Cell suspension culture and plant regeneration of a Brazilian plantain, cultivar Terra

The objective of this study was to establish cell suspension culture and plant regeneration via somatic embryogenesis of a Brazilian plantain, cultivar Terra Maranhão, AAB. Immature male flowers were used as explant source for generating highly embryogenic cultures 45 days after inoculation, which were used for establishment of cell suspension culture and multiplication of secondary somatic embryos. Five semisolid culture media were tested for differentiation, maturation, somatic embryos germination and for plant regeneration. An average of 558 plants per one milliliter of 5% SCV (settled cell volume) were regenerated in the MS medium, with 11.4 µM indolacetic acid and 2.2 µM 6-benzylaminopurine. Regenerated plants showed a normal development, and no visible somaclonal variation was observed in vitro. It is possible to regenerate plants from cell suspensions of plantain banana cultivar Terra using MS medium supplemented with 11.4 µM of IAA and 2.2 µM of BAP.

Screening of Brazilian soybean genotypes with high potential for somatic embryogenesis and plant regeneration

The aim of this work was to identify Brazilian soybean (Glycine max) genotypes with potential to respond to in vitro culture stimuli for primary somatic embryo induction, secondary embryo proliferation and plant regeneration. Differences among eight tested cultivars were observed at each stage. Two cultivars, IAS-5 and BRSMG 68 Vencedora, were selected for the evaluation of the capacity for embryo differentiation and plant regeneration. These cultivars had high embryo induction frequencies, repetitive embryogenic proliferation, and low precocious embryo germination in the initial experiment. The effect of abscisic acid (ABA) and charcoal addition on plant regeneration was investigated. The addition of ABA to proliferation medium and of ABA and activated charcoal to maturation medium increased embryo differentiation rates, which resulted in a higher number of regenerated plants. The BRSMG 68 Vencedora cultivar was found to have a high potential for embryo induction, embryo proliferation and plant regeneration. The potential of this cultivar for somatic embryogenesis was similar to that observed for cultivar IAS-5, which is currently used for soybean transformation in Brazil. BRSMG 68 Vencedora may be a good alternative genotype for soybean genetic engineering via somatic embryogenesis protocols.

Desiccation, postharvest maturity and seed aging of tall oat-grass

The objectives of this work were to determine whether and at which seed physiological maturity stage the diquat desiccant affects the tall oat-grass (Arrhenatherum elatius) seed quality and yield, as well as the proper storage period between harvest and sowing. Diquat desiccation was evaluated in applications during milk or dough seed maturation stages. Seeds conventionally produced and stored under traditional storage conditions were used for the analyses. Seed samples were drawn every 30th day after harvest (DAH). After the 240th DAH, samples were drawn every 90th day up the to 690th DAH. The highest yield were obtained by desiccation applied at the beginning of the seed dough stage, with a satisfactory seed quality. Both final germination and seedling growth parameters achieved their maximum values between 180th and 240th DAH. Oat-grass seeds preserved satisfactory level of final germination (75%) up to 420th DAH. The application of diquat desiccant at the beginning of seed dough maturity stage can be a good solution for seed production of tall oat-grass. Early spring is the best sowing period for freshly harvested seeds of tall oat-grass regarding germination and seedling growth.

Impact of unusual fatty acid synthesis on futile cycling through beta-oxidation and on gene expression in transgenic plants.

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal beta-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward beta-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through beta-oxidation than the expression profile of genes involved in lipid metabolism.

Characterization of rue extract and its potential for controlling rice blast

Abstract: The objective of this work was to purify and standardize the rue (Ruta graveolens) extract and evaluate its effect on Magnaporthe oryzae as an alternative to the integrated management of rice blast. The drug was characterized, the liquid extract was obtained, and the methodology for quantifying the standard markers psoralen and bergapten was validated. Rue extract and the markers, solely or in combination, were assayed in vitro, as well as in greenhouse conditions, for their ability to suppress leaf blast, by the evaluation of mycelial growth, conidial germination, and appressorium formation. Rue extract inhibited M. oryzae mycelial growth (100%), conidial germination (LD50=0.237 mg), and the appressorium formation (LD50=0.121 mg); besides, the extract reduced leaf blast severity by 80.84%. Fluorescence microscopy showed that rue extract did not damage M. oryzae cell wall and plasma membrane, indicating another mode of action. Rue extract has a great potential for controlling rice leaf blast.

Effect of temperature on percentage of germination of canistel seeds (Pouteria campechiana)

The canistel is a fruit originated in Mexico and Central America, being introduced in Brazil in 1986. The plants present medium size, however it can reach up to 15 meters of height; the leaves measure about 10 to 25 cm; the flowers are complete and small and the fruit presents yellow coloration when ripe, with whitish pulp and sweet flavor. The propagation can be realized by seed or grafting. In view of almost total absence of information about the culture and the possibility to have a commercial cultivation, the present work, was live in which the effect of the temperature was evaluated in the percentage of germination of the seeds. It was checked that the best averages were obtained in temperature of 30ºC and the minor in 15ºC, 20ºC and 40ºC could be considerate the worst of them.

