Extensive use of plastic film mulch has resulted in accumulation of a large amount of residual plastic, which will eventually fragment into microplastics in agricultural soils. However, it is unclear ...how microplastics from plastic mulch film affect crops. To address this issue, rice plants exposed to microplastics derived from poly(butyleneadipate-co-terephthalate) (PBAT)-based biodegradable mulch film (BM) and polyethylene (PE) mulch film (PM) were investigated for plant growth, physio-biochemical processes, and gene expressions. Both types of microplastics significantly reduced the height and dry weight of rice plant. Oxidative stress was induced by microplastics in rice shoot and root, with levels of ROS relatively higher under treatment PM than that under treatment BM. Transcriptomic data showed that more genes were down-regulated by treatment PM than that by treatment BM. Genes encoding ammonium and nitrate transporters were down-regulated by both types of microplastics in rice roots at vegetative stage, whereas up-regulated at reproductive stage, as compared to their respective treatment with no microplastics (CK). Similar results regarding phenylpropanoid biosynthesis pathway and lignin content were also observed in rice roots. Net photosynthetic rate and SPAD value were significantly inhibited by treatments BM and PM in rice shoot, and the expression of genes involved in light reaction was reduced at vegetative stage, whereas there were no differences of them at reproductive stage, as compared to their respective treatment CK. Our study suggests that microplastics from BM and PM both affect the growth of rice plants via nitrogen metabolism and photosynthesis. The negative effects imposed by both types of microplastics on rice plant can be mitigated with the growth of plants, and the negative effects of microplastics from PE mulch film on rice plant are relatively stronger than that from the PBAT-based biodegradable film.
Display omitted
•Microplastics affected plant growth of rice via nitrogen metabolism and photosynthesis.•Microplastics down-regulated nitrogen transporter genes and interfered with nitrogen metabolism of rice plants.•Nitrogen deficiency contributed to the reduction of chlorophyll and photosynthesis.•The negative effects can be mitigated with the growth of plants.
Optimization and control of the greenhouse light environment is key to increasing crop yield and quality. However, the light saturation point impacts the efficient use of light. Therefore, the ...dynamic acquisition of the light saturation point that is influenced by changes in temperature and CO
concentration is an important challenge for the development of greenhouse light environment control system. In view of this challenge, this paper describes a light environment optimization and control model based on a crop growth model for predicting cucumber photosynthesis. The photosynthetic rate values for different photosynthetic photon flux densities (PPFD), CO
concentration, and temperature conditions provided to cucumber seedlings were obtained by using an LI-6400XT portable photosynthesis system during multi-factorial experiments. Based on the measured data, photosynthetic rate predictions were determined. Next, a support vector machine(SVM) photosynthetic rate prediction model was used to obtain the light response curve under other temperatures and CO
conditions. The light saturation point was used to establish the light environment optimization and control model and to perform model validation. The slope of the fitting straight line comparing the measured and predicted light saturation point was 0.99, the intercept was 23.46 and the coefficient of determination was 0.98. The light control model was able to perform dynamic acquisition of the light saturation point and provide a theoretical basis for the efficient and accurate control of the greenhouse light environment.
Summary
Stomata mediate gas exchange between the inter‐cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and ...atmospheric CO2. CO2 in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll‐deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll‐deficient. Interestingly, approximately 45% of stomata had an unusual, previously not‐described, morphology of thin‐shaped chlorophyll‐less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole‐leaf photosynthetic parameters (PSII, qP, qN, FV′/FM′) were comparable with wild‐type plants. Time‐resolved intact leaf gas‐exchange analyses showed a reduction in stomatal conductance and CO2‐assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to CO2 shifts. Detailed stomatal aperture measurements of normal kidney‐shaped stomata, which lack chlorophyll, showed stomatal closing responses to CO2 elevation and abscisic acid (ABA), while thin‐shaped stomata were continuously closed. Our present findings show that stomatal movement responses to CO2 and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll‐less stomata cause a ‘deflated’ thin‐shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production.
Significance Statement
In this study, transgenic plants that lack chlorophyll specifically in guard cells were generated and analyzed. The results provide genetic evidence that CO2/ABA‐induced stomatal closure is not directly mediated by guard cell photosynthesis/electron transport. Moreover, approximately 45% of the stomata in these lines are deflated showing a previously not‐described ‘thin‐shaped’ stomatal morphology, which suggests a key function of guard cell photosynthesis for energization and turgor production of stomatal guard cells.
