Abstract: We compared the differences of morphological, anatomical structure and photosynthetic performance of the current-year and one-year-old needles on reproductive and vegetative branches of 40-year-old Korean pine (Pinus koraiensis) trees under full light during the fruiting period of June, July and August. We further analyzed the correlation between various needle indexes of different branch type and needle ages. The results showed that, except stomatal density, needle width and central cylinder area, the other morphological, anatomical structure indexes and moisture content of current-year needles showed significant differences among different months, while the variables of one-year-old needles showed no difference across months. The length of current-year needles in July and August was significantly greater than that in June by 91.0%-110.1% and 122.2%-131.5%, respectively, while the speci-fic needle area was significantly lower by 32.8%-40.9% and 44.8%-52.5%, respectively. The xylem area was significantly higher by 47.3%-70.8% and 75.9%-105.7%, and the phloem area was significantly higher by 29.2%-30.0% and 64.3%-73.2%, respectively. The net photosynthetic rate (P_n) of current-year and one-year-old needles showed opposite trend across different months, with the P_n of current-year needles in July and August was 17.1%-39.8% and 40.3%-51.5% higher compared to June, while the P_n of one-year-old needles in July and August decreased by 40.1%-56.9% and 45.2%-46.1%, respectively. There were significant differences in length and P_n of needles between reproductive and vegetative branches. The current-year needle length on reproductive branches in June and July was significantly shorter than those on vegetative branches by 16.4% and 28.1%. The P_n of current-year and one-year-old needles on reproductive branches was significantly lower than those on vegetative branches by 23.1% and 20.4%, respectively. Capture efficiency of excitation energy in PSⅡ reaction center (F_v′/F_m′) and P_n of current-year needle on reproductive and vegetative branches, as well as the intercellular CO₂ concentration of current-year needles on vegetative branch were closely correlated with other morphological and anato-mical structure indices, except for stomatal density, while one-year-old needles showed weak correlations. Needle age was the primary factor causing differences in morphological and anatomical structures and photosynthetic performance indices of needles, while branch type only significantly affected needle length and P_n.

Key words: Pinus koraiensis, needle age, branch type, needle anatomy, photosynthetic index