The effect of temperature, photoperiod, and light quality on gluconasturtiin concentration in watercress (Nasturtium officinale R. Br.).

The effects of different growth regimes on gluconasturtiin concentration in watercress (Nasturtium officinale R. Br.) were investigated. Watercress plantlets at the 5th mature leaf stage (ca. 2 weeks old) were exposed to different day and night temperatures, to long (16 h) or short (8 h) days, to red (R) or far-red (FR) light given during the main long day photoperiod, and finally to R or FR light given at the end of the main photoperiod. Watercress plants grown under long days contained a 30-40% higher gluconasturtiin concentration and had a higher fresh weight than watercress plants grown under short days. Watercress plants grown under long days and temperatures of 15 or 10 degrees C had at least a 50% higher gluconasturtiin concentration, but a lower fresh weight, than that of plants grown at 20 or 25 degrees C. Watercress plants grown under metal halide light enriched with R light had approximately a 25-40% higher concentration of gluconasturtiin as compared to the FR-enriched plants. Likewise, a brief R light exposure at the end of the main photoperiod resulted in approximately a 25% or higher concentration of gluconasturtiin as compared to a FR end-of-day exposure. These data indicate that the concentration of gluconasturtiin in watercress can be significantly increased by growing plants at lower temperatures, under long days, and by exposure to R light.