João Paulo Rodrigues Alves Delfino Barbosa

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.

Trocas gasosas de cafeeiros (Coffea arabica L.) e seringueiras (Hevea brasiliensis Muell. Arg.) em diferentes sistemas de cultivo na região de larvas, MG

Crop systems that improve conservation of natural resources and diversity of production is a promising practice for farmers seeking low costs and a sustainable agriculture. The coffee - rubber tree intercropping has been studied in the south of Minas Gerais - Brazil. Within this context, the objective of this work was to evaluate the characteristics gas exchange, chlorophyll fluorescence and water relations of coffee and rubber tree in both intercropping and monocroping systems, in the early stage of the plantation establishment. The results showed that the reduction in radiation levels and temperature promote gas exchange increase in coffee, while higher photosynthetic radiation values and soil water availability are favorable to rubber tree in intercropping systems.

Stomatal density distribution patterns in leaves of the Jatobá (Hymenaea courbaril L.)

Stomata are leaf structures that are essential for regulating gas exchange and water balance in terrestrial plants. Accurately quantifying stomatal characteristics is consequently of great importance for understanding the physiological processes of plants under different environmental conditions. The objective of this study was to investigate the spatial distribution pattern of stomata on leaflet surfaces, and the possible mechanisms that influence this pattern, particularly leaf expansion. To achieve this, we used geostatistical tools combined with an analysis of biometric relationships of leaves from Hymenaea courbaril L. Our analysis indicates that stomata show a clear spatial structure in this species: average values of foliar expansion rates (ERs) were different on right and left-hand sides of the primary venation of each leaflet and there was a close relationship between the spatial pattern of stomatal density and leaf expansion rate. Such differences in lateral expansion may therefore be partially responsible for the heterogeneous distribution of stomata documented here and in other studies.

Comportamento germinativo de sementes de talisia subalbens (mart.)radlk. (sapindaceae) submetidas a diferentes temperaturas e condições de secagem

A Talisia subalbens (Mart.) Radlk. (Sapindaceae) e uma especie arbustiva apontada como endemica do Mato Grosso. Objetivou-se neste estudo avaliar os efeitos da temperatura e condicoes de secagem sobre a germinacao de sementes de T. subalbens. No primeiro experimento avaliou-se a germinacao das sementes em diferentes regimes termicos: 15oC-25oC e 25oC-35oC (alternadas), 25oC e 35oC (constante), e no segundo experimento, as sementes foram submetidas a diferentes condicoes de secagem: rapida (estufa a 35oC) e lenta (temperatura ambiente a 28±2oC). Os testes de germinacao foram realizados em câmaras do tipo B.O.D., sob fotoperiodo de 12 horas, utilizando-se vermiculita como substrato. O delineamento foi o inteiramente casualizado, com quatro repeticoes de 25 sementes cada amostra. Os valores medios de porcentagem de germinacao e indice de velocidade de emergencia (IVE) foram comparados pelo teste de Tukey (5%). As sementes germinadas a 25oC, 35oC e 25oC-35oC apresentaram maiores porcentagens de germinacao, nao diferindo entre si, contudo, maior vigor foi observado a 35oC, sendo esta considerada a temperatura otima de germinacao da especie. Os menores valores de germinacao e IVE ocorreram a 15oC-25oC. O grau de umidade inicial das sementes foi de 48%. A velocidade de secagem das sementes afeta negativamente a porcentagem de germinacao, sendo o teor critico de grau de umidade de 25%, e a secagem rapida mais favoravel para a especie.

Plant physiological ecology and the global changes

As mudancas globais englobam importantes alteracoes nos padroes normais de processos bioquimicos e biofisicos da Terra. Os reais efeitos e retroalimentacoes das mudancas globais sobre a vegetacao ainda sao incertos. Parte das incertezas pode ser atribuida a falta de atencao de cientistas e politicos para a vegetacao, enquanto componente do sistema terrestre. Entretanto, algumas questoes sobre as mudancas globais poderiam ser mais bem esclarecidas por abordagens mais voltadas a ecofisiologia vegetal. Nesse artigo, alguns pontos relacionados e esses problemas, como as limitacoes em se abordar a vegetacao como um componente estatico da atmosfera enquanto outros subsistemas do sistema terrestre sao dinâmicos, sao discutidos. Dentro dessa perspectiva, essa revisao traz uma reflexao inicial do papel da vegetacao, em termos de estrutura e funcionamento, no contexto das mudancas globais. Para isso, foi feita uma revisao das terminologias relacionadas as mudancas globais e ao sistema terrestre, buscou-se ilustrar alguns dos principais temas de pesquisa da ecofisiologia vegetal no contexto das mudancas globais. Foram feitas consideracoes em relacao ao tratamento de plantas como sistemas complexos, o que e importante para o estudo de aspectos relacionados a sensibilidade, estabilidade e vulnerabilidade a variacoes ambientais. Finalmente, sao discutidas alternativas que podem ser utilizadas para incorporar aspectos do funcionamento da vegetacao, de forma dinâmica, em estudos de mudancas globais, considerando o desafio de mudanca de escalas. Espera-se que essa revisao possa auxiliar pesquisadores subsidiando suas estrategias de identificacao e compreensao dos efeitos potenciais das mudancas globais sobre os processos mais vulneraveis da vegetacao, da folha ao globo.

Crescimento e características anatômicas de cafeeiro (Coffea arabica L.) e seringueira (Hevea brasiliensis Muell. Arg.) em diferentes sistemas de cultivo: monocultivo e consórcio

This study aimed to evaluate the influence of the cropping system in anatomical characteristics and growth of the rubber tree (Hevea brasiliensis Muell. Arg.) and coffee (Coffea arabica L.), in the beginning of the cultivation period. It was evaluated the growth characteristics of rubber tree plants and the leaf structure in both species in single and intercropped cultivation. The results showed that the cropping system did not influence the rubber tree. In general, the cropping system did not influence the coffee leaf structure, in that developmental phase of cultivation.

Toward a systemic plant physiology

This manuscript brings a critical reflection on the epistemological foundations of the science of plant physiology. We discuss the limits of the reductionist view of the science, indicating new epistemological possibilities to plant physiology, specially based on General System Theory and Complex System paradigm, and the further implications of this major science to the human future.

Effects of paclobutrazol on leaf anatomy and gas exchange of Toona ciliata clones

ABSTRACT Interest in Australian cedar (Toona ciliata M. Roemer var. australis) has increased due to its economic potential as an alternative to the use of native hardwood, and because of its resistance to the Hypsipyla grandella moth, which affects native cedars. The use of growth regulators such as paclobutrazol (PBZ) in the planting of T. ciliata is aimed mostly at obtaining seedlings with greater resistance to H. grandella and a desirable height for handling. However, this growth regulator tends to induce modifications to both leaf anatomy and photosynthetic potential. The present study aimed to evaluate the effect of increasing concentrations of PBZ on the leaf anatomy and gas exchange pattern in different T. ciliata clones. Seedlings from four T. ciliata clones (BV1110, BV1321, BV1120 and BV1151) were propagated by rooting cuttings and exposed to four concentrations of PBZ (0 μM, 0.5 μM, 1.0 μM and 2.0 μM), then the anatomy of the leaf blade and midrib vascular bundles and parameters related to gas exchange were analysed. Clones were significantly different for most of the characteristics studied. PBZ showed an effect only on the thickness of the palisade and spongy parenchyma. There was no effect of PBZ on gas exchange, but higher concentrations of PBZ induced thicker leaflets with scleromorphic characteristics.