Limitations of carbon fixation within spinach leaves due to light and CO2 were investigated. Under equivalent photon fluxes, carbon fixation was higher when leaves were irradiated adaxially compared to abaxially. Maximal carbon fixation occurred in the middle of the palisade mesophyll under adaxial illumination, whereas, maximal carbon fixation occurred in the spongy mesophyll under abaxial illumination. Total carbon fixation and the pattern of carbon fixation across leaves were similar, when leaves were irradiated with 800 µmol quanta m–2 s–1 either adaxially alone or adaxially plus abaxially (1,600 µmol quanta m–2 s–1). In contrast, when both leaf surfaces were irradiated simultaneously with 200 µmol quanta m–2 s–1, total carbon fixation increased and carbon fixation in the middle of the leaf was higher compared to leaves irradiated unilaterally with the low light. Feeding 14CO2 through either the adaxial or abaxial leaf surface did not change the pattern of carbon fixation across the leaf. Increasing 14CO2 pulse-feeding times from 5 s to 60 s allowed more 14CO2 to be fixed but did not change the pattern of 14CO2 fixation across the leaf. We concluded that in spinach, the distribution of both light and Rubisco activity within leaves has significant effects on the patterns of carbon fixation across leaves; whereas CO2 diffusion does not appear to affect the carbon fixation pattern within spinach leaves.
Increasing maize grain yield has been a major focus of both plant breeding and genetic engineering to meet the global demand for food, feed, and industrial uses. We report that increasing and extending expression of a maize MADS-box transcription factor gene, zmm28, under the control of a moderate-constitutive maize promoter, results in maize plants with increased plant growth, photosynthesis capacity, and nitrogen utilization. Molecular and biochemical characterization of zmm28 transgenic plants demonstrated that their enhanced agronomic traits are associated with elevated plant carbon assimilation, nitrogen utilization, and plant growth. Overall, these positive attributes are associated with a significant increase in grain yield relative to wild-type controls that is consistent across years, environments, and elite germplasm backgrounds.
Abstract Nitrogen (N) addition typically increases overall plant growth, but the nature of this response depends upon patterns of plant nitrogen allocation that vary throughout the growing season and depend upon canopy position. In this study seasonal variations in leaf traits were investigated across a canopy profile in Miscanthus ( Miscanthus × giganteus ) under two N treatments (0 and 224 kg ha −1 ) to determine whether the growth response of Miscanthus to N fertilization was related to the response of photosynthetic capacity and nitrogen allocation. Miscanthus yielded 24.1 Mg ha −1 in fertilized plots, a 40% increase compared to control plots. Photosynthetic properties, such as net photosynthesis (A), maximum rate of rubisco carboxylation (V cmax ), stomatal conductance (g s ) and PSII efficiency (F v '/F m '), all decreased significantly from the top of the canopy to the bottom, but were not affected by N fertilization. N fertilization increased specific leaf area ( SLA ) and leaf area index ( LAI ). Leaf N concentration in different canopy layers was increased by N fertilization and the distribution of N concentration within canopy followed irradiance gradients. These results show that the positive effect of N fertilization on the yield of Miscanthus was unrelated to changes in photosynthetic rates but was achieved mainly by increased canopy leaf area. Vertical measurements through the canopy demonstrated that Miscanthus adapted to the light environment by adjusting leaf morphological and biochemical properties independent of nitrogen treatments. GPP estimated using big leaf and multilayer models varied considerably, suggesting a multilayer model in which V cmax changes both through time and canopy layer could be adopted into agricultural models to more accurately predict biomass production in biomass crop ecosystems.
