Environmental stress results in generation of reactive oxygen species in plants and causes oxidative stress. The aim of this work was to study the changes to the antioxidative system in the leaves of three sweet potato varieties, Taoyuan 2, Simon 1, and Sushu 18 as affected by flooding and drought stresses. The experimental design was completely randomized with a split plot arrangement of treatments. Young, fully expended leaves from each plant were clipped for antioxidant activity measurement. We concluded that genotypes exhibited their abilities and specificities on porphyrins, polyphenol, flavonoids, reduction power and scavenging DPPH radical and superoxide anion. The polyphenol content and scavenging superoxide anion percentage of the three sweet potato varieties under the stresses declined significantly. However, the conjugated dienes inhibition percentage increased markedly under the stresses. Inhibiting the conjugated dienes could mitigate flooding and drought stress effects and be useful as a flooding and drought-tolerant index.
