Affect Leaf Shape Research Articles

Effects of Altitude and Leaf Age on Leaf Shape in an Alpine Shrub: The Relevance for the Leaf Area Estimation Model

Nondestructive methods to estimate leaf area (LA) by leaf length (L) and/or width (W) are useful in plant physiology and ecology studies. However, both environmental and ontogenic factors may influence leaf size and/or shape, which may alter the coefficient of LA models. We carried an investigation along an altitudinal gradient in the Sergyemla Mountains, southeast Tibet. In August 2009, we selected nine sites at about every 50 m in altitude from 4,250 m to 4,640 m a.s.l. A total of 4,245 different leaf-aged Rhododendron aganniphum var. schizopeplum (a dominant overstory species) leaves were measured. Compared with the single dimensional models, the two-dimensional model encompassing both L and W (model 5) reflected higher R2 (0.98–0.99) and lower MSE (1.19–3.21) across different leaf age groups for each site, implying that such model could provide the best fit for LA estimation. Analysis of covariance further illustrated that two leaf dimensions model was irrespective of leaf age effects in eight out of the nine sites. Leaf shape (L:W ratio) varied between sites and tended to decrease at higher altitudes (4500–4640 m a.s.l.), leading to significant differences in coefficients of the two-dimension model between every two adjacent sites. For overstory species in alpine habitats, altitude rather than leaf age may affect leaf shape which alters the coefficients of LA estimation models. Since leaf shape of different species (overstory species versus understory ones) may show different responses to a certain environmental gradient, researchers must pay attention to the variation of leaf shape when estimating species-specific LA by measuring L and W, especially when leaves of the top overstory species were collected at different sites.

Tree Size Influences Leaf Shape but Does Not Affect the Proportional Relationship Between Leaf Area and the Product of Length and Width.

The Montgomery equation predicts leaf area as the product of leaf length and width multiplied by a correction factor. It has been demonstrated to apply to a variety of leaf shapes. However, it is unknown whether tree size (measured as the diameter at breast height) affects leaf shape and size, or whether such variations in leaf shape can invalidate the Montgomery equation in calculating leaf area. Here, we examined 60 individual trees of the alpine oak (Quercus pannosa) in two growth patterns (trees growing from seeds vs. growing from roots), with 30 individuals for each site. Between 100 and 110 leaves from each tree were used to measure leaf dry mass, leaf area, length, and width, and to calculate the ellipticalness index, ratio of area between the two sides of the lamina, and the lamina centroid ratio. We tested whether tree size affects leaf shape, size, and leaf dry mass per unit area, and tested whether the Montgomery equation is valid for calculating leaf area of the leaves from different tree sizes. The diameters at breast height of the trees ranged from 8.6 to 96.4 cm (tree height ranged from 3 to 32 m). The diameter at breast height significantly affected leaf shape, size, and leaf dry mass per unit area. Larger trees had larger and broader leaves with lower leaf dry mass per unit area, and the lamina centroid was closer to the leaf apex than the leaf base. However, the variation in leaf size and shape did not negate the validity of the Montgomery equation. Thus, regardless of tree size, the proportional relationship between leaf area and the product of leaf length and width can be used to calculate the area of the leaves.

Silencing of PhLA, a CIN-TCP gene, causes defected petal conical epidermal cell formation and results in reflexed corolla lobes in petunia

