Microalgae hold much promise as a feedstock in liquid biofuel production. Lipid content of microalgae cells range from 30-80% dry weight of biomass. It is projected that microalgae can produce between 1,000-6,500 gallons/acre/year of oil. Currently, production of industrial algae operates in open raceway ponds that use minimal capital and energy inputs to culture algae. Raceway ponds can also be used to grow microalgae from municipal waste streams. Although high biomass productivity can be achieved in these systems, there remains a large production gap between large volumes of biomass cultivation and high lipid content from microalgae cells. Low lipid content has been ameliorated through laboratory manipulations of nitrogen availability and light intensity. This two-part project measured microalgae lipid levels in open raceway ponds located at the San Luis Obispo Water Reclamation Facility (SLO WRF) grown in primary clarifier effluent and then performed nitrogen depletion and light-shift methods on cultures to increase triglyceride (TAG) content. The raceway ponds reached maximum biomass productivity of 24 g/m2-day, but with minimal TAG reserves. Optimization of both biomass productivity and TAG content can be achieved in April and September with 13 g/m2-day productivity and 13% TAG content. Investigation of increased TAG production responses were performed on wastewater microalgae (predominately Scenedesmus sp.) through N-depletion and three light treatments: light-shift on day 3 (before N-depletion), light-shift on day 5 (near N-depletion), and a double-illumination treatment. Highest levels of TAG content were observed in the double-illumination treatment and reached a maximum of 49% TAG in 9 days.

Snow algae are psychrophilic microorganisms, that inhabit snow fields in mountains and polar regions, which creates colored snow in good conditions. Most species belong to order Chlamydomonadales (Chlorophyta) with complicated life cycles, containing flagellates and immobile stages (cysts). Extreme environment of snow is characteristed by low temperature, problems with availability of water and lack of nutrition. Depending on location and phase of life cycle, snow algae have to deal with excess or lack of solar radiation, the important component of which is also dangerous UV radiation. The light conditions differ substantially from open location above the forest level or polar regions to forest habitats. In the first part of this work I compared reactions of photosynthetic apparatus of snow algae strains from forest and forestless habitats to different intensity of radiation, then I dealt with assessing any changes related to long-term cultivation in laboratory. Based on measurement of rapid light curves on PAM fluorometer I have determined some characteristics of photosynthetic apparatus of individual strains (parameters α and Ik), which indicate adaptation to low or high light intensity. For some strains, it was possible to compare the results obtained at a three-year interval. In the second part...

A produção da cianobactéria Arthrospira (Spirulina) platensis é considerada de interesse nas indústrias de alimentos, farmacêuticas e químicas. Diferentes fontes de nitrogênio alternativas têm sido sugeridas na literatura para seu cultivo, incluindo uréia e sais de amônio, visando à diminuição no custo do meio de cultivo. A perda de amônia por degasificação ocorre quando utilizados tanques abertos, justificando dessa forma o uso da associação de fontes de nitrato e de amônia em fotobiorreatores fechados. O nitrato de amônio (NH4NO3) contorna estas condições, proporcionando ao cultivo uma fonte de nitrogênio prontamente assimilável (amônio) e outra de reserva (nitrato), no mesmo composto. Neste trabalho verificou-se, pelo uso de um planejamento fatorial 22 com configuração de estrela, a influência da intensidade luminosa (I) e da adição de diferentes concentrações de NH4NO3 (mM), no crescimento e composição da biomassa de A. platensis em cultivos realizados em fotobiorreator tubular por processo descontínuo alimentado, utilizando um tempo de 6 dias alimentação para a fonte de nitrogênio. Parâmetros cinéticos de crescimento, como concentração celular máxima (Xm), produtividade em células (PX) e o fator de conversão de nitrogênio em células (YX/N), bem como o teor de proteínas e lipídios na biomassa foram avaliados. Através do uso da regressão multivariável para a otimização das condições experimentais, foram obtidos valores de Xm e de PX correspondentes a 4710 mg L-1 e 478,9 mg L-1d-1, respectivamente, pelo emprego de I = 148 µmol fótons m-2 s-1 e a adição de 9,7 mM de NH4NO3. O maior valor de YX/N registrado foi 8,1 mg mg-1, sendo superior aos obtidos com nitrato de sódio (0,80 mg mg-1). Os teores de proteína e de lipídios alcançaram valores de até 63,2 e 17,3 %, respectivamente. O emprego de NH4NO3 conduziu à redução dos custos de produção, sendo gastos em média R$ 15,97 da fonte de nitrogênio por quilograma de células, valor inferior se comparado com outras fontes usadas no cultivo de A. platensis como NaNO3 (R$ 59,10 por quilograma de células). O uso do NH4NO3 em fotobiorreator tubular mostrou-se promissor para o cultivo de A. platensis, ao proporcionar um aumento na