干旱区生态环境知识资源中心

Soil salinity (S) is one of the most important abiotic stresses limiting crop production in arid and semiarid regions. This study was conducted to investigate the interactive effects of S and nitrogen (N) fertilizer on shoot and root biomass allocation of sunflower (Helianthus annuus L.) at different growth stages. Outdoor field and pot experiments were performed in the Hetao Irrigation District, China. The field study consisted of a 3 x 2 factorial design with three salinity levels (S-0: electrical conductivity of a saturatedpaste extract [ECe] = 1.9 dS m(-1); S-1: ECe = 7.4 dS m(-1); S-2: ECe = 12.7 dS m(-1)) and two N application rates (low: 45 kg N ha(-1); moderate: 135 kg N ha-1); the S-2 treatment was not included in pot study. The results indicated that sunflower allocated more biomass to root under saline conditions in the seedling stage. However, a detrimental effect of moderate N application rate on seedling growth could be found at the S-1 level. Moreover, aft er bud initiation, a moderate N application rate accelerated shoot and root biomass accumulation at the S-0 and S-1 levels, but it still aggravated salt stress and inhibited sunflower growth at the flowering and mature stages at the S-2 level. In addition, our study indicated that the sunflowers planted in pots showed enhanced salt tolerance and decreased the root/shoot ratio earlier than sunflowers planted in fields. We suggest applying less N fertilizer before sowing at both the S-1 and S-2 levels and using proper additional N fertilizer in the bud stage at the S-1 level to promote sunflower growth aft er salt tolerance has been enhanced.