Amauri Alves de Alvarenga

Aspectos fisioanatômicos de plantas jovens de Cupania vernalis camb. submetidas a diferentes níveis de sombreamento

Cupania vernalis camb. (Sapindaceae) is a species commonly found in almost all forest associations, mainly in savanna-like vegetation (cerrado) and galeria woods, spreading over the states of Minas Gerais, Mato Grosso, Sao Paulo and reaching as far as Rio Grande do Sul. The species stands out mainly by its use in mixed planting to recover degraded areas of permanent preservation, for its fruits being much appreciated and consumed by birds and, still used in folk medicine against asthma and convulsive coughs. Leaf anatomy studies are highly important for the understanding of the adaptive plasticity of a species subjected to different environmental conditions, as it is correlated with processes such as gas exchanges and CO2 assimilation, as well as other processes inherent to plant growth. This work aimed to study the effect of different shading levels (full sunshine, 30%, 50% and 70%) on leaf anatomy and gas exchanges of Cupania vernalis camb plantlets. The results showed greater photosynthetic rate, increase in stomatal conductance, blade thickness, number of stomata per area and thickness of cell wall on leaves of plants grown under full sunshine and 30% shading. Positive correlations were observed between gas exchange traits and leaf anatomy. Based on these results, it is possible to conclude that the species used in this study has a great anatomic plasticity in relation to the tested shading levels, supporting in this way a better development of the seedlings under different environmental conditions.

Effects of different light levels on the initial growth and photosynthesis of croton urucurana baill. in southeastern Brazil

Four levels of shading (full sunlight (0%), 30, 50, 70% of solar radiation interception on growth, chlorophyll concentration and photosynthetic rate were studied in Croton urucurana Baill., a pioneer plant species. This species seedlings are of potential interest for reforestation projects and recovery of degraded areas. The seedlings were grown in pots containing soil and sand (2:1) and later transferred to plastic bags of 3 dm3 and submitted to different levels of shading (30, 50, 70%) of solar radiation and full sunlight, as control. The experimental design was completely randomized with five replicates and each experimental unit was composed of five plants. The results suggest that plants submitted to 70% shading showed higher dry weight accumulation in leaf and root, and higher plant height and leaf area. However, the seedlings root system showed higher dry biomass under full sunlight. It was observed a tendency to increase chlorophyll concentration and to decrease photosynthetic rate with the increase of the shading level.

Crescimento inicial de plantas de Cryptocaria aschersoniana Mez. submetidas a níveis de radiação solar

The cultivation of native essences with economical or conservacionist purpose needs a serie of cares that need some previous knowledgment of the physiological and ecologic characteristics of the diverses phases of the life cycle. The study of the growth and development of a plant under different environmental conditions offers to the researcher a good clue on which the best conditions to grow a particular species. It was aimed at to evaluate the initial growth and the concentration of chlorophylls in young plants of Cryptocaria aschersoniana Mez. (Canela-Batalha) submitted to levels of reduction of solar radiation: 0% (full sunlight), or 30, or 50 or 70%. The results demonstrate that the concentration of total chlorophyll was larger in the plants grown under 70% of shading, the same happened with the ratio of chlorophyll a/b. The greatest plant height was observed in the plants grown in 50% of shading. From the standpoint of total biomass accumulated and root dry matter, the best performance was observed in the plants under 30% of shading and the higher leaves dry matter accumulation was verified in the plants grown under 30 and 50% shading. It is ended that the best ones growing conditions for seedlings of Cryptocaria aschersoniana Mez. (Canela-Batalha) were the levels of 30 and 50% of reduction of the incident solar radiation.

Anatomia foliar de plantas de alfavaca-cravo cultivadas sob malhas coloridas

In the present research, the effect of spectral control of light was evaluated on anatomical characteristics of Ocimum gratissimum L. leaves. The plants were cultivated during four months under black, red and blue nets with 50% of shade, and full sunlight. Plants grown under full sunlight showed higher leaf thickness, higher stomatal density and higher density of no-glandular and glandular trichomes on the adaxial epidermis. Plants cultivated under colored nets did not show differences in leaf thickness or leaf area. Plants maintained under red net had the lowest stomatal density in adaxial epidermis, as the plants cultivated under blue and red nets exhibited the largest leaf area. The plants maintained under red net showed the smallest stomatal density and the smallest non-glandular and glandular trichomes density in the adaxial epidermis. Such results show that the spectral quality and intensity of light can be modulated during the cultivation of Ocimum gratissimum L. plants in order to obtain desirable anatomical characteristics.