produção de biomassa e diminuir a perda de amônia por degasificação. / The production of the cyanobacterium Arthrospira (Spirulina) platensis is considered of interest to the food, pharmaceutical and chemical industries. Alternative nitrogen sources have been suggested in literature, including urea and ammonium salts, in order to reduce the cost of cultivation medium. Ammonia off-gassing occurs when open ponds are used, thus justifying the utilization of nitrate and ammonia sources association. Ammonium nitrate (NH4NO3) attend this condition, providing the cultivation with a nitrogen source readily assimilated (ammonium) and with one of reserve (nitrate), in the same molecule. In this work, it was verified, using a 22 factorial design with star configuration, the influence of light intensity (I) and the addition of different concentrations of NH4NO3 (mM) on the growth and biomass composition of S. platensis in cultures carried out in tubular photobioreactor by fed-batch process, using a 6-day feeding time of the nitrogen source. Kinetic growth parameters, such as maximum cell concentration (Xm), cell productivity (Px) and yield of nitrogen to biomass (YX/N), as well the biomass content of protein and lipids, were evaluated. Through the use of regression analysis for the optimization of experimental conditions, values of Xm and PX such as 4710 mg L-1 and 478.9 mg L-1d-1, respectively, were obtained by the use of I = 148 µmol photons m-2 s-1 and the addition of 9.7 mM of NH4NO3. The highest value of YX/N obtained was 8.1 mg mg-1, higher than that provided by the use of sodium nitrate (0.80 mg mg-1). The levels of protein and lipid achieved up to 63.2 and 17.3 %, respectively. The use of NH4NO3 led to the reduction of culture medium costs, in which R$ 15.97 (Real/Brazil) were spent on nitrogen source per kilogram of cells, value that is lower if compared to other common sources used for A. platensis growth, such as NaNO3 (R$ 59.10 per kilogram of cells, Real/Brazil). The use of NH4NO3 in tubular photobioreactor proved to be promising for the cultivation of A. platensis, leading to an increase in biomass production and diminishing the ammonia lost by off-gassing.

A Arthrospira (Spirulina) platensis, cianobactéria fotoautotrófica, tem sido cultivada para a produção de biomassa, apresentando em sua constituição proteínas, ácidos graxos poliinsaturados, pigmentos, minerais, vitaminas e aminoácidos. O uso de fontes de nitrogênio de baixo custo, como o sulfato de amônio, pode contribuir para a viabilização da produção de A. platensis. Neste trabalho foram verificados a influência de diferentes intensidades luminosas e protocolos de alimentação utilizando o sulfato de amônio, em cultivos realizados com reatores tubulares por processo descontínuo alimentado. As variáveis dependentes selecionadas foram concentração celular máxima (Xm), produtividade em células (Px), fator de conversão de nitrogênio em células (YX/N), bem como teores de proteínas e lipídios da biomassa. Foram obtidos excelentes resultados em cultivos realizados aplicando-se um protocolo de alimentação de sulfato de amônio, considerando biomassa seca de A. platensis com teor de 7 % de nitrogênio, com valor médio de Xm igual a 11414 mg.L-1. Este protocolo de adição de sulfato de amônio com intensidade luminosa de 240 µmol fótons. m-2.s-1 levou à melhor combinação de obtenção de Xm e Px, com valores finais de 12200 mg.L-1 e 1686 mg.L-1.d-1, respectivamente. Adicionalmente, nesse protocolo de adição de sulfato de amônio, os valores de concentração celular máxima foram da mesma ordem de grandeza que aqueles onde se utilizou nitrato de sódio, evidenciando, assim, a possibilidade do uso do sulfato de amônio como uma fonte de nitrogênio alternativa para o cultivo da A. platensis. / Arthrospira (Spirulina) platensis, a photoautotrophic cyanobacterium, has been cultivated for the production of biomass, and it is constituted by proteins, polyunsaturated fatty acids, chlorophyll, minerals, vitamins and amino acids. The use of low cost nitrogen sources, such as ammonium sulphate can contribute to the A. platensis production viability. It was verified in this work the influence of different light intensities and nutrient feeding protocols in fed-batch cultures developed in tubular reactors, where ammonium sulphate was used as a nitrogen source. The dependent variables were the maximum cell concentration (Xm), cell productivity (Px), nitrogen-to-cell conversion factor (YX/N), as well as proteins and lipids contents of the biomass. Excellent results were obtained when ammonium sulphate protocols were studied, considering A. platensis dry-weight with nitrogen levels of 7%, obtaining an average value of Xm corresponding to 11414 mg L-1. It was also obtained with this protocol, with light intensity of 240 µmol photons. m-2.s-1, the best combination to high values of Xm and Px, corresponding to 12200 mg.L-1 e 1686 mg.L-1.d-1, respectively. Moreover, in this protocol of ammonium sulphate addition, it was obtained values of the maximum cell concentration as high as the ones obtained with sodium nitrate as nitrogen source. This fact highlighted the possibility of using this alternative nitrogen source for the A. platensis cultivation.

