Effects of Growth Temperature on Nitrate Concentration and Nitrate Reductase Activity in Komatsuna (Brassica rapa L. var. perviridis)

To study the effect of the growth temperature on the nitrate concentration and nitrate reductase (NR) activity in komatsuna ( Brassica rapa L. var. perviridis ), cv. ‘Harumi-komatsuna’ and ‘Rakuten’ plants were hydroponically grown under growth temperatures of 10/5, 15/10, 20/15, 25/20, 30/25, and 35/30 ° C, and a 12-hr photoperiod at a PPFD of 300 μ mol ・ m − 2 ・ s − 1 . Generally, the nitrate concentration in ‘Rakuten’ plants was higher than that in ‘Harumi-komatsuna’. As the growth temperature increased, the nitrate concentration increased and NR activity decreased in both cultivars. A negative correlation between NR activity and the nitrate concentration was observed. Under high temperature conditions, the NR activity decreased, and, therefore, the nitrate concentration in komatsuna plants increased.