Mesophyll Structure Research Articles

Ontogenetic reactions of mesophyll of leaves of Betula nana L. on the industrial pollution of the arctic urbanized territory

There was determined to be concentration of heavy metals (Cu, Ni, Zn, Pb, V) in the vicinity of industrial enterprises in the soil of the city of Murmansk. High concentration of Cu, Ni, Zn was revealed. The structure of mesophyll in the ontogenesis of Betula nana leaves was studied. It has been established that under the influence of polymetallic soil contamination, thickening of leaves of B. nana on experimental sites of the city of Murmansk is higher, than in control and occurs due to increasing of palisade or spongy mesophyll during ontogenesis.

Micromorphological and anatomical investigations on Conringia Heist. ex Fabr.

The micromorphological and anatomical investigations on 6 taxa of Conringia Heist. ex Fabr. growing in Turkey were carried out. The anatomy of root, stem and leaves was examined in detail. In micromorphological studies stem and leaf surface of species was examined. Mesophyll type of lamina is dorsiventral (Conringia planisiliqua, C. persica, C. austriaca) and equifacial (C. clavata, C.grandiflora, C. orientalis). Stomata situated on both surfaces, are anisocytic and rarely anomocytic types. Crystals of calcium oxalate observed in only one species (C. grandiflora) was found to have cubic type parenchyma cells of the stem and leaf. In micromorphological studies the surface of the stem and leaves were found to be glabrous. Epidermal surface of leaves was observed to be covered with waxy cuticular particles. Anticlinal walls of the adaxial cells are undulate and rarely straight and anticlinal walls of abaxial epidermis are undulate and rarely sinuate. Periclinal walls were found to be covered with upper waxy layer which was flat. A diagnostic key based on combined stem, leaf and leaf epidermal characteristics are presented. The leaf mesophyll structures, stem vascular bundles number, lignified or unlignified of sclerenchyma, epidermal surface and absence or presence of crystals were found to be important characters for the identification of Conringia species.

Micromorphological and anatomical investigation on six species of Onosma L. (Boraginaceae) from Turkey

Micromorphology and anatomy of six Onosma L. species, viz. O. argentata Hub.-Mor., O. neglecta Riedl, O. proballanthera Rech. f., O. rechingeri Riedl, O. sericea Willd. and O. stenoloba Hausskn. ex Riedl from Turky were investigated. Stem anatomy revealed that cuticle layer ranged from 0.6 µm in O. argentata to 1.7 µm in O. proballanthera. Parenchymatous cells of O. neglecta and O. stenoloba possessed more intense starch than the other species studied. In leaf anatomy, the longest palisade parenchyma was found in O. neglecta, while the smallest was noted in O. argentata. Mesophyll structure of O. argentata, O. sericea and O. rechingeri was equifacial (isobilateral), while O. neglecta, O. proballanthera and O. stenoloba presented bifacial (dorsiventral) structure. Rugose nutlet ornamentation was observed in O. argentata, O. neglecta and O. sericea, whereas reticulate type was found in O. proballanthera, O. rechingeri and O. stenoloba. Onosma stenoloba could easily be distinguished from other species by its aesterotrichous indumentum, and in contrary, other species possessed haplotrichous type of indumentum. Micromorphological features of nutlet surface, anatomical features of epidermal surface (trichomes and stomata), and lamina mesophyll structure (dorsiventral and isobilateral) could be useful in solving taxonomic problem of the genus.

SPECTRAL REFLECTANCE OF IPÊ-AMARELO LEAVES UNDER DIFFERENT FORMS OF STORAGE AND COLLECTION TIME

The application of spectroradiometry techniques to the study of tree species allows the acquisition of information related to plant physiology and morphology, which can be used in conjunction with orbital images. However, it is known that when a leaf is extracted the senescence process is started, which is characterized by cell constituents degradation, loss of water and modifications of the foliar mesophyll structure. In this context, this study aimed to evaluate the influence of the collection time and storage form on the spectral response of ipê-amarelo leaves. Thus, 32 leaves were collected in distinct times (1h, 2h, 24h and 48h) and conditioned with(C) and without(S) thermal storage. The data were evaluated from the visual analysis of the spectral curves, derivative analysis and statistical analysis. The experiment was conducted in a Randomized block design and data were submitted to analysis of variance (ANOVA) and Tukey test (p = 0.05). Results indicated that thermal storage might delay the senescence process of the leaves. Both the collection time and the storage form affect the pattern of spectral behavior of the leaves of ipê-amarelo. The collection time has not shown significant differences between 1-2h. The largest differences were found between 2-24h after collection.

