Effect of photoperiod and end-of-day light quality on alkaloids and phenolic compounds of tobacco.

Tobacco plants (Nicotiana tabacum L.) were grown on long or short photoperiods followed by 5 minutes of red or far red radiation each day. Plants that received 16-hour photoperiods had a significantly higher concentration of total alkaloids and total phenolics than those that received 8-hour photoperiods. Significantly higher total alkaloid content was found in plants that received red rather than far red radiation last each day. Within each photoperiod, plants that received far red had higher concentrations of soluble phenols, particularly of chlorogenic acid. The interactions among these variables upon alkaloid and phenolic contents are discussed.