Increase of the chlorophyll fluorescence ratio F690/F735 during the autumnal chlorophyll breakdown

Summary The chlorophyll content and the fluorescence induction kinetics at two wavelengths (690 nm and 735 nm) have been measured in leaves of nine common broadleaf tree species during the autumnal chlorophyll breakdown. The ratio of the chlorophyll fluorescence maxima F690/F735 was determined at fluorescence maximum (fm) and at steady-state conditions (fs) by the laser-induced fluorescence emission using the two-wavelength fluorometer. The ratio F690/F735 increases with the leaf discolouring during the autumnal chlorophyll breakdown. The relationship between the chlorophyll content and the ratio F690/F735 can be expressed by a power function (curvilinear relationship) which is valid for all the species examined. In most cases the ratio F690/F735 measured in the upper leaf side is lower than that in the lower leaf side, but the trend is the same along the decreasing chlorophyll content. The ratio F690/F735 is always higher at maximum fluorescence than at steady-state fluorescence in the upper as well as lower leaf side and these values are well fitted in a linear correlation. This study confirms the usefulness of the ratio F690/F735 as a suitable non-destructive indicator of the in-vivo chlorophyll content, especially at medium and low chlorophyll content.     

General trait relationships in stems: a study on the performance and interrelationships of several functional and structural parameters involved in corticular photosynthesis

We addressed corticular photosynthesis, focusing on parameters of underlying dark and light reactions as well as structural differentiation. To unveil general stem traits and underlying principles that may be valid across several tree species, CO₂ exchange rates and chlorophyll‐fluorescence parameters were measured in current‐year to 3‐year‐old stems of five deciduous tree species (including climax and pioneer species). Across species, dark CO₂ efflux rates (R_d) of stems exhibited a common regression relationship with photosynthetic rates (A) and light‐adapted quantum efficiency of photosystem II (PSII) (ΔF/Fm′), a pattern analogous to leaf trait correlations. Furthermore, A and ΔF/Fm′ were closely interrelated to each other. Consistent correlations of stem structure and function were also assessed among species. Changes in tissue structure during ageing significantly affected several stem functional parameters. Stem CO₂ efflux during the dark and corticular photosynthetic rates declined with increasing stem age as well as light‐adapted quantum efficiency of PSII. Furthermore, a strong relationship between stem R_d and peridermal PFD‐transmittance (T) as well as between R_d and total bark chlorophyll was evident. Consistent results were found for the relationships between corticular photosynthesis (or primary photosynthetic reactions like ΔF/Fm′) and selected structural traits. The found correlation patterns among functional and/or structural traits of stems and their concordance with leaf trait relationships may aid in identifying underlying mechanisms and scaling relationships that link traits to plant and ecosystem function.     

Chlorophyll fluorescence induction,chlorophyll content,and chromaticity characteristics of leaves as indicators of photosynthetic apparatus senescence in arboreous plants

Parameters of chlorophyll fluorescence induction (CFI) are widely used for assessment of the physiological state of higher plant leaves in biochemical, physiological, and ecological studies and in agricultural applications. In this work we have analyzed data on variability of some CFI parameters — Φ _PSII ^max = F _v/F _m (relative value of variable fluorescence), q _NPQ (non-photochemical quenching coefficient), R _Fd (“vitality index”) — in autumnal leaves of ten arboreous plant species of the temperate climatic zone. The correlation between the chlorophyll content in the leaves and fluorescence parameters characterizing photosynthetic activity is shown for two representative species, the small-leaved linden Tilia cordata and the rowan tree Sorbus aucuparia. During the period of mass yellowing of the leaves, the Φ _PSII ^max value can be used as an adequate characteristic of their photochemical activity, while in summer the q _NPQ or R _Fd values are more informative. We have established a correlation between the Φ _PSII ^max value, which characterizes the maximal photochemical activity of the photosystem II, and “chromaticity coordinates” of a leaf characterizing its color features. The chromaticity coordinates determined from the optical reflection spectra of the leaves serve as a quantitative measure of their hues, and this creates certain prerequisites for a visual expert assessment of the physiological state of the leaves.     

