Drought and low concentration of soil nitrogen (N) limit crop growth and production in arid and semi-arid regions. Improving the efficient use of these limited resources is an important challenge. We tested one-year-old trees of three apple cultivars (Malus domestica cv. ‘Golden Delicious’, ‘Naganofuji No. 2’, and ‘Pink Lady’) grafted on M. hupehensis to determine how water and N supplies influence growth, biomass production, and water-use efficiency (WUE). Two watering regimes (80 and 50% field water capacity) and three N supplies (N0: 0, NL: 75, and NH: 150 mg N kg−1 soil) were used. Drought dramatically diminished plant height (PH), basal diameter (BD), biomass production, total leaf area (LA), specific leaf area (SLA), leaf relative water content (RWC), photosynthetic rate (Pn), stomatal conductance (gs), and WUE, but increased root/shoot ratio. NL significantly increased PH, BD, LA, SLA, RWC, Pn, gs, and WUE, but NH reduced or had little influence on these parameters. Pn, gs, LA, and root biomass significantly and positively correlated with WUE. Our results suggest that water and N are co-related, and NL enhance drought tolerance and WUE through increased photosynthetic capacity and water uptake. Thus, an appropriately low N supply would be recommended under dry condition, but excess N supply should be avoided.
Key words: Biomass production, drought, growth, Malus domestica, nitrogen, water-use efficiency.
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