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CROP PHYSIOLOGY & METABOLISM

Development of Redroot Pigweed Is Influenced by Light Spectral Quality and Quantity

^a Dep. of Plant Agriculture, Crop Science Bldg., Univ. of Guelph, Guelph, ON, Canada N1G 2W1
^b Agronomy Dep., Faculty of Agriculture, Tarbiat Modarres Univ., Tehran, Iran

* Corresponding author (mtollena{at}uoguelph.ca)

Light quantity (photosynthetic photon flux density, PPFD) and quality (red:far-red ratio, R:FR) may affect phenological development of weed species growing under a crop canopy. An indoor study was conducted to quantify the effects of incident PPFD and R:FR on development and dry matter accumulation of redroot pigweed (Amaranthus retroflexus L.). Pigweed was grown in growth cabinets from the one-leaf stage to the initiation of seed set under three different PPFD/R:FR treatments: (i) high PPFD (550 µmol m^-2 s^-1) and high R:FR (1.4) (HH), (ii) low PPFD (180 µmol m^-2 s^-1) and high R:FR (1.4) (LH), and (iii) low PPFD (180 µmol m^-2 s^-1) and low R:FR (0.8) (LL). The experiment was undertaken at 12- and 16-h daylengths with three replications. Rate of leaf appearance (RLA) was accelerated with an increase in PPFD (HH vs. LH) at both daylengths. The FR enrichment (LL) negated the effect of low PPFD on RLA under the 12-h but not under the 16-h daylength. Low PPFD delayed the occurrence of floral primordia, flowering and initiation of seed set. Plant height was a result of the complementary effects of PPFD and R:FR. Total dry matter accumulation and partitioning, with the exception of dry matter accumulation to the stem, were influenced by PPFD only. Results of this study show that both light quality and quantity influence the phenology of pigweed.

Abbreviations: DAE, days after emergence • HH, high PPFD and high R:FR ratio • LH, low PPFD and high R:FR ratio • LL, low PPFD and low R:FR ratio • PPFD, photosynthetic photon flux density • R:FR, red:far-red ratio • RLA, rate of leaf appearance

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This issue in Crop science

Crop Science 2002 42: 1763-1765. [Full Text]