José Antonio Peters

Excess iron-induced changes in the photosynthetic characteristics of sweet potato

Iron (Fe) is an essential nutrient for plant growth and development. In plant tissues, approximately 80% of Fe is found in photosynthetic cells. This study was carried out to determine the effect of different iron concentrations on the photosynthetic characteristics of sweet potato plants. The fluorescence transient of chlorophyll a (OJIP), chlorophyll index and gas exchange were measured in plants grown for seven days in Hoagland solution containing an iron concentration of 0.45, 0.90, 4.50 or 9.00 mM Fe (as Fe-EDTA). The initial and maximum fluorescence increased in the plants receiving 9.00 mM Fe. In the analysis of the fluorescence kinetic difference, L- and K-bands appeared in all of the treatments, but the amplitude was higher in plants receiving 4.50 or 9.00 mM Fe. In plants grown in 9.00 mM Fe, the parameters of the JIP-Test indicated a better efficiency in the capture, absorption and use of light energy, and although the chlorophyll index was higher, the net photosynthesis was lower. The overall data showed that sweet potato plants subjected to high iron concentrations may not exhibit the toxicity symptoms, but the light reactions of photosynthesis can be affect, which may result in a declining net assimilation rate.

Efeito de auxinas e condições de cultivo no enraizamento in vitro de porta-enxertos de macieira 'M-9'

The utilization of trees with desirable characteristics, genetics and sanitary, is an important factor for the success in plant propagation. The micropropagation, in comparison with the traditional vegetative propagation methods, helps to increase the production and to get trees with higher sanitary quality. In this technique rooting is a crucial stage to the development of the plants propagated in vitro. In such context, it was aimed to test cultivation conditions and types and concentrations of auxin for the rooting in vitro of the cv. M-9 apple tree root-stook. Shoots (1cm) were used, and they were cultivated in half MS. medium, with the addition of gelrite for their solidification. The auxins used were IAA, NAA and IBA, in 0.5; 1.0; 5.0; 10.0; 20.0; 50.0 and 100.0 mM concentrations. Two different incubation conditions were tested. In the first one, the explants were kept into the light (30 days), and in the second one, the explants were kept for 5 days in the dark with further transfer to light (25 days). In both conditions, the explants were exposed to plant growth regulators during all the time, or just for ten days, with further transfer to a medium without plant growth regulator. The variables analysed were as follows: rooting percentage; number, length and kind of root, while in the shoot test, apart from these, the survival percentage in the stage of aclimatization was evaluated. IAA induced higher rooting percentage, plants with better root system and leaves in the highest concentrations, but when it was used IBA and NAA these characteristics were observed in the lowest concentrations. When the explants were cultivated for just ten days in medium added writh auxins, they presented, in general, better results.

Efeito da sacarose e do benomyl na multiplicação in vitro da macieira

The purpose of this work was to study the effect of sucrose and benomyl concentrations on in vitro multiplication of apple (Malus prunifolia Willd, Borkh). The culture media composition was MS basal media plus 1 mg L-1 of BAP. Benomyl was harmful to M. prunifolia at all concentrations. The best sucrose concentrations was 30-45 g L-1, evaluated by shoot and bud number. The sucrose concentration of 45 g L-1 gave the biggest shoot length. The best shoot color was obtained at 15-30 g L-1 of sucrose.

Composição do óleo essencial de quatro espécies do gênero Plectranthus

Palavras-chave: plantas medicinais, boldo, hidrodestilacao, CG-MS, GC-FID ABSTRACT: Essential oil composition of four Plectranthus species. Plectranthus has been considered one of the richest genera in essential oils within the Lamiaceae family, which includes several species with medicinal properties. Some of them are commonly known as boldo and present taxonomic similarities and several synonymies, with antidyspeptic, analgesic and digestive actions. The aim of this study was to evaluate quantitatively and qualitatively the essential oils from P. amboinicus, P. barbatus, P. grandis and P. neochilus leaves. The oil was extracted by hydrodistillation using pentane as extracting solvent and was repeated three times for each species. The analysis of essential oil components by GC/MS in the four Plectranthus species identified 14 chemical components, mostly sesquiterpenes. High concentration of trans-caryophyllene was found in the studied oils. Some chemical components were specific for each species and other components had common occurrence in all four species, allowing their differentiation into two groups, one composed of P. amboinicus and P. neochilus and another one by P. grandis and P. barbatus. In conclusion, the four boldo species had significant differences as to essential oil yield and chemical composition.

