| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1151-1 | ||||
Resumo:Plant Growth-Promoting Rhizobacteria (PGPR) are groups of bacteria that have the ability to, directly or indirectly, associated with plants rhizosphere region, promoting a stimulus in the development and growth of their host. A region highly influenced by these microorganisms is the plant root system, wherein they can induce significant alterations in root length, the number of secondary roots, dry mass, and even cellular anatomy. These modifications in the root system are instigated by molecules excreted by rhizobacteria, including various phytohormones, polysaccharides, and flagellins. Nevertheless, few research has been conducted on the mechanisms and primary factors responsible for the influence of PGPR on roots and their cellular-level effects. To better understand this question, we analyzed how the PGPR influence the root cell size, the cell division speed and length root daily. Mitotic index analyses, cortex parenchyma cell size and root length daily measurements were needed to address this question. A collection of 13 strains of Bacillus spp. obtained by the Genetics of Microorganisms Laboratory “Prof João Lúcio de Azevedo” were used. We inoculated the strains + water + culture medium in seeds of tomato cv. MicroTom and roots were collected on two different days – 3 and 6 days after inoculation. The meristematic tips of the roots were stained by Feulgen's method to determine the mitotic index. The region of the root cortex was stained with Fast-Green and photographed in the microscope to measure the size of the parenchyma cells. The roots of each strain were measured daily from germination (third day) until the sixth day of growth. Root images were captured using an HP Scanner G4050, and root length was measured using ImageJ software. We observed that root cell length, mitotic index, and the interaction between these two characteristics are crucial for root growth. However, the response to these factors varied among the strains. Strains RZ3MS27 and RZ5MS10 exhibited significant root elongation, primarily attributed to enlarged cell dimensions. Conversely, strains FS3-7, RZ2MS9, and CNM42 also demonstrated substantial root growth, but it was predominantly driven by an elevated mitotic index. Plausibly, each strain employs distinct mechanisms that differentially influence root development, either through enhanced mitotic division or the enlargement of root cell dimensions. Palavras-chave: Bacillus, plant growth-romoting rhizobacteria, root growth, cell division Agência de fomento:CAPES e CNPq | |||||