Fernando Angelo Piotto

Use of non-hyperaccumulator plant species for the phytoextraction of heavy metals using chelating agents

Soil contamination by heavy metals is a challenge faced by many countries, and engineering technologies to solve this problem are expensive and can cause negative impacts on the environment. One way to minimise the levels of heavy metals in the soil is to use plants that can absorb and accumulate heavy metals into harvestable parts, a process called phytoextraction. Typical plant species used in research involving phytoextraction are heavy metal hyperaccumulators, but plants from this group are not good biomass producers and grow more slowly than most species; thus, they have an important role in helping scientists understand the mechanisms involved in accumulating high amounts of heavy metals without developing symptoms or dying. However, because of their slow growth, it is not practical to use these species for phytoextraction. An alternative approach is to use non-hyperaccumulator plants assisted by chelating agents, which may improve the ability of plants to accumulate more heavy metals than they would naturally. Chelating agents can be synthetic or organic acids, and the advantages and disadvantages of their use in improving the phytoextraction potential of non-hyperaccumulator plants are discussed in this article. We hope to draw attention to ways to improve the phytoextraction potential of non-hyperaccumulator plants that produce a large amount of biomass and to stimulate more research on phytoextraction-inducing substances.

Rapid screening for selection of heavy metal-tolerant plants.

Uma das principais dificuldades nos trabalhos visando a selecao de plantas tolerantes a metais pesados e a propria metodologia para avaliacao eficiente de grande numero de plantas, gerando poucos residuos para o meio ambiente. Por esse motivo, propomos uma metodologia simples e eficaz que pode ser aplicada a metais ou outros elementos quimicos, partindo de um estudo de caso, no qual selecionamos dois mutantes de tomateiro (cv Micro-Tom) tolerantes ao Cadmio, obtidos por mutagenese com etanosulfonato de metila (EMS). Alem destes dois novos mutantes, selecionamos outros 21 com alteracoes potenciais quanto a respostas a este metal. Por fim, chegamos a conclusao de que o sistema proposto e ideal para trabalhos de selecao de plantas tolerantes a metais pesados e possivelmente a outros elementos, devido a facilidade de montagem da estrutura, baixo custo de implantacao, minimizacao de geracao de residuos e possibilidade de uso em varias especies e diferentes metais pesados.

Anatomical analysis of peach palm (Bactris gasipaes) leaves cultivated in vitro, ex vitro and in vivo

The present work characterized and compared the anatomical structures of the leaves of Bactris gasipaes (Arecaceae) plants grown under different cultivation conditions (in vitro, ex vitro and in vivo) with the goal of identifying the origins of the difficulties encountered in acclimatizing micro-plants. The Quant program was used to determine leaf tissue thicknesses and areas, and histochemical tests were performed on leaf sections and analyzed using light microscopy. Stomatal and trichome densities were determined using the epidermal impression method and by scanning electronic microscopy. Our results indicated that there were no discernible alterations of the anatomical characteristics of the leaves of micro-plants cultivated under differing conditions and that the thickening of the mesophyll and the vascular fibers indicated adaptive responses to ex vitro conditions. As such, the observed difficulties in acclimatizing peach palm micro-plants to ex vitro conditions cannot be attributed to plant anatomical characteristics acquired during in vitro cultivation.

Processos evolutivos e a origem das plantas cultivadas

The evolution of crop plants, which began at about 13,000 years ago, is subject to the same natural evolutionary processes, coupled with the action of man, consciously or unconsciously, leading to domestication. This review presents the main evolutionary factors such as mutation, hybridization, migration, selection and genetic drift, which somehow are involved in the origin, evolution and domestication of crop plants. Examples of how these processes influenced in the intra and interespecific diversity of crop plants, with the uprise of new varieties or even of new species, are also presented. In general, these processes have worked well in the increase, maintenance, as well as in the reduction of genetic diversity of crop plants.

