Blue light irradiation promotes growth, increases antioxidants in lettuce seedlings

Dec 12, 2011

The quality of agricultural seedlings is important to crop growth and yield after transplantation. Good quality seedlings exhibit characteristics such as thick stems, thick leaves, dark green leaves, and large white roots. Scientists have long known that plant development and physiology are strongly influenced by the light spectrum, which affects seedling structure. Raising seedlings irradiated with blue light has been shown to increase crop yield after planting because of the high accumulation of phenolic compounds. Although most studies with blue light only or blue mixed with red light have indicated that blue light-containing irradiation produces higher plant biomass, recent research has suggested that yield and crop quality could be improved by controlling light quality.

Researchers from Japan's Central Research Institute of Electric Power Industry premiered a study in that determined the effects of raising seedlings with different light spectra—such as with blue, red, and blue + red LED lights—on seedling quality and yield of red leaf lettuce plants. Photosynthetic pigments, polyphenols, and antioxidant activity of lettuce seedlings treated with different light spectra were also determined.

The team performed experiments in which pregerminated seeds of red leaf lettuce were subjected to various light treatments using blue and red light for one week. At the end of the light treatment (17 days after sowing), the leaf area and shoot fresh weight of the lettuce seedlings treated with red light increased by 33% and 25%, respectively, and the dry weight of the shoots and roots of the lettuce seedlings treated with blue-containing LED lights increased by greater than 29% and greater than 83% compared with seedlings grown under a white fluorescent lamp. The shoot/root ratio and specific leaf area of plants irradiated with blue-containing LED lights decreased.

At 45 days after sowing (DAS), higher leaf areas and shoot fresh weight were obtained in lettuce plants treated with blue-containing LED lights. "The total chlorophyll contents in lettuce plants treated with blue-containing and red lights were less than that of lettuce plants treated with florescent light; the chlorophyll a/b ratio and carotenoid content increased under blue-containing LED lights", the researchers wrote. Polyphenol contents and the total antioxidant status were greater in lettuce seedlings treated with blue-containing LED lights than in those treated with florescent light at 17 DAS.

The scientists concluded that raising seedlings treated with blue light promoted the growth of lettuce plants after transplanting. "This is likely because of high shoot and root biomasses, a high content of photosynthetic pigments, and high antioxidant activities in the lettuce seedlings before transplanting. The compact morphology of lettuce seedlings treated with blue LED light would be also useful for transplanting", noted corresponding author Kazuhiro Shoji.

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More information: The complete study and abstract are available on the ASHS HortScience electronic journal web site: hortsci.ashspublications.org/c… /abstract/45/12/1809

Provided by American Society for Horticultural Science

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Nanobanano
5 / 5 (1) Dec 12, 2011
This is pretty old, or else redundant.

I've seen articles and even television documentaries on Discovery, funded by NASA and JPL, regarding this as much as two years ago.

The growth rates they got with some foods was completely phenomenal, and I've even discussed it here in the past.

I discussed the idea of using light traps and new technology such as meta-materials to modify the wavelengths of sunlight to make super efficient, all solar powered hydroponics facilities.

What I HAVEN'T seen is a study on the molecular nutritional properties of food crops grown in this manner, to ensure all the vitamins and minerals are as they should be. Somehow everyone seems to overlook that aspect of the science.
Pirouette
1 / 5 (2) Dec 12, 2011
I agree that overall size and other factors may have nothing to do with nutritional outcomes of the seedlings at mature stage. I haven't tried blue or red light yet, but it might be worth testing. Heavier yields might be offset by poorer quality of vitamin and mineral uptake from the soil. That's something for me to investigate next year. So far, I've only used white light, but I'm open to beneficial changes.