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There is a great deal of work currently being done in the field of desiccation tolerance. Generally workers studying desiccation-tolerant plant tissues have concentrated on the mechanisms of desiccation tolerance without concomitant studies on why most plants cannot survive desiccation. The present study considers both a desiccation-tolerant plant as well as a range of desiccation-sensitive plants. The work incorporates physiological, biophysical, biochemical and ultrastructural studies in an attempt to get a holistic picture of vegetative material as it dries and then rehydrates. The plant species used in this study are: Craterostigma nanum, a so-called resurrection plant; Garcinia livingstonei, a drought-tolerant small tree; Isoglossa woodii, an understorey shrub which shows a remarkable ability to recover from wilting; Pisum sativum seedlings, which have a very high water content at full turgor; and finally, Adiantum raddianum, the maiden hair fern, which wilts very quickly and does not recover from wilting. The desiccation-tolerant plant, C. nanum, had an unusual pressure-volume (PV) curve which indicated that while large volume changes were taking place there was little concomitant change in pressure or water potential. The unusual nature of this PV curve made it difficult to assess the relative water content (RWC) at which turgor was lost. The desiccation-sensitive plants exhibited standard curvi-linear PV curves. The amount of nonfreezable water in the five species was studied and found to show no correlation with the ability to withstand dehydration or with the lethal water content. There were no differences in the melting enthalpy of tissue water between the tolerant and most of the sensitive plants. Isoglossa woodii had a lower melting enthalpy than the tolerant and the other sensitive species. Survival studies showed that the desiccation-sensitive plants all had similar lethal RWCs. The tolerant plant survived dehydration to as low as 1% RWC, recovering on rehydration within 24 hours. Membrane leakage studies showed that the sensitive plants all exhibited membrane damage at different absolute water contents, but very similar RWCs and water potentials. The increase in leakage corresponded to the lethal RWC for all the sensitive species. The desiccation-tolerant plant recovered from dehydration to very low water contents and did not show an increase in membrane leakage if prior rehydration had taken place. Without prior rehydration this tolerant plant exhibited an increase in leakage at similar RWCs and water potentials to that of the sensitive species. There did not appear to be much difference in the RWC at which damage to membranes occurred whether the material was dried rapidly or slowly. Respiration and chlorophyll fluorescence were studied to determine what effect drying and rehydration have on the electron transport· processes of the leaf. The chlorophyll fluorescence studies gave an indication of damage to the photosynthetic apparatus. Both qualitative changes as well as quantitative changes in fluorescence parameters were assessed. Characteristics like quantum efficiency (Fv/Fm)remained fairly constant for a wide range of RWCs until a critical RWC was reached where there was a sharp decline in Fv/Fm. Upon rehydration, C. nanum recovered to pre-stress levels, I. woodii showed no recovery and no further damage on rehydration, whilst the other species exhibited even more damage on rehydration than they had on dehydration. Respiration remained fairly constant or increased slightly during drying until a critical RWC was reached at which it suddenly declined. The RWC at which this decline occurred ranged from 15% and 20% in P. sativum and C. nanum respectively, to 50% for G. livingstonei. On rehydration respiration exceeded the levels measured in dehydrated material for the sensitive species. Unsuccessful attempts were made to fix material anhydrously for ultrastructural studies so standard fIxation was used. The ultrastructural studies revealed that changes had occurred in the ultrastructure of leaves of the sensitive species dried to 30% RWC particularly in A. raddianum and P. sativum. Drying to 5% RWC revealed extensive ultrastructural degradation which was worsened on rehydration in the sensitive species. The tolerant species showed ultrastructural changes on drying but these were not as severe as occurred in the sensitive species. The cell walls of the tolerant species folded in on drying. This folding was possibly responsible for the unusual PV curves found in this species. At 5% RWC the cells were closely packed and very irregular in shape. The cell contents were clearly resolved and evenly spread throughout the cell. The large central vacuole appeared to have subdivided into a number of smaller vacuoles. On rehydration the cells regained their shape and the cell contents had moved towards the periphery as the large central vacuole was reformed. Beading of membranes, which was common in the sensitive species, was not found in the tolerant species suggesting that membrane damage was not as severe in the tolerant species. Western