Development Of Photosynthetic Capacity Research Articles

Increased atmospheric CO2 concentration enhances the development of photosynthetic capacity beyond the temperature effect for silver birch in simulated future climate

ABSTRACTWe conducted an experiment to find out how future climate conditions will impact the spring development of photosynthetic capacity of silver birch leaves. We had two greenhouse conditions. In the simulated future climate condition, we had both elevated temperatures and CO2 concentration, while for reference we had trees growing under current climate conditions. We used two methods to measure the development of photosynthetic capacity: first, the maximum quantum efficiency of photosystem II with a fluorescence meter; and second, the CO2 assimilation rate with gas exchange measurements. The development of full photosynthetic capacity took around two weeks following the bud burst. The maximum quantum efficiency developed slightly faster than the CO2 assimilation rate. Both measurement methods showed that an elevated CO2 concentration enhanced the development of photosynthetic capacity beyond the impact of temperature only. The enhancement under the conditions of our simulated climate change translates to achieving photosynthetic capacity up to five days earlier, which impact should be taken into account in simulations of photosynthetic productivity.

Transcriptome analyses of early cucumber fruit growth identifies distinct gene modules associated with phases of development.

BackgroundEarly stages of fruit development from initial set through exponential growth are critical determinants of size and yield, however, there has been little detailed analysis of this phase of development. In this study we combined morphological analysis with 454 pyrosequencing to study transcript level changes occurring in young cucumber fruit at five ages from anthesis through the end of exponential growth.ResultsThe fruit samples produced 1.13 million ESTs which were assembled into 27,859 contigs with a mean length of 834 base pairs and a mean of 67 reads per contig. All contigs were mapped to the cucumber genome. Principal component analysis separated the fruit ages into three groups corresponding with cell division/pre-exponential growth (0 and 4 days post pollination (dpp)), peak exponential expansion (8dpp), and late/post-exponential expansion stages of growth (12 and 16 dpp). Transcripts predominantly expressed at 0 and 4 dpp included homologs of histones, cyclins, and plastid and photosynthesis related genes. The group of genes with peak transcript levels at 8dpp included cytoskeleton, cell wall, lipid metabolism and phloem related proteins. This group was also dominated by genes with unknown function or without known homologs outside of cucurbits. A second shift in transcript profile was observed at 12-16dpp, which was characterized by abiotic and biotic stress related genes and significant enrichment for transcription factor gene homologs, including many associated with stress response and development.ConclusionsThe transcriptome data coupled with morphological analyses provide an informative picture of early fruit development. Progressive waves of transcript abundance were associated with cell division, development of photosynthetic capacity, cell expansion and fruit growth, phloem activity, protection of the fruit surface, and finally transition away from fruit growth toward a stage of enhanced stress responses. These results suggest that the interval between expansive growth and ripening includes further developmental differentiation with an emphasis on defense. The increased transcript levels of cucurbit-specific genes during the exponential growth stage may indicate unique factors contributing to rapid growth in cucurbits.

Within-crown Variation in the Development of Photosynthetic Capacity Is Proportional to Growth Temperature in Temperate Deciduous Trees

This study set out to test the hypothesis that the development in the capacity for the maximal rate of ribulose-1,5-bisphosphate carboxylase/oxygenase (VCmax) and the maximum regeneration rate of ribulose-1,5-bisphosphate (Jmax) per unit mass is proportional to the growth temperature under which the leaf develops and to investigate whether the capacity for photosynthetic acclimation to temperature varies genetically within a species by testing genotypes that originated from diverse thermal environments. Acer rubrum L. (red maple) genotypes were subjected to short-term and long-term temperature alteration to investigate the photosynthetic response. We minimized the variation of within-crown light gradients by growing trees in open grown field conditions and controlled temperature on a crown section basis. Thus, we singled out the temperature acclimation affects on the photosynthetic temperature optimum. In response to temperature acclimation, the genotype from the northern United States downregulated both VCmax and Jmax and had a 5 and 3 °C lower temperature optimum than the genotype native to the southern United States. The activation energy increased and was higher for Jmax than for VCmax in both genotypes. With respect to respiration, both genotypes downregulated about 0.5 μmol·m-2·s-1. Although respiration was lower, the increased energy of activation in response to growth temperature resulted in a decrease in maximum net photosynthetic rate (Amax) under saturating light and CO2. The results illustrate that the photosynthetic capacity adjusted in response to growth temperature but the temperature optimum was different among genotypes.

