Effects of polyploidization on photosynthetic characteristics in three Lilium species

Photosynthesis play an important role in plant growth. Generally, it will be increased with increased DNA content per cell. However, in organ levels, the changes of photosynthesis are species dependent. So, for target breeding materials, chromosome duplication how to influence photosynthetic performances need further investigation. In this study, three lily (Lilium) species, L. rosthornii (LRI), L. primulinum var. orchraceun (LPO) and L. regale (LRE), and their colchicine-induced autotetraploids were employed in comparing photosynthetic related characteristics. For anatomic traits, the number of palisade mesophyll cells was significantly increased in LRI and LPO but decreased in LRE after polyploidization. Moreover, except the intercellular space decreased, the mesophyll cell sizes and shapes presented different changes in the three species after polyploidization. For physical-biochemical traits, the chloroplast number, thylakoid grana thickness, and photosynthetic pigments and efficiency were significantly increased in LRI after polyploidization. For LPO, the chloroplast number, and weak light absorbed and CO2 assimilated rates were significantly increased, while others showed no significant changes after polyploidization. Out of expecting, for LRE, the chloroplast number and photosynthetic pigments were significantly decreased after polyploidization. Moreover, the structures of chloroplasts were abnormal with extremely thicker thylakoid grana and more tightly arranged thylakoid layer in tetraploids than in diploids. The photosynthetic rates of LRE were similar in diploid and tetraploid in natural conditions, while the maximum photosynthetic rate (Pmax) of light-/CO2-response curves were higher in diploids than in diploids. After plants withered, larger bulblet with more developed root systems were well observed from the three tetraploid species.