Plant Regeneration and Molecular Characterization of Potato Cultivar Macaca, Obtained from Gamma-Irradiated Explants

ABSTRACT The goals of this study were to verify the influence of gamma radiation (60Co) and culture medium in the regeneration rate of potato explants, cultivar Macaca, and to molecularly characterize the regenerated plants using RAPD markers. Therefore, internodes and leaves were submitted to different gamma radiation doses and cultivated in basic MS medium with two types of cytokinins, benzylaminopurine (BAP) or zeatin (ZEA). It was observed that internodes, when cultivated in medium with BAP, presented higher regeneration rate when compared to leaves, although decreasing with higher doses. It was also verified that in treatments with ZEA, the internodes presented higher regeneration rate than those treated with BAP, decreasing according to radiation doses. For the molecular analysis, ten RAPD primers were used. These primers produced 70 fragments, being 24% polymorphic. The treatment with 500 cGy promoted the highest variation in genetic distances.

Efeito de herbicidas sobre a polimerização dos microtúbulos e indução de micronúcleos em protoplastos de Helianthus maximiliani

In order to verify the kinetics of microtubule depolymerization and dynamics of micronuclei induction, two anti-mitotic herbicides, Amiprophos-methyl (APM) and Oryzalin (ORY), were added to dividing cells of Helianthus maximiliani. The addition of both herbicides to actively dividing cells resulted in a high number of cells with micronuclei through modification of mitosis. Single chromosomes and groups of 2 or more chromosomes were scattered over the cytoplasm. After 2-3 h of herbicide application, microtubules were depolymerized and the metaphase chromosomes changed directly into micronuclei, without centromere division and chromatid separation. The most efficient concentrations were 20 µM ORY and 60 µM APM when incubated for 36 and 48 h, respectively. When the treatment duration was increased, the frequency of cells with deformed micronuclei as well as cell death increased. The presence of citochalasina-B (CB) (20 µM) after 24 h of herbicide application increased the frequency of micronucleation and stabilization of the micronuclei in the cells significantly. The control of microtubules using anti-mitotic toxins provides an efficient tool for micronuclei induction as well as representing an elegant method for partial genome transfer.

Development of rice seedlings grown from pre-hydrated seeds and irradiated with gamma rays

Tecnicas como radiacoes ionizantes, utilizadas para induzir mutacoes constituem ferramenta eficaz no aumento de variabilidade genetica em programas de melhoramento de especies de interesse economico. Neste trabalho, objetivou-se verificar o efeito de diferentes doses de radiacao gama Co60 em sementes previamente embebidas sobre a emergencia e o crescimento inicial de plântulas de duas cultivares de arroz. Lotes de sementes com 25% de umidade das cultivares BRS Querencia e BRS Fronteira foram irradiados com doses de zero (controle), 50, 100, 150 e 200 Gy, sendo, em seguida, semeadas em bandejas contendo solo e mantidas em casa de vegetacao. Os resultados mostraram que a radiacao gama afetou o desenvolvimento das plântulas, sendo que a maior dose testada (200 Gy) reduziu, significativamente, a emergencia e o indice de velocidade de emergencia. Os parâmetros de crescimento apresentaram maior reducao na cv. BRS Querencia. Na atividade das enzimas antioxidantes, a superoxido dismutase expressou pouca variacao para os periodos avaliados. Ja, a ascorbato peroxidase e catalase mostraram expressivo aumento na cv. BRS Fronteira aos 14 DAS, seguidas de incremento para as duas cultivares na atividade da ascorbato peroxidase aos 28 DAS. A maior capacidade antioxidante observada na cv. BRS Fronteira conferiu uma maior tolerância ao estresse causado pela radiacao gama.

