RESUMO
Water deficiency has been recognized as a major abiotic stress that causes losses in maize crops around the world. The maize crop is very important due to the range of products that are derived from this plant. A potential way to reduce the damages caused by water deficiency in maize crops is through the association with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF). To define the mechanisms developed by associative PGPB and AMF in maize that are involved in protection against moderate drought (MD), this study evaluated the biometrical, anatomical, biochemical, and physiological parameters of maize grown under MD and inoculated with different PGPB (Azospirillum brasilense strain Ab-V5 and Bacillus sp. strain ZK) and with AMF. The relative water content did not change in the treatments. The association with ZK increased the shoot:total ratio, total dry weight, maximum quantum yield of photosystem II, vascular cylinder thickness, and vascular cylinder area. The Ab-V5 inoculation led to an increment in root dry weight, the area of metaxylem vessel elements, and nitrate reductase activity. The AMF association did not lead to changes in the measured parameters. The results indicate that the association with PGPB is a relevant alternative to contribute to reducing losses in maize crops under drought. However, AMF is not indicated for this crop under drought.
RESUMO
Forest production has great relevance in the Brazilian economy, characterized by several production sectors, including the production of seedlings. With the focus on maximizing the capacity of survival, development, and adaptation of seedlings, Trichoderma is highlighted as a potentially useful genus of microorganisms for promoting growth and higher product quality. In this sense, this review aims to describe the main mechanisms of fungi action in forest seedlings' production. The different species of the genus Trichoderma have specific mechanisms of action, and the current scenario points to more advances in the number of species. The interaction process mediated by different mechanisms of action begins in the communication with plants, from the colonization process. After the interaction, chemical dialogues allow the plant to develop better because, from colonization, the forest seedlings can maximize height and increase shoot and root development. Fungi promote solubilization and availability of nutrients to seedlings, which show numerous benefits to the development. The use of beneficial microorganisms, such as fungi of the genus Trichoderma, has become a sustainable strategy to enhance seedling development, reducing the use of agrochemicals and industrial fertilizers.
RESUMO
Ground-level ozone is a global air pollutant with high toxicity and represents a threat to plants and microorganisms. Although beneficial microorganisms can improve host performance, their role in connecting environmentally induced maternal plant phenotypes to progeny (transgenerational effects [TGE]) is unknown. We evaluated fungal endophyte-mediated consequences of maternal plant exposure to ozone on performance of the progeny under contrasting scenarios of the same factor (high and low) at two stages: seedling and young plant. With no variation in biomass, maternal ozone-induced oxidative damage in the progeny that was lower in endophyte-symbiotic plants. This correlated with an endophyte-mediated higher concentration of proline, a defence compound associated with stress control. Interestingly, ozone-induced TGE was not associated with reductions in plant survival. On the contrary, there was an overall positive effect on seedling survival in the presence of endophytes. The positive effect of maternal ozone increasing young plant survival was irrespective of symbiosis and only expressed under high ozone condition. Our study shows that hereditary microorganisms can modulate the capacity of plants to transgenerationally adjust progeny phenotype to atmospheric change.
Assuntos
Endófitos/fisiologia , Epichloe/fisiologia , Lolium/fisiologia , Ozônio , Biomassa , Lolium/efeitos dos fármacos , Lolium/microbiologia , Ozônio/farmacologia , Plântula/fisiologia , SimbioseRESUMO
Despite the great diversity of plant growth-promoting bacteria (PGPB) with potential to partially replace the use of N fertilisers in agriculture, few PGPB have been explored for the production of commercial inoculants, reinforcing the importance of identifying positive plant-bacteria interactions. Aiming to better understand the influence of PGPB inoculation in plant development, two PGPB species with distant phylogenetic relationship were inoculated in maize. Maize seeds were inoculated with Bacillus sp. or Azospirillum brasilense. After germination, the plants were subjected to two N treatments: full (N+) and limiting (N-) N supply. Then, anatomical, biometric and physiological analyses were performed. Both PGPB species modified the anatomical pattern of roots, as verified by the higher metaxylem vessel element (MVE) number. Bacillus sp. also increased the MVE area in maize roots. Under N+ conditions, both PGPB decreased leaf protein content and led to development of shorter roots; however, Bacillus sp. increased root and shoot dry weight, whereas A. brasilense increased photosynthesis rate and leaf nitrate content. In plants subjected to N limitation (N-), photosynthesis rate and photosystem II efficiency increased in maize inoculated with Bacillus sp., whilst A. brasilense contained higher ammonium, amino acids and total soluble sugars in leaves, compared to the control. Plant developmental and metabolical patterns were switched by the inoculation, regardless of the inoculant bacterium used, producing similar as well as distinct modifications to the parameters studied. These results indicate that even non-diazotrophic inoculant strains can improve the plant N status as result of the morpho-anatomical and physiological modifications produced by the PGPB.