Alfredo Rodrigues de Sena Neto

This study investigated the effect of incorporating zinc oxide nanoparticles (ZnO-NPs) on the acclimatization and growth of micropropagated seedlings of Paliavana sericiflora Benth. The seedlings were grown in 4.5 cm ³ microcontainer in polypropylene cups using a mini-incubator system. The experimental factor was the concentration of ZnO-NPs added to the polymer in the tubes (PLA), with the following levels: 0, 25, 50, 75, 100 and 1000 mg kg ⁻¹ . After the acclimatization period, the plants were transplanted into 250 cm ³ tubes. The results indicated that the optimal concentration of ZnO-NPs was 100 mg kg ⁻¹ , which promoted greater plant vigour, higher dry matter accumulation, and superior development in terms of height, stem diameter, and leaf area, while also altering the nutritional composition by increasing the levels of N, P, Ca, Mg, and S. This concentration resulted in 100% seedling survival. In contrast, the concentration of 1000 mg kg ⁻¹ of ZnO-NPs had a phytotoxic effect, highlighting the need for more in-depth studies into the relationship between the concentration of ZnO-NPs and the specific characteristics of each plant species. The high correlation between vegetative variables and the ideal concentration of ZnO-NPs suggests that incorporating ZnO-NPs into microcontainer could be a promising strategy for optimizing the acclimatization and growth of micropropagated seedlings of Paliavana sericiflora and other plant species.

Background: Paliavana sericiflora, a vulnerable species. Brazilian endemic from the rupestrian fields, lacks established seedling production methods. Micropropagation offers a promising alternative for its conservation. This study evaluated the influence of spectral quality on in vitro multiplication, elongation, rooting and acclimatization in biodegradable microcontainer of P. sericiflora. Established shoots were subcultured in MS medium with plant growth regulators for bud multiplication under four spectral qualities: white, red, blue, and purple (red and blue combination 1:1). The same spectra were used in the elongation and rooting stages. Results: All light spectra influenced bud multiplication. Buds with the highest vigour were produced under white, blue, and violet light, with values close to 1. Red light induced more elongated buds, but with lower vigour compared to the others. The elongation and rooting stages were most successful under purple or white light, yielding the highest number of roots approximately 12 roots per plant. The use of biodegradable microcontainers resulted in 100% survival, producing more vigorous plants for nursery hardening-off. Conclusion: Spectral quality had no significant effect on bud multiplication, but purple and white lights promoted better elongation, rooting, and plant vigour. These stages can be conducted simultaneously, optimizing time and development. Acclimatization was efficient, and seedlings were ready for hardening-off in approximately 110 days.

O intuito inicial deste trabalho foi estudar a tensão superficial e a viscosidade de óleos e de misturas de óleos visando desenvolver um estudo sobre a miscibilidade desses lubrificantes. Ao fazer os testes descritos, pouca variação foi obtida inviabilizando tal estudo. Nessas condições, optou-se apenas por investir no que já seria a segunda etapa do trabalho: investigar a interação desses óleos e das misturas dos mesmos com uma determinada superfície metálica, visando assim, correlacionar a molhabilidade do óleo na superfície com a eficiência de lubrificação do mesmo. Para isso, foram utilizados dois óleos e três misturas dos mesmos, totalizando cinco amostras. Como resultado final, obteve-se a maior molhabilidade, numa superfície de alumínio, para a mistura 50-50, denotando, assim, que a mesma possuía maior interação com a superfície metálica e, teoricamente, uma maior eficiência de lubrificação. A eficiência citada seria maior desde que os outros componentes dessa mistura não apresentassem uma incompatibilidade muito grande. Evidentemente, a análise química demandada para sanar tal preocupação foi deixada como sugestão para trabalhos futuros.

One of the most widespread applications of poly(lactic acid) (PLA) is as a raw material in the form of filaments for 3D printing. To improve final disposal alternatives and minimize their effects on the environment, the aim of this study is to determine the biodegradability of 3D-printed PLA waste composted in a landfill with leachate soil and garden soil for 90 days and 180 days. The soil characteristics and material properties were evaluated by laboratory analyses. Changes in soil chemical composition and the loss of microorganisms were recorded. The thermal and mechanical properties of PLA did not change significantly, but fungal colonies, encrustation, and changes in the original colour were found, indicating the onset of surface biodegradation of the samples. Controlled conditions or longer periods would be needed to maintain an ecosystem favourable to biodegradation; otherwise, PLA could accumulate in the environment, causing future pollution problems.

Microplants of Eucalyptus microcorys were produced through indirect organogenesis, and the interaction of plant growth regulators (PGRs) (TDZ-thidiazuron and NAA-α-naphthalene acetic acid), juvenile tissues (cotyledon and hypocotyl) and different types of polylactic acid (PLA) microvessels on plant production were evaluated. Cotyledon-derived callus induction increased by 30–60% in all tested combinations of TDZ and NAA concentrations compared the absence of PGRs. Hypocotyl-derived callus induction was improved in most tested combinations of TDZ and NAA concentrations. Moreover, 100% callus induction from both tissues was achieved with TDZ (1, 2 and 3 mg L⁻¹) + NAA (0 mg L⁻¹). Bud induction from cotyledon tissues was improved with TDZ (1 and 3 mg L⁻¹) + NAA (0 mg L⁻¹) and from hypocotyl with TDZ (1 and 2 mg L⁻¹) + NAA (0 mg L⁻¹). Shoot elongation from cotyledon tissues was not improved from any combination of PGRs, whereas TDZ (1 mg L⁻¹) + NAA (0 mg L⁻¹), TDZ (1 mg L⁻¹) + NAA (4 mg L⁻¹), TDZ (2 mg L⁻¹) + NAA (4 mg L⁻¹) and TDZ (3 mg L⁻¹) + NAA (2 mg L⁻¹) improved shoot elongation from hypocotyl tissues. Adventitious rooting and acclimatization of microcuttings ranged from 40 to 70% in three of the tested microvessels. The acclimatized microcuttings had low genetic variability. Successful production of E. microcorys microplants was achieved in this study using hypocotyl tissue and cultivated a culture medium supplemented with TDZ and NAA, using PLA-based microvessels.

In this study, we investigated the influence of isothermal treatment of poly(lactic acid) (PLA) 3D printed samples at different crystallization temperatures. In this case, we analyzed the effect of each crystallization temperature on spherulites formation in printed PLA, affecting the final mechanical properties of pieces. For such, the thermomechanical properties, morphological structure, and crystallization kinetics were analyzed before and after thermal treatment. The 3D printed samples were heat treated at 80°C, 90°C, 100°C, 110°C, and 119°C. With annealing, we observed an improvement in the mechanical PLA properties; however, the exothermic crystallization peak was different for the samples. Pieces before annealing were found to have a low crystallinity index (Ic) of 2%–7%, and the pieces after annealing presented a considerable Ic (27%–34%). Annealing temperatures of 100°C, 110°C, and 119°C produced the fastest crystallization kinetics, while annealing temperatures of 80°C and 90°C resulted in the lowest crystallization kinetics for complete crystallization. After annealing, improvement in the flexural strength (34%–47%) and Young's modulus (26%–51%) for all annealed pieces occurred. The appropriate condition was observed at 100°C, which was the onset temperature of crystallization, owing to the combination of the shorter time of crystallization with the increased mechanical properties.