Number Of Chloroplasts Research Articles

Maternal haploid induction in African marigold (Tagetes erecta L.) through in vitro culture of un-fertilized ovules

A protocol for production of haploids from two heterozygous male sterile lines of Tagetes erecta using un-pollinated ovules as explant was standardized. Various factors affecting the in vitro gynogenic response viz., growth regulators, ovule developmental stage, basal media, sucrose concentration, photoperiod and cold shock duration were assessed in Tagetes erecta. Direct induction of parthenogenic embryos occurred in cultivar ‘Local Orange’ when the un-pollinated ovules were cultured in EMS (MS medium enriched with coconut water, AgNO3, PVP etc.) medium supplemented with 2 mg l−1 BAP and 0.5 mg l−1 NAA or 2 mg l−1 BAP along with 2 mg l−1 2,4-D. The developmental stage of the flower buds was vital in embryo induction from the excised ovules. The ovules collected from half-open flower buds were more responsive to gynogenesis as compared to ovules collected from un-open and fully open flower buds. EMS basal medium was found best for gynogenesis over the other commercially available basal media. Cold pre-treatment of flower buds at 4 oC had no stimulatory effect and negatively affected the gynogenesis. The dark culture condition was imperative for direct parthenogenic embryo induction than 16 h light duration. The ploidy levels of 17 regenerants were determined by cytological studies, revealed 47.06% as diploids, 41.18% as haploids and 11.76% as mixoploids. These results were reconfirmed with flow cytometry analysis. The determination of ploidy level by counting the number of chloroplasts in stomatal guard cells of marigold was also established for rapid screening of haploids. The resultant haploids were successfully diploidised and are being utilized in the hybrid breeding programme at our institute. The standardized protocol for doubled haploids (DHs) production by un-pollinated ovule culture paved the way for Tagetes F1 hybrid breeding. This is the first successful report of in vitro gynogenesis in Tagetes spp for production of doubled haploids (DHs). The protocol for obtaining high frequency parthenogenic embryo induction from unpollinated ovules was standardized and validated for rapid production of homozygous lines.

SCARECROW gene function is required for photosynthetic development in maize.

C4 photosynthesis in grasses relies on a specialized leaf anatomy. In maize, this “Kranz” leaf anatomy is patterned in part by the duplicated SCARECROW (SCR) genes ZmSCR1 and ZmSCR1h. Here we show that in addition to patterning defects, chlorophyll content and levels of transcripts encoding Golden2‐like regulators of chloroplast development are significantly lower in Zmscr1; Zmscr1h mutants than in wild‐type. These perturbations are not associated with changes in chloroplast number, size, or ultrastructure. However, the maximum rates of carboxylation by ribulose bisphosphate carboxylase/oxygenase (RuBisCO, V cmax) and phosphoenolpyruvate carboxylase (PEPC, V pmax) are both reduced, leading to perturbed plant growth. The CO2 compensation point and 13C‰ of Zmscr1;Zmscr1h plants are both normal, indicating that a canonical C4 cycle is operating, albeit at reduced overall capacity. Taken together, our results reveal that the maize SCR genes, either directly or indirectly, play a role in photosynthetic development.Significance statementSCARECROW (SCR) is one of the best studied plant developmental regulators, however, its role in downstream plant physiology is less well‐understood. Here, we have demonstrated that SCR is required to establish and/or maintain photosynthetic capacity in maize leaves.

Ultra- and Mesostructural Response to Salinization in Two Populations of С3–С4 Intermediate Species Sedobassia sedoides

