Plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to phosphorus in acid soils

ABSTRACT Native to subtropical region of South America, yerba mate is responsive to P under some conditions, but the degree of influence of genetic and soil on the growth and composition of the leaf is unknown. The aim of study was to evaluate plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to P application in acid soils. In greenhouse condition, two yerba mate clone seedlings were grown (210 days) in pots, each clone in a completely randomized design in factorial scheme (with and without P; four acid soils). The elemental composition of leaves and the growth of plants were determined. Phosphorus promoted plant growth, but this was not accompanied by increased P in leaf tissue in all conditions tested. The P effect on the elemental composition varied: decrease/null (N, K, Mg, Mn, Cu, Ni, B, Mo, Al, Cd); increase/null (C/N, C, Ca, Fe, V); increase/decrease/null (Zn, Ba, Pb) and; null (Cr). The soils affect the elemental composition of the leaves, especially Mn, with accumulation greater than 1000 mg kg-1. The Ba, Pb, Al and Zn in the leaves varied among clones. Yerba mate response to P was affected by edaphic and plant factors.

Vegetative rescue and ex vitro system production of Tibouchina sellowiana clonal plants by cutting and mini-cutting / Resgate vegetativo e sistema ex vitro de produção de mudas de Tibouchina sellowiana por estaquia e miniestaquia

ABSTRACT: We aimed to evaluate the rooting potential of Tibouchina sellowiana through the experiments: I - Cuttings from current-year shoots and epicormic shoots were submitted to IBA concentrations: 0, 500, 1000, 1500 and 2000mg L-1, in a factorial arrangement 2 x 5 (two types of cuttings x five IBA concentrations), with four replicates and 20 cuttings each; II - mini-stumps of Tibouchina sellowiana were submitted to successive shoots collecting during the four seasons, in a split-plot design, with five replications of ten mini-stumps per experimental unit. From the shoots of mini-stumps, mini-cuttings were produced, which were initially kept in greenhouse and later transferred to full sun, in a 4 x 5 factorial arrangement (four seasons x five collections per season), with four replicates of 12 mini-cuttings. Superiority of epicormic shoots cuttings was reported when compared to the current-year shoots, which showed the highest rooting and leaves maintenance (42.50% and 55.00%, respectively), eliminating the use of IBA. High survival of mini-stumps (over 80%) and the mini-cuttings production (170mini-cuttings m-2 month-1) in clonal mini-garden and the mini-cuttings survival (above 80%) in the greenhouse demonstrated the technical feasibility, with summer as the most appropriate time to collect mini-cuttings.

RESUMO: Objetivou-se avaliar o potencial de enraizamento de Tibouchina sellowiana por meio dos experimentos: I - Estacas provenientes de brotações do ano e epicórmicas foram submetidas às concentrações de IBA: 0, 500, 1000, 1500 e 2000mg L-1, em arranjo fatorial 2 x 5 (dois tipos de estacas x cinco concentrações de IBA), com quatro repetições de 20 estacas cada; II - Minicepas de Tibouchina sellowiana foram submetidas à coletas sucessivas de suas brotações durante as quatro estações do ano, em modelo de parcelas subdivididas no tempo, com cinco repetições de dez minicepas por unidade experimental. A partir das brotações das minicepas foram produzidas miniestacas, as quais foram inicialmente mantidas em casa de vegetação e posteriormente transferidas para pleno sol, em arranjo fatorial 4 x 5 (quatro estações do ano x cinco coletas por estação), com quatro repetições de 12 miniestacas. Verificou-se superioridade das estacas de brotações epicórmicas em comparação às brotações do ano, as quais apresentaram o maior enraizamento e retenção foliar (42,50% e 55,00%, respectivamente), dispensando o uso de IBA. A elevada sobrevivência das minicepas (superior a 80%) e produção de miniestacas (170 miniestacas m-2 mês-1) em minijardim clonal e sobrevivência (acima de 80%) de miniestacas em casa de vegetação demonstram a viabilidade da técnica, sendo o verão a época mais adequada para coleta de miniestacas.