Growth and Physiological Responses of Norway Spruce (Picea abies (L.) H. Karst) Supplemented with Monochromatic Red, Blue and Far-Red Light

Monochromatic red light (R) supplementation is more efficient than blue light (B) in promoting Norway spruce (Picea abies (L.) H. Karst) growth. Transcriptome analysis has revealed that R and B may regulate stem growth by regulating phytohormones and secondary metabolites; however, the effects of light qualities on physiological responses and related gene expression in Norway spruce require further study. In the present study, three-year-old Norway spruce seedlings received sunlight during the daytime were exposed to monochromatic B (460 mm), monochromatic R (660 nm), monochromatic far-red light (FR, 730 nm), and a combination of three monochromatic lights (control, R:FR:B = 7:1:1) using light-emitting diode (LED) lamps for 12 h after sunset for 90 day. Growth traits, physiological responses, and related gene expression were determined. The results showed that light quality significantly affected Norway spruce growth. The stem height, root collar diameter, and current-year shoot length of seedlings treated with R were 2%, 10% and 12% higher, respectively, than those of the control, whereas seedlings treated with B and FR showed significantly lower values of these parameters compared with that of the control. The net photosynthetic rate (Pn) of seedlings under R treatment was 10% higher than that of the control, whereas the Pn values of seedlings treated with FR and B were 22% and 33%, respectively, lower than that of the control. The ratio of phosphoenolpyruvate carboxylase to ribulose-1,5-bisphosphate carboxylase/oxygenase (PEPC/Rubisco) of seedlings after the R treatment (0.581) was the highest and 3.98 times higher than that of the seedlings treated with B. Light quality significantly affected the gibberellic acid (GAs) levels, which was 13% higher in seedlings treated with R (6.4 g/100 ng) than that of the control, whereas, the GAs level of seedlings treated with B and FR was 17% and 19% lower, respectively, than that of the control. In addition, seedlings treated with R achieved the lowest ratio of leaf chlorophyll content to fresh weight (8.7). Compared to the R and control treatments, seedlings received FR treatment had consistently lower values of the quantum yield of electron transport beyond Q(A)(-) (primary quinone, phi Eo) and efficiency, with which a trapped exciton moves an electron into the electron transport chain beyond Q(A)(-) (psi o), while higher values of the relatively variable fluorescence at the J step and normalized relatively variable fluorescence at the K step (W-k). The values of phi Eo, psi O, V-J and W-k in seedlings treated with B were similar to those in the control group. The expression of genes associated with light signal transduction, such as PHYTOCHROME C (PHYC), ELONGATED HYPOCOTYL5 (HY5), CONSTITUTIVE PHOTOMORPHOGENIC 1-2 (COP1-2), and PHYTOCHROME INTERACTING FACTOR 3 (PIF3), was significantly higher in seedlings under B treatment than those under other light treatments. Nevertheless, significant differences were not observed in the expression of COP1-2, HY5, and PIF3 between the R treatment and the control. The expression value of COP1-2 was significantly lower in R than FR light treatments. In conclusion, compared with the control, R promotes, whereas B and FR inhibit Norway spruce growth, which was accompanied by physiological changes and genes expression regulation that may be relate to a changing phytochrome photostationary state (PSS) with the supplemental R in seedlings

Growth and Physiological Responses of Norway Spruce (<i>Picea abies</i> (L.) H. Karst) Supplemented with Monochromatic Red, Blue and Far-Red Light

Monochromatic red light (R) supplementation is more efficient than blue light (B) in promoting Norway spruce (Picea abies (L.) H. Karst) growth. Transcriptome analysis has revealed that R and B may regulate stem growth by regulating phytohormones and secondary metabolites; however, the effects of light qualities on physiological responses and related gene expression in Norway spruce require further study. In the present study, three-year-old Norway spruce seedlings received sunlight during the daytime were exposed to monochromatic B (460 mm), monochromatic R (660 nm), monochromatic far-red light (FR, 730 nm), and a combination of three monochromatic lights (control, R:FR:B = 7:1:1) using light-emitting diode (LED) lamps for 12 h after sunset for 90 day. Growth traits, physiological responses, and related gene expression were determined. The results showed that light quality significantly affected Norway spruce growth. The stem height, root collar diameter, and current-year shoot length of seedlings treated with R were 2%, 10% and 12% higher, respectively, than those of the control, whereas seedlings treated with B and FR showed significantly lower values of these parameters compared with that of the control. The net photosynthetic rate (Pn) of seedlings under R treatment was 10% higher than that of the control, whereas the Pn values of seedlings treated with FR and B were 22% and 33%, respectively, lower than that of the control. The ratio of phosphoenolpyruvate carboxylase to ribulose-1,5-bisphosphate carboxylase/oxygenase (PEPC/Rubisco) of seedlings after the R treatment (0.581) was the highest and 3.98 times higher than that of the seedlings treated with B. Light quality significantly affected the gibberellic acid (GAs) levels, which was 13% higher in seedlings treated with R (6.4 g/100 ng) than that of the control, whereas, the GAs level of seedlings treated with B and FR was 17% and 19% lower, respectively, than that of the control. In addition, seedlings treated with R achieved the lowest ratio of leaf chlorophyll content to fresh weight (8.7). Compared to the R and control treatments, seedlings received FR treatment had consistently lower values of the quantum yield of electron transport beyond QA− (primary quinone, ϕEo) and efficiency, with which a trapped exciton moves an electron into the electron transport chain beyond QA− (ψo), while higher values of the relatively variable fluorescence at the J step and normalized relatively variable fluorescence at the K step (Wk). The values of ϕEo, ψO, VJ and Wk in seedlings treated with B were similar to those in the control group. The expression of genes associated with light signal transduction, such as PHYTOCHROME C (PHYC), ELONGATED HYPOCOTYL5 (HY5), CONSTITUTIVE PHOTOMORPHOGENIC 1-2 (COP1-2), and PHYTOCHROMEINTERACTING FACTOR 3 (PIF3), was significantly higher in seedlings under B treatment than those under other light treatments. Nevertheless, significant differences were not observed in the expression of COP1-2, HY5, and PIF3 between the R treatment and the control. The expression value of COP1-2 was significantly lower in R than FR light treatments. In conclusion, compared with the control, R promotes, whereas B and FR inhibit Norway spruce growth, which was accompanied by physiological changes and genes expression regulation that may be relate to a changing phytochrome photostationary state (PSS) with the supplemental R in seedlings

