Abstract
Treading barley (“Mugifumi” in Japanese) is a barley culturing process that is unique and indispensable in Japan. Generally, roller machines or human feet are used to tread young barley several times (Figure 1). As a model examination, a stainless steel instrument was used for treading barley in this study (Figure 2(a)). Treading damages plants and decreases growth, such as the height and weight of aerial parts, which then recover gradually. In our study, the total amino acid contents increased with the treading stress. The treading stress induced a 1.7-fold increase in aspartic acid contents and an approximately 1.6-fold increase in glutamic acid, proline, cystine, and methionine contents. Isolation and purification suggested that the main components of the methanol-eluted fraction from the young green barley were six known phenolic compounds. Saponarin and lutonarin were the main components. The saponarin content was about 160 mg/g (methanol-soluble fraction) at 10 days after germination. We found that the higher antioxidant activity was due to the increased lutonarin/saponarin ratio from 10% to 24%. Therefore, our results suggest that treading stress is useful for young green barley.
Highlights
Barley (Hordeum vulgare L.) is a plant widely distributed and cultivated as cereal grain
We found that the higher antioxidant activity was due to the increased lutonarin/saponarin ratio from 10% to 24%
As the various function of young barley has become clearer [12,13,14,15,16] and the use of barley has become more widespread, we focus on the changes in amino acid contents, flavonoid contents, and antioxidant activity in young green barley leaves caused by treading stress
Summary
Barley (Hordeum vulgare L.) is a plant widely distributed and cultivated as cereal grain. Since it was one of the earliest cultivated cereal grains, there have been many reports about the effect of external stresses on barley growth, such as the soil mineral content, short-term, drought, light, and harm from insects. Iron is very important for chlorophyll synthesis, and plants subjected to iron deficiency exhibited severe chlorosis, accompanied by a significant biomass reduction [1]. Iron chlorosis is very common in alkaline soils such as calcareous ones, since iron availability is limited by high pH. Plants growing in alkaline soils would be subjected simultaneously to salinity and iron deficiency. For the barley in iron-limiting media, phytosiderophore release from the roots into the rhizosphere is stimulated to dissolve soluble iron compounds and enhance iron uptake in the form of iron-mugineic acid complex [2]
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