Long-term acclimation to drought, salinity and temperature in the thermophilic tree Ziziphus spina-christi: revealing different tradeoffs between mesophyll and stomatal conductance.

Photosynthesis is limited by three main factors: stomatal conductance (gs), mesophyll conductance (gm) and maximum capacity for Rubisco carboxylation (Vcmax). It is unclear how limiting factors vary under stress, particularly during long-term stress acclimation. In this work, we compared for the first time photosynthesis limitation resulting from long-term acclimation to three major abiotic stresses: drought, salinity and temperature. We used saplings of Ziziphus spina-christi, a thermophilic and drought-tolerant tree, which recently became more abundant in the Mediterranean, presumably due to increased winter temperatures. Stress acclimation was investigated by measuring growth, gas exchange, chlorophyll fluorescence and leaf structure. For each stress, photosynthesis-limiting factors were compared. We developed an integrative stress index that allowed us to precisely define stress level, enabling a comparison between stress types. Photosynthesis under all stresses was limited mostly by gs and gm (80-90%); whereas biochemistry (Vcmax) made a minor contribution (10-20%). The relative contribution of gs and gm on photosynthetic limitation was influenced by stress type. During acclimation to drought or salinity, photosynthesis was limited by a decline in gs, while intolerance to low temperatures was driven by decline in gm. In all the stresses, gm decreased only under progressive reduction in leaf physiological functionality and was associated with low turgor under drought, an increase in leaf Na+ under salinity and low leaf hydraulic conductance (Kleaf) at low temperatures. Mesophyll structure (mesophyll surface area exposed to the intercellular air spaces, leaf thickness, % intercellular air spaces) did not explain gm acclimation to stress. Current work gives methodology for stress studies, and defines the main factors underlying the plant response to climate change. The ability to minimize mesophyll-imposed limitations on photosynthesis was found as a strong indicator of progressive stress tolerance. Moreover, the results demonstrate how warming climate benefits the photosynthetic function in thermophilic species, such as Ziziphus spina-christi.

Comparative studies on leaf epidermal micromorphology and mesophyll structure of Elaeagnus angustifolia L. in two different regions of desert habitat

In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses of Elaeagnus angustifolia L.to different environmental factors,epidermal micromorphology was observed by scanning electron microscopy(SEM),and mesophyll structure was studied by light microscopy(LM) and transmission electron microscopy(TEM).Materials were selected from Linze County,Gansu Province(material A) and Qitai County,Xinjiang Uygur Autonomous Region(material B) of China.Results show that lamina thickness was higher in material A,with one layer of epidermal cells in both adaxial and abaxial surfaces,and epidermal cell radial length was significantly longer in the adaxial surface.E.angustifolia leaves are typically bifacial,with a higher ratio of palisade to spongy tissue in material A.The thickness of trichome layer of epidermis was thicker in material A.In contrast,cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B.Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in material A,while only the spindly chloroplast contained starch grains in material B.Multiple layers of peltate or stellate-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B,while the adaxial surface of material B contained few trichomes.Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction.Our results indicate that the leaf structure of E.angustifolia is closely correlated with environmental factors,and the combination of leaf epidermal micromorphology and mesophyll structure afford resistance to environmental stress.

Hydrocarbon micro-seepage detection from airborne hyper-spectral images by plant stress spectra based on the PROSPECT model

Hydrocarbon micro-seepage can result in vegetation spectral anomalies. Early detection of spectral anomalies in plants stressed by hydrocarbon micro-seepage could help reveal oil and gas resources. In this study, the origin of plant spectral anomalies affected by hydrocarbon micro-seepage was measured using indoor simulation experiments. We analyzed wheat samples grown in a simulated hydrocarbon micro-seepage environment in a laboratory setting. The leaf mesophyll structure (N) values of plants in oil and gas micro-seepage regions were measured according to the content of measured biochemical parameters and spectra simulated by PROSPECT, a model for extracting hydrocarbon micro-seepage information from hyper-spectral images based on plant stress spectra. Spectral reflectance was simulated with N, chlorophyll content (Cab), water content (Cw) and dry matter content (Cm). Multivariate regression equations were established using varying gasoline volume as the dependent variable and spectral feature parameters exhibiting a high rate of change as the independent variables. We derived a regression equation with the highest correlation coefficient and applied it to airborne hyper-spectral data (CASI/SASI) in Qingyang Oilfield, where extracted information regarding hydrocarbon micro-seepage was matched with known oil-producing wells.

