The scaling relationship between leaf area and total mass of plant has important implications for understanding resource allocations in the plant.The model of West,Brown and Enquist(WBE model)considers that a 3/4 scal...The scaling relationship between leaf area and total mass of plant has important implications for understanding resource allocations in the plant.The model of West,Brown and Enquist(WBE model)considers that a 3/4 scaling exponent of metabolic rate versus total mass to be optimal for each plant and has been confirmed numerous times.Although leaf area is a better proxy of the metabolic rate than leaf mass,few studies have focused on the scaling exponent of leaf area versus total mass and even fewer have discussed the diversification of this scaling exponent across different conditions.Here,I analyzed the scaling exponent of leaf area versus total mass of sample plots across world plants.I found that as the plant grows,it allocates fewer resources to photosynthetic tissues than expected by the WBE model.The results also empirically show that this scaling exponent varies significantly for different plant leaf habit,taxonomic class and geographic region.Therefore,leaf strategy in response to environmental pressure and constraint clearly plays a significant role.展开更多
Sweet potato is one of the first natural GMOs, genetically modified 8000 years ago by Agrobacterium rhizogenes as reported recently by Kyndt et al. A section of 10 kbp long DNA (Transferred- DNA or T-DNA) of the Ri (R...Sweet potato is one of the first natural GMOs, genetically modified 8000 years ago by Agrobacterium rhizogenes as reported recently by Kyndt et al. A section of 10 kbp long DNA (Transferred- DNA or T-DNA) of the Ri (Root-inducing) plasmid was transferred to the plant genome by A. rhizo-genes and has been maintained in all 291 hexaploid sweet potato cultivars of the world. The maintenance in the sweet potato genome and expression of two T-DNA genes for tryptophan-2-monooxygenease (iaaM) and for indole-3-acetamide hydrolase (iaaH) are likely to be physiologically significant since these enzymes convert tryptophan to indole-3-acetic acid, a major plant growth hormone auxin. Sweet potato (Ipomoea batatas (L.) Lam) is ranked the third most important root crop after potato and cassava, and the seventh in global food crop production with more than 126 million metric tons. Although sweet potato originated in Central or South America, China currently produces over 86% of world production with 109 million metric tons. In the United States, North Carolina is the leading producer with 38.5% of the 2007 sweet potato production, followed by California, Mississippi, and Louisiana with 23%, 19%, and 15.9%, respectively. Leaf curl virus diseases have been reported in sweet potato throughout the world. One of the causal agents is Sweet potato leaf curl virus (SPLCV) belonging to the genus Begomovirus (family Geminiviridae). Although SPLCV does not cause symptoms on Beauregard, one of the most predominant sweet potato cultivars in the US, it can reduce the yield up to 26%. Serological detection of SPLCV is not currently available due to the difficulties in obtaining purified virions that can be used as antigen for antiserum production. In attempts to obtain the coat protein (CP) of SPLCV for antibody production, primers were designed to amplify the CP gene. This gene was cloned into the expression vector pMAL-c2E as a fusion protein with maltose-binding protein, and transformed into Escherichia coli strain XL1-Blue. After gene induction, a fusion protein of 72 kDa was purified by amylose affinity chromatography. The yield of the purified fusion protein was approximately 200 μg/liter of bacterial culture. Digestion with enterokinase cleaved the fusion protein into a 42.5 kDa maltosebinding protein and a 29.4 kDa protein. The latter protein was identified by mass spectrometry analysis as the coat protein of SPLCV based on the fact that the mass spectrometry elucidated the sequences corresponding to 37% of amino acid positions of the SPLCV coat protein.展开更多
Light heterogeneity leads to anatomically and physiologically heterogeneous features in leaves. However, little attention has been paid to the effects of nonuniform illumination on the anatomical and photosynthetic pe...Light heterogeneity leads to anatomically and physiologically heterogeneous features in leaves. However, little attention has been paid to the effects of nonuniform illumination on the anatomical and photosynthetic performance on both sides along the leaf main vein. This study explored such effects by combining in situ determination in the field with shading simulation in the phytotron, on pima cotton that has cupping leaves. Photosynthetic characteristics and morphological structures were measured in the field on both sides along the main vein of eastward, westward, southward, and northward leaves. The results showed that the difference in photosynthetic capacity between the two sides along the main vein in different directions was closely related to the daily photo irridiance(DPI). This result indicates that the photosynthetic heterogeneity between the two sides is related to their intercepted light energy. The conclusion was further verified by the shading simulation experiments. Photosynthetic capacity and leaf thickness of the unshaded sides of leaves in the half-shaded treatment decreased, compared to those in the unshaded treatment. Therefore, it is conjectured that the development of photosynthetic characteristics on one side is systematically regulated by that on the other side. The study provides theoretical guidance on accessing the feasibility of sampling and directional planting.展开更多
Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth.However,few studies have been cond...Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth.However,few studies have been conducted to show how traits and trait-trait relationships change across a range of ontogenetic stage and leaf age for evergreen coniferous species.We divided 67 Pinus koraiensis Sieb.et Zucc.of various sizes(0.3-100 cm diameter at breast height,DBH)into four ontogenetic stages,i.e.,young trees,middle-aged trees,mature trees and over-mature trees,and measured the leaf mass per area(LMA),leaf dry matter content(LDMC),and mass-based leaf nitrogen content(N)and phosphorus content(P)of each leaf age group for each sampled tree.One-way analysis of variance(ANOVA)was used to describe the variation in leaf traits by ontogenetic stage and leaf age.The standardized major axis method was used to explore the effects of ontogenetic stage and leaf age on trait-trait relationships.We found that LMA and LDMC increased significantly and N and P decreased significantly with increases in the ontogenetic stage and leaf age.Most trait-trait relationships were consistent with the leaf economic spectrum(LES)at a global scale.Among them,leaf N content and LDMC showed a significant negative correlation,leaf N and P contents showed a significant positive correlation,and the absolute value of the slopes of the trait-trait relationships showed a gradually increasing trend with an increasing ontogenetic stage.LMA and LDMC showed a significant positive correlation,and the slopes of the trait-trait relationships showed a gradually decreasing trend with leaf age.Additionally,there were no significant relationships between leaf N content and LMA in most groups,which is contrary to the expectation of the LES.Overall,in the early ontogenetic stages and leaf ages,the leaf traits tend to be related to a"low investment-quick returns"resource strategy.In contrast,in the late ontogenetic stages and leaf ages,they tend to be related to a"high investment-slow returns"resource strategy.Our results reflect the optimal allocation of resources in Pinus koraiensis according to its functional needs during tree and leaf ontogeny.展开更多
Litterfall is the largest source of nutrients to for-est soils of tropical rainforests.However,variability in lit-terfall production,nutrient remobilization,and changes in leaf nutrient concentration with climate seas...Litterfall is the largest source of nutrients to for-est soils of tropical rainforests.However,variability in lit-terfall production,nutrient remobilization,and changes in leaf nutrient concentration with climate seasonality remain largely unknown for the central Amazon.This study meas-ured litterfall production,leaf nutrient remobilization,and leaf area index on a forest plateau in the central Amazon.Litterfall was measured at monthly intervals during 2014,while nitrogen,phosphorus,potassium,calcium and mag-nesium concentrations of leaf litter and canopy leaves were measured in the dry and rainy seasons,and remobilization rates determined.Leaf area index was also recorded in the dry and rainy seasons.Monthly litterfall varied from 33.2(in the rainy season)to 87.6 g m^(-2) in the dry season,while leaf area index increased slightly in the rainy season.Climatic seasonality had no effect on concentrations of nitrogen,calcium,and magnesium,whereas phosphorous and potassium responded to rainfall seasonality oppositely.While phosphorous increased,potassium decreased during the dry season.Over seasons,nitrogen,potassium,and phosphorous decreased in leaf litter;calcium increased in leaf litter,while magnesium remained unaffected with leaf aging.Regardless,the five nutrients had similar remobilization rates over the year.The absence of climate seasonality on nutrient remobilization suggests that the current length of the dry season does not alter nutrient remobilization rates but this may change as dry periods become more prolonged in the future due to climate change.展开更多
Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations,since they seem to be exposed to stress and plasticity could be advantageous.Here w...Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations,since they seem to be exposed to stress and plasticity could be advantageous.Here we focused on declining Persian oaks(Quercus brantii Lindl.var.persica(Jaub and Spach)Zohary)in the Zagros Mountains of western Iran,representing the most important tree species of this region.We selected trees with contrasting crown dieback,from healthy to severely defoliated,to investigate the relationships between canopy dieback and leaf morphology,water content and pigments.We also measured esterase and peroxidase,as enzymatic antioxidants and indicators of contrasting genotypes.Trees showing moderate to severe defoliation showed higher leaf mass area(LMA),reduced relative water content(RWC),and lower stomatal density(SD).Increasing LMA indicates a more sclerophyllic structure,according to drier conditions.We did not find significant differences in leaf pigments(chlorophyll a and b,and carotenoids)among crown dieback classes,suggesting that Persian oak trees are able to maintain accurate photochemical efficiency,while reduced RWC and SD suggest hydraulic limitations.Our results do not provide a consistent pattern as regards enzymatic antioxidant defense in Persian oak.Morphological leaf traits would be important drivers of future adaptive evolution in Persian oak,leading to smaller and thicker leaves,which have fitness benefits in dry environments.Nonetheless,drought responses may be critically affecting carbon uptake,as photosynthetic compounds are less effectively used in leaves with higher sclerophylly.展开更多
Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA aga...Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA against environmental stresses. Therefore, plants need to increase both LMA and photosynthesis at high elevations. To examine how deciduous plants maintain a positive carbon balance at high elevations, photosynthesis and related leaf traits for deciduous broad-leaved tree Betula ermanii were measured at three elevations. LMA was greater at middle and high elevations than at low elevation. Leaf δ13C was greater at higher elevations, and positively correlated with LMA, indicating greater long-term deficiency of CO2 in leaves at higher elevations. However, the Ci/Ca ratio at photosynthetic measurement was not low at high elevations. Nitrogen content per leaf mass and stomatal conductance were greater at higher elevations. Photosynthetic rates and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three elevations. Photosynthetic rate showed a strong positive correlation with stomatal conductance on a leaf area basis (R2 = 0.83, P < 0.001). Therefore, this study suggests B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing stomatal conductance, and maintains photosynthesis and PNUE at high elevation as much as at low elevation.展开更多
We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°...We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°N)and southern(62°N) silver birches in a common garden at62°N.ChlF transients were measured five times during two weeks in the middle of summer to avoid seasonal variation.Differences in growth and leaf morphological traits between the provenances were also examined.The northern trees had higher chlorophyll content,larger leaf areas,and higher leaf fresh and dry mass than the southern trees,but the leaf mass per area did not differ between the provenances.The southern trees were taller and showed higher annual shoot growth than the northern trees.For all the ChlF parameters,day-to-day variation was significant and followed the same pattern for both provenances with no significant provenance ×day interaction,suggesting a similar response to environmental variation.The northern provenance had higher values in parameters related to the reduction of end electron acceptors at the Photosystem I(PSI) acceptor side as probed by ChlF.This and higher values for performance indices PI_(abs) and PI_(tot) in northern than in southern trees suggest higher photosynthetic performance of northern trees in line with the latitudinal compensation strategy.Provenance differences in these parameters increased towards the end of the measurement period,suggesting preparation for earlier growth cessation in northern trees triggered by the shortening day length.The study shows that provenance differences in ChlF can be relatively stable regardless of environmental variation but might be influenced by physiological alterations in preparation for future changes in environmental conditions.展开更多
文摘The scaling relationship between leaf area and total mass of plant has important implications for understanding resource allocations in the plant.The model of West,Brown and Enquist(WBE model)considers that a 3/4 scaling exponent of metabolic rate versus total mass to be optimal for each plant and has been confirmed numerous times.Although leaf area is a better proxy of the metabolic rate than leaf mass,few studies have focused on the scaling exponent of leaf area versus total mass and even fewer have discussed the diversification of this scaling exponent across different conditions.Here,I analyzed the scaling exponent of leaf area versus total mass of sample plots across world plants.I found that as the plant grows,it allocates fewer resources to photosynthetic tissues than expected by the WBE model.The results also empirically show that this scaling exponent varies significantly for different plant leaf habit,taxonomic class and geographic region.Therefore,leaf strategy in response to environmental pressure and constraint clearly plays a significant role.
