Solar-induced chlorophyll fluorescence (SIF) is a promising photosynthetic proxy and a valuable phenotyping tool. However, under drought and fluctuating light, the mechanistic linkages between SIF and photosynthesis require further investigation due to complex light energy partitioning. In this study, we measured leaf-level SIF, gas-exchange, and active fluorescence parameters in Ginkgo biloba under drought and fluctuating light. Our results demonstrate a drought-induced decoupling of both leaf-level SIF and PSII-emitted chlorophyll fluorescence (SIFPSII, derived from active fluorescence parameters) from photosynthesis. This was driven by a slight SIFPSII reduction alongside strong photosynthetic suppression. The limited SIFPSII decrease resulted from a stable fluorescence yield (ΦSIF), maintained by the regulatory interplay between non-photochemical quenching (NPQ) and the fraction of open PSII reaction centers (qL), and the low responsiveness of ΦSIF to changes in the maximum photochemical quantum yield (ΦPSIImax). In contrast, photosynthetic suppression was largely due to decreased stomatal conductance (gs). ΦPSIImax and photorespiration are also central to balancing the light and carbon reactions, preventing energy overload. Interestingly, fluctuating light phases did not significantly alter this decoupling. However, when combining data from both high and low light, SIFPSII and photosynthesis remained tightly coupled, likely due to their shared light dependency. These insights improve the physiological interpretation of SIF and underscore the importance of SIF-based multi-trait phenotyping models for accurate field monitoring.
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To explore the differences in the content of terpene lactones and flavonol glycosides and their main components and gene transcription between female and male Ginkgo biloba leaves.
The liquid chromatography-mass spectrometry (LC-MS) and high performance liquid chromatography-ultraviolet (HPLC-UV) were applied to determine the content of terpene lactones and flavonol glycosides in 10 female and 10 male G. biloba leaves, respectively. The transcriptome sequencing was performed on 3 female and 3 male G. biloba leaves with representative contents of terpene lactones and flavonol glycosides.
The contents of terpene lactones and flavonol glycosides and their main components in female leaves were relatively higher than those in male leaves, but only quercetin content was significantly different. Through transcriptome sequencing, a total of 288 023 696 Raw reads, and 257 059 884 Clean reads are obtained. Q30 ≥ 91.24%, GC content ≥ 45.95%, and uniquely mapped reads rate ≥ 85.04%. A total of 676 differentially expressed genes (DEGs) were identified (P < 0.05 and |log2FC| ≥ 1), and compared with female plants, 340 DEGs were up-regulated and 336 DEGs were down-regulated in male plants. GO enrichment analysis showed that 372 DEGs were significantly enriched into 163 GO terms, including oxidation-reduction process, carbohydrate metabolic process, detoxification and catalytic activity. KEGG enrichment analysis showed that the DEGs were mainly related to metabolic pathways such as plant hormone signal transduction, plant-pathogen interaction, other glycan degradation and steroid biosynthesis. The expression of related structural genes in the synthesis pathway of ginkgo terpene lactones and flavonol glycosides was higher in female plants than in male plants, which was consistent with the trend of terpene lactones and flavonol glycosides content in female plants being higher than that in male plants.
The contents of terpene lactones and flavonol glycosides and the expression of genes related to biosynthesis pathways in G. biloba leaves of different sexes are different, female plants are slightly higher than that of male plants. This study provides a theoretical basis for the selection and breeding of excellent germplasm of G. biloba for excellent leaves based on different sexes.
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