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CORN

Effect of Soil Phosphorus on Leaf Development and Senescence Dynamics of Field-Grown Maize

^a INRA, BP 27, 31326 Castanet Tolosan, France
^b USDA-ARS, 808 E. Blackland Rd., Temple, TX 76502 USA

colomb{at}toulouse.inra.fr

Phosphorus deficiency generally decreases plant biomass accumulation by limiting interception of photosynthetically active radiation (PAR) rather than reducing efficiency of conversion of PAR into dry matter. To document the role of P availability in leaf growth and senescence dynamics in maize (Zea mays L.), a 3-yr field experiment was conducted in southern France with very low, moderate, high, or very high soil test P levels. Leaf appearance rate, individual leaf area, and green fraction changes were recorded at weekly intervals. Rates and duration of expansion and senescence processes were derived independently from fitted logistic functions. Phosphorus deficiency slowed the rate of leaf appearance and reduced the final area of leaves located below the main ear by 18 to 27%, depending on year. The reduction in leaf expansion rates accounted for most of the area reduction over leaf position and years. Senescence rates of the lower leaves were reduced by 29%. The expansion and senescence dynamics of upper leaves were little affected by soil P level. The whole plant peak green leaf area was lower under P-stressed conditions (16%), and its date of occurrence was significantly delayed (6%). Plant senescence rate was reduced by 15 to 33% during most of the grain filling period. Leaf area duration from emergence to complete senescence was reduced by 13.5%. The early effects of P deficiency on leaf dynamics accounted for most of the 7 to 10% reduction in the amount of absorbed PAR, observed as soon as canopy development allowed maximum light interception.

Abbreviations: DD, degree-days • GLA, whole plant green leaf area • LAD, leaf area duration • LAI, leaf area index • LED, leaf expansion duration • LER, leaf expansion rate • LLO, leaf longevity • LSD, leaf senescence duration • LSR, leaf senescence rate • MLA, maximum leaf area • n, leaf node number • PAR, photosynthetically active radiation • RSR, whole plant relative senescence rate