Leaf Shape Parameters Research Articles

FAMeLeS: A multispecies and fully automated method to measure morphological leaf traits

Abstract Leaf shape parameters are of key importance to explain the role of energy balance and water economy in plant species distribution, plant productivity and, more generally, in plant–environment interactions. Yet, leaf shape measurements based on image processing are still challenging due to the high diversity of leaf shapes, colours and sizes leading to the development of time‐consuming methods with a narrow field of applicability, sometimes species‐specific or often limited to a few species. We developed a fully automated method for measuring multiple leaf shape parameters (area, perimeter, length, width, circularity and solidity) based on a large image sampling of leaf diversity (including litter) belonging to 587 species and spread over 232 countries worldwide. To evaluate the accuracy of the method to detect small objects, the sampling particularly targeted Mediterranean ecosystems (32 species and 25,205 leaves), in which small leaves often represent methodological challenges. We compared our approach and found that its mean error in leaf area measurement (+0.46%) was 1.7–148 times lower than four existing methods. It was also the only one capable of detecting and measuring all leaves in the test data set, even variegated and small leaves (less than 1 mm2). Its reliability was extensively checked on the largest and most diversified data set ever used. Our method, accessible to the broader scientific community, was simple, rapid and effective on multiple image file types and on a high diversity of leaf size, shape and colour. As such, our approach allows measurement not only on fresh leaves but also on dry leaves, such as leaf litter or leaves from herbaria. This tolerance to leaf characteristics is crucial to increase large‐scale sampling efforts and paves the way for a standardized multispecies approach to measuring leaf morphological traits for ecological and agricultural studies.

Comparative Morphological, Anatomical and Physiological Analyses Explain the Difference of Wounding-Induced Agarwood Formation between Ordinary Agarwood Nongrafted Plants and Five Grafted Qi-Nan Clones (Aquilaria sinensis)

Agarwood is the dark resinous heartwood of injured ordinary Aquilaria sinensis (OA). Recently, some new clones of A. sinensis (Qi-Nan) that intensively produce high-quality agarwood were selected and cultivated by grafted clonal seedlings. However, very little is known about their agarwood formation mechanism, and it is unclear whether the current method of distinguishing Qi-Nan from OA by observing its leaf apparent morphology is scientifically reliable. In this study, the differences between OA and Qi-Nan clones in agarwood formation and their correlation with morphological, anatomical and physiological characteristics were investigated in two types of A. sinensis trees. After the mechanical injury, agarwood yield and essential oil content in agarwood of Qi-Nan were significantly higher than that of OA. There was no significant difference in leaf shape parameters between Qi-Nan and OA, but Qi-Nan showed higher specific leaf weight, total leaf chlorophyll, leaf nitrogen content and net photosynthetic rate. A xylem anatomical analysis showed that Qi-Nan had significantly smaller vessel wall thickness, greater ray cell wall thickness and larger interxylary phloem area than OA. Moreover, Qi-Nan had a greater consumption of non-structural carbohydrates than OA. Agarwood yield and oil content in agarwood showed significantly positive correlations with leaf photosynthetic capacity, the wall thickness of xylem ray cell, interxylary phloem area, starch utilization rate of trees, and a significantly negative correlation with the wall thickness of xylem vessel of trees. In brief, Qi-Nan has a stronger photosynthetic basis to supply more carbon sources, a more efficient xylem structural basis for agarwood production and a higher carbon source utilization rate, leading to a higher agarwood yield and oil content. It is not reliable to distinguish Qi-Nan from OA simply by observing leaf apparent morphology.