Photosynthetic and structural characteristics of canopy and shrub trees in a cool-temperate deciduous broadleaved forest: Implication to the ecosystem carbon gain

To reveal the seasonal change of leaf ecophysiological and canopy characteristics and to evaluate the functional role of canopy and shrub tree species in forest CO 2 uptake, we measured forest canopy leaf area index (LAI) using a hemispherical canopy photography technique, leaf CO 2 gas exchange and shoot architecture for canopy ( Betula ermanii and Quercus crispula) and shrub ( Hydrangea paniculata and Viburnum furcatum) tree species in a deciduous broadleaved forest in a cool-temperate region in central Japan. Canopy LAI and photosynthetic capacity of canopy tree leaves increased rapidly with leaf expansion. LAI reached its maximum in early summer but photosynthetic capacity reached its maximum in late summer. Development of photosynthetic capacity was dependent on the changes of leaf mass per area and leaf chlorophyll content (evaluated by SPAD). The seasonal maximum photosynthetic capacity of the leaves at the forest canopy top ( B. ermanii and sun leaves of Q. crispula) was about more than double of the leaves in the shrub layer ( H. paniculata, shade leaves of Q. crispula and V. furcatum). Light interception and photosynthetic carbon gain at a shoot level were simulated under three air temperature conditions by a three-dimensional canopy photosynthesis model (Y-plant) involving the combined leaf photosynthesis and stomatal conductance responses and shoot architecture. Results showed that (1) calculations without considering the heterogeneous light distribution in a foliage made by geometrical feature of plants would overestimate the photosynthetic carbon gain by +40% even at the canopy surface, and (2) the steep leaf angle in B. ermanii avoided midday depression of photosynthesis while the rather horizontal leaves in Q. crispula received excess light and heat load which led larger midday depression of photosynthesis. In addition to the large capacity of photosynthetic productivity of the canopy top foliage, our model also suggests the functional role of shrub species in forest ecosystem carbon gain, due to their high photosynthetic utilization efficiency of low light incidence available in the forest understory.

Effects of long‐term exposure to elevated CO2 and N fertilization on the development of photosynthetic capacity and biomass accumulation in Quercus suber L.

AbstractThe effects of long‐term (4 year) CO2 enrichment (70 Pa versus 35 Pa) and nitrogen nutrition (8 mm versus 1 mm NO3–) on biomass accumulation and the development of photosynthetic capacity in leaves of cork oak (Quercus suber L., a Mediterranean evergreen tree) were studied. The evolution of photosynthetic parameters with leaf development was estimated by fitting the biochemical model of Farquhar et al. (Planta 149, 78–90, 1980) with modifications by Sharkey (Botanical Review 78, 71–75, 1985) to A–Ci response curves. CO2 enrichment had a small reduction effect on the development of the maximum CO2 fixation capacity by Rubisco (VCmax), and no effect over maximum electron transport capacity (Jmax), day‐time respiration (Rd) and Triose‐P utilization (TPU). However, there was a statistically significant effect of N fertilization and the interaction CO2 × N over the evolution of VCmax, Jmax and TPU. Relative stomatal limitation (estimated from A–Ci curves) was higher (+20%) for plants grown under ambient CO2 than for plants grown under elevated CO2. There was a significant effect of CO2 and N fertilization over total biomass accumulation as well as leaf area. Plants grown at elevated CO2 had 27% more biomass than plants grown at ambient CO2 when given high N. However, for plants grown under low N there was no significant effect of CO2 enrichment on biomass accumulation. Plants grown under low N also had significantly higher root : shoot ratios whereas there were no differences between CO2 treatments. The larger biomass accumulation of Q. suber under elevated CO2 is attributable to a higher availability of CO2 coupled to a larger leaf area, with no significant decrease in photosynthetic capacity under CO2 enrichment and elevated N fertilization. For low N fertilization, the effects of CO2 enrichment over leaf area and biomass accumulation are lost, suggesting that in native ecosystems with low N availability, the effects of CO2 enrichment may be insignificant.

A light-independent developmental mechanism potentiates flavonoid gene expression in Arabidopsis seedlings.

Throughout the plant kingdom expression of the flavonoid biosynthetic pathway is precisely regulated in response to developmental signals, nutrient status, and environmental stimuli such as light, heat and pathogen attack. Previously we showed that, in developing Arabidopsis seedlings, flavonoid genes are transiently expressed during germination in a light-dependent manner, with maximal mRNA levels occurring in 3-day-old seedlings. Here we describe the relationship between developmental and environmental regulation of flavonoid biosynthesis by examining phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) mRNA levels in germinating Arabidopsis seedlings as a function of light, developmental stage and temperature. We show that seedlings exhibit a transient potential for induction of these four genes, which is distinct from that observed for chlorophyll a/b-binding protein(CAB). The potential for flavonoid gene induction was similar in seedlings grown in darkness and red light, indicating that induction potential is not linked to cotyledon expansion or the development of photosynthetic capacity. The evidence for metabolic regulation of flavonoid genes during seedling development is discussed.