BackgroundTCP-domain proteins, plant specific transcription factors, play important roles in various developmental processes. CIN-TCPs control leaf curvature in simple leaf species while regulate leaf complexity in compound leaf species. However, the knowledge was largely based on findings in few model species. To extend our knowledge on this group of proteins in Solanaceae species, we identified a CIN-TCP gene from petunia, and studied its functions using virus-induced gene silencing (VIGS).ResultsConsistently, silencing of CIN-TCPs increases complexity of tomato leaves, and enhances leaf curvature in Nicotiana benthamiana. However, in petunia (Petunia hybrida), silencing of petunia LA, a CIN-TCP, through VIGS did not obviously affect leaf shape. The silencing, however, enhanced petal curvature. The event was associated with petal expansion at the distal portion where epidermal cell size along the midribs was also increased. The enlarged epidermal cells became flattened. Although shapes of PhLA-silenced flowers largely resemble phmyb1 mutant phenotype, PhMYB1 expression was not affected when PhLA was specifically silenced. Therefore, both PhLA and PhMYB1 are required to regulate flower morphology. In corolla, PhLA and miR319 deferentially express in different regions with strong expressions in limb and tube region respectively.ConclusionsIn conclusion, unlike LA-like genes in tomato and N. benthamiana, PhLA plays a more defined role in flower morphogenesis, including petal curvature and epidermal cell differentiation.

A defect in the PINOID serine/threonine kinase affects leaf shape in cucumber.

Leaf shape has important implications for optimizing plant architecture for grain crops and horticultural crops. Examination of the cucumber (Cucumis sativus L.) round leaf (rl) mutant by Song et al. (2019) revealed that the PINOID protein kinase affects leaf shape by altering auxin biosynthesis, transport, and signaling.

Sugar-responsive transcription factor bZIP3 affects leaf shape in Arabidopsis plants.

Sugars are essential for plant metabolism, growth and development. Plants must therefore manage their growth and developmental processes in response to sugar availability. Sugar signaling pathways constitute a complicated molecular network and are associated with global transcriptional regulation. However, the molecular mechanisms underlying sugar signaling remain largely unclear. This study reports that the protein basic-region leucine zipper 3 (bZIP3) is a novel sugar-responsive transcription factor in Arabidopsis plants. The expression of bZIP3 was rapidly repressed by sugar. Genetic analysis indicated that bZIP3 expression was modulated by the SNF1-RELATED KINASE 1 (SnRK1) pathway. Moreover, transgenic plants overexpressing bZIP3 and dominant repressor form bZIP3-SRDX showed aberrant shaped cotyledons with hyponastic bending. These findings suggest that bZIP3 plays a role in plant responses to sugars and is also associated with leaf development.

Mutations in CsPID encoding a Ser/Thr protein kinase are responsible for round leaf shape in cucumber (Cucumis sativus L.).

Two round-leaf mutants, rl-1 and rl-2, were identified from EMS-induced mutagenesis. High throughput sequencing and map-based cloning suggested CsPID encoding a Ser/Thr protein kinase as the most possible candidate for rl-1. Rl-2 was allelic to Rl-1. Leaf shape is an important plant architecture trait that is affected by plant hormones, especially auxin. In Arabidopsis, PINOID (PID), a regulator for the auxin polar transporter PIN (PIN-FORMED) affects leaf shape formation, but this function of PID in crop plants has not been well studied. From an EMS mutagenesis population, we identified two round-leaf (rl) mutants, C356 and C949. Segregation analysis suggested that both mutations were controlled by single recessive genes, rl-1 and rl-2, respectively. With map-based cloning, we show that CsPID as the candidate gene of rl-1; a non-synonymous SNP in the second exon of CsPID resulted in an amino acid substitution and the round leaf phenotype. As compared in the wild type plant, CsPID had significantly lower expression in the root, leaf and female flowers in C356, which may result in the less developed roots, round leaves and abnormal female flowers, respectively in the rl-1 mutant. Among the three copies of PID genes, CsPID, CsPID2 and CSPID2L (CsPID2-like) in the cucumber genome, CsPID was the only one with significantly differential expression in adult leaves between WT and C356 suggesting CsPID plays a main role in leaf shape formation. The rl-2 mutation in C949 was also cloned, which was due to another SNP in a nearby location of rl-1 in the same CsPID gene. The two round leaf mutants and the work presented herein provide a good foundation for understanding the molecular mechanisms of CsPID in cucumber leaf development.