文摘Sweet potato is one of the first natural GMOs, genetically modified 8000 years ago by Agrobacterium rhizogenes as reported recently by Kyndt et al. A section of 10 kbp long DNA (Transferred- DNA or T-DNA) of the Ri (Root-inducing) plasmid was transferred to the plant genome by A. rhizo-genes and has been maintained in all 291 hexaploid sweet potato cultivars of the world. The maintenance in the sweet potato genome and expression of two T-DNA genes for tryptophan-2-monooxygenease (iaaM) and for indole-3-acetamide hydrolase (iaaH) are likely to be physiologically significant since these enzymes convert tryptophan to indole-3-acetic acid, a major plant growth hormone auxin. Sweet potato (Ipomoea batatas (L.) Lam) is ranked the third most important root crop after potato and cassava, and the seventh in global food crop production with more than 126 million metric tons. Although sweet potato originated in Central or South America, China currently produces over 86% of world production with 109 million metric tons. In the United States, North Carolina is the leading producer with 38.5% of the 2007 sweet potato production, followed by California, Mississippi, and Louisiana with 23%, 19%, and 15.9%, respectively. Leaf curl virus diseases have been reported in sweet potato throughout the world. One of the causal agents is Sweet potato leaf curl virus (SPLCV) belonging to the genus Begomovirus (family Geminiviridae). Although SPLCV does not cause symptoms on Beauregard, one of the most predominant sweet potato cultivars in the US, it can reduce the yield up to 26%. Serological detection of SPLCV is not currently available due to the difficulties in obtaining purified virions that can be used as antigen for antiserum production. In attempts to obtain the coat protein (CP) of SPLCV for antibody production, primers were designed to amplify the CP gene. This gene was cloned into the expression vector pMAL-c2E as a fusion protein with maltose-binding protein, and transformed into Escherichia coli strain XL1-Blue. After gene induction, a fusion protein of 72 kDa was purified by amylose affinity chromatography. The yield of the purified fusion protein was approximately 200 μg/liter of bacterial culture. Digestion with enterokinase cleaved the fusion protein into a 42.5 kDa maltosebinding protein and a 29.4 kDa protein. The latter protein was identified by mass spectrometry analysis as the coat protein of SPLCV based on the fact that the mass spectrometry elucidated the sequences corresponding to 37% of amino acid positions of the SPLCV coat protein.
基金supported by the National Natural Science Foundation of China(31860355,U1903302)the Regional Innovation Guidance Plan of Xinjiang Production and Construction Corps,China(2021BB001)。
文摘Light heterogeneity leads to anatomically and physiologically heterogeneous features in leaves. However, little attention has been paid to the effects of nonuniform illumination on the anatomical and photosynthetic performance on both sides along the leaf main vein. This study explored such effects by combining in situ determination in the field with shading simulation in the phytotron, on pima cotton that has cupping leaves. Photosynthetic characteristics and morphological structures were measured in the field on both sides along the main vein of eastward, westward, southward, and northward leaves. The results showed that the difference in photosynthetic capacity between the two sides along the main vein in different directions was closely related to the daily photo irridiance(DPI). This result indicates that the photosynthetic heterogeneity between the two sides is related to their intercepted light energy. The conclusion was further verified by the shading simulation experiments. Photosynthetic capacity and leaf thickness of the unshaded sides of leaves in the half-shaded treatment decreased, compared to those in the unshaded treatment. Therefore, it is conjectured that the development of photosynthetic characteristics on one side is systematically regulated by that on the other side. The study provides theoretical guidance on accessing the feasibility of sampling and directional planting.
