Leaf anatomy affects optical properties and enhances photosynthetic performance under oblique light.

Photosynthesis under oblique illumination has not been studied extensively despite being the prevailing light regime under natural conditions. We studied how photosynthetic rate (An) is affected by the geometrical arrangement between leaf lamina and light rays, in conjunction with key anatomical features; studied plant species selected based on the absence (homobaric) or the occurrence of bundle sheath extensions (BSEs; heterobaric) and the arrangement of these structures, that is, parallel (monocots) or reticulated (dicots). The direction of light ray affected leaf absorptance (Abs) and An; both were maximal when the angle of incidence of light on leaf surface (polar angle, θ) was 90°.

Acclimation of the Grapevine L. cv. Assyrtiko to Water Deficit: Coordination of Structural and Functional Leaf Traits and the Dynamic of Calcium Oxalate Crystals.

Grapevine leaves contain abundant CaO crystals located either within the mesophyll in the form of raphides, or in the bundle sheaths as druses. CaO crystals function as internal carbon pools providing CO for a baseline level of photosynthesis, named "alarm photosynthesis", despite closed stomata; thus, preventing the photoinhibition and the oxidative risk due to carbon starvation under adverse conditions. Structural and functional leaf traits of acclimated grapevine plants ( L.

The Optical Properties of Leaf Structural Elements and Their Contribution to Photosynthetic Performance and Photoprotection.

Leaves have evolved to effectively harvest light, and, in parallel, to balance photosynthetic CO assimilation with water losses. At times, leaves must operate under light limiting conditions while at other instances (temporally distant or even within seconds), the same leaves must modulate light capture to avoid photoinhibition and achieve a uniform internal light gradient. The light-harvesting capacity and the photosynthetic performance of a given leaf are both determined by the organization and the properties of its structural elements, with some of these having evolved as adaptations to stressful environments.

Decomposition of Calcium Oxalate Crystals in under CO Limiting Conditions.

Calcium oxalate (CaOx) crystals are widespread among plant species. Their functions are not yet completely understood; however, they can provide tolerance against multiple environmental stress factors. Recent evidence suggested that CaOx crystals function as carbon reservoirs since its decomposition provides CO that may be used as carbon source for photosynthesis.

Cell wall composition and thickness affect mesophyll conductance to CO2 diffusion in Helianthus annuus under water deprivation.

Water deprivation affects photosynthesis, leaf anatomy, and cell wall composition. Although the former effects have been widely studied, little is known regarding those changes in cell wall major (cellulose, hemicelluloses, pectin, and lignin) and minor (cell wall-bound phenolics) compounds in plants acclimated to short- and long-term water deprivation and during recovery. In particular, how these cell wall changes impact anatomy and/or photosynthesis, specifically mesophyll conductance to CO2 diffusion (gm), has been scarcely studied.

New insights into the functions of carbon-calcium inclusions in plants.

Carbon-calcium inclusions (CCaI) either as calcium oxalate crystals (CaOx) or amorphous calcium carbonate cystoliths are spread among most photosynthetic organisms. They represent dynamic structures with a significant construction cost and their appearance during evolution indicates an ancient origin. Both types of inclusions share some similar functional characteristics providing adaptive advantages such as the regulation of Ca levels, and the release of CO and water molecules upon decomposition.

Cystoliths of Parietaria judaica can serve as an internal source of CO2 for photosynthetic assimilation when stomata are closed.

The recently reported 'alarm photosynthesis' acts as a biochemical process that assimilates CO2 derived from the decomposition of calcium oxalate crystals. This study examined whether CaCO3 cystoliths could also serve as CO2 pools, fulfilling a similar role. Shoots of Parietaria judaica were subjected to carbon starvation, abscisic acid (ABA), or bicarbonate treatments, and the volume of cystoliths and the photochemical parameters of photosystem II (PSII) were determined.

Changes in size and composition of pigweed (Amaranthus hybridus L.) calcium oxalate crystals under CO starvation conditions.

The functional role(s) of plant calcium oxalate (CaOx) crystals are still poorly understood. Recently, it was shown that crystals function as dynamic carbon pools whose decomposition could provide CO to photosynthesis when stomata are closed (e.g.

Changes in the properties of calcium-carbon inclusions during leaf development and their possible relationship with leaf functional maturation in three inclusion-bearing species.

In many plant species, carbon-calcium inclusion (calcium oxalate crystals or cystoliths containing calcium carbonate) formation is a fundamental part of their physiology even necessary for normal growth and development. Despite the long-standing studies on carbon-calcium inclusions, the alterations in their properties during leaf development and their possible association with the maturation of the photosynthetic machinery have not been previously examined. In order to acquire more insights into this subject, we examined three of the most common species bearing abundant inclusions of different types, i.

Reevaluation of the plant "gemstones": Calcium oxalate crystals sustain photosynthesis under drought conditions.

Land plants face the perpetual dilemma of using atmospheric carbon dioxide for photosynthesis and losing water vapors, or saving water and reducing photosynthesis and thus growth. The reason behind this dilemma is that this simultaneous exchange of gases is accomplished through the same minute pores on leaf surfaces, called stomata. In a recent study we provided evidence that pigweed, an aggressive weed, attenuates this problem exploiting large crystals of calcium oxalate as dynamic carbon pools.

Alarm Photosynthesis: Calcium Oxalate Crystals as an Internal CO2 Source in Plants.

Calcium oxalate crystals are widespread among animals and plants. In land plants, crystals often reach high amounts, up to 80% of dry biomass. They are formed within specific cells, and their accumulation constitutes a normal activity rather than a pathological symptom, as occurs in animals.

"Carbon gain vs. water saving, growth vs. defence": two dilemmas with soluble phenolics as a joker.

