Responses of root growth and morphological characteristics of sweet potato plants to varying nitrogen levels under drought

Abstract

A split-root culture pot experiment, using discrete left and right compartments, was conducted in order to investigate the effects of three different nitrogen (N) combinations on fibrous root expansion and tuberous root differentiation under two levels of soil moisture in sweet potatoes. Under these two moisture conditions, sweet potato root biomass and root morphology were higher in the N50 compartment than corresponding N0 compartment in the N0/N50 treatment. Under normal moisture conditions, the root morphological traits in the N150 compartment were higher than in the N0 compartment; under drought stress, the N150 compartment significantly decreased compared with the corresponding N0 compartment. The N50 and N150 compartment root morphological characteristics showed no significant differences under normal moisture conditions. Under drought stress, however, in the N150 compartment, root morphological characteristics decreased compared to in the N50 compartment. The redundancy analysis (RDA) showed that N50 was the ideal amount of N in both normal moisture and drought conditions while the excessive application of N (N150) improved drought stress. The morphological properties of sweet potato roots were significantly affected by various soil moisture levels and local N availability, suggesting that the existence of suitable local N was necessary for root development under different water conditions. This information can be used to further optimize N fertilizer management strategies, allowing agricultural workers to increase crop yields, mitigate drought stress, and improve plant health by helping to ensure the availability of N under different soil moisture conditions.