Screening for drought tolerance in mutant germplasm of sesame (Sesamum indicum) probing by chlorophyll a fluorescence

Drought is one of the major constraints limiting crop productivity in African Sahel. The aim of this study was to select mutant sesame (Sesamum indicum L.) lines with improved levels of drought resistance. Twenty-one M4-M5 sesame lines of unknown drought tolerance, and their three parental sources with well-known and contrasting drought tolerance levels were evaluated at the vegetative stage in a factorial pot experiment, using a completely randomized design with three replicates. After 2 weeks of growth, water was withheld for 16 days as drought stress treatment. Chlorophyll a fluorescence data, as well as stomatal conductance and flag leaf temperature were recorded during the stress period. Recorded chlorophyll a fluorescence transients were analyzed by the JIP-test to translate stress-induced damage in these transients to changes in biophysical parameters allowing quantification of the energy flow through the photosynthetic apparatus. Large genotypic differences in the extent to which drought stress affected chlorophyll a fluorescence transients were observed. Drought stress reduced the performance index and stomatal conductance, and increased flag leaf temperature but had little effect on maximum quantum yield of primary photochemistry. A drought factor index is proposed in this work to screen for improved drought tolerance in twenty-one M4-M5 sesame lines. Mutant lines shi165, lc162, mc112, lc164, icn115, icn141, mt169, dwf172 and cc102 exhibited drought factor index values superior to those of the known drought tolerant cultivars Birkan and 38-1-7. A significant and negative relationship was found between the drought factor index and the leaf temperature index. Finally, we succeeded in obtaining drought tolerant lines with good secondary traits by using mutagenesis and chlorophyll fluorescence technique.     

Photosynthesis and Chlorophyll Fluorescence Characteristics in Relationship to Changes in Pigment and Element Composition of Leaves of Platanus occidentalis L. during Autumnal Leaf Senescence

The loss of chlorophyll and total leaf nitrogen during autumnal senescence of leaves from the deciduous tree Platanus occidentalis L. was accompanied by a marked decline in the photosynthetic capacity of O₂ evolution on a leaf area basis. When expressed on a chlorophyll basis, however, the capacity for light-and CO₂-saturated O₂ evolution did not decline, but rather increased as leaf chlorophyll content decreased. The photon yield of O₂ evolution in white light (400-700 nanometers) declined markedly with decreases in leaf chlorophyll content below 150 milligrams of chlorophyll per square meter on both an incident and an absorbed basis, due largely to the absorption of light by nonphotosynthetic pigments which were not degraded as rapidly as the chlorophylls. Photon yields measured in, and corrected for the absorptance of, red light (630-700 nanometers) exhibited little change with the loss of chlorophyll. Furthermore, PSII photochemical efficiency, as determined from chlorophyll fluorescence, remained high, and the chlorophyll a/b ratio exhibited no decline except in leaves with extremely low chlorophyll contents. These data indicate that the efficiency for photochemical energy conversion of the remaining functional components was maintained at a high level during the natural course of autumnal senescence, and are consistent with previous studies which have characterized leaf senescence as being a controlled process. The loss of chlorophyll during senescence was also accompanied by a decline in fluorescence emanating from PSI, whereas there was little change in PSII fluorescence (measured at 77 Kelvin), presumably due to decreased reabsorption of PSII fluorescence by chlorophyll. Nitrogen was the only element examined to exhibit a decline with senescence on a dry weight basis. However, on a leaf area basis, all elements (C, Ca, K, Mg, N, P, S) declined in senescent leaves, although the contents of sulfur and calcium, which are not easily retranslocated, decreased to the smallest extent.     

