Photoinhibition of Seed Germination in the Maritime Plant Matthiola tricuspidata

Abstract

The three-horned stock, Matthiola tricuspidata (L.) R. Br. is a widespread annual plant of the Mediterranean sandy shores. Its seeds are dark germinating and negatively photosensitive, in accordance with our previous findings for a number of other maritime plants. Full germination was obtained at a wide range of temperatures (5-25 °C) in the dark. Inhibition of germination under light of various spectral qualities could be generally correlated, negatively and positively, respectively, with phytochrome photostationary state (ø) and relative cycling rate of phytochrome (H). The inhibition of germination by white (fluorescent), blue and far-red light, applied either continuously or intermittently, consistently showed a linear dependence upon the logarithm of the flux density of the irradiation. The resulting photoinhibition curves had parallel slopes and, compared to those of other maritime plants, they were shifted to higher flux densities, Continuous blue or far-red irradiations, both establishing a similar ø value (0·26), resulted in statistically similar regression curves, thus favouring the hypothesis that phytochrome is the single photoreceptor in the photoinhibition of seed germination.