Photocontrol of flowering and stem extension of the intermediate-day plant Echinacea purpurea.

Intermediate-day plants (IDP) flower most rapidly and completely under intermediate photoperiods (e.g., 12-14 h of light), but few species have been identified and their flowering responses are not well understood. We identified Echinacea purpurea Moench as an IDP and, based on our results, propose a novel mechanism for flowering of IDP. Two genotypes of E. purpurea ('Bravado' and 'Magnus') flowered most completely (>/=79%) and rapidly and at the youngest physiological age under intermediate photoperiods of 13-15 h. Few (/=230% as the photoperiod or NI duration increased, until plants received a saturating duration (at 14 or 1 h, respectively). Flowering was inhibited when 16-h photoperiods were deficient in red (R, 600-700 nm) light, and was promoted when photoperiods were deficient in far-red (FR, 700-800 nm) light. Because of our results, we propose the flowering behavior of IDP such as E. purpurea is composed of two mechanisms: a light-dependent response operating through light-labile (type I) phytochrome in which flowering is inhibited by an LD, and a light-stable (type II) phytochrome (i.e., phyB, D and E) response in which flowering is promoted by a short-night.

Relationship of light quantity and anthocyanin production in Pennisetum setaceum Cvs. rubrum and red riding hood.

Pennisetum setaceum cvs. Rubrum and Red Riding Hood are purple-pigmented ornamental grasses when grown in high-light environments. In low-light environments, foliage appears light purple or green, and as a result, aesthetic appeal is reduced. The impact of light on anthocyanin pigmentation was compared for P. setaceum Rubrum foliage and flowers and Red Riding Hood foliage grown under different light intensities and light sources. Light environments included UV supplemental light in the greenhouse, high-pressure sodium supplemental light in the greenhouse, cool-white fluorescent light in a growth chamber, and full sun outside. Anthocyanins in two cultivars of P. setaceum were analyzed by HPLC and characterized by (1)H and (13)C NMR spectral experiments. Two anthocyanins, cyanidin 3-glucoside and cyanidin 3-rutinoside, were identified in the leaves and flowers of both cultivars and quantified by HPLC analysis. The major anthocyanin in both cultivars was cyanidin 3-glucoside and had highest concentration (0.199% fresh weight) in Rubrum leaves grown under fluorescent lights in the growth chamber with a photoperiod of 24 h and a daily light integral (DLI) of 13.3 mol m(-)(2) day(-)(1) and in Rubrum and Red Riding Hood leaves and flowers (0.097 and 0.12% fresh weight) from plants grown outside in full sun with a photoperiod ranging from 15 to 13.5 h and DLI of 42 mol m(-)(2) day(-)(1). The minor anthocyanin, cyanidin 3-rutinoside, had the highest quantity in plants grown in low-light-intensity greenhouse environments with a photoperiod ranging from 15 to 13.5 h and DLI of 2.3-7.0 mol m(-)(2) day(-)(1). The functional significance of anthocyanins in P. setaceum Rubrum is discussed.