Mining Candidate Genes and Favorable Haplotypes for Flag Leaf Shape in Rice (Oryza sativa L.) Based on a Genome-Wide Association Study

The shape of the rice flag leaf affects rice yield. Therefore, the detection of quantitative trait loci (QTLs) and alleles related to rice flag leaf shape is of great significance for rice yield improvement. Therefore, in 2019 and 2020, we carried out a genome-wide association study of flag leaf length (FLL), flag leaf width (FLW), flag leaf length–width ratio (FLR), and flag leaf area (FLA), considering 1.3 million single-nucleotide polymorphisms (SNPs) in 173 rice accessions, in order to investigate the effects of various genes on flag leaf shape. An abundance of phenotypic variation was found, with respect to the four flag leaf shape parameters of these accessions. We identified one significant SNP position associated with FLL and FLR on chromosome 5 and one significant SNP position associated with FLW on chromosome 2, which were detected in both of the two years of the study period through general linear model (GLM) and mixed linear model (MLM). Furthermore, three candidate genes—LOC_Os02g56760, LOC_Os05g34380, and LOC_Os05g34600—were found to possibly be significantly related to flag leaf shape in rice. Haplotype analysis indicated that LOC_Os05g34380 is highly associated with flag leaf length and flag leaf length–width ratio, LOC_Os05g34600 is highly associated with flag leaf length, and LOC_Os02g56760 is highly associated with flag leaf width. Our results provide important genetic information for the molecular improvement of rice flag leaf shape, laying the foundation for further cloning and molecular-assisted breeding of flag leaf genes.

Diversity of leaf morphometric parameters in natural Greek populations of Arbutus unedo

Abstract This paper investigates leaf morphology variation of the strawberry tree (Arbutus unedo) within and between two natural contrasting populations of significant latitudinal difference (Kassandreia, Chalkidiki and Ancient Olympia, Peloponnese). This study employed 11 leaf size and shape parameters, recorded by image processing and analyzing software. The results showed that in the measurements of central tendency (parameter means) the northern population of Kassandreia presented the highest values, while in contrast the highest values in the measurements of spread were found in the southern population of Ancient Olympia. Moreover, statistically significant differences between populations were detected in leaf size, but not in leaf shape parameters. Results are discussed in the context of their value in studying quantitative population differentiation and laying the basis of more advanced studies.

Analysis of photosynthetic ability and related physiological traits in nodal leaves of grape

Fruiting shoots are comprised of leaves, fruits, and branches, which determine the grape yield and the quality of produce. Fruiting shoots are also the important structural unit for studying the relationship between the source and sink. The number of leaves, leaf area, photosynthetic activities, and density are directly or indirectly affecting the ability of the fruiting shoot to fix CO2 and provide a carbon source for the fruit growth and development. ‘Summer Black’ is used as the main test material and observed certain differences in appearance, microstructure, photosynthetic pigments, relative water content (RWC), organic acids, carbohydrates, mineral elements, and photosynthetic capacity at different nodal leaves. The net photosynthetic rate (A) was significantly positively correlated with leaf shape parameters (the ratio between branch point to lobe tip and distal sinus to petiolar junction), leaf structure thickness, RWC, carotenoids, soluble sugars, and organic acids, but it was significantly negatively correlated with intercellular CO2 concentration (Ci), Chlorophyll b and phosphorus content. The variations in magnesium, water, glucose, and fructose content in leaves matched the expression patterns of aquaporin, magnesium transporter, and sugar metabolism-related genes in various nodal leaves. In addition, the physiological traits and photosynthetic capacity at different nodal leaves of ‘Shine Muscat’ and ‘Kyoho’ were similar to those of ‘Summer Black’. The results of this study will provide a reference for the differences in leaf sink–source effects at different nodes and provide a basis for reasonably removing leaves.

Construction of a high-density genetic map and its application for leaf shape QTL mapping in poplar.

High-quality and dense genetic maps were constructed, and leaf shape variation was dissected by QTL mapping in poplar. Species in the genus Populus, also known as poplars, are important woody species and considered model plants for perennial trees. High-density genetic maps are valuable genomic resources for population genetics. Here, we generated a high-quality and dense genetic map for an F1 poplar population using high-throughput NGS-based genotyping. A total of 92,097 high-quality SNP markers were developed by stringent filtering and identification. In total, 889 and 1650 SNPs formed the female and male genetic maps, respectively. To test the application of the genetic maps, QTL mapping of leaf shape was conducted for this F1 population. A total of nine parameters were scored for leaf shape variation in three different environments. Combining genetic maps and measurements of the nine leaf shape parameters, we mapped a total of 42 significant QTLs. The highest LOD score of all QTLs was 9.2, and that QTL explained the most (15.13%) trait variation. A total of nine QTLs could be detected in at least two environments, and they were located in two genomic regions. Within these two QTL regions, some candidate genes for regulating leaf shape were predicted through functional annotation. The successful mapping of leaf shape QTLs demonstrated the utility of our genetic maps. According to the performance of this study, we were able to provide high-quality and dense genetic maps and dissect the leaf shape variation in poplar.

