TITLE:
Effects of Irradiation with Light of Different Photon Densities on the Growth of Young Green Barley Plants
AUTHORS:
Tianxiao Meng, Eriko Nakamura, Nobuto Irino, Khem Raj Joshi, Hari Prasad Devkota, Shoji Yahara, Ryuichiro Kondo
KEYWORDS:
Young Green Barley, Light-Emitting Diode, CyanogenicGlucosides, Amino Acid, Tocopherol
JOURNAL NAME:
Agricultural Sciences,
Vol.6 No.2,
February
13,
2015
ABSTRACT:
In recent years,
young green barley has been increasingly used as a functional food ingredient.
Studies have shown that cultivated young green barley has different levels of
amino acids, vitamin C, and polyphenol content depending on the harvest time.
Furthermore, some studies have investigated the effect of the growing
conditions on cultivated barley in particular the use of light-emitting
diodes (LED). Young green barley was exposed to three light sources of
different wavelengths (sun light [ASL], light-emitting diode[LED] - Red 9 + Blue 1 [LED-R9:B1], LED - Red 4 + Green 1+
Blue 1 [LED-R4: G1:B1]). Under light with photon densities of 200 μmolmL-2·s-1,
the dry weight of young green barley was not affected, while the differences
were observed in the morphology of the underground portion of the plant (roots)
depending on the light source. The roots of the plant grown in ASL weighed
twice as much as those that were grown under LED irradiation. Furthermore, LED
irradiation caused an increase in the amino acid content in plants; the amino
acid content of plants grown under LED-R9:B1 was twice as much as that grown
under ASL irradiation. Four kinds of cyanogenicglucosides (CGs) were isolated,
identified, and their levels were measured. The plant grown under LED-RGB
irradiation, including LED-G, produced approximately 20% more CGs as compared
to the plants grown under the other two light sources. Thus, it was inferred
that young green barley exhibited a stress response under LED-G light and
accumulated CGs in the stems and leaves with prepare for any damage that may
occur on the leaf surface. The nitrogen (N) content in the root was the lowest,
while the CG content was the highest in the plant grown under LED-RGB
irradiation. It is inferred that the N content decreased because N was
eliminated from the roots to allow for accumulation of CGs response to stress.
In general, the growth experiments to use an irradiation condition in which the
distance between the light source and plant floor is fixed. It is not clear
whether the photon density level received by the top leaves is fixed according
to plant growth, by changing the height of plant growing shelf. Therefore,
against this background, when the photon density was increased from 200 to 300
μmolmL-2·s-1under ASL irradiation, only a minimal change
was observed in the root weight, while the weight of the part of the plant
above the ground surface (stems and leaves) increased by approximately 30%,
with a 10% increase in the amino acid content.