Journal
PLANT PHYSIOLOGY AND BIOCHEMISTRY
Volume 170, Issue -, Pages 206-217Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.plaphy.2021.12.006
Keywords
Chlorophyll fluorescence; Heteroblastic foliage; Photosynthetic acclimation; Pinus massoniana; Quenching mechanism
Categories
Funding
- National Natural Science Foundation of China [31660201]
- Guizhou Science and Technology Department [[2018] 5261, GNYL [2017] 007]
- Postgraduate Research Project of Guizhou Province [YJSCXJH [2019] 020]
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Primary needles of one-year-old Pinus massoniana seedlings exhibit greater mesophyll tissue and stomata compared to secondary needles. Primary needles show high photoprotection through thermal dissipation, while secondary needles increase Chl b and carotenoids content in November for enhanced photoprotection against low temperatures.
Pine seedlings exhibit heteroblastic foliage (primary and secondary needles) during seedling development. However, few trials have studied how heteroblastic foliage influences pine seedling growth by seasonal variation. This study first investigated the anatomical differences between the primary and secondary needles of one-year-old Pinus massoniana seedlings. We measured chlorophyll fluorescence (ChlF) and evaluated the photoprotective mechanisms and light energy partitioning of these heteroblastic leaves from September to November. The results showed that the primary needles, as juvenile foliage, had a greater fraction of mesophyll tissue and stomata. In addition, the primary needles had two vascular bundles, and shorter distance from xylem and phloem to mesophyll cells, exhibiting a luxury growth strategy of rapidly obtaining high returns. The ChlF parameters indicated that the primary needles maintained a relatively high level of photoprotection by thermal dissipation (nonphotochemical quenching (NPQ)) and nonregulated energy dissipation (Y(NO)). The secondary needles, representing mature foliage, had greater area of xylem and phloem tissues. The contents of Chl b and carotenoids (Car) significantly increased in November, promoting phi Po and photoprotection, which suggested that the secondary needles were more resistant to low temperatures. During the whole light response process of secondary needles, the increases in the electron transfer rate (ETR) and light energy utilization efficiency (alpha) helped to increase the actual photosynthetic quantum yield (Y(II)) by reducing energy dissipation by decreasing the proportion of regulated energy dissipation (Y(NPQ)) and Y(NO). Given the sensitivity of this heteroblastic foliage to environmental changes, the practical use and extension of P. massoniana for afforestation purposes should be carried out with caution.
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