Participation of Photosynthesis in Floral Induction of the Long Day Plant Anagallis arvensis L.

Abstract

The saturating photon flux density (400-700 nm) for induction of flowering of the long day plant A. arvensis L. [ssp. arvensis] was 1900 Mmol/m2/.s (6000 foot-candles) when an 8 h daylength was extended to 24 h by a single period of supplementary irradiation. The saturating photon flux density for photosynthetic CO2 uptake during the same single supplementary light period was lower, at about 1000-650 Mmol/m2/.s (3000-2000 foot-candles). The per cent flowering and mean number of floral buds per plant were significantly reduced when the light extension treatment was given in CO2- free air, and glucose (10 k/m3 in water) relieved this effect. Glucose solution also significantly increased flowering of plants given supplementary light treatment in atmospheric air under a photon flux density of 80 Mmol/m2/.s. Increasing the CO2 concentration to 1.27 g/m3 of CO2 in air during the supplementary light period did not increase flowering. Apparently high photon flux densities promote flowering of Anagallis through both increased photosynthesis and the photomorphogenic action of high irradiance.