بررسي تاثير طول روز، كميت و كيفيت نور بر فتولوژي و نمو علف هرز تاج خروس

Effects of day length, light spectral quality and quantity on phenology and development of redroot pigweed (Amaranthus retroflexus L.)

Light quantity (PPDF) and quality (R:FR ratio) aside from temperature and photoperiod 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 in development and thy matter accumulation of redroot pigweed (Amaranthus reflexus L.). Pigweed was grown in growth cabinets from the 1-leaf stage to the initation of seed set under three different PPFD / R:FR treatments: (i) high PPFD (550 pmol.mʹ.S-Thigh R:FR (1.4) (HH), (ii) low PPFD (180 ,miu mol.ni^2.S^-1)/high R:FR (1.4) (LHI) and (iii) low PPFD (180miu mo1.m^2.S^-1)/low R:FR (0.8) (LL). The experiment was undertaken at 12- and 16-h day lengths with three replications. Rate of leaf appearance (RLA) was accelerated with an increase in PPFD (LH vs LH) at both day lengths and FR enrichment (LL) negated the effect of low PPFD on RLA under the 12-h but not under the 16-h day length. When RLA was calculated for the same accumulated PPFD over time, mean RLA was 14% greater under the 16-h than under the 12-h day length. Low PPFD delayed the occurrence of floral primordium flowering and initiation of seed set. Plant height differences was due to the complementray 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.