Effects of Phosphorus Supply on Root Morphology and Phosphorus Uptake in Maize Seedlings under Different Water Regimes

Water deficit and phosphorus (P) deficiency in soil have become the main limiting factors for the production of maize (Zea mays L.), but it still remains unclear how water and P regulate maize root morphology and P uptake. Through an experiment of potted soil culture, this study has set 4 water gradients [35% (W1), 55% (W2), 75% (W3) and 100% (W4)] of field capacity, and two P levels [high P: 205 mg (P)∙kg-1; low P: 11 mg (P)∙kg-1] to investigate the coupling effects of water and P on root growth and P uptake in maize seedlings. The results have shown that: (1) Regardless of soil P supply, the shoot dry weight, root dry weight, total root length, and root surface area of maize seedlings shows a trend of increasing first and then decreasing with increasing water supply intensity; the soil available P content also shows similar trend; the root mass ratio and mean root diameter shows a downward trend with the increase of water supply intensity; furthermore, the P content and P accumulation of plants shows a steady increase with the increase of water supply intensity; (2) Water deficit (W1) and excess water supply (W4) is not conducive to root growth and dry matter accumulation in maize. Water deficit (W1) inhibits the acquisition of soil P by maize, while excess water supply (W4) causes extravagant absorption of soil P (W4). Mild water stress (W2) can promote the growth and dry matter accumulation of maize roots and reduce the extravagant absorption of soil P, and adequate water supply (W3) can promote root growth, dry matter accumulation and the absorption of soil P; (3) Phosphorus supply significantly increases the dry weight, root dry weight (except W4), total root length, root surface area, plant P content (except W4) and P accumulation of maize seedlings, but reduces the root mass ratio of maize. It is thus evident that water is a key factor controlling the morphology and accumulation of dry matter in maize roots, and P is a key factor controlling P uptake and soil available P content in corn field. The better coupling between water and P can promote maize root growth and dry matter accumulation, as well as reduce the extravagant absorption of soil P.