Taxonomic Significance of Anatomical Characters in Some Species of Brassicaceae family in Iraq

This paper elaborated transverse sections of leaves and stems of nineteen species belongs to 18 genera of Brassicaceae family. Anatomical characteristics were important in separation of taxa. The presence or absence of Collenchyma, Chlorenchyma and Pith, Mesophyll structure and epidermal surface were found to be important characters for the identification of Brassicaceae species. Two types of mesophyll have been recognized, dorsiventral (Bifacial) found in Sinaps alba L., Biscutella didyma L., Sameraria stylophora(Jaub. et Sp.) Boiss., Drabopsis nuda (Bel.) Stapf., Eruca sativa Mill., Capsella bursa-pastoris (L.) Medic., Calepina irregularis(Asso)Thell., Diplotaxis harra (Forssk.) Boiss., Sinapis arvensis L. and Nasturtium officinale R.Br. and isobilateral in the remaining species. Transverse sections of the midrib showed that most of species contains one vascular plants in all the species except Brassica oleracea L., Cheiranthus cheiri L., Crambe orientalis L., Draba bruniifolia Stev. and Sinaps alba L. which contains (1-3) vascular bundles. Collenchyma tissue present only in Diplotaxis harra, sinaps alba, Drabopsis nuda (Bel.) Stapf. Camelina rumelica, Cramba orientalis L., Cheiranthus cheiri L. and Cardaria drab Thell, it was higher in Cardaria drab was (150.50) um and lower in Crambe orientalis was (18.75) um. A diagnostic key based on combined stem and leaf were presented.

Source-sink relations of sunflower plants as affected by a parasite modifies carbon allocations and leaf traits

Sunflower broomrape (Orobanche cumana) is a root holoparasitic plant causing major damage to sunflower (Helianthus annuus L.). Parasite infection initiates source-sink relations between the parasite (sink) and the host (source), allocating carbohydrates, water and nutrients to the parasite. The primary aim of the current study was to explore responses of sunflower to broomrape parasitism, specifically to examine alternations in leaf area, leaf mass per area (LMA), mesophyll structure and root hydraulic conductivity. Leaf changes revealed modifications similar to described previously in shade adapted plants, causing larger and thinner leaves. These traits were accompanied with significantly higher root hydraulics. These changes were caused by carbohydrate depletion due to source-sink relationships between the host and parasite. An Imazapic herbicide (ALS inhibitor) was used for controlling broomrape attachments and by to investigate the plasticity of the traits found. Broomrape infected plants which were treated with Imazapic had leaves similar to non-infected plants, including mesophyll structure and carbon assimilation rates. These results demonstrated source-sink effects of broomrape which cause a low-light-like acclimation behavior which is reversible.

Alteraciones anatómicas e hiperplasia inducidas por Euphorbia mosaic virus aislamiento Yucatan Peninsula en el mesófilo

<p><em>Euphorbia mosaic virus</em> aislamiento Yucatan Peninsula es un begomovirus bipartita con una amplia gama de hospedantes experimentales, que incluyen especies de importancia económica, como frijol, chile y tomate, entre otras. Este virus provocó síntomas severos en hojas de <em>Nicotiana benthamiana</em>, pérdida de identidad celular y tisular, deformaciones de la lámina foliar y de la nervadura central, cambios en la estructura del mesó- filo y proliferación celular, a diferencia de otros begomovirus bipartitas. Activó la expresión de los genes cycA1, cycA2 y cdkB2.2, implicados en la transición G2/M del ciclo celular mitótico y se localizó en el mesófilo de las hojas. EuMV-YP es el primer ejemplo de un begomovirus bipartita capaz de inducir la proliferación celular.</p>

Leaf morphoanatomy traits in white grapevine cultivars with distinct geographical origin