基金The work was financially supported by the National Natural Science Foundation of China(No.31971636)Yong Elite Scientists Sponsorship Program by CAST(2018QNRC001)the Fundamental Research Fund for the Central Universities(2572018CG03).
文摘Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth.However,few studies have been conducted to show how traits and trait-trait relationships change across a range of ontogenetic stage and leaf age for evergreen coniferous species.We divided 67 Pinus koraiensis Sieb.et Zucc.of various sizes(0.3-100 cm diameter at breast height,DBH)into four ontogenetic stages,i.e.,young trees,middle-aged trees,mature trees and over-mature trees,and measured the leaf mass per area(LMA),leaf dry matter content(LDMC),and mass-based leaf nitrogen content(N)and phosphorus content(P)of each leaf age group for each sampled tree.One-way analysis of variance(ANOVA)was used to describe the variation in leaf traits by ontogenetic stage and leaf age.The standardized major axis method was used to explore the effects of ontogenetic stage and leaf age on trait-trait relationships.We found that LMA and LDMC increased significantly and N and P decreased significantly with increases in the ontogenetic stage and leaf age.Most trait-trait relationships were consistent with the leaf economic spectrum(LES)at a global scale.Among them,leaf N content and LDMC showed a significant negative correlation,leaf N and P contents showed a significant positive correlation,and the absolute value of the slopes of the trait-trait relationships showed a gradually increasing trend with an increasing ontogenetic stage.LMA and LDMC showed a significant positive correlation,and the slopes of the trait-trait relationships showed a gradually decreasing trend with leaf age.Additionally,there were no significant relationships between leaf N content and LMA in most groups,which is contrary to the expectation of the LES.Overall,in the early ontogenetic stages and leaf ages,the leaf traits tend to be related to a"low investment-quick returns"resource strategy.In contrast,in the late ontogenetic stages and leaf ages,they tend to be related to a"high investment-slow returns"resource strategy.Our results reflect the optimal allocation of resources in Pinus koraiensis according to its functional needs during tree and leaf ontogeny.
基金supported by the Ministerio da Ciencia,Tecnologia e Inovacoes (MCTI-INPA),Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq,grant number:303913/2021-5)Fundagao de Amparo a Pesquisa do Estado do Amazonas (FAPEAM)Coordenagao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES code 0001).
文摘Litterfall is the largest source of nutrients to for-est soils of tropical rainforests.However,variability in lit-terfall production,nutrient remobilization,and changes in leaf nutrient concentration with climate seasonality remain largely unknown for the central Amazon.This study meas-ured litterfall production,leaf nutrient remobilization,and leaf area index on a forest plateau in the central Amazon.Litterfall was measured at monthly intervals during 2014,while nitrogen,phosphorus,potassium,calcium and mag-nesium concentrations of leaf litter and canopy leaves were measured in the dry and rainy seasons,and remobilization rates determined.Leaf area index was also recorded in the dry and rainy seasons.Monthly litterfall varied from 33.2(in the rainy season)to 87.6 g m^(-2) in the dry season,while leaf area index increased slightly in the rainy season.Climatic seasonality had no effect on concentrations of nitrogen,calcium,and magnesium,whereas phosphorous and potassium responded to rainfall seasonality oppositely.While phosphorous increased,potassium decreased during the dry season.Over seasons,nitrogen,potassium,and phosphorous decreased in leaf litter;calcium increased in leaf litter,while magnesium remained unaffected with leaf aging.Regardless,the five nutrients had similar remobilization rates over the year.The absence of climate seasonality on nutrient remobilization suggests that the current length of the dry season does not alter nutrient remobilization rates but this may change as dry periods become more prolonged in the future due to climate change.
