Comparison of growth, photosynthetic, and chlorophyll fluorescence characteristics of different native cultivars in Castanea henryi

【Objective】The production of Castanea henryi is a new industry in Guizhou province of China. Many native cultivars have been introduced from Fujian province in resent years. Their adaptability remains unclear. The study systematically evaluated the photosynthetic characteristics and chlorophyll fluorescence parameters of 8 C. henryi native cultivars from Fujian in order to provide a scientific basis for the cultivation of C. henryi in Qiandongbei region of Guizhou province.【Methods】This experiment was conducted in mid-July at the Woody Oil Crop Base of Tongren University (27°47′30″ N, 109° 13′16″ E, altitude 466.2 m). The two-year-old grafted trees of 8 native cultivars of C. henryi introduced from Fujian were used as experimental materials. The density of the trees were 4 m×4 m in the plot under conventional irrigation and fertilization management. The relative chlorophyll content (SPAD) was measured using a SPAD-502Plus chlorophyll meter. The leaf area, length, and width were then measured with a Li-3000C portable leaf area meter. The photosynthetic parameters were measured between 08:30 and 11:30 on clear days using an Li-6800 portable photosynthesis system. The target leaves were marked and subsequently photoinduced at a light intensity of 1200 μmol·m-2 ·s -1 for at least 20 minutes until stabilization of the net photosynthetic rate (Pn). The light- response curves were fitted through a rectangular hyperbolic correction model, with parameters recorded including maximum net photosyn-thetic rate (Pnmax), light saturation point (LSP), apparent quantum efficiency (AQY), light compensation point (LCP), and dark respiration rate (Rd). The chlorophyll fluorescence analysis was conducted through overnight dark-adaptation of the leaves achieved by aluminum foil wrapping. With the Li-6800 system maintained at identical chamber settings to those used for light-response curve measurements, a 30-minute light adaptation was performed before parameter determination. The recorded parameters included: initial fluorescent light (F0); maximal fluorescence (Fm), PSⅡ primary light energy conversion efficiency (Fv/Fm), potential efficiency of primary conversion of PSⅡ (Fv/F0), actual photochemical efficiency of PSⅡ (Fv'/Fm'), photochemical quenching coefficient (qP), electron transport rate (ETR), and non-photochemical quenching (NPQ). The Mantel test was applied to conduct correlation analysis for examining the relationships among growth parameters, photosynthetic parameters, and chlorophyll fluorescence parameters. The principal component analysis was applied to identify dominant characteristic parameters between photosynthetic parameters and chlorophyll fluorescence parameters.【Results】The significant growth variations were observed in the growth indexes of different native cultivars of C. henryi. Among all tested cultivars, Youzhen exhibited superior performance in plant height (96.18 cm), ground diameter (20.79 mm), and leaf area (76.15 cm2 ), all significantly higher than those of the other cultivars (P＜0.05). The SPAD values of Youzhen and Dajianzui were significantly higher than those of the other cultivars (P＜0.05). Although the 8 cultivars displayed similar trends in light-response curves, they differed significantly in the key photosynthetic parameters. The AQY ranged from 0.042 to 0.059, with Youzhen and Dajianzui exhibiting the highest values of 0.059. The Pnmax of Bailuzi was significantly lower than that of other cultivars. Changmangzi exhibited the lowest Rd, while Heili had the highest Rd. Meanwhile, Heili had the highest LCP and LSP. The significant variations in chlorophyll fluorescence parameters were observed among 8 C. henryi cultivars. The initial fluorescent light (F0) of Bailuzi was significantly higher than that of other cultivars (P＜0.05). The correlation analysis revealed that plant height had a highly significant and positive correlation (P＜0.01) with ETR, AQY, LSP, LCP, and Rd. The Pnmax was positively correlated with Fm, Fv/Fm, Fv/F0, and Fv'/Fm', while it was negatively correlated with NPQ. Furthermore, the Fv/Fm, Fv/F0, and Fv'/Fm' showed a highly significant and positive correlation (P＜0.05). The chlorophyll fluorescence parameters of Youzhen and Dajianzui were similar, but the NPQ value of Dajianzui was significantly lower than that of Youzhen. Additionally, both Youzhen and Dajianzui showed relatively high values of the Fv'/Fm' and ETR. The Fv'/Fm' of Youzhen was 0.755 and the ETR was 114.677, while those of Dajianzui were 0.765 and 107.148, respectively. The Fv/ F0 of Youzhen was not significantly different from that of Chushuhong, but was significantly higher than that of the other 6 cultivars (P＜0.05). The principal component analysis (PCA) grouped the 13 photosynthetic physiological characteristics into two principal components with a cumulative contribution rate of 77.48%, among them, the first principal component was closely related to Fv/Fm, Fv/F0, and Fv'/Fm', with a contribution rate of 53.72%, while the second principal component was related to LSP and ETR, with a contribution rate of 23.76%. Based on the analysis of the data distribution related to the growth and physiological characteristics of C. henryi cultivars, Youzhen, Dajianzui, and Wukechangmang were closely clustered together in the data distribution pattern. In contrast, Heili and Bailuzi were located far away from the other six native cultivars in the same data distribution context.【Conclusion】 The significant variations in growth parameters and photosynthetic physiological characteristics were observed among different C. henryi native cultivars from Fujian. The Youzhen cultivar demonstrated superior growth performance and high light- use efficiency, consistent with its growth parameter performance, indicating better adaptability in the Qiandongbei region of Guizhou province.