This study aims to compare the leaf morphoanatomical characteristics of sevenVitis viniferasubsp.viniferawhite cultivars with different geographical origin, grown side by side at the same “terroir”. The leaf morphoanatomical traits analyzed under light and scanning electron microscopy (SEM) showed large variability among genotypes. Significant differences between cultivars were observed in single leaf area, specific leaf area, leaf density and in the thickness of cuticle, upper and lower epidermal cells and mesophyll. Leaf dry mass per area presented a significant positive correlation with leaf density but showed no correlation with leaf thickness, results that can be explained by the quite different mesophyll structure, epidermal cells and cuticle thickness. ‘Alvarinho’, ‘Encruzado’, ‘Macabeu’ and ‘Viosinho’ were the cultivars with the highest thickness of cuticle and mesophyll tissues. Under SEM magnification three types of stomata were identified: sunken, at the same level and raised above, with the same level type presenting the higher percentage in all cultivars. Stomata density presented significant differences between cultivars, with ‘Macabeu’ showing the highest value and ‘Alvarinho’ and ‘Arinto’ the lowest ones. The hairs on the lower surface presented a similar woolly aspect in all cultivars. Calcium oxalate crystals, raphids and druses were visible and widely distributed in the parenchyma tissues. The observed differences in leaf traits among genotypes suggest a major role of leaf anatomy in determining grapevine capacity for coping with different environmental conditions.

Features of the leaf mesophyll structure of coastal-aquatic monocotyledonous plants.

Features of the leaf mesophyll structure of coastal-aquatic monocotyledonous plants.

Comparative Anatomical Studies on Three Endemic Ononis L. (Leguminosae) Species Growing in Turkey.

The leaf and stem anatomical characteristics of three endemic Ononis L. (Leguminosae) species were studied for the first time for the evaluated in terms of systematic of similarities and differences in these taxa. Ononis sessilifolia Bornm., Ononis basiadnata Hub.-Mor. and Ononis macrosperma Hub.-Mor. were collected from different provinces of Turkey. In this anatomical study, transversal and superficial sections from the leaves and transversal sections from stems of the species were taken and examined by appropriate reagends. Illustrations were obtained by using an Olympus U-DA 2K 17149 drawing tube attached to an Olympus BX50 microscope. The microphotographs were taken by a Leica DM 4000 B microscope. O. macrosperma is bifacial leaf, the others are monofacial leaf. The leaf of O. basiadnata has eglandular trihomes. If the anatomical similarities between species are to be listed, Rubiaceae type stoma was observed in all three species and solitary crystals were found in stem and leaf sections. Anatomical characteristics, such as mesophyll structure, transmission bundles and crystal structures, may contribute to the taxonomy of Ononis species for future work.

Recognition of Orobanche cumana Below-Ground Parasitism Through Physiological and Hyper Spectral Measurements in Sunflower (Helianthus annuus L.).

Broomrape (Orobanche and Phelipanche spp.) parasitism is a severe problem in many crops worldwide, including in the Mediterranean basin. Most of the damage occurs during the sub-soil developmental stage of the parasite, by the time the parasite emerges from the ground, damage to the crop has already been done. One feasible method for sensing early, below-ground parasitism is through physiological measurements, which provide preliminary indications of slight changes in plant vitality and productivity. However, a complete physiological field survey is slow, costly and requires skilled manpower. In recent decades, visible to-shortwave infrared (VIS-SWIR) hyperspectral tools have exhibited great potential for faster, cheaper, simpler and non-destructive tracking of physiological changes. The advantage of VIS-SWIR is even greater when narrow-band signatures are analyzed with an advanced statistical technique, like a partial least squares regression (PLS-R). The technique can pinpoint the most physiologically sensitive wavebands across an entire spectrum, even in the presence of high levels of noise and collinearity. The current study evaluated a method for early detection of Orobanche cumana parasitism in sunflower that combines plant physiology, hyperspectral readings and PLS-R. Seeds of susceptible and resistant O. cumana sunflower varieties were planted in infested (15 mg kg-1 seeds) and non-infested soil. The plants were examined weekly to detect any physiological or structural changes; the examinations were accompanied by hyperspectral readings. During the early stage of the parasitism, significant differences between infected and non-infected sunflower plants were found in the reflectance of near and shortwave infrared areas. Physiological measurements revealed no differences between treatments until O. cumana inflorescences emerged. However, levels of several macro- and microelements tended to decrease during the early stage of O. cumana parasitism. Analysis of leaf cross-sections revealed differences in range and in mesophyll structure as a result of different levels of nutrients in sunflower plants, manifesting the presence of O. cumana infections. The findings of an advanced PLS-R analysis emphasized the correlation between specific reflectance changes in the SWIR range and levels of various nutrients in sunflower plants. This work demonstrates potential for the early detection of O. cumana parasitism on sunflower roots using hyperspectral tools.

