Effect of Supplementary Light Intensity on Quality of Grafted Tomato Seedlings and Expression of Two Photosynthetic Genes and Proteins

Abstract

Lower quality and longer production periods of grafted seedlings, especially grafted plug seedlings of fruit vegetables, may result from insufficient amounts of light, particularly in rainy seasons and winter. Supplemental artificial lighting may be a feasible solution to such problems. This study was conducted to evaluate light intensity’s influence on the quality of grafted tomato seedlings, ‘Super Sunload’ and ‘Super Dotaerang’ were grafted onto the ‘B-Blocking’ rootstock. To improve their quality, grafted seedlings were moved to a glasshouse and grown for 10 days. The glasshouse had a combination of natural lighting from the sun and supplemental lighting from LEDs (W1R2B2) for 16 h/day. Light intensity of natural lighting was 490 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) and that of supplemental lighting was 50, 100, or 150 μmol·m−2·s−1 PPFD. The culture environment had 30/25 °C day/night temperatures, 70% ± 5% relative humidity (RH), and a natural photoperiod of 14 h as well. Compared with quality of seedlings in supplemental lighting of 50 μmol·m−2·s−1 PPFD, that of seedlings in supplement lighting of 100 or 150 μmol·m−2·s−1 PPFD improved significantly. With increasing light intensity, diameter, fresh weight, and dry weight, which were used to measure shoot growth, greatly improved. Leaf area, leaf thickness, and root biomass were also greater. However, for quality of seedlings, no significant differences were discovered between supplement lighting of 100 μmol·m−2·s−1 PPFD and supplement lighting of 150 μmol·m−2·s−1 PPFD. Expressions of PsaA and PsbA (two photosynthetic genes) as well as the corresponding proteins increased significantly in supplement lightning of 100 and 150 μmol·m−2·s−1 PPFD, especially in 100 μmol·m−2·s−1 PPFD. Overall, considering quality and expressions of two photosynthetic genes and proteins, supplemental light of 100 μmol·m−2·s−1 PPFD (W1R2B1) would be the best choice to cultivate grafted tomato seedlings.

Lighting Direction Affects Leaf Morphology, Stomatal Characteristics, and Physiology of Head Lettuce (Lactuca sativa L.)

“…Photosynthesis is one of the most important chemical reactions in plants, and PSI and PSII are two light energy-driven systems that synergistically function in primary energy conversion reactions [ 43 ]. The PsaA and PsbA genes encode the P700 apoproteins of PSI and the D1 protein of PSII, respectively.…”

Supplemental LED Increases Tomato Yield in Mediterranean Semi-Closed Greenhouse

“…moreover, when giving a small percentage of green (G) light on the RB background, the SL penetration on plant canopy increases [14]. Finally, a SL intensity around 100-150 µmol m −2 s −1 significantly improves photosynthesis, plant growth and tomato quality [15]. These characteristics make LEDs suitable as an SL technology for mediterranean region greenhouse cultivation, particularly during the winter period when the average DLI is a limiting factor to tomato production.…”

Effect of Supplementary Lighting Duration on Growth and Activity of Antioxidant Enzymes in Grafted Watermelon Seedlings

“…In previous studies, the optimal quality and intensity of supplementary lighting were determined [30][31][32][33][34]. Based on these previous studies, three durations of supplementary light (8,12,16 h/day) at 100 µmol•m −2 •s −1 PPFD using mixed LEDs (W 1 R 2 B 1 ) were tested to investigate the effects of different durations of supplementary lighting on the quality of grafted watermelon plug seedlings grown in a glasshouse after the graft healing period.…”