Cadmium exposure triggers genotype-dependent changes in seed vigor and germination of tomato offspring

Although negative effects on the offspring fitness can be triggered by the mother-plant exposure to environmental stresses, some plants are able to “remember” past incidents and enhance the progeny tolerance. Here, the mineral profile, cytogenetic modifications, and physiological potential of seeds from two tomato cultivars, with contrasting tolerance degrees to cadmium (Cd) toxicity, were evaluated after plant exposure to this metal. Both cultivars exhibited high Cd translocation to the seeds; however, the tolerant tomato accumulated more Cd than did the sensitive one. As a consequence of the Cd accumulation, reductions in the Mn concentration in Cd-challenged plants were detected. Surprisingly, seed germination and vigor were increased in the tolerant tomato cultivar after Cd exposure, despite increases in the chromosomal abnormalities. By contrast, seeds from the sensitive cultivar exhibited no changes in their physiological potential after Cd exposure, despite Cd-induced reductions in the mitotic index. Moreover, bunch position exerted effects on the vigor and type of chromosomal abnormality. The results show that maternal plant exposure to Cd can affect tomato offspring by changing the seed physiological potential, and such effect can be partially explained by alterations in the seed-derived elements (essential and non-essential) and genotype-dependent tolerance mechanisms.

Interspecific xenia and metaxenia in seeds and fruits of tomato

Xenia, the transmission of traits from the pollinizer to the females tissues, is a phenomenon hitherto unknown in tomatoes. Here, we describe xenia effects on the seeds and fruits of Solanum lycopersicum, the tomato, elicited by S. galapagense. The wild tomatoes, such as S. galapagense, have highly pilose fruit surface and minute seeds, unlike the domesticated species. Crossings between S. galapagense (pollinizer) and two large-seeded, glabrous cultivars of S. lycopersicum (females) tested the formers ability to raise the trichome density and trichome-to-1000-cell ratio and to reduce the seed weight in the latters fruits. Selfed fruits of the two cultivars, Micro-Tom and Pusa Ruby, were compared to the crossed fruits. The pollen of S. galapagense was able to raise pilosity and to reduce seed weight in the crossed fruits of both cultivars, but with different magnitudes: seed reduction was more intense in Pusa Ruby, while pilosity increase was greater in Micro-Tom, both of which characterize xenia. Pilosity increase is not completely dependent on variation in epidermal cell density, which displayed no xenia effect. The difference between the maternal cultivars in the magnitude of pilosity increase may be due to the higher dilution of a putative male chemical signal (either hormone or RNA) in the larger fruits of Pusa Ruby. However, one cannot use the signal diffusion hypothesis to explain the xenia effects on seed weight.

Cadmium toxicity degree on tomato development is associated with disbalances in B and Mn status at early stages of plant exposure

Cadmium (Cd) toxicity is frequently coupled to its accumulation in plants, but not always the highest Cd concentration triggers the worst damages, indicating that additional events influence the magnitude of Cd side-effects. We investigated the early mechanisms behind the differential Cd-induced impacts on plant development of four tomato accessions with contrasting tolerance to Cd toxicity. At organ level, the highest Cd concentration was not associated with the largest biomass losses. In leaves, changes in superoxide dismutase and catalase activities were not related to differences in Cd concentration, which was unable to provoke H2O2 overproduction on the sixth day of plant exposure to this metal. Further investigation in the mineral profile revealed that magnitude of Cd toxicity depends probably on synergic effects from increased B status, in addition to the own Cd accumulation. Furthermore, disbalances in Mn status (i.e., excess in leaves and deficiency in roots) may enhance Cd toxicity degree. According to data, however, the low magnesium (Mg) status can be linked to tomato tolerance against Cd toxicity. In conclusion, the tomato tolerance degree under short-Cd exposure depends on actively, finely regulation of mineral homeostasis that results in different development of plant organs. The better understanding on the mode of action of Cd toxicity in plants can help in the establishment of strategies to mitigate its impacts on crop yield.

MT BB: tomato cultivar for practical classes of plant genetics and breeding

MT BB cultivar originated from a backcross program which aimed at adding two recessive mutations that alter leaf architecture (potato leaf - c) and flower color (white flower - wf) to Micro-Tom cultivar, which is a tomato miniature. MT BB was developed for use in practical classes of genetics and breeding in both undergraduate and graduate courses.