Search

The concentration of nitrogen fertilizer is matched with the nutrient requirements in different growth stages of plants, which coordinates their vegetative and reproductive growth. In this study, the influences of nitrogen concentration before and after initiation of flower bud differentiation (first and second stage, respectively) on pepper seedling quality were studied. The chlorophyll a content, sucrose synthase activity, and sucrose phosphate synthase activity of pepper seedlings grown under moderate nitrogen (15 mmol L−1) in the first stage combined with high nitrogen (25.61 mmol L−1) in the second stage were 15.7%, 39.3%, and 34.6% higher than those of the same nitrogen concentration (15 mmol L−1) in the first and second stages treatment, respectively. The regression model also showed that the values of flower bud diameter, shoot fresh weight, root fresh weight, and glutamine synthetase activity of pepper were high under the condition of moderate nitrogen in the first stage and higher nitrogen in the second stage. In addition, the results of comprehensive evaluation showed that moderate nitrogen (15 mmol L−1) in the first stage and high nitrogen (25.61 mmol L−1) in the second stage treatment ranked first, which improved carbon and nitrogen metabolism, increased biomass accumulation, and promoted the flower bud differentiation and flowering of pepper seedlings. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L. cv. Zhongza NO. 9) was used as the experimental material to investigate the effects of nocturnal LED supplemental light with the photosynthetic photon flux density (PPFD) of 100, 200, 300 μmol·m−2·s−1, and the light time of 1, 2 h on the seedling quality in a controlled environment, with seedlings without nocturnal supplemental lighting serving as the control. The results demonstrate that an increase in PPFD at night progressively enhances the plant height and leaf number of tomato seedlings, while stem diameter and leaf area initially increase and subsequently decrease. Although light time and light period-of-time at night did not significantly affect seedling morphology, PPFD and light time notably influenced chlorophyll content and net photosynthetic rate. An optimal lighting energy amount at night augmented photosynthetic capacity. However, excessive PPFD induced photoinhibition in the leaves. Additionally, appropriate nocturnal LED supplemental lighting significantly improved the antioxidant capacity of the seedlings, increased proline content, reduced malondialdehyde content, and bolstered the self-protection mechanisms of the seedlings against nocturnal light stress. Both the PPFD and light time at night promoted biomass accumulation in tomato seedlings. Specifically, when supplemental lighting was applied for 2 h at an intensity of 200 μmol·m−2·s−1, both the fresh and dry weights of the shoot and root significantly increased, and the seedling health index was highest. Therefore, appropriate nocturnal LED supplemental lighting positively impacts the health index and photosynthate accumulation of tomato seedlings, but controlling PPFD is essential to avoid photoinhibition. [ABSTRACT FROM AUTHOR]

To achieve high-density tomato seedlings in a plant factory with artificial lighting, tomatoes (Solanum lycopersicum Mill. cv. "Zhongza NO.9") were used as the experimental material. This study expected to analyze the effects of light intensity (150, 200, 250, and 300 μmol·m−2·s−1) and light time (12 and 14 h), as well as daily light integral (DLI, 10.80, 12.60, and 12.96 mol·m−2·d−1) and sowing density (50, 72, and 105 holes per tray), on seedling quality. The results indicated that biomass accumulation, seedling quality, and energy use efficiency of seedlings significantly improved with an increase in DLI. At a DLI of 12.96 mol·m−2·d−1, seedlings sown at a density of 72 holes per tray exhibited comparable growth characteristics and biomass accumulation to those sown at 50 holes per tray. However, under lower DLIs, seedlings at 50 holes per tray displayed superior growth morphology and seedling quality compared to those at 72 holes per tray. This indicates that increasing the DLI can partially mitigate the negative effects of higher sowing density on seedling quality. Light use efficiency (LUE) and energy use efficiency (EUE) were not significantly different between seedlings at 72 and 105 holes per tray but were higher than those at 50 holes per tray. Therefore, optimizing parameters such as DLI and sowing density can effectively enhance the seedling quality, spatial use efficiency, and light use efficiency in industrial seedling production. Based on the results of this study, a DLI of 12.96 mol·m−2·d−1 (achieved with a light intensity of 300 μmol·m−2·s−1 and a light time of 12 h) and sowing density of 72 holes per tray are recommended for cultivating high-quality tomato seedlings while reducing energy consumption. [ABSTRACT FROM AUTHOR]