Regulation of ZnO nanoparticles-induced physiological and molecular changes by seed priming with humic acid in Oryza sativa seedlings

The present investigation explored the capability of priming treatment with 250 mg L−1 of humic acid (HA) to improve nano-ZnO tolerance of two rice cultivars seedlings (Zhu Liang You 06 and Qian You No. 1). The results showed that seed germination, seedling growth, total soluble protein, sugar and starch contents significantly improved by seed priming with HA especially under high nano-ZnO stress (500 and 750 mg L−1) as compared to unprimed seeds. In contrast, electrolyte leakage significantly increased after exposure to 500 and 750 mg L−1 nano-ZnO, but decreased obviously after HA priming in both cultivars. Abscisic acid (ABA) content in the seeds germinated under nano-ZnO stress was higher than those grown under non-stress condition; while gibberellins (GA) content decreased under nano-ZnO stress. HA priming down-regulated the relative expression levels of OsABA8ox2 and OsNCED1, which were key genes in ABA biosynthesis and catabolism of rice seeds. In contrast, up-regulation in OsGA20ox2 and OsGA3ox1 were induced by HA priming. The histochemical analysis reported that higher concentration of hydrogen peroxide (H2O2) and superoxide radical (O2·−) were observed in stressed roots with nano-ZnO as compared with non-stress condition, indicating reduction of root cell viability and severe oxidative burst. However, HA priming reduced obviously H2O2, O2·−, antioxidant enzymes activities (SOD, POD, CAT) and malondialdehyde (MDA) content of rice seedlings under stress. Significant increases in dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDAR) activities were observed in nano-ZnO stressed seedlings, but they were diminished evidently by HA priming. In addition, the improvement of HA on cell ultra structure of root tip and leaf mesophyll was detected under nano-ZnO stress especially 750 mg L−1 concentration. Therefore, it was suggested that HA priming could definitely improve the rice seed germination and seedling growth under nano-ZnO stress to some extent.

Variation of leaf traits and pigment content in three species of steppe plants depending on the climate aridity

Mesophyll structure and content of photosynthetic pigments in the leaves of three species of steppe plants, Centaurea scabiosa L., Euphorbia virgata Waldst. et Kit., Helichrysum arenarium (L.) Moench, were investigated in four geographical sites of the Volga region and the Urals located in the forest-steppe and steppe zones. Variations of the studied parameters between geographical points depended both on the species and on the structural organization of the leaf. The highest level of variation was observed for leaf area and pigment content per unit leaf area, the size and the number of chloroplasts in the cell changed to a lesser extent. The leaf thickness, leaf area and mesophyll cell sizes mostly depended on the plant species. C. scabiosa had large leaves (40–50 cm2) with large thickness (280–290 μm) and large mesophyll cells (up to 15000 μm3). The leaves of H. arenarium and E. virgata were ten times smaller and characterized by 1.5 times smaller thickness and 2−3 times smaller cell size. Geographical location and climate of the region affected leaf density, proportion of partial tissue volume, and the ratio of the photosynthetic pigments. In the southern point of Volga region with the highest climate aridity, all studied species were characterized by maximum values of volumetric leaf density (LD), due to the high proportion of sclerenchyma and vascular bundles, and specificity of the mesophyll structure. With the decline in latitude, chlorophyll (Chl) and carotenoid (Car) contents in leaf area were reduced, the ratio Chl/Car was increased, and the ratio Chl a/b was declined. The reduction of the pigment content in the leaf in all species was associated with a reduction in the amount of Chl per chloroplast, and for C. scabiosa and H. arenarium it was associated also with the reduction of chloroplast amount in the leaf area. In turn, chloroplast number per leaf area and the total cell area (Ames/A) depended on the ratio of the number and size of mesophyll cells inherent to this plant species. At the same time, we found a similar mechanism of spatial organization of leaf restructuring for all studied species—decrease in Ames/A was accompanied by increasing in the proportion of intercellular air spaces in the leaf. It is concluded that variations in structural and functional parameters of the photosynthetic apparatus of steppe plants were associated with plant adaptation to climate features. General direction of the changes of leaf parameters of the studied species with aridity was the increase of LD and the decrease of pigment content per leaf area however the cellular mechanisms of changes in the pigment content and integral parameters of mesophyll were determined by the plant species properties.

Morphology and Structure of Fruits of Some Desert Efemers of the Genus Alyssum L.

