Abstract
Optimizing light conditions for vegetable seedling production in a closed transplant production system is critical for plant growth and seedling production. Additionally, energy use efficiency should be considered by growers when managing the light environment. In the present study, cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) were grown under six different daily light integrals (DLIs) at 8.64, 11.52, 14.40, 17.28, 23.04, and 28.80 mol m−2 d−1 created by two levels of photosynthetic photon flux density (PPFD) of 200 and 400 μmol m−2 s−1 combined with photoperiod of 12, 16 and 20 h d−1 provided by white light-emitting diodes (LEDs) in a closed transplant production system for 21 days. Results indicated that quadratic functions were observed between fresh and dry weights of cucumber seedlings and DLI at 6, 11, 16, and 21 days after sowing. Generally, higher DLI resulted in longer root length, bigger root volume and root surface area accompanied with shorter plant height and hypocotyl length; however, no significant differences were observed in root length, root volume, and root surface area as DLI increased from 14.40 to 28.80 mol m−2 d−1. Photon yield based on fresh and dry weights decreased with increasing DLI. In conclusion, increased DLI resulted in compact and vigorous morphology but reduced photon yield of cucumber seedlings produced in a closed transplant production system. In terms of plant growth and energy use efficiency, DLI at 14.40–23.04 mol m−2 d−1 was suggested for cucumber seedling production in the closed production system. Additionally, different control strategies should be applied at different growth stages of cucumber seedlings.
Highlights
The seedling stage and its subsequent cultivation stage of horticultural crops are often separated due to differences in plant density, environmental conditions, and control strategies in modern agriculture [1,2]
Cucumber seedlings grown with daily light integrals (DLIs) at 8.64 and 17.28 mol m−2 d−1 led to higher plant height and longer hypocotyl than those grown with DLI at 28.80 mol m−2 d−1
No significant differences were observed in fresh and dry weights of cucumber seedlings grown under DLI at 8.6, 11.5 and 14.4 mol m−2 d−1 at 6 days after sowing (DAS)
Summary
The seedling stage and its subsequent cultivation stage of horticultural crops are often separated due to differences in plant density, environmental conditions, and control strategies in modern agriculture [1,2]. The demand for vegetable seedlings is gradually increasing as a result of the increasing market requirement of vegetables. The annual demand for vegetable seedlings in China was more than 680 billion plants in. 2018 [3], and the vegetable seedling market in Korea was estimated to be approximately. Raising high-quality vegetable seedlings is vital for increasing crop yield and farmer income. Cucumber (Cucumis sativus L.) is one of the economically main vegetables cultivated worldwide with annual production at 87.8 million tons with China accounting for 80.1% of the world’s cucumber production
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