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1.
Rice (N Y) ; 13(1): 18, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32170463

RESUMO

BACKGROUND: Abscisic acid (ABA) acts as a signaling hormone in plants against abiotic stress, but its function in energy homeostasis under heat stress is unclear. RESULTS: Two rice genotypes, Nipponbare (wild-type, WT) with flat leaves and its mutant high temperature susceptibility (hts) plant with semi-rolled leaves, were subjected to heat stress. We found significantly higher tissue temperature, respiration rate, and ABA and H2O2 contents in leaves as well as a lower transpiration rate and stomatal conductance in hts than WT plants. Additionally, increased expression of HSP71.1 and HSP24.1 as well as greater increases in carbohydrate content, ATP, NAD (H), and dry matter weight, were detected in WT than hts plants under heat stress. More importantly, exogenous ABA significantly decreased heat tolerance of hts plants, but clearly enhanced heat resistance of WT plants. The increases in carbohydrates, ATP, NAD (H), and heat shock proteins in WT plants were enhanced by ABA under heat stress, whereas these increases were reduced in hts plants. CONCLUSION: It was concluded that ABA is a negative regulator of heat tolerance in hts plants with semi-rolled leaves by modulating energy homeostasis.

2.
Plant Cell Environ ; 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32073150

RESUMO

Studies on the temperature (T) responses of photosynthesis and leaf hydraulic conductance (Kleaf ) are important to plant gas exchange. In this study, the temperature responses of photosynthesis and Kleaf were studied in Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum). Leaf water potential (Ψleaf ) was insensitive to T in Shanyou 63, while it significantly decreased with T in Yannong 19. The differential Ψleaf - T relationship partially accounted for the differing gm -T relationships, where gm was less sensitive to T in Yannong 19 than in Shanyou 63. With different gm -T and Ψleaf -T relationships, the temperature responses of photosynthetic limitations were surprisingly similar between the two lines, and the photosynthetic rate was highly correlated with gm . With the increasing T, Kleaf increased in Shanyou 63 while it decreased in Yannong 19. The different Kleaf -T relationships were related to different Ψleaf -T relationships. When excluding the effects of water viscosity and Ψleaf , Kleaf was insensitive to T in both lines. gm and Kleaf were generally not coordinated across different temperatures. This study highlights the importance of Ψleaf on leaf carbon and water exchanges, and the mechanisms for the gm -T and Kleaf -T relationships were discussed.

3.
J Exp Bot ; 70(19): 5259-5269, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31145797

RESUMO

The rapid response of stomatal conductance (gs) to fluctuating irradiance is of great importance to maximize carbon assimilation while minimizing water loss. Smaller stomata have been proven to have a faster response rate than larger ones, but most of these studies have been conducted with forest trees. In the present study, the effects of stomatal anatomy on the kinetics of gs and photosynthesis were investigated in 16 Oryza genotypes. Light-induced stomatal opening includes an initial time lag (λ) followed by an exponential increase. Smaller stomata had a larger maximum stomatal conductance increase rate (Slmax) during the exponential increase phase, but showed a longer time lag and a lower initial stomatal conductance (gs,initial) at low light. Stomatal size was, surprisingly, negatively correlated with the time required to reach 50% of maximum gs and photosynthesis (T50%gs and T50%A), which was shown to be positively correlated with λ and negatively correlated with gs,initial. With a lower gs,initial and a larger λ, small stomata showed a faster decrease of intercellular CO2 concentration (Ci) during the induction process, which may have led to a slower apparent Rubisco activation rate. Therefore, smaller stomata do not always benefit photosynthesis as reported before; the influence of stomatal size on dynamic photosynthesis is also correlated with λ and gs,initial.

