Abstract: [Objective] This study aimed to understand the pattern of transport and distribution of photosynthates in Pinus massoniana and the formation process of P. massoniana productivity.[Method] In this study, the 1.5-year-old P. massoniana seedlings were fed with pulse-chased ¹³C labeling for 4 h, and then the different organs were collected at 0, 2, 5, 17, 24, 72, 120, 168, 216 and 360 h to analyze the ¹³C levels, to investigate the transport and distribution of recently synthesized photosynthates in the seedlings. Meanwhile, the accumulation of photosynthates (total carbon and non-structural carbohydrate (NSC)) was determined in various organs.[Result] 1) After the labeled photosynthetic products were synthesized in conifers, the labeled photosynthates were found to be transported to the sink organs, however the amount of the transportation gradually decreased with time. It was manifested that most of the photosynthates were transported within 0-24 hours after the labeling, and the transportation was decreased gradually from 24 to 216 hours. In 216 hours, the labeled photosynthates finished outward transport. It was found that more than 59% of the labeled photosynthates were transported to the sink organs within 0-24 hours over the period of 216 hours. 2) After the transport of photosynthates tended to stable, the distribution of recently synthesized photosynthates in each organ was in the order of 1-year leaves > current-year leaves > roots > stem > 1-year branches > current-year branches, which was consistent with the distribution of the biomass, but different from the sink activity, the sink activity was ordered as current-year leaves > current-year branches > 1-year leaves > roots > 1-year branches > stem. 3) The distribution of total carbon and NSC accumulation in various organs was in accordance with the distribution of recently synthetic photosynthates, which was ordered as 1-year leaves > current-year leaves > roots > stem > 1-year branches > current-year branches.[Conclusion] The photosynthates transport rate in P. massoniana seedlings was greater than 0.1 m·h^-1, and more than 59% labeled photosynthates were exported to all sink organs within 0-24 hours after synthesis. The accumulation of new synthesized photosynthates in various organs was mostly in functional organs (leaves and roots). This distribution pattern is conducive to the growth of P. massoniana at seedling stage.

Key words: transport of photosynthates, distribution of photosynthates, accumulation of photosynthates, ¹³C pulse labelling, Pinus massoniana