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Interactive Effects of Photoperiod and Nitrogen Form on the Growth of Leaf Lettuce and Fluctuation of Nutrient Solution pH in Plant Factory Condition

Naoki Hata,Hailong Xu

Published 2020 in Shokubutsu Kankyo Kogaku

ABSTRACT

Beneficial effects of 24-h photoperiod and ammonium (NH 4 -N) fertilization on plant per-formance show potential for application in the production of high value-added vegetables that can only be produced in plant factories. In addition, lettuce is known to be relative-ly resistant to both 24-h photoperiod and NH 4 -N compared to other vegetables. Therefore, in this study, we focused on the interactive effects of photoperiod (12 h or 24 h) and nitrogen form on growth and rhizosphere pH of leaf lettuce cultivated in a plant factory condition. Nitrogen treatments consisted of five nutrient solutions containing the same nitrogen concentration (8 mM) but differing in the NH 4 -N to nitrate (NO 3 -N) ratio (0:100, 25:75, 50:50, 75:25, and 100:0). Under the 12-h and 24-h photoperiods, the pH of the nutrient solution declined to 3.0–3.8 when plants were supplied NH 4 -N, regardless of the NH 4 -N: NO 3 -N ratio. The onset of pH decrease was earlier under the 24-h photoperiod than the 12-h photoperiod, which reflected the differential timing of acceleration in plant growth. Shoot fresh weight at harvest was not significantly different among nitrogen sources containing 0 % to 75 % NH 4 -N under the 12-h photoperiod. On the other hand, early growth under the 24-h photoperiod was superior with nitrogen sources containing 25 % or 50 % NH 4 -N, but growth gradually stagnated probably because of low-pH stress; consequently, shoot weight at harvest was highest in plants supplied with 0 % NH 4 -N and tended to decline with increase in proportion of NH 4 -N. Therefore, little or no posi-tive effect on yield with extension of the photoperiod was observed under NH 4 -N percent-ages ranging from 25 % to 100 % . However, the 24-h photoperiod and NH 4 -N interacted cooperatively to promote leaf greenness.

PUBLICATION RECORD

  • Publication year

    2020

  • Venue

    Shokubutsu Kankyo Kogaku

  • Publication date

    Unknown publication date

  • Fields of study

    Agricultural and Food Sciences, Environmental Science

  • Identifiers
    DOI 10.2525/shita.32.143
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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