Anatomia foliar de Tabebuia serratifolia (Vahl) Nich. (Bignoniaceae) propagadas in vitro, in vivo e durante a aclimatização

As mudas propagadas por tecnicas de micropropagacao geralmente apresentam alteracoes significativas induzidas pelas condicoes in vitro, que diminuem a capacidade de sobrevivencia apos a transferencia para o ambiente ex vitro, sendo fundamental a avaliacao da mudanca estrutural durante o processo de adaptacao. Objetivou-se com este trabalho, identificar as diferencas anatomicas foliares entre plantas de Tabebuia serratifolia (Vahl) Nich. (ipe amarelo), cultivadas in vitro, in vivo e durante a aclimatizacao. Foram utilizadas plântulas mantidas por 43 dias em sala de crescimento, com 20, 40, 60 e 80 dias de aclimatizacao e mudas de 90 dias cultivadas em viveiro. As plântulas foram obtidas via cultura de embrioes em meio MS e transplantadas para tubetes contendo plantmax®, para aclimatizacao em viveiro, sob 50% de sombreamento. Nas mesmas condicoes da aclimatizacao, foram produzidas as mudas in vivo. Cortes transversais e paradermicos foram preparados de acordo com tecnicas usuais em microtecnia vegetal. As plântulas in vitro apresentam os tecidos foliares pouco diferenciados e estomatos maiores e mais abertos, exigindo maiores cuidados na etapa inicial de aclimatizacao. Aos 60 dias de aclimatizacao as novas folhas produzidas possuem alguns aspectos anatomicos que podem conferir maior eficiencia fotossintetica e maior capacidade de regulacao hidrica das plantas.

Germinação in vitro de murici-pequeno (Byrsonima intermedia A. Juss.)

ABSTRACT The murici-pequeno ( Byrsonima intermedia A. Juss.) is a medicinal plant of cerrado that presents difficulties of sexual propagation due to a low rate of seed germination and plant emergency in the field. The objective of this work was study aspects of the in vitro germination of murici-pequeno evaluating the effects of MS and WPM culture media and different concentrations of BAP. Mature fruits were collected from native plants and their seeds and embryos excised and used as explants. The results indicated that the most effective culture media used for the in vitro seed and embryo germination were MS and WPM 50%, both with no sucrose, presenting 60 and 100% germination, respectively. The use of BAP is not required for in vitro embryo germination. Index terms: Germination in vitro , murici-pequeno, medicinal plant, Byrsonima intermedia . (Recebido para publicacao em 23 de outubro de 2003 e aprovado em 13 de agosto de 2004) INTRODUCAO Sao poucos os estudos sobre a germinacao de especies nativas do Cerrado. Com o crescente interesse por parte dos pesquisadores, aos poucos se revela o po-tencial dessa vegetacao (COELHO, 1999). No caso do murici-pequeno (

Germinação de sementes de tanchagem (Plantago tomentosa Lam.): influência da temperatura, luz e substrato

Plantago tomentosa Lam. (Plantaginaceae) e usada na medicina popular como agente anti-tumoral, antimicrobiana e antinflamatoria. Sua propagacao ocorre por meio de sementes, cuja germinacao tem sido pouco investigada. Dessa forma, o presente trabalho teve como objetivo verificar a influencia da luz, temperaturas e substratos sobre a porcentagem total de germinacao/emergencia e indice de velocidade de germinacao/emergencia. Foram testadas diferentes temperaturas (15, 20, 25, 30 e 35°C constantes e, 15-25°C e 20-30°C alternadas) na ausencia e presenca de luz constante. Os substratos testados foram areia, terra de subsolo, vermiculita e Plantmax®, alem da combinacao de terra de subsolo com os demais, na proporcao de 1:1. Pelos resultados obtidos, concluiu-se que as sementes de tanchagem apresentam comportamento fotoblastico positivo, independente da temperatura testada. A temperatura alternada de 15-25°C e 15 e 20°C constantes garantem melhor expressao do vigor. O substrato areia e recomendado para o estudo da emergencia.

