Abstract: To examine photosynthetic characteristics and photoprotection in Amorphophallus konjac K.Coch (AK), which is a shade-tolerant species but can grow under high light, and A.xiei H.Li & Z.L.Dao (AX), which is a shade-demanding species and can not tolerate high light, the photosynthetic capacity, antioxidant enzymes, antioxidant metabolites and photosynthetic pigments were analyzed in these two species grown under 100%, 15%, and 2.0% of full sunlight. Maximum photosynthetic rate (A_max) and stomatal conductance in AK decreased with decreasing light levels (P<0.05); however, A_max in AX reached a maximum value under 15% of full sunlight. In most cases, the activities of SOD, APX, CAT and GR were higher in AK (P<0.05); correspondingly, the activity of POD was higher in AX (P<0.05). Moreover, the activities of antioxidant enzyme were higher under high and moderate lights than under low light (P<0.05). Under 15% of full sunlight, the higher contents of glutathione and ascorbic acid were observed in AK. The content of photosynthetic pigments in AX reached a maximum value under 15% of full sunlight and that in AK a minimum value under 2.0% of full sunlight (P<0.05). In addition, the contents of photosynthetic pigments were generally higher in AK than AX under a light gradient (P<0.01). The results obtained here suggest that the tolerance of AK to high light might be related to the high photosynthetic capacity and the efficient photoprotection.

Key words: Amorphophallus konjac, Amorphophallus xiei, photosynthetic characteristics, photoprotection, shade-demanding species