The plants from two populations (P1 and P2) of xero-halophyte Sedobassia sedoides (Pall.) Freitag & G. Kadereit (Chenopodiaceae) with С3–С4 intermediate type of photosynthesis were examined. Morphophysiological parameters were determined: dry biomass of the above-ground organs, maximum quantum yield of photosystem II (PSII), ultra- and mesostructure of the leaf, carbon isotope discrimination (δ13С) in plants grown under normal conditions and exposed to moderate salinization (0 and 200 mM NaCl). By the values of δ13С and efficiency of PSII, we did not detect significant differences between the populations. Under control conditions, the chloroplasts and mitochondria were located in Kranz-like cells of the bundle sheath of both populations in the region adjacent to vascular bundle, which is characteristic of С2 type of photosynthesis (with photorespiratory СО2 concentrating mechanism). P2 plants were notable for a greater volume of Kranz-like cells of the bundle sheath and more numerous, larger chloroplasts and mitochondria than in P1 plants. By structural leaf parameters, P1 plants may be attributed to a proto-Kranz type of photosynthesis (intermediate between С3 and С2 types) and P2 plants to С2 photosynthesis. Under salinization, the accumulation of dry biomass was reduced in both populations but more considerably in P1. The ultrastructure of organelles in both populations showed different responses to salinization, which was especially pronounced in Kranz-like cells of the bundle sheath. In P1 plants, the area of chloroplasts and mitochondria rose, whereas the area and number of chloroplasts under stress did not change in P2 plants but the area and number of mitochondria decreased. In the cells of plants from both populations, signs of degradation were observed (more pronounced in P1 plants); they were shown in chloroplasts twisting and a disturbance of their granal stacking. In P2 plants, Kranz-like cells of the bundle sheath preserved safer organelles but there occurred the cells with complete degradation of a vacuolar type. Thus, intraspecific ultra- and mesostructural differences were detected in plants from two populations of С3–С4 intermediate species S. sedoides, which reflect different stages of development of photorespiratory СО2 concentrating mechanism. Under salinization, the plants from two different populations showed unlike strategies of adaptation on the level of leaf ultra- and mesostructure.

Photosynthetic and ultrastructural adaptability of Anemone shikokiana leaves to heterogeneous habitats

Anemone shikokiana (Makina) Makina is distributed in two heterogeneous habitats, including mountaintop shrubland and conifer and broad-leaf mixed forest. To better understand the mechanisms used by A. shikokiana in adapting to these different environments, the photosynthetic efficiency, chlorophyll fluorescence and ultrastructure of the leaves were investigated. The findings revealed that, under the same optical quantum flux density, the net photosynthetic rate in the leaves of mountaintop shrubland was significantly higher than that found in the mixed forest, but the stomatal conductance, intercellular CO2 concentrations and transpiration rate were lower. The effective quantum yield of photosystem II (PSII), photochemical quenching coefficient, non-photochemical quenching coefficient and electron transfer rate in the conifer and broad-leaf mixed forest were significantly lower than those values determined for plants in mountaintop shrubland. However, the maximal quantum yield of PSII exhibited no significant difference between the two habitats. Transmission electron micrographs revealed that the numbers of chloroplasts and mitochondria per mesophyll cell and starch grains per chloroplast in the mountaintop shrubs were higher than those found in the conifer and broad-leaf mixed forest samples. Moreover, they showed an increasing trend month by month in April, May and June. It indicated that elevated temperature increased their numbers. These findings illustrate that A. shikokiana efficiently uses environmentally limited resources to adapt to different living environments. The study reveals that the mechanisms that underlie the response of A. shikokiana to heterogeneous habitats involve photosynthetic and ultrastructural variations, thus providing a theoretical basis for future study.

Genetic manipulation of Soc1-like genes promotes photosynthesis in flowers and leaves and enhances plant tolerance to high temperature.

Genetic manipulation of Soc1-like genes promotes photosynthesis in flowers and leaves and enhances plant tolerance to high temperature.

The degradation of chloroplast components during postharvest senescence of broccoli florets is delayed by low-intensity visible light pulses

Abstract Senescence in harvested green organs, such as broccoli inflorescences, is a highly regulated process characterized by a massive degradation of chloroplast components. The dismantling of the chloroplast involves small “senescence-associated vacuoles” (SAVs) with high protease activity. The expression of the senescence associated gene, SAG12 (here BoSAG12), which encodes a senescence associated cysteine protease, correlated with SAVs appearance. One environmental factor that delays senescence is low-intensity visible light. Daily irradiation with pulses of 2 h of low-intensity white light (20–25 μmol m−2 s−1) is a promising technology to delay postharvest senescence of broccoli stored at room temperature. The aim of this study was to analyze the effects of low-intensity white (W) and red (R) light treatments on some events related to chloroplast dismantling during postharvest senescence of broccoli inflorescences. We detected that chloroplasts number did not change during postharvest senescence. We found that SAVs participate in the dismantling of chloroplasts during the postharvest senescence of broccoli florets. SAVs appearance occurred earlier than visible yellowing. The two light treatments used, i.e. pulses of low-intensity W and R light, delayed chloroplast changes, including chlorophyll degradation and SAVs appearance. The delay of SAVs appearance was accompanied by the delay of BoSAG12 induction in broccoli florets. Regarding protein degradation, not all proteins analyzed were affected equally. The light treatments had greater effect on the retention of thylakoid proteins than on Rubisco and apparently, the effects of light treatment were higher on proteins from PSII (LHCII) than on those from PSI (LHCI and PsaA).

