Torreya grandis is a widely cultivated fruit species in China that is valued for its significant economic and agricultural importance. The molecular mechanisms underlying pigment formation and photosynthetic performance in Torreya leaf color mutants remain to be fully elucidated. In this study, we performed transcriptome sequencing and measured photosynthetic performance indicators to compare mutant and normal green leaves. The research results indicate that the identified Torreya mutant differs from previously reported mutants, exhibiting a weakened photoprotection mechanism and a significant reduction in carotenoid content of approximately 33%. Photosynthetic indicators, including the potential maximum photosynthetic capacity (F_v/F_m) and electron transport efficiency (Ψ_o, φ_Eo), decreased significantly by 32%, 52%, and 49%, respectively. While the quantum yield for energy dissipation (φ_Do) increased by 31%, this increase was not statistically significant, which may further reduce PSII activity. A transcriptome analysis revealed that the up-regulation of chlorophyll degradation-related genes—HCAR and NOL—accelerates chlorophyll breakdown in the Torreya mutant. The down-regulation of carotenoid biosynthesis genes, such as LCY1 and ZEP, is strongly associated with compromised photoprotective mechanisms and the reduced stability of Photosystem II. Additionally, the reduced expression of the photoprotective gene psbS weakened the mutant’s tolerance to photoinhibition, increasing its susceptibility to photodamage. These changes in gene expression accelerate chlorophyll degradation and reduce carotenoid synthesis, which may be the primary cause of the yellowing in Torreya. Meanwhile, the weakening of photoprotective mechanisms further impairs photosynthetic efficiency, limiting the growth and adaptability of the mutants. This study emphasizes the crucial roles of photosynthetic pigments and photosystem structures in regulating the yellowing phenotype and the environmental adaptability of Torreya. It also provides important insights into the genetic regulation of leaf color in relation to photosynthesis and breeding.

Successive cropping frequently causes a decline in Chinese Fir (Cunninghamia lanceolata) biomass, a problem intricately tied to soil nutrient shifts and microbial processes. This research investigates the mechanisms governing biomass carbon partitioning and soil nutrient shifts in these plantations. This study investigated five Chinese Fir clones (‘ck’, ‘b44’, ‘K13’, ‘F13’, and ‘kt13’) across two cultivation regimes: continuous cropping (second-generation plantation, G2) and first-generation plantation (G1). The focus was on their biomass and soil nutrient status. The results showed that: (1) The biomass of different Chinese Fir clones at 25 years of age decreased significantly with increasing generations of continuous cultivation. Tree height showed no significant differences among clones within the same generation; however, the G2 cultivation significantly inhibited diameter at breast height (DBH). (2) The changes in soil nutrients and microbial activity under different successive generations (G1, G2) was closely linked to the decline in Chinese Fir biomass carbon. Analysis revealed that the decreases in dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and Catalase (CAT) activity were significantly positively correlated with the reduction in biomass carbon. Concurrently, the decrease in soil pH showed a significant negative correlation with microbial biomass carbon (MBC) and Sucrase (SUC) activity. (3) Regarding growth traits, although tree height showed no significant differences among clones within the same generation, DBH was generally and significantly inhibited under G2 cultivation. An exception was the ‘K13’ clone, which remained largely unaffected. In terms of carbon accumulation, G2 cultivation led to a universal decline in biomass carbon across clones; however, the magnitude of reduction in different components (leaf, branch, stem, root) and total biomass carbon varied clone-specifically. Notably, ‘K13’ exhibited the strongest tolerance, with a significantly smaller decrease in tree biomass carbon compared to the other four clones, which showed substantially lower tree carbon stocks across all components relative to G1 plantations. This indicates that successive cropping of Chinese Fir likely constrains the carbon sequestration capacity of plantations by altering soil nutrient properties, thereby suppressing tree DBH growth and biomass carbon accumulation, likely through reduced net primary productivity. Among the five clones, ‘K13’ was the least affected, demonstrating its high potential for adaptation to continuous cultivation. These findings provide implications for sustainable forest management by guiding clone selection to mitigate productivity decline under successive cropping.