Blot analysis of the proteins present during drying was performed to determine whether a class of desiccation-induced proteins, called dehydrins, were present. These proteins have been suggested to play a protective role in desiccation-tolerant tissue. It was found that C. nanum did, in fact, possess dehydrins, but so did P. sativum. The other three sensitive species did not show any appreciable levels of dehydrin proteins. The presence of dehydrins alone is, therefore, not sufficient to confer desiccation tolerance. While physiologically the damage occurring in the sensitive plants was similar to that of the tolerant plant, at an ultrastructural level the damage appeared less in the tolerant plant. On rehydration from low RWCs damage appeared to become exacerbated in the sensitive plants. This was in contrast to the tolerant plant where damage was apparently repaired. There appears, therefore, to be a combination of protection and repair mechanisms responsible for the ability of C. nanum to tolerate desiccation. The lethal RWC of the sensitive species was higher than that at which protective mechanisms, such as water replacement, might come into play. So it is not just the possible ability to replace tightly bound water that set the tolerant plant aside. It must also have mechanisms to tolerate damage at the higher RWCs which were damaging and lethal to the sensitive plants. The lethal damage to sensitive species appeared to be related to a critical volume, thus it is concluded that the tolerant plant had the ability to tolerate or avoid this mechanical damage during drying as well as the ability to remain viable in the dry state. It is hypothesised that the ability of the walls to fold in and the unusual nature of the PV curve may provide some answers to the enigma of desiccation tolerance. / Thesis (Ph.D.)-University of Natal, 1995.

Densitometric, volumetric and paper-making traits of provenances of Pinus caribaea Morelet, P. oocarpa Schiede and P. patula SchiedeariclDeppe ssp. tecunumanii (Eguiluz and Perry) Styles were evaluated. Provenance mean values of densitometric density (DEN) and within tree density variation (VAR) were significantly different (p<0.05) at seven of the fourteen P.caribaea and at one of the seven of P. oocarpa and P. patula ssp. tecunumanii trials. Provenance mean valuesor volume under bark (VUB)and dry matter index (DMI) were significantly (p<0.05) different at all of the P. caribaea and at five of the P. oocarpa and P. patula ssp. tecunumanii trials. The inland provenances of P. caribaea were generally Higher for DEN and VAR than the coastal provenances, he Camelias, Mountain Pine Ridge, Rafael and Yucul provenances of P. patula ssp. tecunumanii were superior to P. oocarpa provenances for VUB and DMI in all of these trials and were superior to P. caribaea at two sites where the species were growing under similar conditions. Evaluation of densitometric races revealed large differences between species, provenances and sites for the width and density of latewood; this could explain much of the variation in VAR between these sources. The analysis of variance was used to assess genotype by environment interaction of DEN and VAR from eleven provenances of P. caribaea var. hondurensis Barrett and Golfari at eleven sites and from five provenances of P. oocarpa and four provenances of P. patula ssp. tecunumanii at sfx sites. Sites and provenances were significantly different for DEN and VAR in both series of trials out the site by provenance term was not statistically significant in either. Indications were that P. caribaea would be expected to have lower values of DEN and VAR at higher altitude. Provenances of P. oocarpa and P. patula ssp. tecunumanii were lower for VAR at sites of lower latitude but there were no individual site factors which could be correlated with DEN in these provenances. The comparison of full-scale pulping with micropulping of small wood samples from felled trees of six pine species in the Eastern Transvaal, South Africa, revealed positive and significant correlations for the pulp yield and paper strength traits. The correlation of tear index and VAR in these trees was positive and significant. Evaluation and analyses of a number of pine species and provenances by micropulping of cores from standing trees revealed significant differences for certain of the paper strength traits. The Caftas provenance of P. oocarpa was unusual in having high values for both tear index and burst index when grown in Zululand. Similar conclusions were reached for provenances of P. patula ssp. tecunumanii grown in the Eastern Transvaal. The conclusions of this thesis were: 1. Site climatic factors did not affect DEN and VAR of the different species and provenances in the same way; 2. The VAR term varied as a result of site, species and provenance; 3. There was no genotype by environment interaction for DEN«*rJ VAR; 4. The correlation of VAR with pulp and paper-making traits indicated that trees with high VAR were superior for tear index to trees with low VAR; 5. Micropulping of small wood samples could be used to assess the paper-making traits of individual trees.