4.
Field Crops Res ; 234: 66-72, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31007365

RESUMO

Identifying cropping systems with small global warming potential (GWP) per unit of productivity is important to ensure food security while minimizing environmental footprint. During recent decades, double-season rice (DR) systems in central China have progressively shifted into single-crop, middle-season rice (MR) due to high costs and labor requirements of double-season rice. Ratoon rice (RR) has been proposed as an alternative system that reconciliates both high annual productivity and relatively low costs and labor requirements. Here we used on-farm data collected from 240 farmer fields planted with rice in 2016 to evaluate annual energy balance, environmental impact, and net profit of MR, DR, and RR cropping systems in central China. Energy factors, emission values, and commodity prices obtained from literature and official statistics were used to estimate energy balance, GWP, and economic profit. Average annual yield was 7.7, 15.3. and 13.2 Mg ha-1 for MR, DR, and RR systems, respectively. Average total annual energy input (36 GJ ha-1), GWP (9783 kg ha-1), and production cost (3057 $ ha-1) of RR were 35-48% higher than those of MR. However, RR achieved 72-129% higher annual grain yield (13.2 Mg ha-1), net energy yield (159 GJ ha-1), and net economic return (2330 $ ha-1) than MR. Compared with DR, RR produced statistically similar net energy yield while doubling the net economic return, with 32-42% lower energy input, production costs, and GWP. Consequently, RR exhibited significantly higher net energy ratio and benefit-to-cost ratio, and substantially lower yield-scaled GWP than the other two cropping systems. In the context of DR being replaced by MR, our analysis indicated that RR can be a viable option to achieve both high annual productivity and large positive energy balance and profit, while reducing the environmental impact.

5.
Nat Commun ; 10(1): 1725, 2019 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-30979872

RESUMO

China produces 28% of global rice supply and is currently self-sufficient despite a massive rural-to-urban demographic transition that drives intense competition for land and water resources. At issue is whether it will remain self-sufficient, which depends on the potential to raise yields on existing rice land. Here we report a detailed spatial analysis of rice production potential in China and evaluate scenarios to 2030. We find that China is likely to remain self-sufficient in rice assuming current yield and consumption trajectories and no reduction in production area. A focus on increasing yields of double-rice systems on general, and in three single-rice provinces where yield gaps are relatively large, would provide greatest return on investments in research and development to remain self-sufficient. Discrepancies between results from our detailed bottom-up yield-gap analysis and those derived following a top-down methodology show that the two approaches would result in very different research and development priorities.

6.
Physiol Plant ; 166(3): 748-761, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30187482

RESUMO

Glutathione S-transferases (GSTs) are important plant proteins involved in biotic and abiotic stress responses. A gene from Juglans regia, JrGSTTau1 was previously cloned and functionally characterized as an enzyme involved in improving cold tolerance in plants. To clarify the functional mechanism of JrGSTTau1 and its role in stress response, here, the JrGSTTau1 promoter including the up-stream regulators was examined using yeast one-hybrid together with transient expression assays, and the osmotic stress response ability was confirmed by comparing with wild-type plants. The 1500 bp JrGSTTau1 promoter displayed high GUS expression activity and was enhanced by mannitol stress. The promoter is composed of abundant cis-elements, some of which were osmotic stress response-related motifs, such as ABRE, DRE and MYB, indicating that the expression of JrGSTTau1 is regulated by potential up-stream regulators under abiotic stress. The transcription factors (TFs) of JrDREB2A, JrMYC2, JrMYB44, JrDof1 and JrWRKY7 were identified, which shared a similar response with JrGSTTau1 when exposed to PEG6000 in walnut leaf and root. These results implied that JrDREB2A, JrMYC2, JrMYB44, JrDof1 and JrWRKY7 may act as up-stream regulators of JrGSTTau1 to regulate or combine functionality with JrGSTTau1 in osmotic stress response. Furthermore, compared with the WT plants, the transgenic tobacco plants that overexpress JrGSTTau1 showed improved tolerance to drought induced by osmotic stress, in which antioxidant enzymes, proline and reactive oxygen species (ROS) are involved. Our results demonstrated the positive role played by JrGSTTau1 in osmotic tolerance, which is regulated by multiple up-stream regulators.


Assuntos
Juglans/metabolismo , Pressão Osmótica/fisiologia , Proteínas de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas/fisiologia , Juglans/genética , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
7.
Environ Sci Pollut Res Int ; 26(5): 4901-4912, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30569357

