Nitrate is a major source of the inorganic nitrogen taken up by the roots of plants. Nitrate sources are generally derived from inorganic minerals by an energy-consuming chemical process; as a result, the price of chemical fertilizers is gradually increasing year by year. NO₃-N, generated from N₂ using the plasma technique, is an alternative method of producing nitrate from the air. Therefore, in this research, we aimed to determine the efficiency of generating NO₃-N using plasma-activated water (PAW) to replace nitrates from chemical fertilizer in a nutrient solution. Green oak lettuce (Lactuca sativa L.) was grown in a hydroponics system using the double-pot technique. The plants were supplied with three different nutrient solutions (based on Hoagland’s solution), i.e., T1, no nitrate in the nutrient solution (NO₃⁻ = 0); T2, using nitrate sourced from a commercial chemical fertilizer (normal nitrate); and T3, using a nitrate source generated using the pinhole plasma jet technique (plasma nitrate). The other macronutrients and micronutrients in each treatment were equally supplied. The results show that, at the harvested stage (21 days after the plants received treatment), the no-nitrate (T1) treatment provided lower growth and yields. Moreover, compared with the normal nitrate (T2) and plasma nitrate (T3), the results indicate that most growth and yields showed no statistical differences. In terms of nitrate accumulation within plants, it was found that the normal nitrate treatment (T2) had the highest levels of nitrate accumulation, in both the underground and aboveground parts of green oak lettuce. These results confirmed that plasma nitrate could be an alternative source of nitrate N which provided a safer way for the environment and human health in terms of nitrate accumulation. In addition, data related to the chemical analysis of free amino acid concentrations in each treatment are discussed in this research.

This study examines the effects of different LED light spectra and intensities on the growth, photosynthetic performance, and biochemical composition of the ‘Daruma’ cultivar of wasabi (Eutrema japonicum). The primary objective is to enhance the efficiency of indoor cultivation techniques for this economically significant crop. Wasabi seedlings were cultivated under LED lighting with four light intensities (35, 60, 90, and 140 µmol m⁻² s⁻¹) and three spectral combinations: red and white (1:1); red, white, and blue (1:1:1); and white. Growth parameters, including plant height, petiole length, leaf number, and yield metrics such as fresh weight and leaf area, were measured alongside photosynthetic activity and chemical analysis of glucosinolate levels. The results indicate that higher light intensities (particularly 140 µmol m⁻² s⁻¹) greatly enhance overall plant biomass, with red-dominant spectra promoting more significant growth and glucosinolate accumulation, a key secondary metabolite in wasabi. Lower intensities increased chlorophyll content and produced darker green foliage but decreased growth performance. Additionally, the interaction of red and blue light spectra with increased light intensity suggests that specific red light conditions are optimal for maximizing wasabi biomass and biochemical yield. These findings contribute valuable insights for optimizing light regimes for wasabi and similar shade-adapted crops in controlled indoor farming systems, potentially improving yield and quality in plant factories and supporting the future of indoor farming.

Nitrogen (N) is an essential determinant of strawberry growth and productivity. However, plants exhibit varying preferences for sources of nitrogen, which ultimately affects its use efficiency. Thus, it is imperative to determine the preferred N source for the optimization of indoor strawberry production. This study employed the ¹⁵N-tracer technique to investigate the effects of N sources on N uptake, distribution, and use efficiency, as well as the plants’ growth, for ‘Praratchatan 80’ strawberries in a greenhouse. Five treatments were applied: T1 (5.0 mM ¹⁵NO₃⁻), T2 (2.5 mM ¹⁵NO₃⁻ + 2.5 mM NH₄⁺), T3 (5.0 mM ¹⁵NH₄⁺), T4 (2.5 mM ¹⁵NH₄⁺ + 2.5 mM NO₃⁻), and T5 (N-free, control) in a completely randomized design. Significant (p < 0.05) differences were observed in N uptake and distribution and total N concentration among the treatments. Sole NH₄⁺ promoted early N uptake and accelerated flowering, while NO₃⁻ enhanced vegetative growth and later-stage nitrogen use efficiency (NUE). The application of combined NO₃⁻ and NH₄⁺ was most efficacious, balancing the benefits of both N forms. NO₃⁻ treatment enhanced ¹⁵NUE by 46% compared to NH₄⁺, and mixed N sources demonstrated superior and consistent ¹⁵NUE over time. NH₄⁺, alone or with NO₃⁻, expedited flowering by 20 days compared to sole NO₃⁻ and N-free treatments. This study elucidates the importance of the sources of N in optimizing strawberry growth and flowering, providing a foundation for developing tailored N-management strategies. Future research should focus on refining mixed N application ratios and timings, exploring molecular mechanisms of N metabolism, and evaluating long-term impacts on strawberry production sustainability.

