Lighting intensity and photoperiod serves tailoring nitrate assimilation indices in red and green baby leaf lettuce

• Published in: Journal of the science of food and agriculture 2019-11, Vol.99 (14), p.6608-6619
• Main Authors: Viršilė, Akvilė, Brazaitytė, Aušra, Vaštakaitė‐Kairienė, Viktorija, Miliauskienė, Jurga, Jankauskienė, Julė, Novičkovas, Algirdas, Samuolienė, Giedrė
• Format: Article
• Language: English
• Subjects: Amino acids; Assimilation; Biological assimilation; Chlorophyll; Chlorophyll - analysis; Chlorophyll - metabolism; Color; Cultivars; daily light integral; Energy metabolism; Energy utilization; Flux density; free amino acids; Lactuca - chemistry; Lactuca - growth & development; Lactuca - metabolism; Lactuca - radiation effects; Leaves; Lettuce; Lettuces; Light; Light intensity; Luminous intensity; Nitrates; Nitrates - analysis; Nitrates - metabolism; nitrites; Nitrites - analysis; Nitrites - metabolism; Organic chemistry; Parameters; Photoperiod; Photoperiods; Photosynthesis; Physiological effects; Physiology; Plant growth; Plant Leaves - chemistry; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Leaves - radiation effects; Shortages; total proteins
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.9948

BACKGROUND Understanding plant responses to light quantity in indoor horticultural systems is important for optimising lettuce growth and metabolism as well as energy utilisation efficiency. Light intensity and photoperiod sufficient for normal plant growth parameters might be not efficient for nitrate assimilation. Therefore, this study explored and compared the effects of different light intensities (100–500 μmol m−2 s−1) and photoperiods (12–24 h) on the growth and nitrate assimilation in red and green leaf lettuce (Lactuca sativa L.). RESULTS For efficient nitrate assimilation, 300–400 μmol m−2 s−1 photosynthetic photon flux density (PPFD) and 16–18 h photoperiod is necessary for red and green lettuces. The insufficient light quantity resulted in reduced growth and remarkable increase in nitrate and nitrite contents in both cultivars. Short photoperiods, similarly to low PPFD, growth parameters, chlorophyll indices and nitrate assimilation indices showed the shortage of photosynthetic products for normal plant physiological processes. Short photoperiods had the least pronounced effect on nitrate and nitrite contents in lettuce leaves. CONCLUSION Light intensity was superior compared to photoperiods for efficient nitrate assimilation in both lettuce cultivars. Under short photoperiods, similarly to low intensity, growth parameters, chlorophyll index and nitrate assimilation indices showed a shortage of photosynthetic products for normal physiological processes. The free amino acid concentration increased, but it was not efficiently incorporated in proteins, as their level in lettuce was lower compared to those for moderate photoperiods. © 2019 Society of Chemical Industry