Ecological stress memory: Evidence in two out of seven species through the examination of the relationship between leaf fluctuating asymmetry and photosynthesis

Increased morphological fluctuating asymmetry is considered as an indication that the extent of a natural stress has surpassed the ability of the genotype to maintain the normal symmetry in the body plan. Young leaves can suffer by a variety of stresses, such as nutrient deficiencies, drought, heat and cold in combination with high light. Therefore, increased morphological fluctuating asymmetry in mature leaves may be considered as an ecological indicator of such environmental pressures. Hence, deviations from symmetry in a mature leaf may be a reminder of an adversity having occurred when the leaf was young and developing. We argued that a past stress may stigmatize future photosynthesis and we searched for correlations between leaf fluctuating asymmetry and photosynthetic parameters obtained from fast chlorophyll a fluorescence rise curves in mature leaves from seven tree species. The results were species-specific, with four species (Arbutus unedo, Cercis siliquastrum, Platanus orientalis and Populus alba) showing both maximum quantum yield of photosystem II and photosynthetic performance index (PI_total sensu Strasser) to be independent of the alleged juvenile stress, while in one species (Ceratonia siliqua) the two parameters were negatively correlated to leaf fluctuating asymmetry. Interestingly, in two species (Olea europaea and Pistacia lentiscus), higher leaf asymmetry was linked with lower risk of chronic photoinhibitory damage and higher photosynthetic capacity. An ‘ecological stress memory’ may be inferred for some species improving their tolerance to future adversities and global change.     

Gap effects on leaf traits of tropical rainforest trees differing in juvenile light requirement

The relationships of 16 leaf traits and their plasticity with the dependence of tree species on gaps for regeneration (gap association index; GAI) were examined in a Neotropical rainforest. Young saplings of 24 species with varying GAI were grown under a closed canopy, in a medium-sized and in a large gap, thus capturing the full range of plasticity with respect to canopy openness. Structural, biomechanical, chemical and photosynthetic traits were measured. At the chloroplast level, the chlorophyll a/b ratio and plasticity in this variable were not related to the GAI. However, plasticity in total carotenoids per unit chlorophyll was larger in shade-tolerant species. At the leaf level, leaf mass per unit area (LMA) decreased with the GAI under the closed canopy and in the medium gap, but did not significantly decrease with the GAI in the large gap. This was a reflection of the larger plasticity in LMA and leaf thickness of gap-dependent species. The well-known opposite trends in LMA for adaptation and acclimation to high irradiance in evergreen tropical trees were thus not invariably found. Although leaf strength was dependent on LMA and thickness, plasticity in this trait was not related to the GAI. Photosynthetic capacity expressed on each basis increased with the GAI, but the large plasticity in these traits was not clearly related to the GAI. Although gap-dependent species tended to have a greater plasticity overall, as evident from a principle component analysis, leaf traits of gap-dependent species are thus not invariably more phenotypically plastic.     

The vertical leaf distribution of Ulmus laevis Pall.

Vertical leaf distribution and relative irradiance were ascertained for the dominant species Ulmus laevis Pall. at the level of the individual tree and at the level of the stand in a mixed broad-leaved forest in South Moravia, the Czech Republic. The study consisted of detailed, destructive measurement of five selected sample trees and the establishment of basic biometric parameters for the entire stand. Using allometric relationships, measurements from sample trees were generalized to diameter at breast height (DBH) classes and were then scaled up to the level of the imaginary pure stand of elm; the selected independent variables were tree height and DBH. The vertical leaf distribution was unimodal in trees with smaller dimensions and bimodal in trees with larger dimensions. The leaf area index (LAI) of the stand was 4 (6.4 including the undergrowth), and the sunlit leaf area index (SLAI) was 1.7. Dominant trees had a higher proportion of sunlit leaf area than subdominant and suppressed trees. Determination of appropriate methods and intensity of thinning can lead to optimizing of irradiation control, vitality increase of the elm stands and subsequently to a higher resistance to Dutch elm disease vector and disease itself.     