Produção de betacianina em erva-de-jacaré cultivada in vitro com diferentes concentrações de sulfato de cobre

The manipulation of concentration of trace elements in the culture medium represents a good strategy to increase the production of secondary metabolites in tissue culture. This study aimed to demonstrate the influence of copper sulphate in the production of betacyanin and the multiplication of plants of Alternanthera philoxeroides (alligator weed) cultured in vitro. Nodal segments, obtained from plants pre-stablished and after three subcultures, were inoculated in basic MS with different concentrations of CuSO4 (0, 25, 75, 125, 175, 200µM). The results were subjected to analysis of variance, polynomial regression and correlation analysis between the morphological variables and the production of betacyanin. The experimental design was completely randomized with six concentration of CuSO4 and five replicates represented by a bottle containing four explants. Concentrations above 75µM decreased the height of the plant, number of shoots and buds and root growth, while the concentration of 125µM resulted in the highest fresh mass production. Betacyanin production increased 60% over control with 175µM CuSO4. Plant growth occurred in all tested concentrations of CuSO4, with the exception of 200µM which was toxic.

Rooting and acclimatization of the Japanese plum tree, cv. América

Rooting and acclimatization are limiting steps in plant micropropagation, especially in woody plant species. This study aimed to evaluate the IAA and IBA effect on the in vitro rooting and acclimatization of micropropagated shoots of Japanese plum (Prunus salicina Lindl.) cv. America. Shoots from 3 to 4 cm long were inoculated in MS medium with half salt and vitamin concentrations (MS/2) added with IAA and IBA (0, 0.25, 0.5, 0.75 and 1 mg L-1). After a 20-day period in in vitro cultivation, the shoots were evaluated, and then transferred to a greenhouse, and evaluated after 30 days. At the end of the in vitro cultivation period, no significant interactions were observed for number of roots per shoot and rooting percentage, but a significant effect was recorded for auxin type only, for which shoots grown in media added with IBA showed high values - 0.87 and 41.95%, respectively. A linear increase response from 1.45 to 5.75 cm was verified for root length of shoots cultivated in IBA medium; however, no significant effect was observed, and a 0.86 cm average root length per shoot grown in medium added with IAA was found. After 30 days of acclimatization period, the largest survival percentage was obtained from shoots cultivated in medium with 1 mg L-1 of IBA and IAA (88% and 92%, respectively). Although, IBA provided the highest in vitro rooting, most of the surviving shoots were those originated in IAA-added medium, probably because IBA promoted longer fibrous roots, less appropriate for transplant and soil fixation, as they are easily damaged. It was concluded that in vitro rooting with the addition of the highest IAA concentration (1 mg L-1) provided the greatest plant survival during the acclimatization period of the Japanese plum cv. America.

Diversidade genética entre acessos de espinheira-santa (Maytenus ilicifolia Mart. ex Reis.) coletados no estado do Rio Grande do Sul, Brasil

Maytenus ilicifolia Mart. ex Reis., popularmente conhecida como espinheira-santa, e especie autoctone pertencente a familia Celastraceae, usada para tratamento de ulceras gastricas e gastrites. Devido a importância medicinal, houve aumento no extrativismo das populacoes naturais, tornando-a uma especie prioritaria para a conservacao, a fim de evitar a erosao genetica. Buscou-se com este trabalho analisar a diversidade genetica de 20 acessos de M. ilicifolia coletados em diferentes localidades no Rio Grande do Sul. Utilizando marcadores moleculares do tipo AFLP, foram testadas oito combinacoes de primers, que geraram 455 bandas eletroforeticas, 100% polimorficas. As combinacoes de primers E-ACC/M-CAA, E-ACG/M-CTA, E-ACG/M-CTC apresentaram o maior numero de bandas eletroforeticas, 71 cada, totalizando 46,80% do polimorfismo total. Os valores de similaridade genetica calculada pelo coeficiente simple matching foram utilizados para gerar o dendrograma de similaridade pelo metodo UPGMA. Foi obtido alto coeficiente de correlacao cofenetica (r=0,94), demonstrando elevada representatividade dos dados de similaridade genetica no dendrograma. Pela AMOVA verificou-se que 89,33% da diversidade total ocorreram entre individuos dentro das populacoes. A caracterizacao molecular de acessos de Maytenus ilicifolia por meio de AFLP foi eficiente para identificar diversidade genetica. Atraves da analise de similaridade genetica o banco de germoplasma poderia ser composto com os acessos que apresentaram menor similaridade e maior numero de alelos, permitindo com que estes fornecessem ampla cobertura do genoma que compoem Maytenus ilicifolia. Os acessos que ficaram agrupados em mesmo cluster e com numero reduzido de alelos podem ser descartados deste banco. A diversidade genetica intrapopulacional identificada por esse marcador foi muito maior do que aquela entre populacoes.