105(3)_str32

ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 105, No. 3 (2018), p. 249–256
DOI  10.13080/z-a.2018.105.032

Pre-harvest LED lighting strategies for reduced nitrate contents in leafy vegetables

Akvilė VIRŠILĖ, Aušra BRAZAITYTĖ, Julė JANKAUSKIENĖ, Jurga MILIAUSKIENĖ,
Viktorija VAŠTAKAITĖ, Ingrida ODMINYTĖ, Algirdas NOVIČKOVAS, Giedrė SAMUOLIENĖ

Abstract

Short-term pre-harvest red light treatment was evaluated as a tool to reduce nitrate (NO₃) contents in leafy vegetables, cultivated under low-light conditions in a greenhouse. Corn salad (Valerianella locusta L., ‘Vit’), amaranth (Amaranthus chlorostachys Willd., ‘Red Army’) and tatsoi (Brassica rapa var. rosularis L., ‘Rozetto F1’) were cultivated under low-light conditions and 1–7 days before harvest were treated with 638 nm red light emitting diode light. The effects of light treatment on NO₃ and nitrite (NO₂) contents, reducing enzyme activities and plant photosynthetic performance of different leafy vegetable species were explored seeking for comprehensive approach for the control of NO₃ metabolism. Nitrate, nitrite, total protein contents and reducing enzyme activity depend on plant species, lighting treatment duration and their interaction. A remarkable decrease in nitrates and an increase in NO₃ reductase activity were observed 3 days after red light treatment. It followed by a significant increase in NO₂ and protein contents in corn salad and amaranth. A medium correlation between photosynthetic rate and NO₃ contents was determined for tatsoi and corn salad. A negative statistically insignificant correlation between these indicators was established for amaranth. Short-term pre-harvest red light treatment can be applied as a technological tool to reduce NO₃ contents in green vegetables, cultivated under low-light conditions. The obtained results confirm the significant relationship between plant photosynthetic rate and nitrate metabolism, as well as indicate the sensitive, but differential physiological response of different vegetable species to the applied lighting.

Key words: light emitting diodes, nitrate reductase, nitrite reductase, nitrites, photosynthesis, proteins.

Full text: 105_3_str32.pdf