Bioactive constituents in Prunus africana: Geographical variation throughout Africa and associations with environmental and genetic parameters

Prunus africana – an evergreen tree found in Afromontane forests – is used in traditional medicine to cure benign prostate hyperplasia. Different bioactive constituents derived from bark extracts from 20 tree populations sampled throughout the species’ natural range in Africa were studied by means of GC–MSD. The average concentration [mg/kg w/w] in increasing order was: lauric acid (18), myristic acid (22), n-docosanol (25), ferulic acid (49), β-sitostenone (198), β-sitosterol (490), and ursolic acid (743). The concentrations of many bark constituents were significantly correlated and concentration of n-docosanol was highly significantly correlated with all other analytes. Estimates of variance components revealed the highest variation among populations for ursolic acid (66%) and the lowest for β-sitosterol (20%). In general, environmental parameters recorded (temperature, precipitation, altitude) for the samples sites were not correlated with the concentration of most constituents; however, concentration of ferulic acid was significantly correlated with annual precipitation. Because the concentration of compounds in bark extracts may be affected by tree size, the diameter of sampled plants at 1.3 m tree height (as proxy of age) was recorded. The only relationship with tree diameter was a negative correlation with ursolic acid. Under the assumption that genetically less variable populations have less variable concentrations of bark compounds, correlations between variation parameters of the concentration and the respective genetic composition based on chloroplast and nuclear DNA markers were assessed. Only variation of β-sitosterol concentration was significantly correlated with haplotypic diversity. The fixation index (F_IS) was positively correlated with the variation in concentration of ferulic acid. Principal Components Analysis (PCA) indicated a weak geographic pattern. Mantel tests, however, revealed associations between the geographic patterns of bioactive constituents and the phylogenetic relationship among the populations sampled. This suggests an independent evolution of bark metabolism within different phylogeographical lineages, and the molecular phylogeographic pattern is partly reflected in the variation in concentration of bark constituents. The results have important implications for the design of strategies for the sustainable use and conservation of this important African tree species.     

Remote Probing of Plant Photosynthetic Apparatus by Measuring Laser-Induced Fluorescence

Laser-induced fluorescence of birch, pine, and aspen trees was studied. The fluorescence of birch leaves, excited with a Xe–Cl laser at a wavelength of 308 nm, was measured under laboratory conditions. A persistent directly proportional dependence was found between the measured fluorescence signals and the chlorophyll content. An apparatus for measuring laser-induced fluorescence under field conditions was designed. Deciduous trees were found to have a wider range of fluorescence variability when compared to conifers, with the fluorescence intensity increasing in the leaves of deciduous trees before the autumn fall of leaves, during leaf yellowing. It is concluded that the method of lidar probing can be used for identifying tree species and assessing the condition of leaf and needle canopies.     

基于引力模型的林木竞争分析

引力模型是否可以应用于森林群落林木竞争关系分析是值得研究的问题。基于引力模型建立林木相对活力圈能反映竞争木活力大小,基于竞争木的相对活力圈建立引力竞争指数能准确反映林木生长与林木竞争的关系。以浙江省天目山国家级自然保护区针阔混交林为研究对象,将V_Hegyi竞争指数、引力竞争指数分别与胸径进行相关分析,胸高断面积生长量分别与2种竞争指数进行相关分析,胸径生长率与2期引力竞争指数的比值(2021年与2006年的引力竞争指数之比)进行相关分析,此外,对相对活力圈直径与胸径进行相关分析,并比较分析了活立木与枯死木的竞争指数大小。结果表明: 2种竞争指数与胸径均呈显著负相关,且均服从幂函数关系。林木胸高断面积生长量与2种竞争指数均呈显著负相关,但引力竞争指数比V_Hegyi竞争指数更能反映林木生长与林木竞争的关系。相对于V_Hegyi竞争指数的比值,2期引力竞争指数的比值更能说明林木生长与林木竞争的关系。在针阔混交林中,阔叶树种的生长与竞争的相关性>针叶树种生长与竞争的相关性。林木枯损受竞争的显著影响。林木相对活力圈大小与林木胸径大小呈显著负相关。引力模型是反映空间相互作用的重要模型之一,可以应用于林木竞争关系的研究,且基于引力模型建立的引力竞争指数可以作为评价林木竞争和林木活力的一个空间结构指标,比V_Hegyi竞争指数更能反映林木生长与林木竞争的关系。     