The effect of the substrate on the anatomical and morphophysiological parameters of Pimpinella saxifraga L. on the ash dump

The structural and functional features of the species Pimpinella saxifraga L., which grows in the ash dumpof the Verkhnetagil State District Power Station, were investigated, compared with the natural habitat. We studied suchindicators as biomass distribution, parameters of the leaf mesostructure (the area and thickness of the leaf blade, thethickness of the mesophyll and epidermis, the size of cells and chloroplasts and their number per unit area of the leaf, thenumber of chloroplasts in cell, etc.). Pimpinella saxifraga, growing on the ash dump, showed a change in morphologicalparameters, compared with the control: a decrease in the weight of the roots, an increase in the weight of the aerialorgans, a decrease in the area of the leaf blade and the thickness of the leaf. The structural adaptation of mesophyll toenvironmental conditions consisted in changing the number and size of cells without changing the parameters of theplastid apparatus (number and size of chloroplasts). The properties of the substrate did not significantly influence on theinternal leaf area. Such adaptive changes allows this species to grow on technogenic substrates.

Comprehensive transcriptome profiling of tea leaves (Camellia sinensis) in response to simulated acid rain

Tea plants (Camellia sinensis (L.) O. Kuntze), which are typically cultivated in high-elevation mountainous regions in southern China, are severely affected by acid rain. Our recent study indicated that simulated acid rain (SAR) at pH 2.5 produced necrotic spots on the leaf surface, impaired plant development by inhibiting photosynthesis and the antioxidant defense system, and caused metabolic disorders. In contrast, a pH of 4.5 had no toxic effects on tea seedlings. However, molecular-level evidence for these conclusions is still lacking. In this study, we explored the changes in leaf micromorphology under different SAR treatments using electron microscopy, and presented the first case study on the systemic responses of the tea leaf transcriptome to SAR. An examination of leaves using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that SAR (pH 4.5 and pH 3.5) did not impair the epidermis or chloroplast structures, but SAR (pH 2.5) reduced the number of chloroplasts, corroded epicuticular wax and trichomes, and altered stomatal density and size. Transcriptomic analysis revealed that the expression of multiple genes related to photosynthesis and carbohydrate, nitrogen, and sulfur metabolism were altered under SAR. Additionally, epicuticle wax biosynthesis and plant hormone signal transduction pathways were found to significantly influenced by high-acidity SAR. Taken together, our results suggest that tea plant responses to intense SAR stress incorporate three aspects: (1) stress resistance via altering metabolic pathways to enable survival; (2) stress avoidance via restraining uncontrolled non-stomatal gas exchange; and (3) stress escape via redistributing nitrogen from stress damaged leaves. These findings provide valuable insights into plant responses to acid rain stress.

Special issue in honour of Prof. Reto J. Strasser - Dorsoventral variation in photosynthesis during leaf senescence probed by chlorophyll a fluorescence induction kinetics in cucumber and maize plants

Although photosynthesis has been intensively studied during leaf senescence, it is unclear whether the changes of photosynthetic function in various mesophyll tissues can be detected using chlorophyll a fluorescence induction kinetics (CFI) in vivo. To clarify this question, leaf structure and CFI were carefully examined in senescent leaves. The results showed declines in chlorophyll content and photosynthetic rate in both cucumber and maize plants as leaves aged. In cucumber leaves, the number of chloroplasts decreased more rapidly in the palisade tissue compared to the sponge tissue as senescence progressed. Under various pulse light intensities, the enhancement of the relative variable fluorescence in the CFI curves measured on the adaxial side was larger than that on the abaxial side of senescent cucumber leaves, indicating senescence in the palisade tissue progressed more quickly than that in the sponge tissue. JIP-test parameters further showed that the loss of photosynthetic electron transport activity in palisade tissue was faster than that in sponge tissue. However, during leaf senescence in maize, there were no such dorsoventral differences. We therefore propose that the decline of photosynthesis in cucumber leaves is largely determined by the senescence of palisade tissue. The changes in photosynthesis in palisade and sponge tissues with leaf aging can be probed effectively by CFI measured on both sides of cucumber leaves in vivo.