Leaf Shape Responds to Temperature but Not CO2 in Acer rubrum

The degree of leaf dissection and the presence of leaf teeth, along with tooth size and abundance, inversely correlate with mean annual temperature (MAT) across many plant communities. These relationships form the core of several methods for reconstructing MAT from fossils, yet the direct selection of temperature on tooth morphology has not been demonstrated experimentally. It is also not known if atmospheric CO2 concentration affects leaf shape, limiting confidence in ancient climate reconstructions because CO2 has varied widely on geologic timescales. Here I report the results of growing Acer rubrum (red maple) in growth cabinets at contrasting temperature and CO2 conditions. The CO2 treatment imparted no significant differences in leaf size and shape, while plants grown at cooler temperatures tended to have more teeth and more highly dissected leaves. These results provide direct evidence for the selection of temperature on leaf shape in one species, and support a key link in many leaf-climate methods. More broadly, these results increase confidence for using leaf shape in fossils to reconstruct paleoclimate.

Natural Variation in Biogenesis Efficiency of Individual Arabidopsis thaliana MicroRNAs

Like protein-coding genes, loci that produce microRNAs (miRNAs) are generally considered to be under purifying selection, consistent with miRNA polymorphisms being able to cause disease. Nevertheless, it has been hypothesized that variation in miRNA genes may contribute to phenotypic diversity. Here we demonstrate that a naturally occurring polymorphism in the MIR164A gene affects leaf shape and shoot architecture in Arabidopsis thaliana, with the effects being modified by additional loci in the genome. A single base pair substitution in the miRNA complementary sequence alters the predicted stability of the miRNA:miRNA(∗) duplex. It thereby greatly reduces miRNA accumulation, probably because it interferes with precursor processing. We demonstrate that this is not a rare exception and that natural strains of Arabidopsis thaliana harbor dozens of similar polymorphisms that affect processing of a wide range of miRNA precursors. Our results suggest that natural variation in miRNA biogenesis resulting from cis mutations is a common contributor to phenotypic variation in plants.

Whole organ, venation and epidermal cell morphological variations are correlated in the leaves of Arabidopsis mutants

Despite the large number of genes known to affect leaf shape or size, we still have a relatively poor understanding of how leaf morphology is established. For example, little is known about how cell division and cell expansion are controlled and coordinated within a growing leaf to eventually develop into a laminar organ of a definite size. To obtain a global perspective of the cellular basis of variations in leaf morphology at the organ, tissue and cell levels, we studied a collection of 111 non-allelic mutants with abnormally shaped and/or sized leaves, which broadly represent the mutational variations in Arabidopsis thaliana leaf morphology not associated with lethality. We used image-processing techniques on these mutants to quantify morphological parameters running the gamut from the palisade mesophyll and epidermal cells to the venation, whole leaf and rosette levels. We found positive correlations between epidermal cell size and leaf area, which is consistent with long-standing Avery's hypothesis that the epidermis drives leaf growth. In addition, venation parameters were positively correlated with leaf area, suggesting that leaf growth and vein patterning share some genetic controls. Positional cloning of the genes affected by the studied mutations will eventually establish functional links between genotypes, molecular functions, cellular parameters and leaf phenotypes.

Diverse Targets of Phytoplasma Effectors: From Plant Development to Defense Against Insects

Phytoplasma research begins to bloom (75). Indeed, this review shows that substantial progress has been made with the identification of phytoplasma effectors that alter flower development, induce witches' broom, affect leaf shape, and modify plant-insect interactions. Phytoplasmas have a unique life cycle among pathogens, as they invade organisms of two distinct kingdoms, namely plants (Plantae) and insects (Animalia), and replicate intracellularly in both. Phytoplasmas release effectors into host cells of plants and insects to target host molecules, and in plants these effectors unload from the phloem to access distal tissues and alter basic developmental processes. The effectors provide phytoplasmas with a fitness advantage by modulating their plant and insect hosts. We expect that further research on the functional characterization of phytoplasma effectors will generate new knowledge that is relevant to fundamental aspects of plant sciences and entomology, and for agriculture by improving yields of crops affected by phytoplasma diseases.