ABSTRACT Chlorophyll fluorescence and internal patterns of 14 CO 2 fixation were measured in sun and shade leaves of spinach after treatment with various light intensities. When sun leaves were irradiated with 2000μmol m −2 s −1 for 2h, F V / F M decreased by about 15%, but 14 CO 2 fixation was unaffected, whereas shade leaves exhibited a 21% decrease in F v / F M and a 25% decrease in 14 CO 2 fixation. Irradiation of sun and shade leaves with 4000μmol m −1 for 4 h decreased F V / F M by 30% in sun leaves and 40% in shade leaves, while total 14 CO 2 fixation decreased by 41% in sun leaves and 55% in shade leaves. After light treatment, gradients of CO 2 fixation across leaves were determined by measuring 14 CO 2 fixed in paradermal leaf sections after a 10s pulse of 14 CO 2 . Gradients of 14 CO 2 fixation in control sun and shade leaves were identified when expressed on a relative basis and normalized for leaf depth. Treatment of leaves with 2000 μmol PAR m −2 s −1 for 2h did not after patterns of carbon fixation across sun leaves, but slightly altered the pattern in shade leaves. In contrast, treatment of sun and shade leaves with 4000μmol m −2 s −1 for 4h decreased carbon fixation more in the palisade mesophyll cells than in the spongy mesophyll cells of sun and shade leaves, and fixation in medial tissue of shade leaves was dramatically decreased compared to the adaxial and abaxial tissue. The interaction between leaf anatomy and biochemical parameters involved in tolerance to photoinhibition in spinach is discussed.
Xiangaiyou 63 (O.sativa L.subsp hsien Ting) is a new hybrid variety of rice.The culture characters, population development, net photosynthetic rates, grain ripening rates and plant characteristics were determined and studied.The results showed that, of the four yield-forming factors, the effect of number of grains per panicle was the most important, number of panicles per mu the second, percentage of fertile grains the third and weight of 1000 grains the fourth.The ideal type of plant for high yield looked like the form of waist drum.It was also showed that the variety had larger transection area for the macro-vascular bundles in the base internode, larger panicle, larger leaf area index, larger leaf area duration, higher net photosyntheic rate, higher dry matter productivity and had certain yield producing potental.But the variety was unstable in percentage of fertile grains.Multiple effect triazole (MET) had some effects on plant type and sink-source relation.An approach to high yield cultivation by means of earlier control at the mid-growth period, stable promotion at the late-growth period, striving for larger panicles and increase of total number of grains per mu was put forward.
Abstract Background Aortic dissection (AD) is an acute critical disease of the cardiovascular system characterized by high mortality and morbidity. According to reports, immune cell infiltration is associated to AD. However, the intrinsic molecular mechanisms underlying the pathogenesis of AD still need to be clarified. Methods Four datasets (GSE52093, GSE98770, GSE153434 and GSE190635) were download through the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) of each dataset were screened by robust rank aggregation (RRA) algorithms. Gene ontology (GO) functional enrichment analysis and Kyto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to DEGs. Using the Search Tool for Retrieval of Interacting Genes/Proteins (STRING) database, a protein–protein interaction (PPI) network was constructed, and the hub genes were identified by Cytoscape. And, after correcting for nonbiological effects between four datasets by Rank-In algorithm, we obtained a merged matrix. Furthermore, we adopted this merged matrix to evaluate immune infiltration by using CIBERSORT and single sample gene set enrichment analysis (ssGSEA). Finally, we calculated the correlation between hub genes and immune cells. Results Sixty-two integrated DEGs were identified. These DEGs were mainly enriched in 69 biological process (BP) terms and the ATP-binding cassette (ABC) transporters pathways. By applying 12 methods from Cytoscape plugin CytoHubba respectively, we selected final hub genes. The final hub genes consist of angiotensin Ⅰ converting enzyme (ACE), angiotensin converting enzyme 2 (ACE2), calsequestrin 2 (CASQ2) and TIMP metallopeptidase inhibitor 1 (TIMP1). CIBERSORT showed that monocytes ( P < 0.001) and activated mast cells ( P < 0.05) were higher fraction in AD group. ssGSEA showed that regulatory T cell ( P < 0.05), CD56 bright natural killer (NK) cell ( P < 0.01), central memory CD4 T cell ( P < 0.01), T follicular helper cell ( P < 0.01), activated dendritic cell ( P < 0.001), myeloid derived suppressor cells (MDSC) ( P < 0.001), monocytes ( P < 0.001), NK T cell ( P < 0.001), type 1 T helper cell (Th1) ( P < 0.001) and Th17 cell ( P < 0.001) were higher fraction in AD group. Conclusion ACE, ACE2, CASQ2 and TIMP1 are engaged in the process of AD, which can be used as molecular biomarkers for the screening and diagnosis of AD. Immune cell infiltration plays a major role in the development of AD.