Interspecific Gene Flow and Selective Sweeps in Picea wilsonii, P. neoveitchii and P. likiangensis

Genome-wide single nucleotide polymorphism (SNP) markers were obtained by genotyping-by-sequencing (GBS) technology to study the genetic relationships, population structure, gene flow and selective sweeps during species differentiation of Picea wilsonii, P. neoveitchii and P. likiangensis from a genome-wide perspective. We used P. jezoensis and P. pungens as outgroups, and three evolutionary branches were obtained: P. likiangensis was located on one branch, two P. wilsonii populations were grouped onto a second branch, and two P. neoveitchii populations were grouped onto a third branch. The relationship of P. wilsonii with P. likiangensis was closer than that with P. neoveitchii. ABBA-BABA analysis revealed that the gene flow between P. neoveitchii and P. wilsonii was greater than that between P. neoveitchii and P. likiangensis. Compared with the background population of P. neoveitchii, the genes that were selected in the P. wilsonii population were mainly related to plant stress resistance, stomatal regulation, plant morphology and flowering. The genes selected in the P. likiangensis population were mainly related to plant stress resistance, leaf morphology and flowering. Selective sweeps were beneficial for improving the adaptability of spruce species to different habitats as well as to accelerate species differentiation. The frequent gene flow between spruce species makes their evolutionary relationships complicated. Insight into gene flow and selection pressure in spruce species will help us further understand their phylogenetic relationships and provide a scientific basis for their introduction, domestication and genetic improvement

Climate of origin shapes variations in wood anatomical properties of 17 Picea species

Abstract Background Variations in hydraulic conductivity may arise from species-specific differences in the anatomical structure and function of the xylem, reflecting a spectrum of plant strategies along a slow-fast resource economy continuum. Spruce (Picea spp.), a widely distributed and highly adaptable tree species, is crucial in preventing soil erosion and enabling climate regulation. However, a comprehensive understanding of the variability in anatomical traits of stems and their underlying drivers in the Picea genus is currently lacking especially in a common garden. Results We assessed 19 stem economic properties and hydraulic characteristics of 17 Picea species grown in a common garden in Tianshui, Gansu Province, China. Significant interspecific differences in growth and anatomical characteristics were observed among the species. Specifically, xylem hydraulic conductivity (K s) and hydraulic diameter exhibited a significant negative correlation with the thickness to span ratio (TSR), cell wall ratio, and tracheid density and a significant positive correlation with fiber length, and size of the radial tracheid. PCA revealed that the first two axes accounted for 64.40% of the variance, with PC1 reflecting the trade-off between hydraulic efficiency and mechanical support and PC2 representing the trade-off between high embolism resistance and strong pit flexibility. Regression analysis and structural equation modelling further confirmed that tracheid size positively influenced K s, whereas the traits DWT, D_r, and TSR have influenced K s indirectly. All traits failed to show significant phylogenetic associations. Pearson’s correlation analysis demonstrated strong correlations between most traits and longitude, with the notable influence of the mean temperature during the driest quarter, annual precipitation, precipitation during the wettest quarter, and aridity index. Conclusions Our results showed that xylem anatomical traits demonstrated considerable variability across phylogenies, consistent with the pattern of parallel sympatric radiation evolution and global diversity in spruce. By integrating the anatomical structure of the stem xylem as well as environmental factors of origin and evolutionary relationships, our findings provide novel insights into the ecological adaptations of the Picea genus

DataSheet_1_Climatic responses and variability in bark anatomical traits of 23 Picea species.docx

In woody plants, bark is an important protective tissue which can participate in photosynthesis, manage water loss, and transport assimilates. Studying the bark anatomical traits can provide insight into plant environmental adaptation strategies. However, a systematic understanding of the variability in bark anatomical traits and their drivers is lacking in woody plants. In this study, the bark anatomical traits of 23 Picea species were determined in a common garden experiment. We analyzed interspecific differences and interpreted the patterns in bark anatomical traits in relation to phylogenetic relationships and climatic factors of each species according to its global distribution. The results showed that there were interspecific differences in bark anatomical traits of Picea species. Phloem thickness was positively correlated with parenchyma cell size, possibly related to the roles of parenchyma cells in the radial transport of assimilates. Sieve cell size was negatively correlated with the radial diameter of resin ducts, and differences in sieve cells were possibly related to the formation and expansion of resin ducts. There were no significant phylogenetic signals for any bark anatomical trait, except the tangential diameter of resin ducts. Phloem thickness and parenchyma cell size were affected by temperature-related factors of their native range, while sieve cell size was influenced by precipitation-related factors. Bark anatomical traits were not significantly different under wet and dry climates. This study makes an important contribution to our understanding of variability in bark anatomical traits among Picea species and their ecological adaptations.</p