Fig. 4. Relationship between the maximal quantum yield of PSII photochemistry for dark-adapted state (Fv/Fm) in sweet potatoes having different leaf colors and photosynthetic photon flux density (PPFD) at dusk. Closed and open symbols indicate that the average temperature (16:00–17:00 h) was below and above 20°C, respectively. Each line represents the mean of 24 points. * and ***: p<0.02 and 0.001, respectively.
