ABSTRACT. The objective of this study was to evaluate the the ability of foliar application of potassium nitrate (KNO3) to induce water deficit tolerance in sorghum plants (Sorghum bicolor cv. P898012) subjected to water deficit at pre-flowering. The experiment was conducted under greenhouse conditions with 4 treatments: field capacity (FC), water deficit (WD), field capacity + KNO3 (FC + KNO3), and water deficit + KNO3 (WD + KNO3). Two foliar applications of 3% (m/v) KNO3 were made, the first on day zero of stress and the second on the fifth day. All analyses were performed after 12 days of stress (end of stress). Foliar application of KNO3 to irrigated plants led to increases in relative chlorophyll content, photosynthetic rate, stomatal conductance, transpiration, and carboxylation efficiency. It also induced increases in leaf concentrations of P, Mg, S, Cu, and Fe, in addition to height growth. Under water deficit conditions, plants treated with KNO3 presented higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency, and higher levels of P, K, Mg, S, Cu, and Fe than those not treated with KNO3. The morphometry of the root system was not altered by the treatments. In addition, plants treated with KNO3 under water deficit conditions showed higher growth and a grain yield 32.2% higher than those that did not receive KNO3. These results demonstrated that KNO3 applied to the leaves induced water deficit tolerance in sorghum plants subjected to severe water stress at pre-flowering.

RESUMO O abacaxi ornamental é uma planta rústica e de alto valor comercial. Normalmente, a propagação convencional é realizada por divisão de touceira apresenta baixo rendimento e ainda podendo causar disseminação de doenças. A cultura de tecidos da espécie mostra-se viável, produzindo plantas com alta qualidade genética e fitossanitária em curto espaço de tempo. O presente trabalho teve por objetivo avaliar a multiplicação in vitro de plantas de abacaxi ornamental (Ananas comosus var. bracteatus L.) em diferentes sistemas de micropropagação em associação com concentrações de benziloaminopurna (BAP). Foram utilizadas plantas com cerca de 2 cm de comprimento, transplantadas para os diferentes tratamentos: biorreator, ventilação natural e convencional, combinados com 3 concentrações de BAP (0, 1 e 2 mg L−1). O meio básico utilizado foi o composto pelos sais do meio MS. Maior número de brotos e crescimento da cultura in vitro foram obtidos com o emprego do biorreator e meio de cultura contendo 2 mg L−1 de BAP. O biorreator de imersão temporária permite a renovação do ar no interior dos frascos possibilitando melhor desempenho do cultivo in vitro do abacaxi ornamental quando comparado à micropropagação convencional.

ABSTRACT Ornamental pineapple is a hard plant with significant landscaping value. Typically, conventional propagation is performed by clump division with low yields, and may even spread diseases. Plant tissue culture is viable, yielding plants with a high phytosanitary and genetic quality over a short time period. This study aimed to verify the in vitro multiplication of ornamental pineapple plants (Ananas comosus var. bracteatus L.) in different micropropagation systems, in association with BAP concentrations. Plants with about 2 cm were used, transplanted to the different treatments: bioreactor, natural ventilation and conventional micropropagation, combined with 3 BAP concentrations (0, 1 and 2 mg L−1). The basic medium used consisted of MS salts. The highest number of shoots and in vitro culture growth were obtained with the use of bioreactor and culture medium containing 2 mg L−1 BAP. The temporary immersion bioreactor allows air renewal inside the bottles, leading to a better performance of in vitro cultivation of ornamental pineapple, when compared to conventional micropropagation.

O objetivo do presente trabalho foi verificar o crescimento in vitro de orquídeas em diferentes sistemas de micropropagação, sendo cultivado em biorreator, sistema de ventilação natural e convencional. Plantas de Cattleya walkeriana foram obtidas a partir da germinação de sementes em meio de cultura. Após o a germinação, as plantas foram uniformizadas com aproximadamente 1,0cm de comprimento e inoculadas nos diferentes tratamentos. Os tratamentos contaram dois sistema de micropropagação (convencional e ventilação natural) e três meios de cultura (líquido, sólido com 5 e 6g L-1 de ágar). Foram realizados dois tratamentos adicionais em biorreator de imersão temporária e contínua. O delineamento foi o inteiramente casualizado, consistindo de um fatorial 2x3 com dois tratamentos adicionais, totalizando oito tratamentos com três repetições. O biorreator de imersão temporária promoveu o maior crescimento da parte aérea e do sistema radicular, maior acúmulo de massa seca e melhor controle da perda de água das plantas. O biorreator de imersão temporária é o melhor sistema de micropropagação para o crescimento in vitro de C. walkeriana.

The aim of the present research was to verify the in vitro growth of orchids in different systems of micropropagation, being cultivated in a bioreactor, with natural ventilation and conventional systems. Cattleya walkeriana plants were obtained from the germination of seeds in culture medium. After 8 months, seedlings with 1 cm of length were placed in a culture vessel according to the treatments, which counted with two micropropagation systems (conventional and natural ventilation) in three media of culture (liquid, solid with 5 or 6g L-1 of agar). Two additional treatments in bioreactor of temporary and continuous immersion were performed. The design was entirely randomized (ERD), consisting of a 2x3 factorial with two additional treatments, totaling 8 treatments with three repetitions. The temporary immersion bioreactor promoted a bigger growth of the aerial part and of the root system, bigger accumulation of dry mass and better control of water loss by the plants. The temporary immersion bioreactor is the best micropropagation system for the C. walkeriana growth in vitro.