Influence of the temperature in germination of seeds of jabuticaba tree

The jaboticaba tree (Myrciaria spp.) is originated from the center-south of Brazil and presents different types. It's a medium size tree, with tendency to form a crown with great number of branches. A characteristic considered as limitant for the commercial crop is the great juvenility, advicing producing good rootstocks of seedlings and graft wanted varieties, and other vegetative processes. With the purpose of evaluating the effect of temperature on germination of three clones of jaboticaba tree, was carried out a laboratorial research. It was observed influence of the temperature on germination. The highest percentage of germination was obtained at low temperature (15ºC and 20ºC). When it was used the temperature of 35ºC, two clones had only 8% of germination, while the other one was verified 35%. These values show the possibility of the ocurrence of variability among the clones of jaboticaba tree.

Influence of the substrate in germination of lychee seeds

The lychee is, all over the world, considered as the "queen of the fruits" due to the delicacy of its appearance and flavor. Although it was only recently that it started to have economical importance in Brazil, the lychee is already calling the attention of numerous farmers, mainly those who cultivate citric fruits and/or sugarcane in the State of São Paulo, due to the constant and at the same time growing necessity of finding new alternative crops. Considering that the commercial cultivation of lychee plants in the field requires the previous obtainment of rootstocks viewing to reduce the genetic variability and the length of the juvenile period displayed by plants resulting directly from the seeds, finding ways to improve the germination performance of lychee seeds for the production of rootstock plants is of considerable economic importance. Thus, the objective of this experiment was to test five substrates for the germination of lychee seeds: (1) vermiculite, (2) washed sand, (3) filter paper, (4) carbonized rice hull, and (5) sphagnum. The results showed that the period of time required by a lychee seed to germinate is a short one thus reinforcing the importance of providing a suitable substrate for the germination to take place. It was found that the substrates which apparently allowed the best combinations of water and oxygen availability for the seeds - washed sand and carbonized rice hull - were those leading to the fastest and highest germination values.

A germination study of herbicide-resistant field poppies in Spain

Field poppy, Papaver rhoeas L., is a very common weed in winter cereals in North-Eastern Spain. Its control is becoming difficult due to expanding herbicide resistance. To control field poppies there are alternative strategies such as non-chemical control that take into account the weed emergence period. However, there is a lack of knowledge of P. rhoeas emergence patterns in semi-arid conditions. Thus, here we conducted pot experiments on the emergence of P. rhoeas. We aimed to describe the emergence period and to quantify the emergence of a susceptible and of a herbicide-resistant P. rhoeas population at two locations in Catalonia, Spain, from 1998 to 2001 and until 2004 at one of them. Therefore, pots containing seeds of both populations were established at the two locations and emergence was recorded monthly. We studied the origin of the population, the sowing location, the effect of cultivation and the sowing year. First, we found that the main emergence peaks in our experiments occurred in autumn, accounting for between 65.7 and 98.5% of the annual emergence from October to December, and only little emergence was recorded in spring. This emergence pattern is different from those found in the literature corresponding to Northern European countries, where in some cases main flushes occur only in autumn, in spring and winter or only in spring. The emergence was mainly affected by cultivation, but the effect of light stimulus was observed several months later. As a consequence, cultivation should be done in early autumn, promoting emergence during the whole autumn and winter so that emerged seedlings can be controlled before sowing a spring crop. Second, most experiments showed that the emergence was significantly higher in the first autumn than in the following seasons, e.g. 4.1% emergence in the first year and only 2.1, 2.3, 0.5 and 0.6% new emergence at one of the locations for the second, third, fourth and fifth years. Thus, after having a severe P. rhoeas infestation causing a big seed rain, emergence should be stimulated by autumn cultivation in the following season and seedlings controlled by trying to deplete the soil seed bank as much as possible. Despite the fact that emergence will be staggered throughout several years and that there was a significant relationship between rainfall and emergence, so that dry years will cause a smaller emergence rate of the weed, these findings define a cultural management strategy to reduce P. rhoeas infestations and to contribute to integrated weed management strategies combining it with other tools.