Leaf shape variation and taxonomic boundaries in two sympatric rupicolous species of Helichrysum (Asteraceae: Gnaphalieae), assessed by linear measurements and geometric morphometry

Quantifying and understanding the causes of population differentiation in plants are critical for assessing the taxonomic structure of species, as the level of differentiation among populations may correspond to incipient speciation. Using linear and geometric morphometric approaches, phenotypic variation and associations between leaf traits and geographic and environmental characteristics were investigated in Helichrysum crassifolium and the widespread and sympatric Helichrysum pendulum: two species exhibiting conspicuous leaf variation in size and shape. The morphometric results show that both species have distinct patterns of leaf shape variation. However, overlapping values link the ranges of variation: a significant variance is explained by within-individual and population differentiation, and some environmental variables are moderately correlated with leaf shape parameters in both species. The fact that reproductive barriers between both species are weak, and that the morphological plasticity detected in both species appears to be non-adaptive, and to a high extent non-environmentally induced, allow us to postulate that the variations observed could be mediated by hybridization processes. Our results suggest that niche differentiation, which involves the colonization of a specialized rupicolous habitat, does not necessarily lend itself as an effective strong reproductive barrier between closely related species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 498–513.

Leaf area estimation by simple measurements and evaluation of leaf area prediction models in Cabernet-Sauvignon grapevine leaves

For two growing seasons (2005 and 2006), leaves of grapevine cv. Cabernet-Sauvignon were collected at three growth stages (bunch closure, veraison, and ripeness) from 10-year-old vines grafted on 1103 Paulsen and SO4 rootstocks and subjected to three watering regimes in a commercial vineyard in central Greece. Leaf shape parameters (leaf area − LA, perimeter − Per, maximum midvein length − L, maximum width − W, and average radial − AR) were determined using an image analysis system. Leaf morphology was affected by sampling time but not by year, rootstock, or irrigation treatment. The rootstock×irrigation×sampling time interaction was significant for all the leaf shape parameters (LA, Per, L, W, and AR) and the means of the interaction were used to establish relationships between them. A highly significant linear function between L and LA could be used as a non-destructive LA prediction model for Cabernet-Sauvignon. Eleven models proposed for the non-destructive LA estimation in various grapevine cultivars were evaluated for their accuracy in predicting LA in this cultivar. For all the models, highly significant linear functions were found between calculated and measured LA. Based on r 2 and the mean square deviation (MSD), the model proposed for LA estimation in cv. Cencibel [LA = 0.587(L×W)] was the most appropriate.

Nitrogen fertilization effects on leaf morphology and evaluation of leaf area and leaf area index prediction models in sugar beet

In a two-year experiment (2002–2003), five N application rates [0, 60, 120, 180, and 240 kg(N) ha−1, marked N0, N60, N120, N180, and N240, respectively] were applied to sugar beet cv. Rizor arranged in a Randomized Complete Block design with six replications. Leaf shape parameters [leaf area (LA), maximum length (L), maximum width (W), average radial (AR), elongation (EL), and shape factor (SF)] were determined using an image analysis system, and leaf area index (LAI) was non-destructively measured every two weeks, from early August till mid-September (four times). Years, samplings, and their interaction had significant effects on the determined parameters. Fertilization at the highest dose (N240) increased L and sampling×fertilization interaction had significant effects on LA, L, W, and SF. For this interaction, W was the best-correlated parameter with LA and LAI meaning that W is a good predictor of these parameters. Two proposed models for LA estimation were tested. The model based on both leaf dimensions [LA = 0.5083 (L×W) + 31.928] predicted LA better than that using only W (LA = 21.686 W − 112.88). Instrumentally measured LAI was highly correlated with predicted LAI values derived from a quadratic function [LAI = −0.00001 (LA)2 + 0.0327 LA − 2.0413]. Thus, both LA and LAI can be reliably predicted non-destructively by using easily applied functions based on leaf dimensions (L, W) and LA estimations, respectively.