A Cryptomeria japonica D. Don. "elegans" é uma conífera pertencente à família Taxodiaceae, que apresenta crescimento rápido e boas respostas à fertilização. Dez variações nas concentrações de nitrato e amônio presentes no meio de cultura MS foram realizadas no cultivo 'in vitro' de brotações obtidas a partir de explantes primários de ápices caulinares durante 90 dias. A cada 30 dias foram avaliados, a taxa de crescimento relativo e o incremento em massa vegetal seca. Ao final de 90 dias, foram realizadas análises dos teores de proteínas solúveis totais, aminoácidos solúveis totais, carboidratos não-estruturais totais e eletroforese de proteínas totais em gel de poliacrilamida. Os tratamentos que exibiram resultados mais satisfatórios foram utilizados em um experimento com diferentes relações auxina/citocinina, onde foram avaliadas a produção de brotações e a altura média das mesmas aos 30, 60 e 90 dias de cultivo. As concentrações de nitrato e amônio entre 25 e 31mmol.L -1 e até 5mmol.L -1, respectivamente, foram as mais efetivas para o crescimento e desenvolvimento do material vegetal cultivado 'in vitro'. Durante o experimento com diferentes concentrações de ANA e BAP, foi possível observar que a produção de brotações, etapa essecial para um processo de micropropagação eficiente, foi superior quando as combinações entre nitrato e amônio foram 22,5 + 2,5mmol.L -1 e 25,0 + 5,0mmol.L -1. / Cryptomeria japonica D. Don. "elegans" is a fast-growing tree belonging to the Taxodiaceae and it is considered a responsive species 'in vitro'. The aim of this work was to evaluate the effect of ten different concentrations of nitrate and ammonium in morphogenesis 'in vitro' of Cryptomeria japonica D. Don. "elegans" explants. Analysis of relative growth rate, total soluble proteins, total soluble aminoacids, total non structural carbohydrates and electrophoresis of total proteins was performed in order to observe the role of different nitrogen sources on the growth and development of the explants cultivated 'in vitro'. The concentratios of nitrate and ammonium that showed the best results were selected and used in an experiment with different concentrations of NAA and BAP to observe the shoot production. Each experiment was analised at the 30 th , 60 th and 90 th days of culture. The biochemical analysis was performed only at 90 th day of cultive. Concentrations from 26 to 31mmol.L -1 of NO3 - and lower than 5mmol.L -1 of NH4 + were the most effective for growth and development of the explants. However, the experiment with different concentrations of NNA and BAP showed that the best shoot production was achieved on 22,5mmol.L -1 of NO3- + 2,5mmol.L -1 of NH4 + and on 25,0mmol.L -1 of NO3 - + 5,0mmol.L -1 of NH4 + and with 2,0mg.L -1 of BAP + 1,0mg.L -1 of NNA.