基金Ministerio de Economía y Competitividad,Spain(CGL2013-48843-C2-2-R)European Union FEDER 0087(TRANSHABITAT)Tarbiat Modares University(Doctorate support to AH)
文摘Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations,since they seem to be exposed to stress and plasticity could be advantageous.Here we focused on declining Persian oaks(Quercus brantii Lindl.var.persica(Jaub and Spach)Zohary)in the Zagros Mountains of western Iran,representing the most important tree species of this region.We selected trees with contrasting crown dieback,from healthy to severely defoliated,to investigate the relationships between canopy dieback and leaf morphology,water content and pigments.We also measured esterase and peroxidase,as enzymatic antioxidants and indicators of contrasting genotypes.Trees showing moderate to severe defoliation showed higher leaf mass area(LMA),reduced relative water content(RWC),and lower stomatal density(SD).Increasing LMA indicates a more sclerophyllic structure,according to drier conditions.We did not find significant differences in leaf pigments(chlorophyll a and b,and carotenoids)among crown dieback classes,suggesting that Persian oak trees are able to maintain accurate photochemical efficiency,while reduced RWC and SD suggest hydraulic limitations.Our results do not provide a consistent pattern as regards enzymatic antioxidant defense in Persian oak.Morphological leaf traits would be important drivers of future adaptive evolution in Persian oak,leading to smaller and thicker leaves,which have fitness benefits in dry environments.Nonetheless,drought responses may be critically affecting carbon uptake,as photosynthetic compounds are less effectively used in leaves with higher sclerophylly.
文摘Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA against environmental stresses. Therefore, plants need to increase both LMA and photosynthesis at high elevations. To examine how deciduous plants maintain a positive carbon balance at high elevations, photosynthesis and related leaf traits for deciduous broad-leaved tree Betula ermanii were measured at three elevations. LMA was greater at middle and high elevations than at low elevation. Leaf δ13C was greater at higher elevations, and positively correlated with LMA, indicating greater long-term deficiency of CO2 in leaves at higher elevations. However, the Ci/Ca ratio at photosynthetic measurement was not low at high elevations. Nitrogen content per leaf mass and stomatal conductance were greater at higher elevations. Photosynthetic rates and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three elevations. Photosynthetic rate showed a strong positive correlation with stomatal conductance on a leaf area basis (R2 = 0.83, P < 0.001). Therefore, this study suggests B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing stomatal conductance, and maintains photosynthesis and PNUE at high elevation as much as at low elevation.
基金supported by the University of Eastern FinlandCzech University of Life Sciences doctoral research funding to O.A+5 种基金North Karelia Regional Fund to O.A (grant number 55232028)University of Eastern Finland(strategic fundingproject 931060)the Academy of Finland(C-NEUT,project number 347862)part of the Academy of Finland Flagship on Photonics Research and Innovation (PREIN) decision (320166)the Finnish National Plant Phenotyping Infrastructure (NaPPI/Biocenter Finland)
文摘We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°N)and southern(62°N) silver birches in a common garden at62°N.ChlF transients were measured five times during two weeks in the middle of summer to avoid seasonal variation.Differences in growth and leaf morphological traits between the provenances were also examined.The northern trees had higher chlorophyll content,larger leaf areas,and higher leaf fresh and dry mass than the southern trees,but the leaf mass per area did not differ between the provenances.The southern trees were taller and showed higher annual shoot growth than the northern trees.For all the ChlF parameters,day-to-day variation was significant and followed the same pattern for both provenances with no significant provenance ×day interaction,suggesting a similar response to environmental variation.The northern provenance had higher values in parameters related to the reduction of end electron acceptors at the Photosystem I(PSI) acceptor side as probed by ChlF.This and higher values for performance indices PI_(abs) and PI_(tot) in northern than in southern trees suggest higher photosynthetic performance of northern trees in line with the latitudinal compensation strategy.Provenance differences in these parameters increased towards the end of the measurement period,suggesting preparation for earlier growth cessation in northern trees triggered by the shortening day length.The study shows that provenance differences in ChlF can be relatively stable regardless of environmental variation but might be influenced by physiological alterations in preparation for future changes in environmental conditions.