Leaf shape and its relationship with Leaf Area Index in a sugar beet (Beta vulgaris L.) cultivar

Heteroblasty of sugar beet cultivar Rizor was studied under field conditions for three growing seasons (2003, 2005, 2006) in a Randomized Complete Block (RCB) design experiment. Eleven leaf samplings, from early June till the end of October, were conducted each year and leaf shape parameters [leaf area (LA), centroid X or Y (CX or CY), length (L), width (W), average radial (AR), elongation (EL), shape factor (SF)] were determined by an image analysis system. During samplings, Leaf Area Index (LAI) was measured non-destructively. Significant year and sampling effects were found for all traits determined. With the progress of the growing season, leaves became smaller (LA, L, W, and AR were decreased) and rounded. The largest leaves were sampled in 2006 when LAI was highest. LA was strongly correlated with L and W with simple functions (y = 0.1933 x2.2238, r 2 = 0.96, p<0.001, and y = 28.693 x − 192.33, r 2 = 0.97, p< 0.001, respectively), which could be used for non-destructive LA determination. Also, LAI was significantly related with LA and leaf dimensions (L, W) suggesting that an easy, non-destructive determination of LAI under field conditions is feasible for sugar beet cv. Rizor.

Leaf shape and its relationship with Leaf Area Index in a sugar beet (Beta vulgaris L.) cultivar

Heteroblasty of sugar beet cultivar Rizor was studied under field conditions for three growing seasons (2003, 2005, 2006) in a Randomized Complete Block (RCB) design experiment. Eleven leaf samplings, from early June till the end of October, were conducted each year and leaf shape parameters [leaf area (LA), centroid X or Y (CX or CY), length (L), width (W), average radial (AR), elongation (EL), shape factor (SF)] were determined by an image analysis system. During samplings, Leaf Area Index (LAI) was measured non-destructively. Significant year and sampling effects were found for all traits determined. With the progress of the growing season, leaves became smaller (LA, L, W, and AR were decreased) and rounded. The largest leaves were sampled in 2006 when LAI was highest. LA was strongly correlated with L and W with simple functions (y = 0.1933 x2.2238, r 2 = 0.96, p<0.001, and y = 28.693 x - 192.33, r 2 = 0.97, p< 0.001, respectively), which could be used for non-destructive LA determination. Also, LAI was significantly related with LA and leaf dimensions (L, W) suggesting that an easy, non-destructive determination of LAI under field conditions is feasible for sugar beet cv. Rizor.

A Comparison of Isozyme and Morphological Markers to Assess the Within Population Variation in Small Populations of European aspen (Populus tremula L.) in Spain

Summary European aspen (Populus tremula L.) has been traditionally thought to establish new stands by vegetative propagation through root suckers produced by very few individuals (often only one). Morphological traits and isozyme patterns were studied in five small stands in northern Spain. Both isozyme and morphological approaches showed variation within and between stands. Estimated intrapopulational variation was higher than the expected, and clusters of individuals with the same isozyme multilocus patterns within each population have been identified. In order to check to what extent morphological markers are affected by the genotypes or clones, comparisons between leaf parameters and isozyme patterns were performed by hierarchical ANOVA and tests of hypothesis were constructed from the components of variance. Leaf shape parameters show a good correlation with the isozyme multilocus patterns. On the other hand, leaf size parameters, were more influenced by environmental factors. These traits may be useful as tools for the definition of in situ conservation units in endangered European aspen stands.