As áreas de pastagens no Brasil ocupam cerca de 180 milhões de hectares, que são responsáveis por cerca de 90% da carne bovina produzida no país. No entanto, em torno de 80% das pastagens cultivadas apresentam algum grau de degradação, sendo este apontado como o maior problema relacionado com a sustentabilidade da produção animal em pastagens. Uma das principais razões para esse fato está relacionada a erros grosseiros no manejo das pastagens, conseqüência do desconhecimento dos limites ecofisiológicos e de resistência ao pastejo das plantas forrageiras. Dentro desse contexto, o objetivo deste experimento foi determinar quantitativamente o índice de área foliar, os teores e estoques de carboidratos não estruturais e frações nitrogenadas (N total, N solúvel, N aminoácidos, N amônio, N nitrato) de reserva, a taxa de acúmulo e a produção de forragem em pastos de Brachiaria brizantha cv. Marandu pastejados por bovinos em regime de lotação contínua e taxa de lotação variável. O experimento foi realizado em área do Departamento de Produção Animal da USP/ESALQ, em Piracicaba, SP, entre 27 de agosto de 2001 e 28 de fevereiro de 2002. Os tratamentos corresponderam a quatro alturas de pasto (10, 20, 30 e 40 cm), mantidas em steady state, e foram alocados às unidades experimentais conforme um delineamento de blocos completos casualizados, com quatro repetições. Os valores de IAF (1,7; 3,5; 4,0 e 3,8) foram crescentes para as alturas de pasto estudadas (10, 20, 30 e 40 cm, respectivamente) e semelhantes para as alturas de 20, 30 e 40 cm. Comportamento semelhante foi identificado para as taxas de acúmulo (102,0; 118,5; 121,6 e 113,9 kg ha -1 dia -1 MS) e acúmulo total de forragem (10.300; 13.340; 12.620 e 13.880 kg ha -1 ). Os teores (88,5; 111,7; 109,8 e 118,4 g kg -1 ) e estoques (0,152; 0,167; 0,180 e 0,157 kg m -2 ) de carboidratos não estruturais foram crescentes com as alturas de pasto (10, 20, 30 e 40 cm, respectivamente), ao passo que o inverso foi detectado para os teores e estoques de todas as frações nitrogenadas (10,65; 8,93; 8,64; 8,04 g kg -1 N total e 0,018; 0,017; 0,014; 0,012 kg m -2 N total, respectivamente). Com relação ao meses, houve uma redução acentuada ao longo do período experimental nos teores (118,8 para 87,2 g kg -1 de setembro a fevereiro) e estoques (0,225 para 0,111 kg m -2 de setembro a fevereiro) de carboidratos não estruturais e, também nos teores e estoques correspondentes às frações nitrogenadas (12,76 para 3,98 g kg -1 N total e 0,031 para 0,005 kg m -2 N total de setembro a fevereiro), motivadas inicialmente pelo início do verão (estação de crescimento) e posteriormente pelo início do desenvolvimento reprodutivo das plantas. Os estoques de carboidratos e de frações nitrogenadas foram consistentemente maiores para a base do colmo relativamente às raízes, tendo sido utilizados como fonte preferencial de matéria prima para o crescimento das plantas, razão pela qual sofreram as maiores reduções ao longo do tempo. As inflorescências se mostraram drenos metabólicos muito fortes durante a fase reprodutiva, assim como os meristemas apicais durante a fase vegetativa. O teor de N total nas folhas dos perfilhos diminuiu com o tempo (17,4 para 13,1 g kg -1 de dezembro a fevereiro), sendo os valores crescentes para folhas senescentes, maduras e em expansão (11,4, 14,0 e 16,7 g kg -1 , respectivamente). A altura de pasto de 10 cm correspondeu a uma condição de desfolha drástica, de modo que o manejo do pastejo deveria ser efetuado entre as condições de pasto de 20 e 40 cm. A escolha da condição de pasto mais indicada deve ser feita mediante o objetivo da atividade e a natureza da exploração animal proposta. / Grassland areas in Brazil occupy around 180 million hectares and support about 90% of the country’s beef production. However, approximately 80% of the cultivated pasture areas present some degree of degradation, that being the main problem related to the sustainability of pasture-based animal production systems. One of the main reasons for this is the mismanagement of pastures, consequence of the lack of knowledge and understanding about the ecophysiological limits and tolerance to grazing of forage plants. Against this background, the objective of this experiment was to determine the leaf area index (LAI), concentrations and pools of non structural carbohydrates (NSC) and nitrogenous reserve compounds (total N, soluble N, amino acid N, ammonium N, nitrate N), herbage dry matter accumulation rates and forage yield from Brachiaria brizantha cv. Marandu pastures continuously stocked by cattle, with variable stocking rate. The experiment was carried out at Departamento de Produção Animal, USP/ESALQ, Piracicaba, SP, from 27 August 2001 until 28 February 2002. Treatments corresponded to four steady state conditions characterized by sward surface heights (SSH) of 10, 20, 30 and 40 cm, assigned to experimental units according to a complete randomized block design, with four replications. LAI values (1.7, 3.5, 4.0 and 3.8) increased with increasing SSH (10, 20, 30 and 40 cm, respectively) and were not different among the 20, 30 and 40 cm treatments. Similar trend was recorded for herbage accumulation rates (102.0, 118.5, 121.6 and 113.9 kg ha -1 ) and forage yield (10,300, 13,340, 12,620 and 13,880 kg ha -1 ). The concentration (88.5, 111.7, 109.8 and 118.4 g kg -1 ) and pool (0.152, 0.167, 0.180 and 0.157 kg m -2 ) of NSC increased with increasing SSH (10, 20, 30 and 40 cm, respectively), whereas the inverse occurred with the concentration and pool of all nitrogenous compounds (10.65, 8.93, 8.64 and 8.04 g kg -1 total N and 0.018, 0.017, 0.014 and 0.012 kg m -2 total N, respectively). In relation to time of the year, there was a sharp decrease in the concentration and pool of NSC throughout the experimental period (118.8 to 87.2 g kg -1 and 0.225 to 0.111 kg m -2 , respectively, from September to February) as well as in the concentration and pool of all nitrogenous compounds (12.76 to 3.98 g kg -1 total N and 0.031 to 0.005 kg m -2 total N, respectively, from September to February), initially motivated by the commencement of summer (growing season) and followed by the beginning of reproductive development of plants. Pools of NSC and all nitrogenous compounds stored in stem base were consistently higher than those stored in roots and comprised the prime source of substances for plant growth, that being the reason for presenting the greatest reductions throughout the experimental period. Reproductive stems proved to be very strong metabolic drains during the reproductive phase of plant development as well as tiller growing points during the vegetative phase. The total N concentration in tiller leaves decreased with time (17.4 to 13.1 g kg -1 from December to February), with values increasing for senescent, mature and elongating leaves (11.4, 14.0 and 16.7 g kg -1 , respectively). The 10 cm SSH corresponded to a drastic defoliation condition, indicating that grazing management should be conducted within the 20 to 40 cm SSH range. The choice of the most appropriate SSH condition must take into account the main objective and nature of the animal production system proposed.

As áreas de pastagens no Brasil ocupam cerca de 180 milhões de hectares, que são responsáveis por cerca de 90% da carne bovina produzida no país. No entanto, em torno de 80% das pastagens cultivadas apresentam algum grau de degradação, sendo este apontado como o maior problema relacionado com a sustentabilidade da produção animal em pastagens. Uma das principais razões para esse fato está relacionada a erros grosseiros no manejo das pastagens, conseqüência do desconhecimento dos limites ecofisiológicos e de resistência ao pastejo das plantas forrageiras. Dentro desse contexto, o objetivo deste experimento foi determinar quantitativamente o índice de área foliar, os teores e estoques de carboidratos não estruturais e frações nitrogenadas (N total, N solúvel, N aminoácidos, N amônio, N nitrato) de reserva, a taxa de acúmulo e a produção de forragem em pastos de Brachiaria brizantha cv. Marandu pastejados por bovinos em regime de lotação contínua e taxa de lotação variável. O experimento foi realizado em área do Departamento de Produção Animal da USP/ESALQ, em Piracicaba, SP, entre 27 de agosto de 2001 e 28 de fevereiro de 2002. Os tratamentos corresponderam a quatro alturas de pasto (10, 20, 30 e 40 cm), mantidas em steady state, e foram alocados às unidades experimentais conforme um delineamento de blocos completos casualizados, com quatro repetições. Os valores de IAF (1,7; 