Dynamic growth program regulated by LANCEOLATE enables flexible leaf patterning

During their development, leaves progress through a highly controlled yet flexible developmental program. Transcription factors from the CIN-TCP family affect leaf shape by regulating the timing of leaf maturation. Characterization of mutants in the tomato (Solanum lycopersicum) CIN-TCP gene LANCEOLATE (LA) led us to hypothesize that a threshold LA-like activity promotes leaf differentiation. Here, we examined the relationship between LA activity, leaf maturation, and final leaf size and shape. Leaves of diverse shapes from various Solanaceae species or from different positions on the tomato plant differed in the timing of growth and maturation, and these were often associated with altered LA expression dynamics. Accordingly, genetic manipulations of LA activity in tomato altered leaf growth and maturation, leading to changes in leaf size and shape. LA expression sustained until late stages of tomato leaf development, and stage-specific overexpression of miR319, a negative regulator of CIN-TCP genes, confirmed that LA-like proteins affect leaf development through these late stages. Together, our results imply that dynamic spatial and temporal leaf maturation, coordinated by LA-like genes, enables the formation of variable leaf forms.

Functional design space of single-veined leaves: role of tissue hydraulic properties in constraining leaf size and shape.

Morphological diversity of leaves is usually quantified with geometrical characters, while in many cases a simple set of biophysical parameters are involved in constraining size and shape. One of the main physiological functions of the leaf is transpiration and thus one can expect that leaf hydraulic parameters can be used to predict potential morphologies, although with the caveat that morphology in turn influences physiological parameters including light interception and boundary layer thickness and thereby heat transfer and net photosynthesis. An iterative model was used to determine the relative sizes and shapes that are functionally possible for single-veined leaves as defined by their ability to supply the entire leaf lamina with sufficient water to prevent stomatal closure. The model variables include the hydraulic resistances associated with vein axial and radial transport, as well as with water movement through the mesophyll and the leaf surface. The four parameters included in the model are sufficient to define a hydraulic functional design space that includes all single-veined leaf shapes found in nature, including scale-, awl- and needle-like morphologies. This exercise demonstrates that hydraulic parameters have dissimilar effects: surface resistance primarily affects leaf size, while radial and mesophyll resistances primarily affect leaf shape. These distinctions between hydraulic parameters, as well as the differential accessibility of different morphologies, might relate to the convergent evolutionary patterns seen in a variety of fossil lineages concerning overall morphology and anatomical detail that frequently have evolved in linear and simple multi-veined leaves.

MAX1 and MAX2 control shoot lateral branching in Arabidopsis.

Plant shoots elaborate their adult form by selective control over the growth of both their primary shoot apical meristem and their axillary shoot meristems. We describe recessive mutations at two loci in Arabidopsis, MAX1 and MAX2, that affect the selective repression of axillary shoots. All the first order (but not higher order) axillary shoots initiated by mutant plants remain active, resulting in bushier shoots than those of wild type. In vegetative plants where axillary shoots develop in a basal to apical sequence, the mutations do not clearly alter node distance, from the shoot apex, at which axillary shoot meristems initiate but shorten the distance at which the first axillary leaf primordium is produced by the axillary shoot meristem. A small number of mutant axillary shoot meristems is enlarged and, later in development, a low proportion of mutant lateral shoots is fasciated. Together, this suggests that MAX1 and MAX2 do not control the timing of axillary meristem initiation but repress primordia formation by the axillary meristem. In addition to shoot branching, mutations at both loci affect leaf shape. The mutations at MAX2 cause increased hypocotyl and petiole elongation in light-grown seedlings. Positional cloning identifies MAX2 as a member of the F-box leucine-rich repeat family of proteins. MAX2 is identical to ORE9, a proposed regulator of leaf senescence ( Woo, H. R., Chung, K. M., Park, J.-H., Oh, S. A., Ahn, T., Hong, S. H., Jang, S. K. and Nam, H. G. (2001) Plant Cell 13, 1779-1790). Our results suggest that selective repression of axillary shoots involves ubiquitin-mediated degradation of as yet unidentified proteins that activate axillary growth.

