Emanuela Garbin Martinazzo

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.

Crescimento e fotossíntese de plantas de pinhão-manso cultivadas em diferentes condições de luminosidade

Jatropha curcas L. has been prominent in the scenario of biodiesel due to the percentage of oil contained in the seeds and its adaptive capacity. The cultivation of J. curcas in the country has as proposal the agronomic development and its consortium may be important for small producers. This study aimed to characterize the phenological behavior of J. curcas grown under different light conditions, full sun and 50% shade, relating them to the climatic seasonality, comparing their development with chlorophyll a fluorescence and gas exchange. Plants showed vegetative growth with seasonal pattern, with growth peak at the beginning of March, when the leaf senescence began. The analysis of the kinetic of the transient fluorescence of chlorophyll presented a relationship between certain parameters of the test JIP and the environmental fluctuations. The PIABS and the PItotal demonstrated that in the shaded treatment plants were sensitive to luminosity reduction. The liquid assimilation rate and the carboxylation efficiency decreased throughout the experiment, accompanying the decline of the solar radiation. J. curcas plants respond negatively to these shaded conditions.

Respostas na germinação e no crescimento inicial de rabanete sob ação de extrato aquoso de Piper mikanianum (Kunth) Steudel

This study evaluated the allelopathic effects of an extract from P. mikanianum leaves on the germination and early growth of radish (Raphanus sativus L.). Leaf extracts were prepared at concentrations of 2, 4 and 8%. The pH and osmotic potential of the extracts were determined. Germination bioassay consisted of five replicates of 25 radish seeds distributed in Petri dishes with germitest paper and 7 mL of extract or water, and were kept at 25oC in B.O.D. for five days. Germination percentage (PG), germination speed (VG), germination speed index (IVG) and index of allelopathic effect (RI) were determined. For bioassay initial growth, seeds were germinated until the protrusion of the radicle was 2 mm and transferred to Gerbox boxes containing germitest paper and 15 mL of extract or water, which were kept for seven days at 25oC in B.O.D. to evaluate the length of the radicle and hypocotyl, fresh and dry mass, water content and chlorophyll content (a, b ​​and total). Leaf extracts from P. mikanianum negatively affected all parameters examined for germination (PG, VG, IVG and RI). The extracts affected the initial growth, causing reduction of the radicle length and stimulating the growth of the hypocotyl. In addition, the extracts at 8% concentration reduced fresh weight and water content. Extracts at concentrations of 2 and 4% increased the content of chlorophyll b and total chlorophyll. Thus, Piper mikanianum exerted an allelopathic effect on radish.

Effects of flooding stress in ‘Micro-Tom’ tomato plants transformed with different levels of mitochondrial sHSP23.6

Soil flooding is an environmental stressor for crops that can affect physiological performance and reduce crop yields. Abiotic stressors cause changes in protein synthesis, modifying the levels of a series of proteins, especially the heat shock proteins (HSP), and these proteins can help protect the plants against abiotic stress. The objective of this study was to verify if tomato plants cv. Micro-Tom from different genotypes with varying expression levels of MT-sHSP23.6 (mitochondrial small heat shock proteins) have different responses physiological to flooding. Plants from three genotypes (untransformed, MT-sHSP23.6 sense expression levels and MT-sHSP23.6 antisense expression levels) were cultivated under controlled conditions. After 50 days, the plants were flooded for 14 days. After this period half of the plants from each genotype were allowed to recover. Chlorophyll fluorescence, gas exchange, chlorophyll index, leaf area and dry matter were evaluated. Flood stress affected the photosynthetic electron transport chain, which is related to inactivation of the oxygen-evolving complex, loss of connectivity among units in photosystem II, oxidation-reduction of the plastoquinone pool and activity of photosystem I. The genotype with MT-sHSP23.6 sense expression levels was less sensitive to stress from flooding.

Fluorescência da clorofila a em plantas de pessegueiro da cultivar maciel enxertada sobre diferentes porta-enxertos

The objective of this study was to evaluate characteristics of chlorophyll fluorescence in peach trees cv. Maciel grafted on six rootstocks. The analysis of the chlorophyll a fluorescence, the chlorophyll content and length of the leaves began after the winter period and were repeated until approximately 150 days, totaling six samples. The early ontogeny of the leaves was characterized by some higher fluorescence parameters. High rainfall, which occurred between 61 and 112 days of the beginning of the experiment, was the environmental factor that caused the greatest change in the parameters of the JIP Test, especially those related to photosystem I. The chlorophyll content was not influenced by the effect of associations cup x rootstock. Fall in the PITOTAL were in the period of highest rainfall, behavior that was independent of the rootstock, except for plants grafted on rootstock Rubira, who had minor damage to the photosynthetic apparatus. In general, rootstocks studied in combination with cv. Maciel did not affect the absorption and utilization of light energy by photosynthetic system.

Production components in transformed and untransformed ‘Micro-Tom’ tomato plants

Changes to the amounts of certain proteins have resulted in several studies, among them the so-called heat shock proteins (HSP), which take many forms, most of them constitutive. However, other forms may be inducible by a particular stress factor. The ‘Micro-Tom’ tomato is considered a model for experimental studies due to having suitable characteristics, such as reduced size, short generation time, and ease of transformation. Growth and production components were therefore evaluated in ‘Micro-Tom’ tomato plants transformed for different levels of mitochondrial HSP (MT-sHSP23.6). Plants from genotypes of the ‘Micro-Tom’ tomato (untransformed, and transformed with overexpression and with expression silencing) were grown under controlled conditions of temperature, photoperiod and photon flux density. To obtain the data, successive collections were carried out at regular intervals (21 days) throughout the development cycle of the plants, starting from the 21st day after transplanting (DAT). Total dry matter, leaf area, dry-weight partitioning between the plant organs, and production components were determined in the three genotypes. From interpretation of the results, it was found that plants transformed with overexpression of MT-sHSP23.6 displayed greater production capacity, considering the fresh weight of the fruit; but in general, the data showed that genetic transformation did not bring about major changes in growth, since the three genotypes displayed similar behaviour.