3,5; 4,0 e 3,8) foram crescentes para as alturas de pasto estudadas (10, 20, 30 e 40 cm, respectivamente) e semelhantes para as alturas de 20, 30 e 40 cm. Comportamento semelhante foi identificado para as taxas de acúmulo (102,0; 118,5; 121,6 e 113,9 kg ha -1 dia -1 MS) e acúmulo total de forragem (10.300; 13.340; 12.620 e 13.880 kg ha -1 ). Os teores (88,5; 111,7; 109,8 e 118,4 g kg -1 ) e estoques (0,152; 0,167; 0,180 e 0,157 kg m -2 ) de carboidratos não estruturais foram crescentes com as alturas de pasto (10, 20, 30 e 40 cm, respectivamente), ao passo que o inverso foi detectado para os teores e estoques de todas as frações nitrogenadas (10,65; 8,93; 8,64; 8,04 g kg -1 N total e 0,018; 0,017; 0,014; 0,012 kg m -2 N total, respectivamente). Com relação ao meses, houve uma redução acentuada ao longo do período experimental nos teores (118,8 para 87,2 g kg -1 de setembro a fevereiro) e estoques (0,225 para 0,111 kg m -2 de setembro a fevereiro) de carboidratos não estruturais e, também nos teores e estoques correspondentes às frações nitrogenadas (12,76 para 3,98 g kg -1 N total e 0,031 para 0,005 kg m -2 N total de setembro a fevereiro), motivadas inicialmente pelo início do verão (estação de crescimento) e posteriormente pelo início do desenvolvimento reprodutivo das plantas. Os estoques de carboidratos e de frações nitrogenadas foram consistentemente maiores para a base do colmo relativamente às raízes, tendo sido utilizados como fonte preferencial de matéria prima para o crescimento das plantas, razão pela qual sofreram as maiores reduções ao longo do tempo. As inflorescências se mostraram drenos metabólicos muito fortes durante a fase reprodutiva, assim como os meristemas apicais durante a fase vegetativa. O teor de N total nas folhas dos perfilhos diminuiu com o tempo (17,4 para 13,1 g kg -1 de dezembro a fevereiro), sendo os valores crescentes para folhas senescentes, maduras e em expansão (11,4, 14,0 e 16,7 g kg -1 , respectivamente). A altura de pasto de 10 cm correspondeu a uma condição de desfolha drástica, de modo que o manejo do pastejo deveria ser efetuado entre as condições de pasto de 20 e 40 cm. A escolha da condição de pasto mais indicada deve ser feita mediante o objetivo da atividade e a natureza da exploração animal proposta. / Grassland areas in Brazil occupy around 180 million hectares and support about 90% of the country’s beef production. However, approximately 80% of the cultivated pasture areas present some degree of degradation, that being the main problem related to the sustainability of pasture-based animal production systems. One of the main reasons for this is the mismanagement of pastures, consequence of the lack of knowledge and understanding about the ecophysiological limits and tolerance to grazing of forage plants. Against this background, the objective of this experiment was to determine the leaf area index (LAI), concentrations and pools of non structural carbohydrates (NSC) and nitrogenous reserve compounds (total N, soluble N, amino acid N, ammonium N, nitrate N), herbage dry matter accumulation rates and forage yield from Brachiaria brizantha cv. Marandu pastures continuously stocked by cattle, with variable stocking rate. The experiment was carried out at Departamento de Produção Animal, USP/ESALQ, Piracicaba, SP, from 27 August 2001 until 28 February 2002. Treatments corresponded to four steady state conditions characterized by sward surface heights (SSH) of 10, 20, 30 and 40 cm, assigned to experimental units according to a complete randomized block design, with four replications. LAI values (1.7, 3.5, 4.0 and 3.8) increased with increasing SSH (10, 20, 30 and 40 cm, respectively) and were not different among the 20, 30 and 40 cm treatments. Similar trend was recorded for herbage accumulation rates (102.0, 118.5, 121.6 and 113.9 kg ha -1 ) and forage yield (10,300, 13,340, 12,620 and 13,880 kg ha -1 ). The concentration (88.5, 111.7, 109.8 and 118.4 g kg -1 ) and pool (0.152, 0.167, 0.180 and 0.157 kg m -2 ) of NSC increased with increasing SSH (10, 20, 30 and 40 cm, respectively), whereas the inverse occurred with the concentration and pool of all nitrogenous compounds (10.65, 8.93, 8.64 and 8.04 g kg -1 total N and 0.018, 0.017, 0.014 and 0.012 kg m -2 total N, respectively). In