The leaf, inner bark and latex cyanide potential of Hevea brasiliensis: Evidence for involvement of cyanogenic glucosides in rubber yield

The latex of Hevea brasiliensis, expelled upon bark tapping, is the cytoplasm of anastomosed latex cells in the inner bark of the rubber tree. Latex regeneration between two tappings is one of the major limiting factors of rubber yield. Hevea species contain high amounts of cyanogenic glucosides from which cyanide is released when the plant is damaged providing an efficient defense mechanism against herbivores. In H. brasiliensis, the cyanogenic glucosides mainly consist of the monoglucoside linamarin (synthesized in the leaves), and its diglucoside transport-form, linustatin. Variations in leaf cyanide potential (CNp) were studied using various parameters. Results showed that the younger the leaf, the higher the CNp. Leaf CNp greatly decreased when leaves were directly exposed to sunlight. These results allowed us to determine the best leaf sampling conditions for the comparison of leaf CNp. Under these conditions, leaf CNp was found to vary from less than 25 mM to more than 60 mM. The rubber clones containing the highest leaf CNp were those with the highest yield potential. In mature virgin trees, the CNp of the trunk inner bark was shown to be proportional to leaf CNp and to decrease on tapping. However, the latex itself exhibited very low (if any) CNp, while harboring all the enzymes (β-d-diglucosidase, linamarase and β-cyanoalanine synthase) necessary to metabolize cyanogenic glucosides to generate non-cyanogenic compounds, such as asparagine. This suggests that in the rubber tree bark, cyanogenic glucosides may be a source of buffering nitrogen and glucose, thereby contributing to latex regeneration/production.     

Photosynthetic acclimation to light in woody and herbaceous species: a comparison of leaf structure, pigment content and chlorophyll fluorescence characteristics measured in the field

Acclimation of foliage photosynthetic properties occurs with varying time kinetics, but structural, chemical and physiological factors controlling the kinetics of acclimation are poorly understood, especially in field environments. We measured chlorophyll fluorescence characteristics, leaf total carotenoid (Car), chlorophyll (Chl) and nitrogen (N) content and leaf dry mass per area (LMA) along vertical light gradients in natural canopies of the herb species, Inula salicina and Centaurea jacea, and tree species, Populus tremula and Tilia cordata, in the middle of the growing season. Presence of stress was assessed on the basis of night measurements of chlorophyll fluorescence. Our aim was to compare the light acclimation of leaf traits, which respond to light availability at long (LMA and N), medium (Chl a/b ratio, Car/Chl ratio) and short time scales (fluorescence characteristics). We found that light acclimation of nitrogen content per unit leaf area (N(area)), chlorophyll content per unit dry mass (Chl(mass)) and Chl/N ratio were related to modifications in LMA. The maximum PSII quantum yield (F(v) /F(m)) increased with increasing growth irradiance in I. salicina and P. tremula but decreased in T. cordata. Leaf growth irradiance, N content and plant species explained the majority of variability in chlorophyll fluorescence characteristics, up to 90% for steady-state fluorescence yield, while the contribution of leaf total carotenoid content was generally not significant. Chlorophyll fluorescence characteristics did not differ strongly between growth forms, but differed among species within a given growth form. These data highlight that foliage acclimation to light is driven by interactions between traits with varying time kinetics.     