Wild-type (wt) Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were grown in hydroponics under two levels of nitrate, 0.2 versus 6 mM, and two levels of CO(2), 35 versus 100 Pa. Growth (fresh weight and leaf area basis) was highest in wt plants, lower in TL46, and much lower in TL25 plants under a given treatment. It is surprising that the inability to synthesize starch restricted leaf area development under both low N (N(L)) and high N (N(H)). For each genotype, the order of greatest growth among the four treatments was high CO(2)/N(H) > low CO(2)/N(H), > high CO(2)/N(L), which was similar to low CO(2)/N(L). Under high CO(2)/N(L), wt and TL46 plants retained considerable starch in leaves at the end of the night period, and TL25 accumulated large amounts of soluble sugars, indicative of N-limited restraints on utilization of photosynthates. The lowest ribulose-1,5-bisphosphate carboxylase/oxygenase per leaf area was in plants grown under high CO(2)/N(L). When N supply is limited, the increase in soluble sugars, particularly in the starch mutants, apparently accentuates the feedback and down-regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase, resulting in greater reduction of growth. With an adequate supply of N, growth is limited in the starch mutants due to insufficient carbohydrate reserves during the dark period. A combination of limited N and a limited capacity to synthesize starch, which restrict the capacity to use photosynthate, and high CO(2), which increases the potential to produce photosynthate, provides conditions for strong down-regulation of photosynthesis.
Abstract Wild-type Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were evaluated by noninvasive in situ methods for their capacity for net CO2 assimilation, true rates of photosynthetic O2 evolution (determined from chlorophyll fluorescence measurements of photosystem II), partitioning of photosynthate into sucrose and starch, and plant growth. Compared with wild-type plants, the starch mutants showed reduced photosynthetic capacity, with the largest reduction occurring in mutant TL25 subjected to high light and increased CO2 partial pressure. The extent of stimulation of CO2 assimilation by increasing CO2 or by reducing O2 partial pressure was significantly less for the starch mutants than for wild-type plants. Under high light and moderate to high levels of CO2, the rates of CO2assimilation and O2 evolution and the percentage inhibition of photosynthesis by low O2 were higher for the wild type than for the mutants. The relative rates of14CO2 incorporation into starch under high light and high CO2 followed the patterns of photosynthetic capacity, with TL46 showing 31% to 40% of the starch-labeling rates of the wild type and TL25 showing less than 14% incorporation. Overall, there were significant correlations between the rates of starch synthesis and CO2 assimilation and between the rates of starch synthesis and cumulative leaf area. These results indicate that leaf starch plays an important role as a transient reserve, the synthesis of which can ameliorate any potential reduction in photosynthesis caused by feedback regulation.
Abstract Current background ozone (O3) concentrations over the northern hemisphere’s midlatitudes are high enough to damage crops and are projected to increase. Soybean (Glycine max) is particularly sensitive to O3; therefore, establishing an O3 exposure threshold for damage is critical to understanding the current and future impact of this pollutant. This study aims to determine the exposure response of soybean to elevated tropospheric O3 by measuring the agronomic, biochemical, and physiological responses of seven soybean genotypes to nine O3 concentrations (38–120 nL L−1) within a fully open-air agricultural field location across 2 years. All genotypes responded similarly, with season-long exposure to O3 causing a linear increase in antioxidant capacity while reducing leaf area, light absorption, specific leaf mass, primary metabolites, seed yield, and harvest index. Across two seasons with different temperature and rainfall patterns, there was a robust linear yield decrease of 37 to 39 kg ha−1 per nL L−1 cumulative O3 exposure over 40 nL L−1. The existence of immediate effects of O3 on photosynthesis, stomatal conductance, and photosynthetic transcript abundance before and after the initiation and termination of O3 fumigation were concurrently assessed, and there was no evidence to support an instantaneous photosynthetic response. The ability of the soybean canopy to intercept radiation, the efficiency of photosynthesis, and the harvest index were all negatively impacted by O3, suggesting that there are multiple targets for improving soybean responses to this damaging air pollutant.
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