Comparison of the photosynthetic characteristics of old world bluestem at different stages of growth

In order to compare the photosynthetic characteristics of old world bluestem (Bothriochloa ischaemum) populations at different stages of growth, populations with good photosynthetic characteristics and their best utilization periods were chosen. In this study, the Li-6400 photosynthesis system was used to measure the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci), water use efficiency (WUE), and other parameters of old world bluestems belonging to the Pinglu, Pingding, Dai County, and Taigu populations, at different stages of growth. The photosynthetic indices of the four different old world bluestem populations at five different growth stages were analyzed and evaluated comprehensively by the grey correlative system. The results showed that the values of Pn, Tr, and Gs significantly differed among the Pinglu, Pingding, Dai County, and Taigu populations at different stages of growth (P<0.05). The Ci and Gs of the Taigu population were higher than those of the other three populations at the five growth stages, with the exception of Gs at the ripening stage. The average values of Pn, Tr, Gs, Ci, and WUE at each stage were the highest in the Taigu population. Additionally, among the four populations of old world bluestem, the poorest photosynthetic characteristics were observed for the Pingding population at anthesis and ripening stages, while the Pingding and Dai County populations showed the poorest characteristics at the booting stage. The best photosynthetic characteristics were observed for the Taigu population at the anthesis stage; all stages of the Pinglu population exhibited medium photosynthetic characteristics. With respect to the growth stages, old world bluestem had good photosynthetic characteristics at the heading stage (0.6000< Δi<0.7000).