The Effects of Development and Salinity Stress on Mannitol Biosynthesis in Celery Leaves

In celery (Apium graveolens L.), up to 50% of newly assimilated carbon may be partitioned into mannitol in mature leaves. Mannitol biosynthesis involves three unique enzymatic steps, and mannose 6-phosphate reductase (M6PR) is the critical regulatory step in the pathway. We measured M6PR enzyme activities, M6PR protein levels (using an immunological method) and M6PR transcript levels (by Northern blotting) to assess effects of leaf development on mannitol biosynthesis. M6PR was limited to green tissues and was under tight transcriptional regulation during leaf initiation, expansion, and maturation. M6PR expression was also closely correlated with the capacity of leaves to partition newly fixed carbon into mannitol (measured by 14C pulse/chase on intact leaves). Previous studies have also shown salt stress to lead to mannitol accumulation in celery. Using the methods outlined above we also investigated the combined effects of salt stress and leaf development on M6PR expression and the capacity of leaves to partition C to mannitol. Under salt stress M6PR expression and the capacity to synthesize mannitol occurred in younger leaves than in control plants. Thus, the increase in mannitol pool size in salt-stressed celery plants is due, in part, to enhanced de novo synthesis in young leaves. The data also confirmed the relationship between development of photosynthetic capacity, mannitol synthesis and M6PR activity. Supported by USDA-NRI grant # 940-1439.

Molecular cloning of mannose-6-phosphate reductase and its developmental expression in celery.

Compared with other primary photosynthetic products (e.g. sucrose and starch), little is known about sugar alcohol metabolism, its regulation, and the manner in which it is integrated with other pathways. Mannose-6-phosphate reductase (M6PR) is a key enzyme that is involved in mannitol biosynthesis in celery (Apium graveolens L.). The M6PR gene was cloned from a leaf cDNA library, and clonal authenticity was established by assays of M6PR activity, western blots, and comparisons of the deduced amino acid sequence with a celery M6PR tryptic digestion product. Recombinant M6PR, purified from Escherichia coli, had specific activity, molecular mass, and kinetic characteristics indistinguishable from those of authentic celery M6PR. Sequence analyses showed M6PR to be a member of the aldo-keto reductase superfamily, which includes both animal and plant enzymes. The greatest sequence similarity was with aldose-6-phosphate reductase (EC 1.1.1.200), a key enzyme in sorbitol synthesis in Rosaceae. Developmental studies showed M6PR to be limited to green tissues and to be under tight transcriptional regulation during leaf initiation, expansion, and maturation. These data confirmed a close relationship between the development of photosynthetic capacity, mannitol synthesis, and M6PR activity.

Leaf expansion and development of PHOTOSYNTHETIC CAPACITY AND PIGMENTS IN Liquidambar styraciflua (Hamamelidaceae)—EFFECTS OF UV‐B RADIATION

In order to perform their functions as photosynthetic organs, leaves must cope with excess heat and potentially damaging ultraviolet radiation. Possible increases in the UV‐B portion of the solar spectrum may place an additional burden on leaves, and this could be particularly important for young expanding leaves with poorly developed UV‐B defense mechanisms. We evaluated the effects of supplemental UV‐B radiation on leaf expansion and the development of photosynthetic capacity and pigments in sweetgum (Liquidambar styraciflua L.) seedlings. Seedlings were grown in the field under either ambient or ambient plus 3 or 5.0 kJ of biologically effective supplemental UV‐B radiation. Although final leaf size was unaffected, the rate of leaf elongation and accumulation of leaf area was slower in leaves exposed to the lower supplemental UV‐B irradiance. In contrast, chlorophyll accumulation and the development of photosynthetic capacity was more rapid in plants exposed to the higher, compared to the lower supplemental UV‐B irradiance. The accumulation of anthocyanins and other putative flavonoids or UV‐absorbing compounds was scarcely affected by exposure to supplemental UV‐B radiation. These results suggest that the UV‐B portion of the solar spectrum may, in the absence of gross affects on biomass, exert subtle influences on leaf ontogeny and the development of photosynthetic pigments and capacity in sweetgum.

