A B S T R A C TIn semi-arid environments, the plants are subject to stressful conditions due to high temperatures, light intensity and long drought, which are limiting for the establishment of seedlings. One way of minimizing stress is by inoculating rhizobacteria which promote plant growth (RPGP). The objective of this study was to evaluate the effectiveness of RPCP inoculation in the development of Myracrodruon urundeuva Allemão seedlings in different light conditions. Four treatments were applied: full sun with inoculum; full sun without inoculum; 70% shade with inoculum and 70% shade without inoculum. Data were collected biweekly for height, diameter, the number of leaves and leaf temperature (Tf). The vapor pressure deficit was determined by the temperature and humidity of the air. Parameters of leaf water potential, biomass, leaf area, specific leaf area and root area were evaluated. The seedlings presented higher growth under shading, demonstrating a mechanism to develop better in low light, and inoculation of the bacterium provided an increase in height and diameter of the seedlings, besides higher Tf on most days. The seedlings of the treatments in the sun invested more in radicular biomass, whereas in the shading they invested more in the aerial part. The water potential did not vary among the treatments, indicating that they adjusted to the submitted conditions. The use of RPGP is very promising, especially for the implantation of plant species in the recovery of degraded areas, as well as the condition of greater shading favors the initial stage of development of the seedlings.
Em regiões semiáridas, o déficit hídrico é um fator que limita o estabelecimento das plântulas, as quais necessitam de estruturas morfoanatômicas mais eficientes. As Rizobactérias Promotoras do Crescimento de Plantas (RPCPs) promovem uma melhor performance em plantas cultivadas, entretanto, os registros são escassos para espécies nativas do semiárido. Objetivou-se avaliar as variações anatômicas de folhas de quatro espécies de plantas jovens de mata ripária da caatinga inoculadas com Azospirillum lipoferum cultivadas sob diferentes níveis de déficit hídrico. O experimento foi conduzido em viveiro coberto com sombrite 70%. Foram postas para germinar 240 sementes de cada espécie (Triplaris gardneriana, Handroanthus impetiginosus, Licania rigida e Myracrodruon urundeuva), sendo metade das sementes inoculadas com a cepa de Azospirillum lipoferum (BR-11080). Três níveis de irrigação foram adotados: 25, 50 e 100% da Evapotranspiração de Referência (ET0). Após três meses foi coletada uma folha de cada indivíduo para caracterização anatômica. A. lipoferum conferiu um maior espessamento do mesofilo foliar (0,65 a 57%), epiderme (50 a 95%), parênquima clorofiliano (40 a 80%) e espessura da parede do xilema (63%), especialmente nos tratamentos de maior estresse (25 e 50% da ET0). Verificou-se deposição dos componentes bioquímicos especialmente nas plantas com inóculo, nos tratamentos de maior estresse. Estes resultados mostram que as RPCPs conferem mudanças nas estruturas anatômicas de plantas jovens do semiárido, tornando-as mais tolerantes ao déficit hídrico e, portanto, apresentando forte potencial para uso em reflorestamento e recuperação de áreas degradadas.
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