Effects of end-of-day red and far-red radiation on free sugars, organic acids and amino acids of tobacco

Abstract

Tobacco plants ( Nicotiana tabacum L.) were given 5 min of red (R) or far-red (FR) radiation at the end of each day, following full intensity long (16-hr) and short (8-hr) photoperiods. Contents of free sugars, organic acids and amino acids in the plants were examined along with photo-induced differences in morphological development. Plants under long photoperiods grew more than those under short photoperiods. Within each photoperiod, plants irradiated with R developed shorter stems and darker green leaves than did those irradiated with FR. Long photoperiods resulted in higher concentrations of free sugars and lower concentrations of organic acids than did short photoperiods. Within each photoperiod, plants receiving terminal FR radiation had higher concentrations of free sugars and organic acids than did those receiving terminal R radiation. Plants grown under short photoperiods had a higher amino acid concentration than did those under long photoperiods. Concentration of amino acids in plants grown under long photoperiods was not affected by terminal R or FR. However, under short photoperiods plants irradiated with R had higher amino acid concentrations than did those irradiated with FR.