The structure of the fetus, seed, embryo of 3 species of ephemerals of the genus Alyssum, collected in the southwestern Kyzylkum, is described. Fetus of the Alyssum species is rounded, wide-pated silicle, with fetus stems of a truncated-conical (A. dasycarpum) shape. Pericarp is 4 - 5 layered. The fetus is seedless (2 - 4), and the seeds are protein-free, with a large embryo. At the general plan of a structure, species have diagnostic signs distinguishing them on the form of a fetus, weight of seeds, the structure of embryo mesophyll.

C4 photosynthesis in C3 rice: a theoretical analysis of biochemical and anatomical factors.

Engineering C4 photosynthesis into rice has been considered a promising strategy to increase photosynthesis and yield. A question that remains to be answered is whether expressing a C4 metabolic cycle into a C3 leaf structure and without removing the C3 background metabolism improves photosynthetic efficiency. To explore this question, we developed a 3D reaction diffusion model of bundle‐sheath and connected mesophyll cells in a C3 rice leaf. Our results show that integrating a C4 metabolic pathway into rice leaves with a C3 metabolism and mesophyll structure may lead to an improved photosynthesis under current ambient CO2 concentration. We analysed a number of physiological factors that influence the CO2 uptake rate, which include the chloroplast surface area exposed to intercellular air space, bundle‐sheath cell wall thickness, bundle‐sheath chloroplast envelope permeability, Rubisco concentration and the energy partitioning between C3 and C4 cycles. Among these, partitioning of energy between C3 and C4 photosynthesis and the partitioning of Rubisco between mesophyll and bundle‐sheath cells are decisive factors controlling photosynthetic efficiency in an engineered C3–C4 leaf. The implications of the results for the sequence of C4 evolution are also discussed.

Fluspect-B: A model for leaf fluorescence, reflectance and transmittance spectra

Abstract We present the Fluspect-B model (generally referred to as Fluspect), which simulates leaf chlorophyll fluorescence (ChlF), reflectance and transmittance spectra. The existing PROSPECT model and its concept of a compact leaf are used as a starting point, and the differential equations for radiative transfer within the leaf are solved by an efficient doubling algorithm. Due to the simplicity of these equations, Fluspect offers a high computational speed. With incident light provided as the main input parameter, Fluspect calculates the emission of ChlF on both the illuminated and shaded side of the leaf. Other input parameters are chlorophyll and carotenoid concentrations, leaf water, dry matter and senescent material (brown pigments) content, leaf mesophyll structure parameter and ChlF quantum efficiency for the two photosystems, PS-I and PS-II. We investigated the model performance using measurements of leaf reflectance, transmittance and ChlF spectra, collected for barley and sugar beet leaves in both a laboratory and outdoors setting. The plants had been grown under various illumination conditions to increase between-leaf variability of leaf biochemical and structural properties. We retrieved the model parameters, compared them to corresponding destructive measurements and finally, used them to simulate ChlF on either side of the leaf at several light intensities. The results show that the model reproduces observed SIF accurately, especially for leaves measured under natural illumination. Most of the observed between-leaf variability of ChlF could be explained from differences in leaf biochemical and structural properties, with potential additional information held by ChlF emission efficiency parameters.

Photosynthesis adaptation of the desert-steppe shrub Caragana bungei to larch forest conditions at mountainous slopes in Mongolian Khangai

Leaf parameters, gas exchange parameters, photosynthetic pigments content, mesophyll structure, and sizes of shrubs were studied for Caragana bungei Ledeb. in contrasting habitats of the mountain slope—herb-grass-shrub steppe and larch forest. It was shown that the adaptation of photosynthetic apparatus of C. bungei to forest conditions does not lie in biochemical and primary photosynthetic processes but consists of quantitative changes in the leaf tissue-cellular structure. Steppe and forest individuals differed neither in photosynthetic capacity nor in kinetic parameters of photosynthesis. It is assumed that the development of Caragana’s leaves at high light in the spring larch forest leads to the formation of a strong photosynthetic apparatus as a preadaptation to fluctuating light under the forest canopy. At the same time, forest shrubs had thinner and less dense leaves due to the decreased size and number of mesophyll cells. The decrease in the structural complexity of the mesophyll was compensated for by enhancement of the photosynthetic capacity of cells and chloroplasts. The low rate of real photosynthesis under the forest canopy shadow was observed, but it was compensated by a high relative mass and area of the leaves. As a result there were no differences in shrub sizes between steppe and forest shrubs of Caragana. We concluded that photosynthesis adaptation at the levels of leaf mesophyll and of the ratio of photosynthetic organs allow this species to maintain growth and to gain an advantage in an open larch forest.