Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8886835 | Environmental and Experimental Botany | 2018 | 35 Pages |
Abstract
Shade-avoidance responses can be triggered by a decrease in the red (R, 600-700â¯nm) to far-red (FR, 700-800â¯nm) radiation ratio, by a decrease in photosynthetic photon flux density (PPFD), or both. The effects of decreased PPFD on plant responses are often confounded with the effects of reduced blue (B, 400-500â¯nm) photon flux density, which is another signaling factor for shade-avoidance responses. We postulated that PPFD would not influence R:FR-mediated shade-avoidance responses if B photon flux density was constant. We grew seedlings of petunia (Petunia Ãhybrida), geranium (Pelargonium Ãhortorum), and coleus (Solenostemon scutellariodes) under three R:FR (1:0, 2:1, and 1:1) at two PPFDs (96 and 288â¯Î¼molâ¯m-2â¯s-1), all with a B photon flux density of 32â¯Î¼molâ¯m-2â¯s-1. As R:FR decreased, stem length in all species increased. Decreasing R:FR increased individual leaf area of petunia, and shoot dry weight of petunia and coleus. Increasing PPFD decreased chlorophyll concentration and increased leaf mass per area, net CO2 assimilation, whole-plant net assimilation, and dry weight in at least two species, independent of R:FR. In petunia, a long day plant, decreasing R:FR promoted subsequent flowering at both PPFDs, but to a greater extent under the lower PPFD. In day-neutral geranium, the addition of FR had no effect on flowering, irrespective of PPFD. We conclude that with a constant B photon flux density, decreases in R:FR promote stem elongation and leaf expansion, and subsequent dry mass accumulation, independent of PPFD. However, for flowering of long-day plant petunia, the promotive effect of low R:FR is greater under lower PPFD.
Keywords
Red to far-red ratioDLIphytochrome photoequilibriumPFRPHYBPPEHPSPSILMAPSIIChlPPFDLEDsDaily light integralLHCPhotosynthetically active radiationLeaf mass per areaParLight-emitting diodesChlorophyllREDphotosystem Iphotosynthetic photon flux densityPhotosystem IIPhytochromephytochrome BNet assimilation ratedry weight
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Authors
Yujin Park, Erik S. Runkle,