Causal Mechanisms of Leaf Dimorphism in the Aquatic Angiosperm Callitriche heterophylla

This report investigates the physiological basis for the production of dimorphic leaves on the aquatic angiosperm Callitriche heterophylla. In nature, the leaf morphology of this plant depends on whether the shoot apex is submerged in or emergent from water. The water-form leaves that develop on submerged apices assume a long, linear shape in contrast to the short, obovate appearance of land forms on emergent apices. The parameters of length/width ratio and stomatal density were used as developmental indices to characterize how natural conditions, fluctuating water levels and other experimental treatments affect leaf shape. Transferring submerged and emergent shoots to the alternative culture conditions caused immature leaves to assume the characteristics appropriate to their new environment. Moreover, the treatments of 0.24 mol mannitol, high temperature (30 C) and 10−-5 m abscisic acid induced submerged shoots to produce land-form leaves whereas 10−-5 m gibberellic acid mediated the development of water-form leaves on emergent shoots. Water, osmotic and pressure potentials of immature leaves in the control and experimental treatments were determined by thermocouple psychrometry. Under natural conditions, growing water forms exhibited high turgors (3–5 bars) while developing land forms showed much lower turgors (0–1 bar). Similar correlations between turgor pressure and leaf morphology were observed in the case of the gibberellic acid and mannitol treatments. However, abscisic acid and high temperature caused the developing land-form leaves to exhibit high turgors without a concomitant change to the water-form morphology. Microscopic measurements of epidermal cells established that irrespective of the experimental conditions, water-form leaves had longer and narrower epidermal cells with less convoluted anticlinal walls than land forms. Cell counts indicated that the numbers of epidermal cells did not account for the observed differences in leaf morphology. The results are interpreted in terms of how cell expansion might regulate leaf morphology in aquatic angiosperms.

CAUSAL MECHANISMS OF LEAF DIMORPHISM IN THE AQUATIC ANGIOSPERM CALLITRICHE HETEROPHYLLA

This report investigates the physiological basis for the production of dimorphic leaves on the aquatic angiosperm Callitriche heterophylla. In nature, the leaf morphology of this plant depends on whether the shoot apex is submerged in or emergent from water. The water‐form leaves that develop on submerged apices assume a long, linear shape in contrast to the short, obovate appearance of land forms on emergent apices. The parameters of length/width ratio and stomatal density were used as developmental indices to characterize how natural conditions, fluctuating water levels and other experimental treatments affect leaf shape. Transferring submerged and emergent shoots to the alternative culture conditions caused immature leaves to assume the characteristics appropriate to their new environment. Moreover, the treatments of 0.24 mol mannitol, high temperature (30 C) and 10−‐5 m abscisic acid induced submerged shoots to produce land‐form leaves whereas 10−‐5 m gibberellic acid mediated the development of water‐form leaves on emergent shoots. Water, osmotic and pressure potentials of immature leaves in the control and experimental treatments were determined by thermocouple psychrometry. Under natural conditions, growing water forms exhibited high turgors (3–5 bars) while developing land forms showed much lower turgors (0–1 bar). Similar correlations between turgor pressure and leaf morphology were observed in the case of the gibberellic acid and mannitol treatments. However, abscisic acid and high temperature caused the developing land‐form leaves to exhibit high turgors without a concomitant change to the water‐form morphology. Microscopic measurements of epidermal cells established that irrespective of the experimental conditions, water‐form leaves had longer and narrower epidermal cells with less convoluted anticlinal walls than land forms. Cell counts indicated that the numbers of epidermal cells did not account for the observed differences in leaf morphology. The results are interpreted in terms of how cell expansion might regulate leaf morphology in aquatic angiosperms.