Alternative partial root-zone irrigation enhances leaf flavonoid accumulation and water use efficiency of Ginkgo biloba

Alternative partial root-zone irrigation (APRI) is an irrigation management technique that enhances water use efficiency (WUE) and fruit quality without yield reduction. However, little information is available on the response of plantation forest exposed to APRI. To investigate the effects of APRI on WUE and flavonoid accumulation in leaves of ginkgo (Ginkgo biloba) seedlings, a split-root experiment was conducted with three irrigation modes: APRI, fixed partial root-zone drip irrigation (FD), and whole root-zone drip irrigation (WD). For each irrigation mode, three irrigation quotas were applied: normal water supply (75 % of the field water-holding capacity), mild drought (55 % of field capacity), and severe drought (35 % of field capacity). APRI increased the root:shoot ratio, feeder root biomass, total biomass, WUE, and leaf flavonoid concentration, but decreased transpiration rate under the mild drought condition compared with that under FD and WD. Linear regression analyses showed that leaf flavonoid concentration was significantly and positively correlated with WUE and root:shoot ratio, but was negatively correlated with total biomass of ginkgo seedlings. On the basis of the improvements in yield, WUE, and flavonoid accumulation observed in this study, we recommend applying the APRI mild-drought treatment for water management in ginkgo leaf-producing plantations.