Marcos Antonio Bacarin

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.

An evaluation of non-destructive methods to estimate total chlorophyll content

The portable chlorophyll (Chl) meter (CL-01, Hansatech) has been successfully used for a rapid and direct estimation of total Chl content in the leaves of some crops. We compared CL-01 meter readings (Chl value) and Chl contents in leaves of Zea mays, Cucumis sativus, Raphanus sativus, and Ceiba speciosa. Chl index was linearly and positively correlated to Chl content in all the species.

EFEITO DO ESTRESSE SALINO SOBRE A CONCENTRAÇÃO DE PIGMENTOS E PROLINA EM FOLHAS DE ARROZ (1)

In order to analyse the effect of salt (0, 25, 50, 75 and 100 mM) concentration on chlorophylls, total carotenoids and proline contents, an experiment was carried out in greenhouse conditions with cultivars BRS Bojuru, IAS 12-9 Formosa and BRS Agrisul. Total contents were determined 30 days after soil salinization. The salinity strongly reduced chlorophylls and total carotenoids contents on Agrisul genotype, but pigments were not quite affected on Bojuru and Formosa. Proline contents were ligher in Agrisul than in the Bujuru and Formosa genotypes, and the proline accumulation was accentuated with increase in salt concentration. A threshhold of salt concentration that starts the process of proline accumulation in leaves was verified, being 50 mM to cultivar BRS Agrisul (sensitive) and 75 mM to cultivars BRS Bojuru and IAS 12-9 Formosa (tolerants).

CRESCIMENTO E PARTIÇÃO DE ASSIMILADOS EM CULTIVARES DE ARROZ DIFERINDO NO POTENCIAL DE PRODUTIVIDADE DE GRÃOS

Foram estudados o crescimento, a particao de assimilados e a producao de graos nas cultivares de arroz BRS Pelota (maior produtividade) e BRS Firmeza (menor produtividade). O experimento foi realizado em casa de vegetacao, com plantas cultivadas em vaso. Utilizou-se o delineamento experimental inteiramente casualizado, com duas cultivares, nove coletas e quatro repeticoes por tratamento. Com a cultivar BRS Pelota houve maior acumulo de materia seca total (Wt), principalmente no fim do ciclo, bem como maior area foliar (Af). A materia seca alocada para o colmo + bainha e as paniculas tambem foi maior em BRS Pelota. Porem, a porcentagem de Wt destinada as paniculas aos 125 DAE foi semelhante entre as cultivares. Em BRS Firmeza, o aumento em Wt nas raizes pode ter influenciado o direcionamento de fotoassimilados para os graos e contribuido para o atraso na senescencia das plantas. A produtividade de BRS Pelota foi maior que a de BRS Firmeza (17,4 contra 11,8 g por vaso) e seu numero de paniculas por planta por vaso foi tres vezes superior em relacao a cultivar BRS Firmeza. O componente de producao de maior expressao no rendimento foi o numero de paniculas. A maior produtividade da cultivar BRS Pelota pode estar relacionada a maior area foliar e sua duracao, o que permite o fornecimento de elevada quantidade de fotoassimilados por um periodo maior.

Composição química e respiração de crescimento em frutos de Psidium cattleyanum sabine durante o ciclo de desenvolvimento

The experiment was carried out under field conditions, where the fruits were harvest in Brazilian guava trees with six years old, growing on orchard of EMBRAPA- Temperate weather. The aim of the research was to determine the chemical composition, the efficiency of glucose conversion in new compounds and growth respiration estimate of the fruits during its ontogeny. The macronutrients content decreased with fruit development cycle. The contents of starch, total soluble sugars, reduced sugars, lipids and organic acids augmented as the fruits aged, while the protein contents and the components of cell wall decreased during fruit ontogeny, with strong accumulation during ripening. The carbohydrates were the major organic compounds, determining low cost of fruit respiration. The Brazilian guava showed to be an efficient fruit on glucose conversion in other organic compounds. The respiratory coefficient decreased as the fruit aged. The growth respiration rate increased until the middle of accelerate growth phase of the fruit.

The chlorophyll a fluorescence as an indicator of the temperature stress in the leaves of Prunus persica

Plants growing in temperate regions are often exposed to stress conditions caused by high temperatures. Photosynthesis is one of the metabolic processes most sensitive to high temperature stress, and it is often inhibited before other cellular functions. Using peach leaf disks, we studied the transient chlorophyll a fluorescence along with the gas exchanges at temperatures of 25 (control) 30, 35, 40 and 45°C in the dark for a period of 30 minutes. Temperatures above 35°C caused significant changes in the transient fluorescence of chlorophyll a, including an increase in the initial fluorescence (F0), a decrease in maximum fluorescence values (FM) and the appearance of K and L bands. The values of the net assimilation rate decreased as the temperature increased and reached negative values at 45°C.

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.

Produção e teor de carboidratos não estruturais em tubérculos de batata obtidos em duas épocas de plantio

Tuberculos de batata cv. Atlantic e Perola, obtidos do cultivo de outono (53; 68 e 100 dias apos o plantio - DAP) e primavera (70; 78 e 99 DAP) foram levados ao laboratorio e classificados quanto ao diâmetro ( 50mm), contados e determinada individualmente a massa fresca. Em seguida, coletaram-se amostras para analise dos teores de amido, carboidratos soluveis totais, acucares redutores e sacarose. Durante o cultivo de outono, a cultivar Atlantic apresentou maior massa fresca dos tuberculos ao final do ciclo e a cv. Perola apresentou maior numero de tuberculos em todas as colheitas. No cultivo da primavera a cv. Perola apresentou maior massa fresca media dos tuberculos, sendo que em ambas cultivares, observou-se reducao da produtividade ao final do ciclo, talvez em resposta ao estresse hidrico verificado no periodo. Considerando o fator cultivar, observa-se que o teor de amido foi significativamente maior nos tuberculos da cv. Perola aos 53 e 100 DAP do cultivo de outono, enquanto a cv. Atlantic apresentou valores significativamente maiores de carboidratos soluveis totais aos 53 DAP. Houve reducao nos teores de acucares redutores, em ambas cultivares, ao final do cultivo de outono, o que tambem foi verificado para os teores de sacarose. Os teores de amido e carboidratos soluveis totais reduziram, em ambas cultivares ao longo do ciclo de primavera, sendo que nao houve diferenca entre as cultivares em relacao aos teores de acucares redutores e sacarose ao final do cultivo de primavera.

Crescimento de plantas de soja em função de doses de sulfentrazone

The effect of sulfentrazone rates was evaluated on growth of soybean cv. BR-16, inoculated with strain SEMIA 5079, under greenhouse conditions. The sulfentrazone phytotoxicity increased as herbicide rates enhanced at V2 and R5 stages, aggravating the damage with the time. Leaf area, organs and total dry matter accumulations, plant heigh and roots length were reducted by sulfentrazone at R3 and R5 stages. The roots growth was more affected by sulfentrazone than shoot, occuring increment of shoot/roots ratio with augment on herbicide rates. The soybean cv. BR-16 showed low tolerance to sulfentrazone, based on the negative effect of the herbicide for all parameters studied.

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.