Accelerating the growth and increasing the nutritional value of chard (Beta vulgaris L. var. cicla) by applying yellow coloured filters

To study the spectral light effects and enhance health promoting pigmentation in leafy vegetables or salads in a greenhouse in Tunja, Colombia, chard plants were exposed to sunlight filtered through polypropylene films of green, yellow, blue, red colour or transparent (control). Leaves of chard plants growing under coloured covers, developed a higher chlorophyll a/b ratio of 1.6-1.8:1 compared with those grown under transparent cover. The ratio of carotenoids/ chlorophyll((a+b)) was diminished 7.99.5% under yellow, green and blue covers compared to control, while red cover showed no difference with transparent cover. Accumulated dry mass was largest (4.8 g DM) under yellow film than in any other treatment (2.32.8 g DM). The present study found that the yellow cover induced better growth judged as dry matter, as compared to the control treatment as a consequence of the different contents on the amount of chlorophyll and carotenoids, as well as the higher photochemical quantum yield of PSII (F-v/F-m). These results are discussed with relation to the intensity and spectral quality of light, and to the ratio of red/far-red light (660/730 nm). Chard is used here as an example and the results may be transferable to other leafy vegetables or salads.