Despite that phenolics are considered as a major weapon against herbivores and pathogens, the primal reason for their evolution may have been the imperative necessity for their UV-absorbing and antioxidant properties in order for plants to compensate for the adverse terrestrial conditions. In dry climates the choice concerning the first dilemma (carbon gain vs. water saving) needs the appropriate structural and metabolic modulations, which protect against stresses such as high UV and visible radiation or drought, but reduce photosynthesis and increase oxidative pressure.

Wettability, polarity, and water absorption of holm oak leaves: effect of leaf side and age.

Plant trichomes play important protective functions and may have a major influence on leaf surface wettability. With the aim of gaining insight into trichome structure, composition, and function in relation to water-plant surface interactions, we analyzed the adaxial and abaxial leaf surface of holm oak (Quercus ilex) as a model. By measuring the leaf water potential 24 h after the deposition of water drops onto abaxial and adaxial surfaces, evidence for water penetration through the upper leaf side was gained in young and mature leaves.

Photosynthetic capacity is negatively correlated with the concentration of leaf phenolic compounds across a range of different species.

Background And Aims: Phenolic compounds are the most commonly studied of all secondary metabolites because of their significant protective-defensive roles and their significant concentration in plant tissues. However, there has been little study on relationships between gas exchange parameters and the concentration of leaf phenolic compounds (total phenolics (TP) and condensed tannins (CT)) across a range of species. Therefore, we addressed the question: is there any correlation between photosynthetic capacity (A(max)) and TP and CT across species from different ecosystems in different continents?

Methodology: A plethora of functional and structural parameters were measured in 49 plant species following different growth strategies from five sampling sites located in Greece and Australia.

New insights into the properties of pubescent surfaces: peach fruit as a model.

The surface of peach (Prunus persica 'Calrico') is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles.

Erinea formation on Quercus ilex leaves: anatomical, physiological and chemical responses of leaf trichomes against mite attack.

Structures on the surfaces of leaves, such as dense layers of non-glandular trichomes, strongly affect phylloplane mite activities. On the other hand the feeding of eriophyoid mites on leaf surfaces can cause hyperplasia of leaf trichomes (erinea formation). In many cases the hyperplasia is accompanied by the accumulation of pigments within trichome cells, causing an impressive red-brown colouration of the erineum.

Should structure-function relations be considered separately for homobaric vs. heterobaric leaves?

Tree and shrub species can be differentiated into two major groups based on their substantially different leaf anatomy: heterobaric and homobaric. In contrast to homobaric leaves, heterobaric leaves have bundle sheath extensions (BSEs) that create transparent regions on their lamina. Recent studies have shown that BSEs transfer visible light to internal mesophyll layers, thus affecting the photosynthetic performance of heterobaric leaves.

Leaf anatomy affects the extraction of photosynthetic pigments by DMSO.

Dimethylsulfoxide (DMSO) is a widely used solvent for the extraction of chlorophylls (Chls) from leaves of higher plants. The method is preferred because the time-consuming steps of grinding and centrifuging are not required and the extracts are stable for a long time period. However, the extraction efficiency of this solvent is not comparable among plant species, whereas the particular leaf anatomical characteristics responsible for this unevenness remain unknown.

Photosynthetic characteristics of olive tree (Olea europaea) bark.

Functional and structural characteristics of corticular photosynthesis of sun-exposed bark of olive tree (Olea europaea L.) were examined. Stomata are only sporadically present during stem primary growth.

The photoprotective role of epidermal anthocyanins and surface pubescence in young leaves of grapevine (Vitis vinifera).

Background And Aims: Depending on cultivar, surfaces of young leaves of Vitis vinifera may be glabrous-green ('Soultanina') or transiently have anthocyanins ('Siriki') or pubescence ('Athiri'). A test is made of the hypothesis that anthocyanins and pubescence act as light screens affording a photoprotective advantage to the corresponding leaves, and an assessment is made of the magnitude of their effect.

Methods: Measurements were made on young leaves of the three cultivars in spring under field conditions.

Research note: Low-boron acclimation induces uptake of boric acid against a concentration gradient in root cells of Olea europaea.

Low concentrations of boron (B) in the external medium can induce uptake mechanisms whereby plants can develop a concentration gradient for B against the external medium. These mechanisms seem to be widespread among herbaceous species. In this study, olive (Olea europaea L.

Boron deficiency and concentrations and composition of phenolic compounds in Olea europaea leaves: a combined growth chamber and field study.

Boron deficiency is the most frequent micronutrient disorder in olive (Olea spp.) orchards. We tested the hypothesis that plant boron status affects phenolic metabolism, which, in turn, influences several ecophysiological traits of olive (Olea europaea L.

Boron remobilization at low boron supply in olive (Olea europaea) in relation to leaf and phloem mannitol concentrations.

For plant species in which a considerable portion of the photoassimilates are translocated in the phloem as sugar alcohols, boron is freely translocated from mature organs to growing tissues. However, the effects of decreased plant boron status on boron remobilization are poorly understood. We conducted a growth chamber experiment (CE) and a field experiment (FE) to study the effects of low boron supply on boron remobilization in olive (Olea europaea L.

The relationship between anatomy and photosynthetic performance of heterobaric leaves.

Heterobaric leaves show heterogeneous pigmentation due to the occurrence of a network of transparent areas that are created from the bundle sheaths extensions (BSEs). Image analysis showed that the percentage of photosynthetically active leaf area (Ap) of the heterobaric leaves of 31 plant species was species dependent, ranging from 91% in Malva sylvestris to only 48% in Gynerium sp. Although a significant portion of the leaf surface does not correspond to photosynthetic tissue, the photosynthetic capacity of these leaves, expressed per unit of projected area (Pmax), was not considerably affected by the size of their transparent leaf area (At).