The effect of inoculation of potato ( Solanumtuberosum L.) microplants with arbuscular mycorrhizal fungi on tuber yield and tuber size distribution

Potato microplants were inoculated with three commercial arbuscular mycorrhizal inoculants, Vaminoc (MicroBio, Hemel Hempstead, HP2 7SU, UK), Endorize IV and Glomus intraradices (both produced by Societe Biorize, 21000 Dijon, France) at establishment in the glasshouse. Monitoring of percentage root length colonization confirmed the persistence of all the mycorrhizal fungi during the trial. Colonization with Vaminoc and Endorize IV levelled-off at approximately 8 weeks and with G. intraradices at 12 weeks. Image analysis of leaf shape parameters at 4 weeks in the field indicated that the control uninoculated microplants and the microplants from the Vaminoc treatment were significantly the most mature of the microplant-derived populations. Microplants from the Endorize IV treatment were significantly less mature than from the Vaminoc treatment and those from the G. intraradices treatment significantly the least mature. The G. intraradices treatment was late flowering. The Vaminoc and Endorize treatments promoted flowering, 80 and 76%, respectively, at 2 months after planting, relative to the microplant control (60% at 2 months), the G. intraradices treatment reduced flowering, 14% at 2 months. Mycorrhizal dependency determined at harvest showed that Vaminoc and Endorize IV promoted growth relative to the control wherea s G. intraradices reduced growth. Average tuber yield for a seed-tuber-derived control was 1.2 kg per plant, and the average yield per plant for the microplant control was significantly lower at 0.9 kg. The Vaminoc treatment was not significantly different from the microplant control. The Endorize IV and G. intraradices yields were significantly lower at 0.64 and 0.41 kg per plant, respectively. Since the objective was to evaluate the potential of mycorrhizal fungi to improve yield of seed grade tubers from microplants, tuber size distribution was analysed. The average number of seed grade tubers for the respective treatments were, 1.2 for the seed-tuber crop, 3.8 for the control microplants, 3.8 for the G. intraradices, 6 for Vaminoc and 8.5 for Endorize IV crops, respectively. It has been shown here that mycorrhizal inoculation can influence the yield quality of potato microplants. These results support previous findings that mycorrhizal fungi can increase or decrease yield depending on the mycorrhizal isolate and host genotype. Leaf image analysis has been shown to have predictive value in evaluating the potential of mycorrhizal treatments. The determinants of tuber yield and tuber size distribution in potato are complex and results, such as those obtained here, would require to be repeated in multiple sites and successive years to confirm the stability of the interactions reported.

The use of image analysis to study developmental variation in micropropagated potato (Solanum tuberosum L.) plants

Potato leaf morphology changes during plant development with the phase shift from vegetative growth to flowering. Image analysis can detect differences in leaf morphology and has been used here to distinguish differences in leaf morphology between potato crops derived from seed tubers and minitubers and between crops derived from different micropropagation protocols. Further, leaf shape parameters can be used to determine the relative maturity of crops. This finding is of economic importance since differences in plant development, for example delayed flowering, are associated with yield parameters. It is hypothesised that image analysis of established microplants can be used as an early evaluation of micropropagation protocols for potato.

A quantitative comparison of foliage development among allopatric ferns,Dryopteris crassirhizoma, D. coreano-montana andD. filix-mas

A quantitative comparison was conducted on the foliage development during sporophyte development of three allopatric ferns in cool temperate and subalpine regions of Hokkaido and Tirol, European Alps. The foliage development ofDryopteris crassirhizoma, D. coreano-montana andD. filix-mas was quantitatively described by the leaf development (NV, number of veins); NV correlates the leaf-shape complexity from a circle (DI, L/2(3.14×S)1/2). Nearly similar patterns were detected on frequency distribution of fertile leaves, fertility increase and number of leaves in threeDryopteris ferns which exhibit funnel-shaped foliage arrangements in mature sporophyte. No difference was found in number of leaves, maximum NV, fertility rate and leaf-shape parameters among three ferns. A positive difference was found only on changes in order of pinnae with maximum number of costa branches (NVP) and the DI of outline of pinnae betweenD. crassirhizoma andD. filix-mas. These allopatricDryopteris ferns seem to have a similar foliage structure, in spite of some sympatricDryopteris ferns capable of producing putative hybrids (D. austriaca andD. amurensis; D. tokyoensis andD. monticola) having different foliage structures in Hokkaido.