Background: Shoot architecture is one of the fundamental traits in plants that diversifies their visual appearance. It is also an important agronomic trait as it substantially affects productivity and labor costs in crop species. Cucumber ( Cucumis sativus L.) is a widely cultivated vegetable due to its economic value. As cucumber plants enter the vegetative and reproductive phases simultaneously, the shoot apical meristem continues to produce nodes bearing leaves, each capable of flower development in the axil. Therefore, the characteristics of node formation rate, which is generally recognized as a component of plant growth index ‘shoot vigor’ by growers, are expected to influence fruit yield. However, it remains unclear how and to what extent cultivar-dependent differences in node formation rate contribute to variation in yield. Results: We examined four Japanese cucumber cultivars (‘Josho-661’ [‘Josho’], ‘S-30’, ‘Green-Flush’, and ‘Yusho’), which are considered to differ in shoot vigor. ‘Josho’ exhibited the highest node formation rate and the highest fruit yield (36.3 kg m ^–2 ), whereas ‘Yusho’ developed fewer nodes and achieved the lowest yield (28.1 kg m ^–2 ). However, ‘S-30’ showed the highest dry-matter productivity, although ‘Josho’ exhibited better dry-matter partitioning to fruits. These results revealed that node formation rate and the consequent dry-matter allocation rather than dry-matter productivity can become limiting factors in cucumber yield. In addition, we conducted a comparative mRNA sequencing analysis of shoot tips to explore transcriptomic diversity and functional enrichment underlying the cultivars, which implied that variations in SAM maintenance gene, mitotic activity in SAM, and shoot tip temperature might be behind the difference in node formation rate. Conclusions: The growth analysis revealed that dry-matter productivity was not necessarily correlated with fruit yield and highlighted the potential impact of shoot vigor, particularly node formation rate, on cucumber fruit yield. Transcriptomic diversity observed in this study would genetically reinforce cucumber yield model.

Using organic fertilizer made from waste materials is beneficial for both the economy and the environment, promoting sustainability and reducing pollution. In hydroponics, decomposition converts these materials into fertilizer, with multiple parallel mineralization (MPM) enabling efficient nutrient conversion by microorganisms. The tomato cultivar “Momotaro Next” was cultivated hydroponically in order to determine whether organic fertilizer derived from soluble bonito fish waste (OF) through MPM could be used in tomato hydroponic cultivation compared with a chemical nutrient solution treatment (CF). In this study, ammonium (NH₄⁺) was generated through the OF decomposition process. During cultivation, the ammonium concentration tended to increase, while the nitrate (NO₃⁻) concentration tended to decrease. The total yield (TY), total dry matter (TDM), and leaf area index (LAI) were lower after OF treatment than after CF treatment. Notably, the TY, TDM, and LAI were 5.4 kg m⁻², 594 g plant⁻¹, and 1.7 for OF and 6.8 kg m⁻², 895 g plant⁻¹, and 3.8 for CF, respectively. The results of the tomato fruit qualities show no significant differences for total soluble solids (TSS) (%Brix), lycopene, glucose, fructose, or sucrose. However, significant differences were observed for gamma-aminobutyric acid (GABA), glutamate, aspartate, and citric acid. The lower yield and quality of the tomato crop with the OF treatment were caused by the high concentration of NH₄⁺ that occurred during cultivation due to a nonoptimal mineralization process. Therefore, a well-managed MPM process could improve crop quality by reducing the risk of high NH₄⁺.