Chlorophyll fluorescence in the evaluation of photosynthetic electron transport chain inhibitors in the pea

The study aimed to evaluate the behavior of the chair of photosynthetic electron transport in the presence of DCMU and atrazine in detached leaves of pea through simultaneous measurements of the kinetics of fluorescence transient, fluorescence delayed and modulated reflection at 820 nm. The petioles of the leaves were immersed for two hours in solution of inhibitors at concentrations of 0 (control), 25, 50, 100, 250 and 500 µM. Measurements of the kinetics of fluorescence transient and fluorescence delayed and modulated reflection at 820 nm were recorded simultaneously by the M-PEA fluorometer. Simultaneous measurement of fluorescence transient, fluorescence delayed and modulated 820 nm reflection is important for assessments of the photosynthetic electron transport chain activity tool. The use of specific inhibitors of the electron transport chain allows you to collect and correlate a lot of information about the effect of different inhibitors at specific points in the photosynthetic electron transport chain. DCMU and atrazine are inhibitors of photosystem II and the concentration of 500 mM affects more strongly the flow of photosynthetic electrons.

Composição do substrato, vigor e parâmetros fisiológicos de mudas de timbaúva (Enterolobium contortisiliquum (vell.) morong)

Este trabalho objetivou avaliar a influencia da composicao de um substrato organoarenoso sobre a emergencia e parâmetros fisiologicos de crescimento de plântulas de timbauva. As sementes foram submetidas a germinacao nas seguintes composicoes do substrato: T1) 100% areia; T2) 75% areia + 25% Tecnomax®; T3) 50% areia + 50% Tecnomax®, T4) 25% areia + 75% Tecnomax®; e T5) 100% Tecnomax®. As avaliacoes foram efetuadas aos 45, 90, 135 e 180 dias apos a semeadura, aferindo a altura da parte area e o diâmetro do coleto. Aos 180 DAS, determinaram-se a massa da materia seca de parte aerea, a massa da materia seca de raizes, a massa da materia seca total e os teores de clorofila a, b e clorofila total. A emergencia e os parâmetros fisiologicos de crescimento foram afetados negativamente pela composicao exclusiva de Tecnomax®, assim como os valores de clorofila b. O substrato comercial associado ao material inerte (areia) proporcionou maior expressao do vigor das sementes, teores de clorofila b e maior crescimento de mudas de timbauva.

Alagamento do solo: efeito no crescimento inicial da aveia branca (Avena sativa L.)

The soil waterlogging reduces oxygen content near the roots, affecting energy metabolism and absorption of water and nutrients. Thus, the objective of this study was to evaluate the effect of different periods of soil waterlogging on physiological characteristics of initial growth in oat plants. The treatments consisted of soil in field capacity and soil flooding for 72 and 120 hours, with six replications. To analyze the initial growth were observed the number of leaves, leaf area, leaf area ratio and leaf weight, specific leaf area, dry weight of leaf, stem and roots, length of shoot and primary root. The i ncreasing of the period of flooding reduced the accumulation of root dry matter, the leaf area and the specific leaf area. However, the length of shoot and root were not affected by periods of soil flooding. The flooding periods negatively affect physiological attributes of initial growth in oat plants.

Isoenzymatic expression of red rice seeds and seedlings under the action of extracts of two Araceae species.

Several plant extracts have phytotoxic potential on seeds and seedlings, while the evaluation of isoenzymes is an important tool in assessing seed quality. In this study, we aimed to evaluate the effect of extracts the two species of the Araceae family (Zantedeschia aethiopica, Philodendron bipinnatifidum) on the isoenzymatic expression of red rice seeds and seedlings. We used the following extract concentrations: 0; 12; 25; 50 and 75%. Evaluation stages were seed, first count, and germination test. Expression of the isoenzymes esterase, acid phosphatase, glutamate oxaloacetate transaminase and peroxidase was determined by the vertical electrophoresis system in polyacrylamide gel, and interpretation of results was made by visual analysis of the gels. The extracts of the Araceae family species altered the isoenzymatic expression, and the intensity and number of bands varied according to the concentration and the stage of evaluation. Expressão isoenzimática de sementes e plântulas de arroz-vermelho sob ação do extrato de duas espécies Araceae Isoenzymatic expression of red rice seeds and seedlings under the action of extracts of two Araceae species Tiago Zanatta Aumonde1* Tiago Pedó1 Emanuela Garbin Martinazzo2 Junior Borella2 Francisco Amaral Villela1 1Universidade Federal de Pelotas – UFPel, Faculdade de Agronomia Eliseu Maciel, Departamento de Fitotecnia, Campus Capão do Leão, CP 354, 96010-900, Pelotas, RS, Brasil 2Universidade Federal de Pelotas – UFPel, Instituto de Biologia, Departamento de Botânica, Campus Capão do Leão, CP 354, 96010-900, Capão do Leão, RS, Brasil Autor Correspondente: *E-mail: tiago.aumonde@gmail.com PALAVRAS-CHAVE Oryza sativa Zantedeschia aethiopica Philodendron bipinnatifidum Alelopatia