A Arthrospira (Spirulina) platensis, cianobactéria fotoautotrófica, tem sido cultivada para a produção de biomassa, apresentando em sua constituição proteínas, ácidos graxos poliinsaturados, pigmentos, minerais, vitaminas e aminoácidos. O uso de fontes de nitrogênio de baixo custo, como o sulfato de amônio, pode contribuir para a viabilização da produção de A. platensis. Neste trabalho foram verificados a influência de diferentes intensidades luminosas e protocolos de alimentação utilizando o sulfato de amônio, em cultivos realizados com reatores tubulares por processo descontínuo alimentado. As variáveis dependentes selecionadas foram concentração celular máxima (Xm), produtividade em células (Px), fator de conversão de nitrogênio em células (YX/N), bem como teores de proteínas e lipídios da biomassa. Foram obtidos excelentes resultados em cultivos realizados aplicando-se um protocolo de alimentação de sulfato de amônio, considerando biomassa seca de A. platensis com teor de 7 % de nitrogênio, com valor médio de Xm igual a 11414 mg.L-1. Este protocolo de adição de sulfato de amônio com intensidade luminosa de 240 µmol fótons. m-2.s-1 levou à melhor combinação de obtenção de Xm e Px, com valores finais de 12200 mg.L-1 e 1686 mg.L-1.d-1, respectivamente. Adicionalmente, nesse protocolo de adição de sulfato de amônio, os valores de concentração celular máxima foram da mesma ordem de grandeza que aqueles onde se utilizou nitrato de sódio, evidenciando, assim, a possibilidade do uso do sulfato de amônio como uma fonte de nitrogênio alternativa para o cultivo da A. platensis. / Arthrospira (Spirulina) platensis, a photoautotrophic cyanobacterium, has been cultivated for the production of biomass, and it is constituted by proteins, polyunsaturated fatty acids, chlorophyll, minerals, vitamins and amino acids. The use of low cost nitrogen sources, such as ammonium sulphate can contribute to the A. platensis production viability. It was verified in this work the influence of different light intensities and nutrient feeding protocols in fed-batch cultures developed in tubular reactors, where ammonium sulphate was used as a nitrogen source. The dependent variables were the maximum cell concentration (Xm), cell productivity (Px), nitrogen-to-cell conversion factor (YX/N), as well as proteins and lipids contents of the biomass. Excellent results were obtained when ammonium sulphate protocols were studied, considering A. platensis dry-weight with nitrogen levels of 7%, obtaining an average value of Xm corresponding to 11414 mg L-1. It was also obtained with this protocol, with light intensity of 240 µmol photons. m-2.s-1, the best combination to high values of Xm and Px, corresponding to 12200 mg.L-1 e 1686 mg.L-1.d-1, respectively. Moreover, in this protocol of ammonium sulphate addition, it was obtained values of the maximum cell concentration as high as the ones obtained with sodium nitrate as nitrogen source. This fact highlighted the possibility of using this alternative nitrogen source for the A. platensis cultivation.