Introduction: Liquid digestate produced from manure-based methane fermentation contains organic and inorganic forms of nitrogen, phosphorus, potassium, and other micronutrients that have potential as plant nutrients, but its use in soilless horticulture requires appropriate microbial processing due to high ammonium concentrations and possible salinity-related constraints. Ammonium (NH ₄ ⁺ ), the predominant nitrogen form in methane fermentation digestate, must be converted to nitrate (NO ₃ ^- ) by nitrifying microorganisms before application in hydroponic systems. The multiple parallel mineralization (MPM) method enables controlled microbial nitrification of digestate nitrogen. Methods: In this study, MPM-processed methane fermentation digestate (MPM digestate) generated nitrate through microbial nitrification, maintaining an average nitrate–nitrogen concentration of approximately 226 mg L ^- ¹ in the hydroponic nutrient solution throughout the cultivation period. Yield components of the tomato cultivar ‘Momotaro Hope’ grown in an open hydroponic system were compared between MPM-digestate and chemical fertilizer (CF) treatments for up to 124 days after transplanting (DAT), corresponding to the harvest of the seventh fruit truss. Results: While total season yield and fruit quality parameters, including total soluble solids (TSS), lycopene, and γ-aminobutyric acid (GABA), did not differ significantly between treatments, plant growth responses varied temporally. The cultivation period was divided into three growth stages (Stages I–III) based on key growth indicators. During Stage III (88–124 DAT), the MPM-digestate treatment exhibited significantly lower total dry matter (TDM), light use efficiency (LUE), and stage-specific cumulative yield than the CF treatment, although the proportion of dry matter allocated to fruit was 18% higher under MPM digestate during this stage. Discussion: These late-stage reductions may be associated with elevated electrical conductivity (EC) in the drainage solution observed during Stage II (34–87 DAT) under the MPM-digestate treatment. Increased EC values approaching 5 mS cm ^- ¹, likely influenced by elevated Na ⁺ and Cl ^- concentrations, may have induced osmotic stress or ion-specific nutrient imbalances that affected subsequent plant performance. Conclusion: MPM-processed methane fermentation digestate can be utilized in hydroponic tomato cultivation when drainage EC is carefully managed, achieving fruit quality comparable to conventional fertilization, although late-stage biomass accumulation and yield may be reduced under elevated salinity conditions.

In eggplant production, parthenocarpic cultivars are increasingly adopted to reduce labor associated with exogenous hormone applications for fruit set. Although optimizing training systems is essential to maximize the potential of these cultivars, associated quantitative evaluations of key physiological determinants, such as dry matter production and source–sink balance, remain limited. In this study, we investigated the effects of stem numbers on the yield and physiology of parthenocarpic eggplants grown in a soilless culture. Three treatments were established with varying stem numbers per plant (one, two, and four stems) and uniform stem density per area (3.75 stems m⁻²). The total yield and fruit number per unit area were highest in the one-stem treatment (1S) (8.5 kg m⁻² and 60.0 fruits m⁻², respectively), followed by the two-stem (2S) (7.1 kg m⁻² and 50.9 fruits m⁻²) and four-stem (4S) (6.4 kg m⁻² and 46.6 fruits m⁻²) treatments. Total dry matter production (TDM) varied similarly and was significantly higher in the 1S treatment than in the other systems. The 1S treatment exhibited rapid canopy development, reaching a higher leaf area index in the early stages, which contributed to greater cumulative light interception. Light use efficiency did not differ significantly among the treatments (5.2, 4.6, and 4.3 g MJ⁻¹ for the 1S, 2S, and 4S treatments, respectively). Correlation analysis revealed a strong positive relationship between TDM and yield, whereas dry matter partitioning to fruit remained stable across treatments. These results indicated that the yield under these conditions was strongly driven by source capacity. We conclude that this single-stem training system represents an effective strategy for enhancing the canopy development and yield of parthenocarpic eggplants.

Zucchini is a unisexual plant that produces both male and female flowers, and the number of female flowers is higher in the upper node. Because the rate of female flower production increases over the long term, the number of fruits harvested and the yield can increase. Therefore, we investigated the relationship between the rate of female flowers, dry matter production, and fruit yield in long-term production over 168 days (from 7 Oct. 2020 to 24 Mar. 2021). The proportion of female flowers with nodes higher than the 40th was 86.2%, which was reduced to 67% or 50% by trimming the young female flowers. No significant difference in total dry matter production or the fraction of dry matter distributed to the fruit was observed between the untreated control and the 67% of female flower plants at the end of the experiment. The light extinction coefficient of the zucchini canopy was k = 1.05. The photosynthetically active radiation intercepted by the plants was estimated from the light extinction coefficient, leaf area index (LAI), and light use efficiency (LUE). The fresh fruit yield was the highest in the control plants and was 6.9 ± 0.2 kg·m−2 at the end of the experiment. Although fresh fruit yield decreased in the 50% female-flower restricted plants, a difference in fresh fruit yield between the control and 50% female-flower restricted plants was not observed until 126 days after transplanting (DAT), i.e., 10 Feb. 2021. Therefore, the excess female flower rate in the upper node did not increase the fresh fruit yield under lower solar radiation. In this study, we estimated the values required to develop a model to predict fruit yield and a potential increase in yield during long-term zucchini production.