Ecological Morphology of Proto-Epiphyte Fern Lemmaphyllum microphyllum C. Presl and Its Relation to the Adaptogenesis

A study of the ecological morphology of plants is a necessary condition in solving a number of fundamental and applied problems of ecology, botany, geography, and physiology of plants when monitoring global and regional environments, as well as the problems of selecting and introducing plants. This approach is successfully used to study flowering plants of different botanical and geographical zones. At the same time, ferns usually fall outside of the field of interest of botanists. The aim of this study is to investigate a photosynthetic apparatus of sporophytes of proto-epiphyte fern Lemmaphyllum microphyllum at different cell organization levels and determine the ways it adapts to environmental conditions. The morphology and structure of a photosynthetic apparatus of plants are analyzed using a Siams Mesoplant laboratory complex. This equipment makes it possible to analyze L. microphyllum at the level of fronds, mesophyll cells, and plastid apparatus, as well as obtain parameters such as the specific surface density of fronds, the number of cells per frond unit area, the number of chloroplasts per cell, the frond thickness, the surface area and volume of chloroplasts, the cell area and volume, etc. We have found that the fern uses different organs and functions for adapting to habitats on tree trunks and branches and on humus-free flat rock surfaces. Adaptations to the light and humidity conditions are characterized by the maximum manifestations in its morphology and anatomy. Such adaptations include the maximum light interception and light excess protection, as well as both the minimization of water losses and the ability to excrete water. They are manifested at different organizational levels and include combinations of xero-, meso-, helio-, and sciomorphic traits, allowing the species to form stable populations in coenoses. In the case of frond-area reduction, the optimum compensatory strategy includes the development of a water-retaining capacity of cells and tissues (succulentization) based on the polyfunctionality of a chlorenchyma, as well as the improvement of conductive xylem elements due to the appearance of vessels. These characteristics do not solve the problem of long-term dehydration, since they provide only a tolerance to short-term water deficiency. For this reason, such ferns can be called cryptic succulents or subsucculents.

AP2/ERF transcription factors regulate salt-induced chloroplast division in the moss Physcomitrella patens.

Chloroplast division is a critical process for the maintenance of appropriate chloroplast number in plant cells. It is known that in some plant species and cell types, environmental stresses can affect chloroplast division, differentiation and morphology, however the significance and regulation of these processes are largely unknown. Here we investigated the regulation of salt stress-induced chloroplast division in protonemal cells of the moss, Physcomitrella patens, and found that, salt stress as one of the major abiotic stresses, induced chloroplast division and resulted in increased chloroplast numbers. We further identified three APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors (TFs) that were responsible for this regulation. These AP2/ERF genes were up-regulated under salt stress, and amino acid sequences and phylogenetic analyses indicated that all TFs possess only one conserved AP2 domain and likely belong to the same subgroup of ERF-B3 in the AP2/ERF superfamily. Overexpression of these TFs significantly increased the chloroplast number even in the absence of NaCl stress. On the contrary, inducible overexpression of the dominant repressor form of these TFs suppressed salt stress-induced chloroplast division. Thus, our results suggest that salt stress induced-chloroplast division is regulated through members of the AP2/ERF TF superfamily.

Leaf structure and chlorophyll content in Torreya grandis 'Merrillii' with Nalepella abiesis infestation