A produção da cianobactéria Arthrospira (Spirulina) platensis é considerada de interesse nas indústrias de alimentos, farmacêuticas e químicas. Diferentes fontes de nitrogênio alternativas têm sido sugeridas na literatura para seu cultivo, incluindo uréia e sais de amônio, visando à diminuição no custo do meio de cultivo. A perda de amônia por degasificação ocorre quando utilizados tanques abertos, justificando dessa forma o uso da associação de fontes de nitrato e de amônia em fotobiorreatores fechados. O nitrato de amônio (NH4NO3) contorna estas condições, proporcionando ao cultivo uma fonte de nitrogênio prontamente assimilável (amônio) e outra de reserva (nitrato), no mesmo composto. Neste trabalho verificou-se, pelo uso de um planejamento fatorial 22 com configuração de estrela, a influência da intensidade luminosa (I) e da adição de diferentes concentrações de NH4NO3 (mM), no crescimento e composição da biomassa de A. platensis em cultivos realizados em fotobiorreator tubular por processo descontínuo alimentado, utilizando um tempo de 6 dias alimentação para a fonte de nitrogênio. Parâmetros cinéticos de crescimento, como concentração celular máxima (Xm), produtividade em células (PX) e o fator de conversão de nitrogênio em células (YX/N), bem como o teor de proteínas e lipídios na biomassa foram avaliados. Através do uso da regressão multivariável para a otimização das condições experimentais, foram obtidos valores de Xm e de PX correspondentes a 4710 mg L-1 e 478,9 mg L-1d-1, respectivamente, pelo emprego de I = 148 µmol fótons m-2 s-1 e a adição de 9,7 mM de NH4NO3. O maior valor de YX/N registrado foi 8,1 mg mg-1, sendo superior aos obtidos com nitrato de sódio (0,80 mg mg-1). Os teores de proteína e de lipídios alcançaram valores de até 63,2 e 17,3 %, respectivamente. O emprego de NH4NO3 conduziu à redução dos custos de produção, sendo gastos em média R$ 15,97 da fonte de nitrogênio por quilograma de células, valor inferior se comparado com outras fontes usadas no cultivo de A. platensis como NaNO3 (R$ 59,10 por quilograma de células). O uso do NH4NO3 em fotobiorreator tubular mostrou-se promissor para o cultivo de A. platensis, ao proporcionar um aumento na produção de biomassa e diminuir a perda de amônia por degasificação. / The production of the cyanobacterium Arthrospira (Spirulina) platensis is considered of interest to the food, pharmaceutical and chemical industries. Alternative nitrogen sources have been suggested in literature, including urea and ammonium salts, in order to reduce the cost of cultivation medium. Ammonia off-gassing occurs when open ponds are used, thus justifying the utilization of nitrate and ammonia sources association. Ammonium nitrate (NH4NO3) attend this condition, providing the cultivation with a nitrogen source readily assimilated (ammonium) and with one of reserve (nitrate), in the same molecule. In this work, it was verified, using a 22 factorial design with star configuration, the influence of light intensity (I) and the addition of different concentrations of NH4NO3 (mM) on the growth and biomass composition of S. platensis in cultures carried out in tubular photobioreactor by fed-batch process, using a 6-day feeding time of the nitrogen source. Kinetic growth parameters, such as maximum cell concentration (Xm), cell productivity (Px) and yield of nitrogen to biomass (YX/N), as well the biomass content of protein and lipids, were evaluated. Through the use of regression analysis for the optimization of experimental conditions, values of Xm and PX such as 4710 mg L-1 and 478.9 mg L-1d-1, respectively, were obtained by the use of I = 148 µmol photons m-2 s-1 and the addition of 9.7 mM of NH4NO3. The highest value of YX/N obtained was 8.1 mg mg-1, higher than that provided by the use of sodium nitrate (0.80 mg mg-1). The levels of protein and lipid achieved up to 63.2 and 17.3 %, respectively. The use of NH4NO3 led to the reduction of culture medium costs, in which R$ 15.97 (Real/Brazil) were spent on nitrogen source per kilogram of cells, value that is lower if compared to other common sources used for A. platensis growth, such as NaNO3 (R$ 59.10 per kilogram of cells, Real/Brazil). The use of NH4NO3 in tubular photobioreactor proved to be promising for the cultivation of A. platensis, leading to an increase in biomass production and diminishing the ammonia lost by off-gassing.

