Phosphorus Deficiency Affects the Rate of Emergence and Number of Maize Adventitious Nodal Roots

Abstract

Root growth is critical for P uptake, especially when soil P availability is low. We studied the effects of P deficiency on the rate of appearance and number of adventitious nodal roots of field‐grown maize plants (Zea mays L.). Experiments were conducted in 1995, 1996, and 1997 on a long‐term P fertilization trial with three P fertilization regimes, located on a sandy soil in southwest France. Phosphorus deficiency had a negative effect on leaf area index (LAI). The amount of photosynthetically active radiation (PAR) absorbed by the canopy and plant growth were reduced, especially during the first phases of the crop cycle (between the 7‐ and 14‐visible‐leaf stage). The emergence of adventitious roots was delayed for P‐deficient plants, but the synchrony between root and leaf emergence was not disturbed. The final number of roots was significantly lower for P‐deficient plants for phytomers 4 to 7. These phytomers were those for which root differentiation occurred when the PAR absorbed by the canopy was most severely reduced relative to the fertilized P treatments. A unique relationship was found for all years and P treatments between the cumulative amount of PAR absorbed by the plant and the number of emerged adventitious roots. We concluded that the reduced number of adventitious roots for phytomers 4 to 7 on P‐deficient plants may be caused by the negative effect of P deficiency on LAI and its subsequent effect on PAR absorption and C nutrition of plants during the period of root emergence from specific phytomers.