Objective The aim is to provide a theoretical basis for the prevention and control of Nalepella abiesis and to study the damage mechanism and chlorophyll content from N. abiesis on leaves of Torreya grandis 'Merrillii'. Method Dynamic changes in leaf tissue structure, stomatal structure, chloroplast ultrastructure, and chlorophyll content were studied using the fluorescence microscope, transmission electron microscope (TEM), scanning electron microscope (SEM), and spectrophotometer. Result The palisade cells changed in shape and decreased in number for an increase in days after inoculation (DAI) with mites. By the 40th day, thickness of the palisade tissue decreased considerably; spongy cells shrank; spongy tissue became looser; around stomata the cuticular peg was destroyed; guard cells shrank; and stomata shrank revealing obvious injury. Mesophyll cells gradually swelled and became deformed with the gap between cells becoming larger and larger. Also, the number of chloroplasts gradually decreased with the appearance of starch grains. By the 12th day, the number of osmiophilic granules within the chloroplast had increased with grana lamellae becoming more and more irregular in structure, especially on the 25th day, and finally disintegrating and disappearing on the 40th day. There was no significant difference in chlorophyll content between ck and the treatment with mite infection from 0 to 12 d, but a significant difference occurred from 25 to 40 d(P Conclusion N. abiesis infestation could destroy the structure of the mesophyll cells and leaf stomata of T. grandis 'Merrillii' leading to a decreased chlorophyll content that could affect photosynthesis.

Effects of light intensity on physio-biochemical characteristics of Chrysanthemum indicum

By analyzing the effects of light intensity on the growth, physiological and biochemical characteristics of Chrysanthemum indicum, the light intensity suitable for the growth of Ch. indicum was revealed, which provided a reference for the planting of Ch. indicum. There were five treatment groups of Ch. indicum, which was planted under 100%, 80%, 60%, 40% and 20% all natural light intensity conditions, respectively. In the meantime, these indicators of photosynthetic physiology, such as relative growth, photosynthetic pigment content, photosynthetic parameters, and chlorophyll fluorescence parameters etc. were measured in the peak period of growth of Ch. indicum as well as related indicators of the protective enzyme system, and the ultrastructure of chloroplast was observed with the use of transmission electron microscope technique. In our study, the results showed that the leaves of Ch. indicum occurred yellow phenomenon in different degrees when Ch. indicum was placed at more than 80% of the total natural light intensity condition, the height and stem diameter of plant reached the maximum at 60% of the total natural light intensity. More importantly, the number of branches of Ch. indicum was significantly increased under the total natural light intensity of more than 60%. Both the content of photosynthetic pigment and net photosynthetic rate were negatively correlated with light intensity, while photosynthetic parameters and chlorophyll fluorescence parameters showed a trend of rising first and then decreasing with the decrease of light intensity. The physiological indexes of Ch.indicum including stomatal conductivity, intracellular CO_2 concentration, transpiration rate, water use efficiency and actual photochemical quantum yield of PS Ⅱ had been determined, and the results showed that all of them were at the highest level under 60% total natural light intensity condition. The chloroplast structure of Ch. indicum was not obviously abnormal under 60% and 80% total natural light intensity treatments, but the stroma lamella was broken under 100% total natural light intensity, and not only the number of chloroplast, but also the number and volume of starch grains were decreased significantly under 20% and 40% total natural light intensity. With the decrease of light intensity, the enzymes activities of SOD and CAT decreased, the activity of POD increased in the early stage and decreased in the later stage, and the content of MDA showed a decreasing trend. The analysis of results indicated that the Ch. indicum can grow under 20%-100% total natural light intensity, but the best growth condition was under 60% total natural light intensity.

From Fuzziness to Clarity: Regulation of DRP5B Ring Dynamics at the Chloroplast Division Site.

Plant cells harbor a varying number of chloroplasts, and chloroplasts multiply by division to maintain the continuity of chloroplasts. Chloroplast division is performed by the constriction of two self-assembling GTPase rings in the middle of the chloroplast: the FtsZ ring on the stromal side and the

In Vitro Polyploidy Induction of Patchouli (Pogostemon Cablin Benth.) by Colchicine

Patchouli (Pogostemon cablin Benth.; 2n = 32) is an aromatic herbaceous plant commonly cultivated for use in the the fragrance industry. As patchouli is propagated by cuttings polyploidization induction by colchicine treatment was conducted to obtain a new genotype with high patchouli alcohol content. This research aimed to increase patchouli genetic diversity with colchicine treatment by the formation of a polyploid plant. Axillary buds from single node cutting of aseptic plantlets were used as the explants. The experiment was arranged using a factorial completely randomized design with two factors, namely the concentration of colchicine and the immersion duration. Genetic diversity of patchouli was successfully enhanced by adjusting the colchicine concentration and immersion treatment. lethal concentration (LC) of 50% in patchouli was 0.132% and the LC 50% for soaking time was 60.16 hours. The number of chloroplasts, stomatal length and chromosome number increased with increasing ploidy, whereas stomatal density and the number of trichomes decreased. The chromosome number of 16 patchouli mutants in generation 4 was still unstable, and a chimera was found with mixoploidy between 20-80. A hierarchical dendogram clustered 16 patchouli mutants into four different groups.