relation to time of the year, there was a sharp decrease in the concentration and pool of NSC throughout the experimental period (118.8 to 87.2 g kg -1 and 0.225 to 0.111 kg m -2 , respectively, from September to February) as well as in the concentration and pool of all nitrogenous compounds (12.76 to 3.98 g kg -1 total N and 0.031 to 0.005 kg m -2 total N, respectively, from September to February), initially motivated by the commencement of summer (growing season) and followed by the beginning of reproductive development of plants. Pools of NSC and all nitrogenous compounds stored in stem base were consistently higher than those stored in roots and comprised the prime source of substances for plant growth, that being the reason for presenting the greatest reductions throughout the experimental period. Reproductive stems proved to be very strong metabolic drains during the reproductive phase of plant development as well as tiller growing points during the vegetative phase. The total N concentration in tiller leaves decreased with time (17.4 to 13.1 g kg -1 from December to February), with values increasing for senescent, mature and elongating leaves (11.4, 14.0 and 16.7 g kg -1 , respectively). The 10 cm SSH corresponded to a drastic defoliation condition, indicating that grazing management should be conducted within the 20 to 40 cm SSH range. The choice of the most appropriate SSH condition must take into account the main objective and nature of the animal production system proposed.

A Cryptomeria japonica D. Don. "elegans" é uma conífera pertencente à família Taxodiaceae, que apresenta crescimento rápido e boas respostas à fertilização. Dez variações nas concentrações de nitrato e amônio presentes no meio de cultura MS foram realizadas no cultivo 'in vitro' de brotações obtidas a partir de explantes primários de ápices caulinares durante 90 dias. A cada 30 dias foram avaliados, a taxa de crescimento relativo e o incremento em massa vegetal seca. Ao final de 90 dias, foram realizadas análises dos teores de proteínas solúveis totais, aminoácidos solúveis totais, carboidratos não-estruturais totais e eletroforese de proteínas totais em gel de poliacrilamida. Os tratamentos que exibiram resultados mais satisfatórios foram utilizados em um experimento com diferentes relações auxina/citocinina, onde foram avaliadas a produção de brotações e a altura média das mesmas aos 30, 60 e 90 dias de cultivo. As concentrações de nitrato e amônio entre 25 e 31mmol.L -1 e até 5mmol.L -1, respectivamente, foram as mais efetivas para o crescimento e desenvolvimento do material vegetal cultivado 'in vitro'. Durante o experimento com diferentes concentrações de ANA e BAP, foi possível observar que a produção de brotações, etapa essecial para um processo de micropropagação eficiente, foi superior quando as combinações entre nitrato e amônio foram 22,5 + 2,5mmol.L -1 e 25,0 + 5,0mmol.L -1. / Cryptomeria japonica D. Don. "elegans" is a fast-growing tree belonging to the Taxodiaceae and it is considered a responsive species 'in vitro'. The aim of this work was to evaluate the effect of ten different concentrations of nitrate and ammonium in morphogenesis 'in vitro' of Cryptomeria japonica D. Don. "elegans" explants. Analysis of relative growth rate, total soluble proteins, total soluble aminoacids, total non structural carbohydrates and electrophoresis of total proteins was performed in order to observe the role of different nitrogen sources on the growth and development of the explants cultivated 'in vitro'. The concentratios of nitrate and ammonium that showed the best results were selected and used in an experiment with different concentrations of NAA and BAP to observe the shoot production. Each experiment was analised at the 30 th , 60 th and 90 th days of culture. The biochemical analysis was performed only at 90 th day of cultive. Concentrations from 26 to 31mmol.L -1 of NO3 - and lower than 5mmol.L -1 of NH4 + were the most effective for growth and development of the explants. However, the experiment with different concentrations of NNA and BAP showed that the best shoot production was achieved on 22,5mmol.L -1 of NO3- + 2,5mmol.L -1 of NH4 + and on 25,0mmol.L -1 of NO3 - + 5,0mmol.L -1 of NH4 + and with 2,0mg.L -1 of BAP + 1,0mg.L -1 of NNA.