Germination : a means to improve the functionality of oat

Selostus: Idättämällä voi muokata kaurasta uudenlaisia elintarvikeraaka-aineita

Conservation of Campomanesia adamantium (CAMB.) O. berg seeds in different packaging and at varied temperatures

This article aims at evaluating the effects of different packaging and varied storage temperatures on the germination potential of seeds of Campomanesia adamantium Camb. O. Berg. The seeds were packaged in glass, aluminum foil and plastic containers, or maintained inside intact fruits at 5, 10 and 15 ºC during 0, 7, 14 and 21 days. After these periods the seeds were sown in Germitest® germination paper and maintained in incubation chambers at 25 ºC under constant white light for 42 days. Seed moisture contents were evaluated both before and after storage, as well as germination percentages, germination speed index, root and aerial portion of seedlings lengths, and total dry weights. All possible combinations of packing materials, temperatures and storage times were tested, with four repetitions of 25 seeds for each treatment. C. adamantium seeds showed initial water contents of 31.5%. Glass and aluminum packaging were efficient at maintaining the water content of the seeds, and provided greater germination speed index than the other packaging materials. Germination percentages, seedlings lengths and dry weights did not vary among the different temperatures tested. C. adamantium seeds can be stored for up to 21 days at temperatures between 5 and 15 ºC without altering their physiological quality. In terms of cost-benefit efficiencies, these seeds can be stored without significant damage for 21 days while still inside the fruits at temperatures of 5, 10 or 15 ºC.

Water uptake by Annona diversifolia Saff. and A. purpurea Moc. & sessé ex dunal seeds (Annonaceae)

Annonaceae seeds are known by presenting dormancy mechanisms, whose reports ranging from coating impermeable to the physiological dormancy. By this way, the present study aimed to evaluate water uptake in Annona diversifolia Saff and Annona purpurea Moc & Sessé ex Dunal seeds. For this study, seeds were placed under immersion in distilled water, and used four replicates of 25 seeds of each species, which were weighed during the 480 hours that were immersed. To determine the place of purchase of water, Annona diversifolia seeds were sealed with paraffin at different locations. Based on the results, seeds from both species reached the phases I and II of water uptake, which indicates they are not hard; however, germination (Phase III) was not reached. Annona diversifolia seeds completed Phase I with, 50h and Annona purpurea with 70h from imbibitions begin, which shows that even slowly, water is acquire.

Pre-dispersal predation effect on seed packaging strategies and seed viability.

An increased understanding of intraspecific seed packaging (i.e. seed size/number strategy) variation across different environments may improve current knowledge of the ecological forces that drive seed evolution in plants. In particular, pre-dispersal seed predation may influence seed packaging strategies, triggering a reduction of the resources allocated to undamaged seeds within the preyed fruits. Assessing plant reactions to pre-dispersal seed predation is crucial to a better understanding of predation effects, but the response of plants to arthropod attacks remains unexplored. We have assessed the effect of cone predation on the size and viability of undamaged seeds in populations of Juniperus thurifera with contrasting seed packaging strategies, namely, North African populations with single-large-seeded cones and South European populations with multi-small-seeded cones. Our results show that the incidence of predation was lower on the single-large-seeded African cones than on the multi-small-seeded European ones. Seeds from non-preyed cones were also larger and had a higher germination success than uneaten seeds from preyed cones, but only in populations with multi-seeded cones and in cones attacked by Trisetacus sp., suggesting a differential plastic response to predation. It is possible that pre-dispersal seed predation has been a strong selective pressure in European populations with high cone predation rates, being a process which maintains multi-small-seeded cones and empty seeds as a strategy to save some seeds from predation. Conversely, pre-dispersal predation might not have a strong effect in the African populations with single-large-seeded cones characterized by seed germination and filling rates higher than those in the European populations. Our results indicate that differences in pre-dispersal seed predators and predation levels may affect both selection on and intraspecific variation in seed packaging.

Photomorphogenesis and Photoreceptors

Plants use light as their main source of energy and to gather information about their surroundings. The light environment is monitored through an extensive set of photoreceptors and largely dictates plant development through induction of processes such as germination and flowering, entrainment of the circadian clock and photomorphogenic responses. Plants display remarkable phenotypic plasticity upon perception of changes in the light, ranging from seedling de-etiolation to shade avoidance and phototropic responses in competition for light. Here, we describe photomorphogenic responses and their underlying mechanisms such as they occur in a leaf canopy. This shade avoidance review will largely focus on the model plant species Arabidopsis thaliana as the underlying mechanisms controlling shade avoidance are particularly well elucidated in this species.

Synthesis and antifungal activity of halogenated aromatic bis-γ-lactones analogous to avenaciolide

Here we describe the total syntheses and characterization by elemental analyses, infrared and NMR spectroscopy of three new compounds analogous to avenaciolide, a bis-γ-lactone isolated from Aspergillus avenaceus that possesses antifungal activity, where the octyl group of the natural product was replaced by aromatic groups containing chlorine and fluorine atoms. The effects of the avenaciolide, the novel compounds and their synthetic precursors on mycelia development and conidia germination of Colletotrichum gloeosporioides and Fusarium solani were evaluated in vitro. The title compounds were almost as active as avenaciolide. The absolute structures of the chlorinated analogs were determined by X-ray diffraction analysis.