The effect of soil and climatic conditions on the distribution of nutrients in Actinidia arguta leaves

The patterns of the distribution of nutrients in kiwiberry (Actinidia arguta (Siebold & Zucc.) Planch. ex Miq.), family Actinidiaceae (Gilg & Werderm), leaves growing under different soil and climatic conditions (Ukraine and China) were studied. Using scanning electron microscopy, significant differences were shown in the distribution of assimilates and mineral nutrients in the leaves of kiwiberry cultivated under different climate and soil conditions (Kyiv city, Ukraine and Jiamusi, China). The leaves of plants grown in China have higher concentration of all of the studied nutrients exception for silicon. The differences found in the content of macro- and microelements in plant tissues are consistent with their total content in the soil, and depend on the synthesis of low molecular weight organic compounds, namely, hydroxybenzoic, benzoic and triterpene acids. An increase in the silicon content in the leaves of kiwiberry plants grown in Ukraine indicates the moisture deficit in the soil. This conclusion is confirmed by the anatomical differences viz. the presence of additional integumentary formations and fewer stomata number per 1 mm2 of leaf surface. The specific feature of ‘Perlyna sadu’ cultivar was high concentrations of sodium and aluminum in the foliar tissues, regardless of the place of growth. The analysis of the distribution of nutrients in the leaves located along the stem showed remobilization of the former within the three layers: the lower one nourishes the roots, the upper one nourishes the leaves in the active growth phase and the middle one allocates the assimilates in both directions. A significant positive relationship was found between the biosynthesis of photosynthetic pigments and electrophysiological activity, especially for the leaves of the lower zone. The revealed differentiation into layers differing in polarity of bioelectric potentials and the distribution of assimilates suggests functional differentiation of the kiwiberry leaves. In particular, the leaves of the lower layer perform a storage function. The middle part is less conservative and characterized by higher sensitivity to environmental factors performs a mainly synthetic function. The upper layer performs an active growth function. The results of the comparative analysis of the indicators of the number of chloroplasts in the mesophyll cells proved that the obtained dependence can be used as a diagnostic criterion in assessing the predicted plant productivity at the early stages of their development.

Photosynthetic Mechanisms of Metaxenia Responsible for Enlargement of Carya cathayensis Fruits at Late Growth Stages.

Fruits of hickory (Carya cathayensis) are larger and their peel is greener after interspecific pollination by pecan (Carya illinoinensis; later pp fruits) than after intraspecific pollination by hickory (later ph fruits). Previous studies have found little genetic differences between offspring and their maternal parent, indicating that the observed trait differences between pp and ph fruits are due to metaxenia. Fruit development depends on the amount of photosynthetic assimilate available. Since there is no difference in photosynthesis of the associated leaves between pp and ph fruits, the larger size of the pp fruits might be attributed to changes in fruit photosynthesis caused by the different pollen sources. To elucidate to the photosynthetic mechanisms behind the metaxenia effect on fruit development in hickory, the effects of intraspecific and interspecific pollination regimes were examined in the present study. We observed the photosynthetic capacity in the peel of fruits and the related ecophysiological and morphological traits of both ph and pp fruits over a period of 120 days after pollination. Significant differences in the appearance and dry weight between ph and pp fruits were observed at 50 days after pollination (DAP). More than 70% of dry matter accumulation of the fruits was completed during 60–120 DAP, while the true photosynthetic rate of the associated leaves significantly decreased by about 50% during the same period. In several cell layers of the peel, the number of chloroplasts per cell was significantly higher in pp than in ph fruits. Similarly, the ribulose 1, 5-bisphosphate carboxylase (Rubisco) activity, the total chlorophyll content, and the nitrogen content were all significantly higher in pp than in ph fruits during all growth stages; and all of these physiological quantities were positively correlated with the gross photosynthetic rate of the fruits. We conclude that the enhanced photosynthetic capacity of pp fruits contributes to their fast dry matter accumulation and oil formation. This result will provide a theoretical basis for improving hickory fruit yields in practical cultivation.

