Previously, we reported that there are no differences in biotin contents and expression levels of bio2 gene, which is a key enzyme in biotin biosynthesis pathway, in pea sprouts among various cultivation conditions. We also found that biotin required for the growth of pea sprout is sufficiently supplied from the seed. In this study, we investigated whether biotin biosynthesis is affected by cultivation conditions (temperature and insolation) using pea sprouts hydroponically cultivated without seeds.
Seeds were removed after their germinations, and then pea sprouts were grown with culture fluid without biotin under 5 conditions: Control (C), 25°C/12-h light; Small amount of insolation (SI), 25°C/4-h light; No insolation (NI), 25°C/0-h light; Moderate low temperature (MLT), 12°C/12-h light; Low temperature (LT), 4°C/12-h light.
Biotin contents in SI and NI were approximately 67% and 43% of C, and decreased in proportion to the amount of insolation (p &;lt 0.05 and p &;lt 0.001, respectively). Biotin content in LT was also lower than C (p &;lt 0.05).
Secondly, to clarify the seasonal differences of biotin contents in green vegetables, we measured biotin contents in garland chrysanthemum (shungiku), spinach, and potherb mustard (mizuna) harvested in summer and winter in Niigata, Japan.
Bitoin contents in shungiku and spinach in winter decreased to about 56% and 47% of those in summer. (p &;lt 0.001, respectively)
These results strongly suggest that biotin biosynthesis in plants fluctuates responding to the cultivation conditions, especially the amount of insolation. This may lead to seasonal differences of biotin contents in green vegetables.