The seedlings of benitade (Polygonum hydropiper L.) were monthly grown in pots for 8-14 days from April to October to clarify the effect of different growing seasons on their anthocyanin content.
The anthocyanin contents per plant and per mg fresh weight increased rapidly at earlier than later stages of seedlings in all growing seasons. In some months, the increase of anthocyanin content per mg fresh weight was not found in later stages. In comparison among different months, the anthocyanin contents per plant and per mg fresh weight tended to be always higher in April and particularly in May, and lower in July, August and September.
The anthocyanin contents per plant and per rng fresh weight at the emergence of the first true leaf, at the commercial harvesting stage, were also higher in April and May, lower in July, August and September, being less than 60% of the former, and medium in June and October.
Until eight days after the unfolding of cotyledons, with few exceptions, the anthocyanin contents per plant and per mg fresh weight were significantly correlated negatively with mean daily temperature, independently of daily solar radiation, and positively with daily solar radiation, independently of mean daily temperature. At the emergence of the first true leaf, the partial correlation coefficients between anthocyanin content per mg fresh weight and mean daily temperature, daily solar radiation, or number of days after the unfolding of cotyledons were -0.667 (P< 0.01), 0.504 (P<0.05) or -0.019 (P>0.50), respectively.
In addition, cotyledons were higher in anthocyanin content than hypocotyl until the emergence of the first true that more anthocyanin could be synthesized leaf.
From the above results, it is presumed that more anthocyanin could be synthesized in Polygonum seedlings in the seasons with lower temperature or higher solar radiation.