Saturday, December 31, 2011

Blue Light Promotes Healthy Growth




The take home here is that augmenting blue light produces healthier and way more robust seedlings.  Thus we can expect protocols to quickly evolve to take advantage on this phenomenon.  Light starved lettuce is typically weak and this work quantifies the factors involved.

An obvious engineering project is to produce spectrum shading for green houses.  They need shading in any event and if the system blocked red light then the available light would be the beneficial blue light.  The result would be strongly boosted yields with a much higher take up of minerals.

A Fresnel filter should work well here and may be produced by etching the glass if glass is used.  Regardless it is solvable and an obvious improvement that could pay off handsomely.

Blue light irradiation promotes growth, increases antioxidants in lettuce seedlings

by Staff Writers

Abiko, Japan (SPX) Dec 13, 2011

This image shows morphology of red leaf lettuce plants treated with a white fluorescent lamp (FL), blue (B), red (R), and blue+red (BR) LED lights 17 days after sowing (DAS). Credit: Photo by Masafumi Johkan. 



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 HortScience 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.

The complete study and abstract are available on the

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