Application of chlorophyll fluorescence in ecophysiology

Summary In vivo chlorophyll fluorescence measurements have become a valuable tool in ecophysiology. Fluorescence emission spectra are influenced by the reabsorption of the tissue and indicate the composition of the antenna system and are influenced by the chlorophyll content per leaf area. The fluorescence induction kinetics (Kautsky effect) can be used to study photosynthetic activity. These rapid, non-destructive methods can be applied for ecophysiological field research to check the vitality of plants and to document stress effects on the photosynthetic apparatus. The Rfd-values (Rfd=fd/fs), the ratio of the fluorescence decrease (fd) to the steady state fluorescence (fs), can be taken as a rapid vitality index of the leaves and trees. We here describe fundamental chlorophyll fluorescence results of leaves which are needed for the interpretation of in vivo fluorescence signatures in stress physiology and in the forest dieback research.     

The dark side of green fluorescent protein

Here, severe interference of chlorophyll with green fluorescent protein (GFP) fluorescence is described for medicago (Medicago truncatula), rice (Oryza sativa) and arabidopsis (Arabidopsis thaliana). This interference disrupts the proportional relationship between GFP content and fluorescence that is intrinsic to its use as a quantitative reporter. The involvement of chlorophyll in the loss of GFP fluorescence with leaf age was shown in vivo, by the removal of chlorophyll through etiolation or by ethanol extraction, and in vitro, by titration of a GFP solution with chlorophyll solutions of various concentrations. A substantial decrease in fluorescence in early development of medicago and rice leaves correlated with chlorophyll accumulation. In all three species tested, removal of chlorophyll yielded up to a 10-fold increase in fluorescence. Loss of GFP fluorescence in vitro was 4-fold greater for chlorophyll b than for chlorophyll a. Differences exist between plant species for the discrepancy between apparent GFP fluorescence and its actual level in green tissues. Substantial errors in estimating promoter activity from GFP fluorescence can occur if pigment interference is not considered.     

不同品系福建山樱花叶功能性状研究

为了解福建山樱花(Prunus campanulata)的叶片功能性状,对4个品系的叶形指数、比叶面积、叶绿素含量以及叶干物质含量进行了研究。结果表明,福建山樱花不同品系间的叶功能性状都存在显著差异。叶功能性状间存在一定的相关性,叶形指数与叶干物质含量存在显著负相关(P<0.05);比叶面积与叶绿素含量存在极显著正相关(P<0.01),其与叶干物质含量呈极显著负相关(P<0.01)。经过综合评价,池边3号品系的叶绿素含量、叶干物质含量较大,花期长,花量稠密,可推荐作为园林观赏和行道树种。     

Endophytic aquatic hyphomycetes in roots of riparian tree species of two Western Ghat streams

Bubble chamber incubation of surface sterilized segments of root bark and xylem of 10 riparian tree species of the Sampaje (475–500 m asl) and V?Badaga (765–800 m asl) stream reaches of the Western Ghats yielded 20 species of endophytic aquatic hyphomycetes. Anguillospora crassa, A. longissima and Cylindrocarpon sp. were among the top five species in streams. A two-way ANOVA showed significantly higher species richness and counts of conidium in the tree species of Sampaje compared to V?Badaga (p < 0.001), while two variables were not significantly different between bark and xylem. The total number of species recovered was slightly higher in bark than in xylem (14–19 vs. 13–17 spp.) and the average species richness between tissues did not differ significantly except for one tree species (Madhuca neriifolia: p < 0.05). The release of conidia from bark of only three tree species was significantly higher than from xylem (M. neriifolia and Canarium strictum: p < 0.05; Vateria indica: p < 0.01). Sørensen’s similarity index for bark as well as xylem between tree species was higher in Sampaje stream than in V?Badaga stream (0.45–0.78 vs. 0.25–0.61). The diversity of aquatic hyphomycetes in bark and xylem was higher in the trees of Sampaje than V?Badaga (3.1–3.3 vs. 2.7). A cluster analysis of aquatic hyphomycetes in bark and xylem resulted in two groups coinciding with the two streams. The results of this study revealed that assemblage and diversity of endophytic aquatic hyphomycetes in riparian tree roots are high in the mid-altitude Sampaje stream as previously documented for saprotrophic aquatic hyphomycetes.     