Physiological and Anatomical Differences and Differentially Expressed Genes Reveal Yellow Leaf Coloration in Shumard Oak.

Shumard oak (Quercus shumardii Buckley) is a traditional foliage plant, but little is known about its regulatory mechanism of yellow leaf coloration. Here, the yellow leaf variety of Q. shumardii named ‘Zhongshan Hongjincai’ (identified as ‘ZH’ throughout this work) and a green leaf variety named ‘Shumard oak No. 23’ (identified as ‘SO’ throughout this work) were compared. ‘ZH’ had lower chlorophyll content and higher carotenoid content; photosynthetic characteristics and chlorophyll fluorescence parameters were also lower. Moreover, the mesophyll cells of ‘ZH’ showed reduced number of chloroplasts and some structural damage. In addition, transcriptomic analysis identified 39,962 differentially expressed genes, and their expression levels were randomly verified. Expressions of chlorophyll biosynthesis-related glumly-tRNA reductase gene and Mg-chelatase gene were decreased, while pheophorbide a oxygenase gene associated with chlorophyll degradation was up-regulated in ‘ZH’. Simultaneously, carotenoid isomerase gene, z-carotene desaturase gene, violaxanthin de-epoxidase gene and zeaxanthin epoxidase gene involved in carotenoid biosynthesis were up-regulated in ‘ZH’. These gene expression changes were accompanied by decreased chlorophyll content and enhanced carotenoid accumulation in ‘ZH’. Consequently, changes in the ratio of carotenoids to chlorophyll could be driving the yellow leaf coloration in Q. shumardii.

Leaf growth in early development is key to biomass heterosis in Arabidopsis.

Arabidopsis thaliana hybrids have similar properties to hybrid crops, with greater biomass relative to the parents. We asked whether the greater biomass was due to increased photosynthetic efficiency per unit leaf area or to overall increased leaf area and increased total photosynthate per plant. We found that photosynthetic parameters (electron transport rate, CO2 assimilation rate, chlorophyll content, and chloroplast number) were unchanged on a leaf unit area and unit fresh weight basis between parents and hybrids, indicating that heterosis is not a result of increased photosynthetic efficiency. To investigate the possibility of increased leaf area producing more photosynthate per plant, we studied C24×Landsberg erecta (Ler) hybrids in detail. These hybrids have earlier germination and leaf growth than the parents, leading to a larger leaf area at any point in development of the plant. The developing leaves of the hybrids are significantly larger than those of the parents, with consequent greater production of photosynthate and an increased contribution to heterosis. The set of leaves contributing to heterosis changes as the plant develops; the four most recently emerged leaves make the greatest contribution. As a leaf matures, its contribution to heterosis attenuates. While photosynthesis per unit leaf area is unchanged at any stage of development in the hybrid, leaf area is greater and the amount of photosynthate per plant is increased.

Using optical fibers to measure absorption in intact conifer leaves, relative numbers of chloroplasts, and pigment content.

For investigations of ongoing processes in plants, such as photosynthesis in conifer leaves, nondestructive and noninvasive measuring techniques are needed. In this paper, a novel approach has been developed for the measurement of chloroplasts' numbers and pigment contents in conifer leaves based on the measurements of leaf absorption spectra using optical fibers and an array spectrophotometer. To eliminate the effect of scattering on the measured absorption spectra, a strategy has been applied taking advantage of the combined use of thin optical fibers normal to the needle's longitudinal axis and the phenomenon that scattering is largest in the forward direction. The optical path in the leaf is nearly the distance between the fiber tips; thus, we were able to obtain the absorption spectrum of the pigments in situ. A effect of the measured absorption spectra, occurring due to the organization of pigments in the leaf and interaction between light and leaf interior, can be accounted for by using the so-called Duysens transformation. Using this transformation, pigment contents and the relative number of chloroplasts can be obtained from the measured absorption spectra. We applied the method to observe pigment concentrations in different stages of the greening process in the leaves of two conifer species, Taxus baccata and Picea abies. The presented method may be used to estimate changes in chloroplast number and pigment content during various phases of greening of a species and to observe differences among various species.