Photosynthetic Product Allocations to the Organs of <i>Pinus massoniana</i> Are Not Affected by Differences in Synthesis or Temporal Variations in Translocation Rates

• Main Authors: Xiuxiu Deng, Zheng Shi, Lixiong Zeng, Lei Lei, Xuebing Xin, Shunxiang Pei, Wenfa Xiao
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Forests
• Subjects: photosynthetic rate; translocation of photosynthetic products; allocation of photosynthetic products; diurnal variation; <i>Pinus massoniana</i>
• Online Access: https://www.mdpi.com/1999-4907/12/4/471

Photosynthesis and the allocation of photosynthetic products are the two main factors that determine plant growth. To understand the growth and productivity of <i>Pinus massoniana</i> Lamb., the diurnal changes in photosynthetic rate were continuously monitored. Furthermore, the translocation and allocation of the photosynthetic products synthesized in the morning and afternoon were explored using ¹³C pulse labeling. The results showed that: (1) on sunny days, the diurnal variation of the net photosynthetic rate showed a “double peak” curve, with an obvious “a depression” when temperatures were highest and humidity lowest. On cloudy days, it showed an irregular “jagged” curve, which was curve consistent with the variations in photosynthetically active radiation (PAR). Meanwhile, the photosynthetic rate changed with the transient changes in environmental factors such as PAR, temperature, and humidity. (2) The mean value of the net photosynthetic rate in the morning was higher than in the afternoon, and the response of the net photosynthetic rate to environmental change (PAR, temperature, humidity, and CO₂ concentration) in the morning was greater than that in the afternoon. (3) The translocation of photosynthetic products synthesized in the afternoon was faster than that in the morning. Shortly after synthesis of photosynthetic products, the translocation of products synthesized in the morning tended toward upper organs (including current-year leaves and 1-year leaves), while the translocation of products synthesized in the afternoon decreased in the upper organs. However, after 15 days of ¹³C pulse labeling, the allocation of the photosynthetic products synthesized in the morning and afternoon tended to be the same. These results indicate that the differences in the photosynthetic products synthesized and the temporal differences in the translocation rates did not affect the final allocation of the photosynthetic products in the various organs of the <i>P. massoniana</i>. These results improve our knowledge of the functional phases of <i>P. massoniana</i> during the diurnal cycle.