Growing Hippeastrum in an open field or a greenhouse requires precision irrigation and fertilizer to promote plant growth and development. Therefore, this research aimed to study the effect of irrigation level combined with fertilization rate on the growth and development of Hippeastrum. Two experiments were carried out to determine the influence of irrigation and fertilizer on the growth, flowering, and bulb quality of Hippeastrum. In the first experiment, bulbs of Hippeastrum ‘Red Lion’ with circumferences of 25 cm were grown in plastic plots using mixed soil as growing media under a 50% shading net. Plants were irrigated daily until drainage and water contained in macropores by gravity action (Field capacity: FC) for 90 days after planting (DAP) and supplied with three different 15N-15P₂O₅-15K₂O fertilization rates, i.e., 0, 2.5, and 5 g per pot. Plant growth and water use efficiency were measured at 45, 60, and 90 DAP. The results showed that plants supplied with 0 g of fertilizer had the lowest plant height and number of leaves per plant at 90 DAP, whereas there was no significant effect of fertilizer rate treatments on flower quality. The water use efficiency, evapotranspiration rate (ET), crop evapotranspiration under standard condition (ETc), crop coefficient (Kc), photosynthetic rate, and stomatal conductance were decreased when plants were supplied with fertilizer at a rate of 0 g per pot at 90 DAP. In the second experiment, plants were irrigated with four levels, i.e., 100, 75, 50, and 25% ETc combined with three fertilization rates, i.e., 0, 2.5, and 5 g per pot. At 180 DAP, the results showed that water deficit treatment (50 and 25% ETc) decreased plant growth and bulb quality. Irrigation with 100% ETc combined with 2.5 or 5 g per pot and irrigation with 75% ETc combined with 5 g per pot were the optimum levels to promote plant growth and bulb quality in Hippeastrum.

Vanda is an economically important orchid that is widely produced in Thailand. Usually, growers apply large amounts of fertilizer throughout the plant, covering the leaves and roots to ensure good quality products. Nitrogen fertilizer, in terms of ammonium (NH₄⁺) and nitrate (NO₃⁻), is generally used as an N source. In addition, nitrogen organic fertilizer (glutamine) is increasingly being used to promote rapid growth in some plants. However, the absorption efficiency of organic N compared with the inorganic form (NH₄⁺ and NO₃⁻) via the roots or leaves of Vanda has not been evaluated. Therefore, this research aimed to compare the fate of organic N (in glutamine form) and inorganic N in Vanda using a ¹⁵N tracer. Vanda ‘Patchara Delight’ was grown in a plastic greenhouse under a 50% shading net at an average temperature of 25 °C and 80% relative humidity (RH). The plants were sprayed weekly via roots or leaves with 100 mL of ¹⁵N solution, 2.5 mM ¹⁵NO₃⁻ + 2.5 mM NH₄⁺ (N1), 2.5 mM NO₃⁻ + 2.5 mM ¹⁵NH₄⁺ (N2), and 2.5 mM glutamine (¹⁵N₂)(N3) for 4 weeks. The plants were then sampled and separated into leaves and roots, and ¹⁵N abundance was analyzed using an elemental analyzer coupled with an isotope-ratio mass spectrometer or IRMS. The plants that received only glutamine via roots showed the highest ¹⁵N use efficiency (¹⁵NUE) of about 28.19% at 30 days after the first feeding (DAF), whereas ¹⁵NH₄⁺ resulted in the lowest ¹⁵NUE among ¹⁵N sources. Regardless of the application site, plants supplied with ¹⁵NH₄⁺ showed a lower labeled N concentration and labeled N content in stems and leaves than those fed with a combination of ¹⁵NO₃⁻ or a sole application of ¹⁵N-glutamine. The largest labeled N concentrations in stems, leaves and roots were found in plants supplied with sole glutamine via roots. At 30 DAF, ¹⁵N solution either combined with ¹⁵NO₃⁻ or solitary ¹⁵N-glutamine did not affect the labeled N concentration in leaves. Therefore, supplying organic N in glutamine form to Vanda can provide a 4–7% higher NUE than inorganic N, especially when supplying the solution to the roots.

Strawberries are valued globally for their nutritional, aesthetic, and economic benefits. Optimizing blue-to-red LED ratios and nitrogen levels is essential for sustainable indoor strawberry cultivation. This factorial study investigated the effects of blue and red LED combination ratios (L1; 1:3, L2; 1:4, and L3; 1:6) and nitrogen levels (N1; 100 and N2; 200 mg/L) on the physiology and performance of strawberries in a plant factory. The results revealed that the interaction of L3 coupled with N2 maximized the vegetative growth of strawberry plants, whereas L2 and N2 produced the greatest biomass, while L2 interacted with N1 to expedite flowering. Photosynthesis and transpiration were enhanced by L3, particularly with 100 mg/L of nitrogen. The highest fruit yield and total soluble solids were obtained at the interaction of L3 and N1. Leaf nutrient analysis showed the highest nitrogen concentration at L1, while potassium increased with higher red LED ratios. The 100 mg/L nitrogen treatment resulted in higher leaf potassium concentrations than the 200 mg/L. These findings emphasize that LED spectra and nitrogen levels interact to optimize the physiology, vegetative and reproductive growth, maximizing fruit yield and quality in indoor strawberry cultivation. The study also concludes that the application of blue and red LED in the ratio of 1:6 with 100 mg/L nitrogen can improve indoor ‘Praratchatan 80’ strawberry performance.