Many algae respond to the COsub.2 limitation in seawater by inducing a COsub.2 concentrating mechanism (CCM) to obtain sufficient inorganic carbon to meet their photosynthetic needs, and Ulva sp. is ...a model population suitable for studying the ecological adaptability of macroalgae. As the dominant species of green tide disaster, Ulva sp. often faces strong inorganic carbon restriction due to its rapid growth and high population density and must have evolved a variety of carbon acquisition strategies, such as CCM, to overcome these limitations. This paper briefly summarizes the position and function of the important components of CCM (inorganic carbon transporters, carbonic anhydrase, Rubisco, and pyrenoid) and introduces several indexes suitable for evaluating the relative function of CCMs in macroalgae from the aspects of affinity between photosynthesis and Rubisco for COsub.2, and carbonic anhydrase inhibitor. The methods of judging the carbon sequestration pathway of Ulva sp., the CCM responses of diversity under different carbon sources, and the related genes that may be involved in the operation of CCMs were summarized. This work could provide a reference for revealing the CCMs of macroalgae and lay a foundation for further research on the inorganic carbon utilization strategy of the Ulva sp.
Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is ...first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire–bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.
Main conclusion
We developed a more realistic modeling framework by integrating stem photosynthesis into the canopy carbon assimilation model to compare the photosynthetic productivity between the ...stem and leaf of
Eucalyptus urophylla
plantations.
Stems of
Eucalyptus
species with smooth outer bark have photosynthetic green tissue that can recycle internal stem CO
2
. However, the potential contribution of stem photosynthesis to forest productivity has not previously been adequately quantified, and we also do not know how it compares to leaf photosynthetic productivity. To assist in addressing this knowledge gap, we conducted field surveys in
Eucalyptus urophylla
plantations of different ages and developed a more realistic modeling framework by integrating stem photosynthesis into the existing canopy carbon assimilation model. We calculated the proportion of tree stems shaded by neighboring tree trunks based on Poisson spatial point process. Under the stand density of 2000 trees per hectare, the light absorption area of tree trunks of 2-year-old and 7-year-old
E. urophylla
plantations were 0.11 (± 0.15) and 0.35 (± 0.12) m
2
stem m
−2
land, the stem photosynthetic productivity (
GPP
stem
) was 0.72 (± 0.45) and 1.81 (± 1.12) mol C m
−2
month
−1
, and the ratios of
GPP
stem
to leaf photosynthetic productivity (
GPP
leaf
) were 5.10 and 8.17% for 2- and 7-year-old plantations, respectively. Overall, this study presents the feasibility of incorporating stem photosynthesis into the productivity prediction of
E. urophylla
plantations by developing the stem light absorption model.
C4 photosynthesis, a biochemical CO2‐concentrating mechanism (CCM), evolved more than 60 times within the angiosperms from C3 ancestors. The genus Flaveria, which contains species demonstrating C3, ...C3–C4, C4‐like or C4 photosynthesis, is a model for examining the molecular evolution of the C4 pathway. Work with carbonic anhydrase (CA), and C3 and C4Flaveria congeners has added significantly to the understanding of this process. The C4 form of CA3, a β‐CA, which catalyses the first reaction in the C4 pathway by hydrating atmospheric CO2 to bicarbonate in the cytosol of mesophyll cells (mcs), evolved from a chloroplastic C3 ancestor. The molecular modifications to the ancestral CA3 gene included the loss of the sequence encoding the chloroplast transit peptide, and mutations in regulatory regions that resulted in high levels of expression in the C4 mesophyll. Analyses of the CA3 proteins and regulatory elements from Flaveria photosynthetic intermediates indicated C4 biochemistry very likely evolved in a specific, stepwise manner in this genus. The details of the mechanisms involved in the molecular evolution of other C4 plant β‐CAs are unknown; however, comparative genetics indicate gene duplication and neofunctionalization played significant roles as they did in Flaveria.
Tropospheric ozone concentrations have increased by 60-100% in the Northern Hemisphere since the 19(th) century. The phytotoxic nature of ozone can impair forest productivity. In addition, ozone ...affects stomatal functions, by both favoring stomatal closure and impairing stomatal control. Ozone-induced stomatal sluggishness, i.e., a delay in stomatal responses to fluctuating stimuli, has the potential to change the carbon and water balance of forests. This effect has to be included in models for ozone risk assessment. Here we examine the effects of ozone-induced stomatal sluggishness on carbon assimilation and transpiration of temperate deciduous forests in the Northern Hemisphere in 2006-2009 by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. An analysis of results by ozone FACE (Free-Air Controlled Exposure) experiments suggested that ozone-induced stomatal sluggishness can be incorporated into modelling based on a simple parameter (gmin, minimum stomatal conductance) which is used in the coupled photosynthesis-stomatal model. Our simulation showed that ozone can decrease water use efficiency, i.e., the ratio of net CO2 assimilation to transpiration, of temperate deciduous forests up to 20% when ozone-induced stomatal sluggishness is considered, and up to only 5% when the stomatal sluggishness is neglected.
PDF
![Diversity of CO[sub.2] Conc...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2077-1312/small "Diversity of CO[sub.2] Concentrating Mechanisms in Macroalgae Photosynthesis: A Case Study of IUlva/I sp")