The response of cucumber (Cucumis sativus L.) plants to various root and shoot environments (solution depth, temperature, ionic strength, nitrogen and calcium level and light intensity) were studied. Cucumber plants were grown in continuously circulating-solution in a heated-glasshouse. Dry weights of leaves, stems and roots, leaf area, leaf number, root length and root number were measured as well as uptake of potassium, calcium and nitrogen. The relationship between shoot and root in terms of functional equilibrium equations was also examined. The results presented show that: 1. Shoot growth of cucumber plants was reduced if grown in solutions of less than 50mm in depth; 2. When roots were grown in shallow solution depths at 1 or 5mm the dry weight allocated to the root increased. The ratio of root number/root length(no./cm) also increased. Lowering solution temperature to 12.5±2.5°C enhanced the production of root number relctive to root length, and 5 and 2% of full strength and 5% of full strength nitrogen level solution stimulated the growth of root length relative to root number; 3. Under low solution temperature treatment leaf number was maintained at the expense of leaf area. Under low total ionic strength and low nitrogen solution, enhanced root length growth was at the expense of leaf area growth; 4. Low solution temperature enhanced the dry weight allocated to the stem relative to the leaf. Low total ionic strength and low nitrogen solution increased the dry weight allocated to the leaf relative to the stem; 5. The specific activity of root, represented by specific absorption rate, increased when the shoot was under light stress and, the specific activity of shoot, represented by unit shoot rate, increased when the root was under nitrogen-stress; 6. The form of equation developed by Thornley (∆M = fm∆W, where ∆M is the increment in weight of element M and ∆W the increment in total plant dry weight during a time period ∆t with fm a constant) showed a better relationship than the equation developed by Davidson [root mass x rate(absorption) ∝ leaf mass x rate(photosynthesis)] and subsequently used by Hunt in the form of mass ratio(root/shoot) ∝ l/activity ratio; 7. The equation developed by Chung et al, total plant weight/(leaf number/leaf area) ∝ total "k"/(root number/root length), where k represents the total contents of elements or compounds, showed a good approximation of the relationship between shoot and root under all the environmental stresses imposed with the exception of calcium uptake. The results support the concept that the activity of the root or shoot in carrying out its function is influenced by the demand created by the opposite organ and appears to be a better assumption than that which proposes that the activity of an organ is solely dependent on its own size.

Methionine sulfoxide reductase A (MSRA) and MSRB are responsible for the repairing of methionine-R-sulfoxide (Met-S-SO) and methionine-S-sulfoxide (Met-R-SO) back to me-thionine, respectively. Five MSRA isoforms and four MSRB isoforms are discovered in the unicellular green alga Chlamydomonas reinhardtii. Whether high light regulates CrMSR ex-pression via photosynthetic electron transport (PET) was examined. By checking the se-quence of PCR product of each isoform, quantitative real-time primers were designed for discrimination of isoform expression. Light ≥ 300 £gE m-2 s-1 and PET inhibitors inhibited PSII activity (Fv/Fm, Fv´/Fm´) and photosynthetic O2 evolution rate, particularly 1,000 £gE m-2 s-1, in which it did not recover after 3 h. A transfer to dark decreased CrMSRA2, CrMSRA3, CrMSRB1.1, CrMSRB1.2, CrMSRB2.1 mRNA levels but increased CrMSRA4 mRNA levels. When exposed to 50, 300, 600, or 1,000 £gE m-2 s-1, CrMSRA2, CrMSRA3, CrMSRA5, CrMSRB1.1, CrMSRB2.1 and CrMSRB2.2 mRNA levels increased as light ≥ 300 £gE m-2 s-1, and concomitantly CrMSRA4 mRNA level decreased. Changes in mRNA levels increased as light intensity increased. The treatment of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) in 1,000 £gE m-2 s-1 inhibited high light effect, and the treatment of 2,5-dibromo-3-methyl-6- isopropyl-p- benzoquinone (DBMIB) in 50 £gE m-2 s-1 increased CrMSRA3, CrMSRA5 and CrMSRB2.2 mRNA levels but decreased CrMSRA4 mRNA level. The application of phena-zine methosulfate (PMS), an electron donor to P700+ that promotes cyclic electron transport, in 300 £gE m-2 s-1 enhanced the increase of CrMSRA3 and CrMSRA5 mRNA levels by high light but inhibited the decrease of CrMSRA4 mRNA level, reflecting a role of cyclic PET. The above results let us to draw a conclusion that plastoquinone as reduced status mediates the expression of CrMSRA3, CrMSRA4, CrMSRA5 and CrMSRB2.2 by high light. The im-plication of linear electron transport and cyclic electron transport on the regulation of CrMSR gene expression will be discussed.We speculated that the high light up-regulation of CrMSR mRNA expression offers the resistance of Chlamydomonas to photooxidative stress.