Leaf Expansion and Development of Photosynthetic Capacity and Pigments in Liquidambar styraciflua (hamamelidaceae)-Effects of UV-B Radiation

Leaf Expansion and Development of Photosynthetic Capacity and Pigments in Liquidambar styraciflua (hamamelidaceae)-Effects of UV-B Radiation

Correlation Between the Development of Photorespiration and the Change in Activities of NH3 Assimilation Enzymes in Greening Oat Leaves

The development of photosynthetic capacity and photorespiration during chloroplast development in 7-day-old etiolated oat (Avena sativa L.) primary leaves was investigated together with changes in the activity of possible NH3-assimilating enzymes. The development of photosynthetic CO2 fixation and photorespiration capacity, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and glutamine synthetase (GS) activities comparable to green leaves were completed within 48 h of continuous illumination. Chlorophyll synthesis and glutamate synthase (GOGAT) activity continued to increase beyond this time. Within this 48-h period, the activities of Rubisco, GS and GOGAT increased 2.3, 2 and 3 times repectively. Throughout the greening treatment, the GS and GOGAT activities were always high enough to sustain the expected rate of photorespiratory NH3 production. In contrast, glutamate dehydrogenase activity decreased during greening, and its measured rate was not high enough for photorespirtory NH3 assimilation. These results support the idea that the GS/GOGAT pathway is the major, if not the only, route for photorespiratory NH3 assimilation in the light in leaves of higher plants.

Beeinflußt der UV-Ausschluß das Ergebnis von Photosynthesemessungen mit Gaswechselmeßanlagen? Ein Beitrag zum Küvettenproblem

Summary Young plants of Lactuca sativa L. and Rumex alpinus L. grown in assimilation cuvettes show different development of photosynthetic capacity depending on whether they are made from material allowing (Quartz) or not allowing (Plexiglass) transmission of U.V. light. For Rumex alpinus this was the case in experiments both with natural and artificial light sources where as for Lactuca sativa it was only the case when the light source had a relatively high U.V. value, i. e. Mercurylamps (Osram H qil and Osram Vitalux). These results show that with cuvettes made from non U. V. transparent material results from measurement of photosynthesis may be incorrect, an indeed depending on species and U.V. intensity may be positively or negatively influenced. Normalglass and U.V.-transparent Plexiglass are for various reasons not suitable as substitues for Quartz.

The Dual Functions of the Cotyledons of Acacia iteaphylla F. Muell. (Mimosoideae)

The storage of reserve materials in the seeds of Acacia iteaphylla F. Muell. occurs mainly in the cotyledons of the embryo which occupy the major part of the seed volume. After germination, the mobilization of reserve proteins (albumins and globulins) occurs in two distinct phases: an initial slow phase of about 2 weeks, during which a decline of c. 70% in cotyledon dry matter occurs, followed by a rapid phase in the third week, accompanying the development of photosynthetic capacity in the cotyledons and the initial expansion of the primary leaf. The possession of both storage and photosynthetic functions by the cotyledons in Acacia places the Mimosoideae in an intermediate position with respect to the Caesalpinioideae (seeds with endosperm, cotyledons leaf-like) and the Lotoideae (Papilionoideae), with many representatives showing cotyledons adapted entirely for storage.

The effect of oxygen concentration on the development of photosynthetic capacity by etiolated bean seedlings upon illumination

Summary The effects of oxygen concentration on 14 CO 2 uptake, the time required to compensation of respiration by photosynthesis and the greening of etiolated seedlings of bean upon illumination were investigated. It has been found that this factor had a large inhibitory action on the processes examined. In atmospheres of 1 and 21 % O 2 the fixation of 14 CO 2 was observed after 3 hours of illumination, while in 100% O 2 after 8 hours. The time required for compensation of respiration by photosynthesis was in order of 8 hours in 1% O 2 , 10 hours in 21 % O 2 and 20 hours in 100 % O 2 respectively. The chlorophyll a + b biosynthesis followed the similar pattern of inhibition by O 2 as photosynthesis. The lag phase for the appearance of chlorophyll biosynthesis in 1 and 21 % O 2 was 3 hours while in 100%O 2 6 hours.

Effect of age and carbon-dioxide concentration on assimilation by detached leaves of tea and sunflower

A simple method has been described for measuring photosynthesis of detached leaves.The reduced rate of photosynthesis of the tea leaf, immediately after excision, is due to stomatal closure. In mature detached leaves, kept well supplied with water in diffuse light or darkness and in a humid atmosphere, normal stomatal opening and maximum photosynthetic rates were obtained between 12 and 30 hr. from excision. Stomata on sunflower leaves do not close on excision.Variation in the initial concentration of CO2between 1·0 and 4·0% vol. with a final concentration not below 0·5% did not affect the rate of photosynthesis of sunflower leaves at 25° C. and under 32 klux light intensity. Under the same conditions of light and temperature, there was no change in the photosynthetic rates of tea leaves in 1 and 2% initial and 0·2% final CO2concentrations. There were indications that CO2concentrations below 1·0% might be rate-limiting for certain tea leaves, assimilating under low light (4 klux).The development of photosynthetic capacity in the young leaves of tea and sunflower is a gradual process. In sunflower, the photosynthetic capacity develops fully before, and in tea after the leaf reaches half its final size.