation of qE quenching. *Dark reduction of QA occuring as a result of lowered internal Cj concentration in the dark. Far red induced luminescence decay kinetics and fluorescence induction kinetics, when analyzed with multivariat data analysis, were shown to contain information allowing prediction of the state of frost hardiness in artificially hardened seedlings of Scots pine. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1988, härtill 8 uppsatser.</p> / digitalisering@umu

京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第24982号 / 生博第511号 / 新制||生||68(附属図書館) / 京都大学大学院生命科学研究科統合生命科学専攻 / (主査)教授 河内 孝之, 教授 荒木 崇, 教授 中野 雄司 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

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Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Inselbergs são afloramentos rochosos isolados que emergem abruptamente acima das planícies que os circundam, formados principalmente por afloramentos de rochas graníticas e gnáissicas. São lugares com alta diversidade e endemismo, e caracterizados por alto grau de insolação, temperaturas do ar e do solo, com ventos fortes e solos com baixa retenção de água. Sementes de três espécies típicas dos inselbergs (Alcantarea glaziouana, Barbacenia purpurea e Tibouchina corymbosa) foram estudadas para avaliar o efeito das temperaturas constantes (15 a 40C) e alternada (20-30C), o estresse hídrico (&#936;w = 0,0 a -1,2 MPa) promovido por soluções de polietileno glicol 6000 (PEG) e a qualidade da luz sob diferente valores de razão vermelho: vermelho extremo (V:VE), na porcentagem final e velocidade de germinação. Os resultados mostraram que todas as espécies têm sementes muito leves, variando entre 0,005 - 0,04 g. As três espécies apresentaram alta germinação sob temperaturas entre 20C e 30C, e não germinaram a 40C, exceto A. glaziouana. A máxima germinação foi obtida em água destilada (0 MPa) e as diferentes condições de estresse hídrico reduziram a percentagem e a velocidade de germinação de todas as espécies estudadas. A. glaziouana foi a espécie menos sensível a redução do potencial hídrico. As sementes de todas as espécies necessitam de exposição a luz para a máxima germinação (fotoblásticas positivas) e a porcentagem final de germinação foi inibida sob baixos valores de V:VE. A razão V:VE que resultou em 50% da máxima germinação variou entre as espécies. Estes resultados demonstram que a germinação pode limitar a capacidade das espécies em colonizar tanto novas áreas como área perturbadas, além de contribuir para a distribuição das espécies nos inselbergs. / Inselbergs are isolated rock outcrops that rise abruptly above the surrounding plains, mainly formed by outcrops of granitic and gneissic rocks. They are places with high diversity and endemism, and are characterized by high degree of insolation, air temperatures and soil, with high winds and soils with low water retention. Seeds of three typical inselberg taxa (Alcantarea glaziouana, Barbacenia purpurea and Tibouchina corymbosa) were studied to evaluate the effect of constant (15 to 40C) and alternating (20-30C) temperatures, water stress (&#936;w = 0.0 to -1.2MPa) promoted by solutions of polyethylene glycol 6000 (PEG) and light quality under different red:far red (R:FR) ratios on the percentage and germination rate. The results showed that all species have very light seeds, ranging from 0.005 to 0.04 g. All species presented high germination under temperatures between 20C and 30C, and did not germinate under 40C, except A. glaziouana. Maximum germination was obtained in distilled water (0 MPa) and water stressed conditions reduced the percentage and rate of germination in all species studied; A. glaziouana was less sensitive to low water potentials. Seeds of all species required light for maximum germination (photoblastic positive) and the final germination percentage was inhibited at low R:FR ratios. The R:FR value that resulted in 50% of maximum germination varied among species. These results show that germination can limit the ability of species to colonize newly and disturbed habitats and also contributes to inselbergspecies distribution.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Inselbergs são afloramentos rochosos isolados que emergem abruptamente acima das planícies que os circundam, formados principalmente por afloramentos de rochas graníticas e gnáissicas. São lugares com alta diversidade e endemismo, e caracterizados por alto grau de insolação, temperaturas do ar e do solo, com ventos fortes e solos com baixa retenção de água. Sementes de três espécies típicas dos inselbergs (Alcantarea glaziouana, Barbacenia purpurea e Tibouchina corymbosa) foram estudadas para avaliar o efeito das temperaturas constantes (15 a 40C) e alternada (20-30C), o estresse hídrico (&#936;w = 0,0 a -1,2 MPa) promovido por soluções de polietileno glicol 6000 (PEG) e a qualidade da luz sob diferente valores de razão vermelho: vermelho extremo (V:VE), na porcentagem final e velocidade de germinação. Os resultados mostraram que todas as espécies têm sementes muito leves, variando entre 0,005 - 0,04 g. As três espécies apresentaram alta germinação sob temperaturas entre 20C e 30C, e não germinaram a 40C, exceto A. glaziouana. A máxima germinação foi obtida em água destilada (0 MPa) e as diferentes condições de estresse hídrico reduziram a percentagem e a velocidade de germinação de todas as espécies estudadas. A. glaziouana foi a espécie menos sensível a redução do potencial hídrico. As sementes de todas as espécies necessitam de exposição a luz para a máxima germinação (fotoblásticas positivas) e a porcentagem final de germinação foi inibida sob baixos valores de V:VE. A razão V:VE que resultou em 50% da máxima germinação variou entre as espécies. Estes resultados demonstram que a germinação pode limitar a capacidade das espécies em colonizar tanto novas áreas como área perturbadas, além de contribuir para a distribuição das espécies nos inselbergs. / Inselbergs are isolated rock outcrops that rise abruptly above the surrounding plains, mainly formed by outcrops of granitic and gneissic rocks. They are places with high diversity and endemism, and are characterized by high degree of insolation, air temperatures and soil, with high winds and soils with low water retention. Seeds of three typical inselberg taxa (Alcantarea glaziouana, Barbacenia purpurea and Tibouchina corymbosa) were studied to evaluate the effect of constant (15 to 40C) and alternating (20-30C) temperatures, water stress (&#936;w = 0.0 to -1.2MPa) promoted by solutions of polyethylene glycol 6000 (PEG) and light quality under different red:far red (R:FR) ratios on the percentage and germination rate. The results showed that all species have very light seeds, ranging from 0.005 to 0.04 g. All species presented high germination under temperatures between 20C and 30C, and did not germinate under 40C, except A. glaziouana. Maximum germination was obtained in distilled water (0 MPa) and water stressed conditions reduced the percentage and rate of germination in all species studied; A. glaziouana was less sensitive to low water potentials. Seeds of all species required light for maximum germination (photoblastic positive) and the final germination percentage was inhibited at low R:FR ratios. The R:FR value that resulted in 50% of maximum germination varied among species. These results show that germination can limit the ability of species to colonize newly and disturbed habitats and also contributes to inselbergspecies distribution.

No description available.

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