Microscopic green algae produce a number of beneficial substances. The commercially used ones include mainly pigments, especially secondary carotenoids. While primary carotenoids are part of the photosynthetic apparatus, secondary carotenoids are produced only under certain specific conditions (e.g. high exposure to light, nitrogen deficiency). Secondary carotenoids have antioxidant properties that protect the cell from adverse effects. The strains currently in commercial use and the strains that are tested for potential use come almost exclusively from algal collections, so this thesis focuses on strains isolated from nature. Two strains of aeroterrestrial green unicellular algae, which showed potential of producing carotenoids, were found and isolated. These strains were identified as Tetracystis pulchra (clade Dunaliellinia) and Tetracystis sp., a strain related to Tetracystis tetraspora SAG 98.80, belonging to the clade Stephanosphaerinia. The culture conditions for T. pulchra were subsequently optimized and then the culture was subjected to a series of experiments, examining the effect of stress factors on carotenoid formation and accumulation. Specifically, the effect of nitrogen starvation, light intensity, temperature and UVA radiation was tested. It has been shown that especially the light...

The response of yarrow (Achillea millefolium L.) seedlings to reduced light, interference from barley (Hordeum vulgare) and some aspects of regeneration from rhizomes were the subject of investigations from 1976 until 1980. Seedlings grown under four intensities of photosynthetically active radiation (100, 46.8, 23.7 and 6.4% of full summer daylight) were harvested on six occasions and the changes with time in the logarithms of leaf area, leaf, stem, root and total dry weights per plant were described by polynomial regression equations. Relative growth (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR) were derived directly from the growth curves. SLA and LWR increased with increased shading causing LAR to rise, while NAR declined. Response curves of RGR on light intensity, derived from linear regressions of LAR and NAR on the logarithm of relative light intensity predicted maximum RGR to occur at light intensities which decreased with time. This was a consequence of ontogenetic changes in LAR, and changes in NAR apparently related to self shading. Linear regressions of LAR and NAR at a constant total plant dry weight of 1.62 g showed that the increase in LAR almost completely compensated for the reduction in NAR down to approximately 40% full daylight, and maximum RGR was predicted to occur at 59% full daylight. The light compensation point was estimated to be 3.6% full daylight. Yarrow populations established from 25 and 50 10 cm rhizome fragments m⁻² were grown alone and with barley at 194 or 359 plants m⁻². The barley populations were also grown alone. Growth analysis employing the regression technique showed the RGR of yarrow was reduced by barley from before jointing (Feekes Scale, Stage 6) as a consequence of reduced NAR. The NAR of yarrow was significantly reduced in the continued presence of barely, which by the time of the final barely harvest resulted in 91 and 94% reduction in the accumulated yarrow dry matter at 194 and 359 barely plants m⁻² respectively. The proportion of total dry matter allocated to seed and rhizome was also reduced by barley but the barley was unaffected by the yarrow. During the autumn and early winter, after removal of the barley, the suppressed yarrow had a higher RGR than the unsuppressed population, owing to higher LAR and NAR. Rhizome growth was vigorous during both autumn and winter in all yarrow populations, but the RGR of rhizome dry matter was higher in the suppressed yarrow during the autumn. This resulted in a progressive reduction in the difference in rhizome dry matter between suppressed and unsuppressed populations. Several aspects of the development and regenerative potential of rhizomes were investigated. In the first experiment, plants were established from seed and rhizome fragments and harvested on several occasions. Plants from both propagules formed rhizomes on which approximately 97% of auxiliary buds remained dormant, as long as the plants were undisturbed. Buds on rhizomes attached to the parent plant formed rhizome branches when the apex was damaged, had emerged from the soil, or in situations where internodes were congested. In the second experiment, rhizome fragments of 4, 8 and 16 cm in length were planted in soil at depths of 0, 2.5, 5.0, 10.0, 20.0 and 30.0 cm. All fragments on the soil surface died without forming shoots owing to desiccation whilst 100% mortality at 20 and 30 cm was probably the result of flooding. Within the 2.5 to 10.0 cm range, an increasing percentage of fragments survived (produced an aerial shoot(s)) as burial depth was reduced and fragment length increased. Within this depth range, the percentage of buds which had become active on undecayed fragments declined with increased length and burial depth. In the third experiment, single-node rhizome pieces were excised from rhizomes retrieved from field populations over a one year period, and incubated at 25°C for 10 days in darkness. More than 90% of buds formed vertical shoots throughout the year, indicating there was no period of innate dormancy in isolated buds. The effect of time of planting on the pattern of early regenerative development was assessed in the fourth experiment, in which 10 cm rhizome fragments were planted at 5 cm depth in soil on two occasions (in November and April). The developmental pattern was the same regardless of month of planting and new rhizomes were initiated at nodes on the vertical subterranean shoots when 5 to 6 aerial leaves had developed. The planted rhizome fragments declined in dry weight and a minimum weight occurred at about the time when rhizome initiation began.