Aspectos anatômicos e fisiológicos de plantas de guaco submetidas a diferentes fotoperíodos

Guaco (Mikania glomerata Sprengel) is a medicinal species known because of its bronchi-dilating activity. Many studies have indicated changes in anatomical and physiological characteristics of medicinal plants when submitted to different conditions of light. The effect of photoperiods (8; 12; 16 and 20 h) on leaf anatomy, content of chlorophyll and stomatal conductance in distinct regions of guaco plants were analyzed. Adult plants of different sizes influenced by distinct photoperiods were submitted to anatomical and physiological analyses. 90 days after starting photoperiod treatments the chlorophyll content was higher in plants submitted to photoperiods of 8 and 12 hours in the superior and intermediary regions of plant, decreasing at 8 h of photoperiod treatment in the basal region of the plants. The conductance and stomatal density presented inverse relation to increase of photoperiod, decreasing from apical to basal regions of the plants. The thickness of the superior epidermis increased in the intermediary and basal regions of the plants submitted to a photoperiod up to 16 h. These regions presented a progressive increase of the lacunose parenchyma thickness under a photoperiod up to 20 h. The size and organization of the vascular bundles were influenced by the photoperiods.

Superação de dormência em sementes de Zeyheria montana Mart.

Zeyheria montana Mart. (Bignoniaceae) e uma especie medicinal conhecida como bolsa de pastor que se encontra com risco de extincao, sendo fundamental o desenvolvimento de metodologias para sua propagacao e preservacao. Neste estudo, avaliou-se a porcentagem de germinacao e o indice de velocidade de germinacao de sementes de bolsa de pastor submetidas a diferentes metodos de superacao de dormencia: lavagem por diferentes periodos, retirada total e parcial da expansao alada, combinacao de lavagem com retirada parcial da expansao alada e imersao em acido cloridrico e sulfurico, em diferentes concentracoes. Como testemunha, utilizaram-se sementes intactas. O experimento foi conduzido em câmara de germinacao do tipo BOD, temperatura de 25°C, fotoperiodo de 12 horas e 100% de UR. Sementes submetidas a lavagem em agua corrente por 6 horas, com a retirada parcial da expansao alada, tiveram vigor e porcentagens de germinacao superiores aos outros tratamentos. Os resultados demonstram que a causa de dormencia em sementes dessa especie e complexa, sendo causada por interferencia no alongamento embrionario e possivel presenca de inibidores.

Taxa de multiplicação e efeito residual de diferentes fontes de citocinina no cultivo in vitro de Hancornia speciosa Gomes

A mangabeira destaca-se por possuir um grande potencial como planta frutifera. Suas sementes apresentam recalcitrância, dificultando sua propagacao, o que torna evidente a necessidade da obtencao de mudas por via assexuada. Neste contexto, a cultura de tecidos apresenta-se como uma alternativa a ser utilizada. Entre os fatores que afetam a morfogenese in vitro, as citocininas merecem destaque, pois influenciam na diferenciacao de gemas e no crescimento das brotacoes. Assim sendo, avaliou-se, neste trabalho, a influencia de tres diferentes fontes de citocinina (6-benzilaminopurina BAP, cinetina CIN e thidiazuron TDZ) na inducao de brotacoes in vitro de mangabeira, bem como o efeito residual dessa classe de reguladores no enraizamento e na multiplicacao em subcultivos sucessivos. Os resultados mostraram que, entre as citocininas testadas, a 6-benzilaminopurina foi a que induziu maior numero de brotacoes (1,98), gemas (19,22) e folhas (18,86) por explante, tendo promovido a formacao de brotos de maior comprimento (4,55 cm). As brotacoes oriundas de meio WPM basal apresentaram maior facilidade de enraizamento. A 6-benzilaminopurina foi responsavel pela maior taxa de multiplicacao (9,61) de brotacoes de mangabeira. Os subcultivos sucessivos diminuiram a capacidade de multiplicacao de explantes caulinares da especie.