Effect of Leaf Detachment on Chlorophyll Fluorescence during Chilling Experiments

The effect of leaf detachment on chlorophyll fluorescence was analyzed for Zea mays, Cucumis sativus, Phaseolus vulgaris, and Echinochloa crus-galli. Results clearly indicate that detachment hastens the decrease in chlorophyll fluorescence during the course of chilling experiments. For maize and bean, the activity of photosystem II of chloroplasts isolated from detached leaves is lower than that of chloroplasts isolated from attached leaves. There are also large differences in ionic loss between detached and attached leaves of barnyard grass which could correlate with changes in leaf water status. The detached leaves lost some 50% of their total ionic content. Finally, detachment alters the ranking of the species with regard to their chilling tolerance.     

Spectral reflectance indices and pigment functions during leaf ontogenesis in six subtropical landscape plants

Pigment combinations are regulated during leaf ontogenesis. To better understand pigment function, alterations in chlorophyll, carotenoid and anthocyanin concentrations were investigated during different leaf development stages in six subtropical landscape plants, namely Ixora chinensis Lam, Camellia japonica Linn, Eugenia oleina Wight, Mangifera indica L., Osmanthus fragrans Lowr and Saraca dives Pierre. High concentrations of anthocyanin were associated with reduced chlorophyll in juvenile leaves. As leaves developed, the photosynthetic pigments (chlorophyll and carotenoid) of all six species increased while anthocyanin concentration declined. Chlorophyll fluorescence imaging of Φ_PSII (effective quantum yield of PSII) and of NPQ (non-photochemical fluorescence quenching) and determination of electron transport rate-rapid light curve (RLC) showed that maximum ETR (leaf electron transport rate), Φ_PSII and the saturation point in RLC increased during leaf development but declined as they aged. Juvenile leaves displayed higher values of NPQ and Car/Chl ratios than leaves at other developmental stages. Leaf reflectance spectra (400–800 nm) were measured to provide an in vivo non-destructive assessment of pigments in leaves during ontogenesis. Four reflectance indices, related to pigment characters, were compared with data obtained quantitatively from biochemical analysis. The results showed that the ARI (anthocyanin reflectance index) was linearly correlated to anthocyanin concentration in juvenile leaves, while a positive correlation of Chl NDI (chlorophyll normalized difference vegetation index) to chlorophyll a concentration was species dependent. Photosynthetic reflectance index was not closely related to Car/Chl ratio, while a structural-independent pigment index was not greatly altered by leaf development or species. Accordingly, it is suggested that the high concentration of anthocyanin, higher NPQ and Car/Chl ratio in juvenile leaves are important functional responses to cope with high radiation when the photosynthetic apparatus is not fully developed. Another two leaf reflectance indices, ARI and Chl NDI, are valuable for in vivo pigment evaluation during leaf development.     

Strength of winter leaf redness as an indicator of stress vulnerable individuals in Pistacia lentiscus

Leaf anthocyanins are believed to afford protection against photoinhibition, yet the dependence of protection on actual anthocyanin concentrations has not been investigated. To that aim, non-invasive optical methods (spectral reflectance and chlorophyll fluorescence) were used to assess the levels of anthocyanins and chlorophylls as well as photosystem II photochemical efficiency in hundreds of leaves from the mastic tree (Pistacia lentiscus), which displays in the field a continuum of leaf tints during winter from fully green to fully red. Contrary to expectations based on the photoprotective hypothesis, the strength of leaf redness was positively correlated to the extent of mid-winter chronic photoinhibition and negatively correlated to leaf chlorophyll contents. Hence, a photoprotective role for anthocyanins is not substantiated. Instead, we argue that winter leaf redness may be used reliably, quickly and non-invasively to locate vulnerable individuals in the field.