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Photocontrol of flowering and stem extension of the intermediate‐day plant Echinacea purpurea
Author(s) -
Runkle Erik S.,
Heins Royal D.,
Cameron Arthur C.,
Carlson William H.
Publication year - 2001
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2001.1120318.x
Subject(s) - photoperiodism , echinacea (animal) , phytochrome , biology , light intensity , long day , botany , horticulture , red light , zoology , physics , optics
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 (≤14%) plants flowered under 10‐ or 24‐h photoperiods, indicating E . purpurea is a strongly quantitative IDP. Plants were also induced to flower when 15‐h dark periods were interrupted with as few as 7.5 min of low‐intensity lighting (night interruption, NI). Flowering was progressively earlier as the NI increased to 1 h, but was delayed when the NI was extended to 4 h. Stem length increased by ≥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.