RESUMO

Currently, the urgency of balancing rice production and environmental risk from nitrogen (N) fertilization is gaining scientific and public attention. As such, a field experiment was conducted to investigate the rice yield and the fate of applied-15N for Yangliangyou 6 (a two-line hybrid cultivar) and Lvdaoq 7 (an inbred cultivar) using 10 combinations of N rates and splitting ratios in the middle reaches of the Yangtze River. The results showed that N application primarily affected fertilizer N loss to the environment, followed by plant N absorption, but had little effect on grain yield. Generally, there was no significant increase in grain yield and N accumulation in the aboveground plant when N inputs surpassed 130 or 170 kg ha-1. Fertilizer N residue in soil peaked at approximately 48 kg ha-1 at an N rate of 170 kg ha-1 for both varieties; however, a sharp increase of fertilizer N loss occurred with further incrementally increasing N rates. Although a higher ratio of panicle-N fertilizer together with a lower ratio of tillering-N fertilizer at rates of 130, 170, and 210 kg ha-1 had no grain yield benefit, it promoted aboveground N accumulation and plant N accumulation derived from fertilizer, and it reduced the amount of N residue in soil and N loss to the environment. Overall, reducing tillering-N ratios and increasing panicle-N ratios at an N rate between 130 and 170 kg ha-1 using fertilizer rates of 90-0-40 kg ha-1 and 90-40-40 kg ha-1 N at basal-tillering-panicle initiation stages could reduce the adverse environmental risks of chemical N from rice production without sacrificing rice yield.


Assuntos
Produção Agrícola/métodos , Fertilizantes/análise , Nitrogênio/análise , Oryza/crescimento & desenvolvimento , Rios/química , Poluição Química da Água/prevenção & controle , China , Grão Comestível/química , Risco , Solo/química
8.
Front Plant Sci ; 9: 1128, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30108604

RESUMO

More than 4 billion inhabitants in Asia depend on rice for 35-60% of the calories consumed in their diets, but new rice cultivars frequently do not reach expected yields because of poor rice grain filling. Here, we quantified the activities of enzymes involved in starch metabolization in rice to investigate the mechanisms regulating the accumulation and translocation of stem non-structural carbohydrates (NSC) under different levels of nitrogen fertilizer application. A pot experiment was conducted using two rice cultivars, Liangyoupeijiu (LYPJ) and Shanyou63 (SY63), under high and low nitrogen applications. Compared with high nitrogen application (HN), low nitrogen application (LN) increased stem NSC concentration before the heading stage and NSC translocation during the grain filling stage; concomitantly, LN significantly shortened the active grain filling period and increased the grain filling rate in superior spikelets. Compared with the LYPJ cultivar, SY63 exhibited a higher grain weight, higher grain filling percentage, and higher stem NSC concentration before heading and greater NSC translocation after heading. During the period between panicle initiation and heading, the activities of adenosine diphosphate-glucose pyrophosphorylase (AGP), starch synthase (StS), and starch branching enzyme (SBE), all enzymes involved in starch synthesis, increased under the LN treatment and positively correlated with increases in stem NSC. During grain filling, the activities of enzymes involved in starch-to-sucrose conversion [α-amylase, ß-amylase, and sucrose phosphate synthase (SPS)] increased under the LN treatment and positively correlated with stem NSC remobilization. Overall, the investigated enzymes exhibited higher activities in SY63 than in LYPJ. Our results suggest that low nitrogen increases the activities of AGP, StS, SBE, α-amylase, ß-amylase, and SPS, leading to increased accumulation and remobilization of stem starch and NSC in SY63. We conclude that calculated reductions in nitrogen application and the choice of an appropriate cultivar may improve rice grain yields via enhanced stem NSC accumulation and translocation, thereby reducing the costs and increasing the sustainability of rice production.

9.
Sci Rep ; 8(1): 12891, 2018 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-30150736

RESUMO

Post-anthesis nitrogen uptake and translocation play critical roles in photosynthetic assimilation and grain filling. However, their effects on leaf stay-green characteristics, dry matter accumulation, and translocation after anthesis remain unclear. In this study, post-anthesis N uptake and translocation between two different rice genotypes (Yongyou12 and Zhongzheyou1) were compared through soil nitrogen leaching treatments at the meiosis stage (MST) and anthesis stage(AST) respectively, and their effects on leaf stay-green duration, photosynthesis, dry matter accumulation and translocation during ripening and yield formation were estimated. The results showed that the soil nitrate-N and ammonium-N contents in Yongyou12 pots decreased significantly, and post-anthesis N uptake was 2.0-3.4 fold higher in Yongyou12 than in Zhongzheyou1. The activities of N-metabolism enzymes and antioxidant enzymes were higher, and flag-leaf photosynthesis and dry matter accumulation during ripening were greater, in Yongyou12 than in Zhongzheyou1. However, insufficient available soil N led to significant decreases in the activities of N- metabolism enzymes, decreased flag-leaf photosynthesis, increased translocation of dry matter and N pre-anthesis, accelerated leaf senescence, shorter duration of the leaf stay-green period, and decreased dry matter accumulation and grain plumpness. In addition, the effect of N uptake after anthesis on yield is greater for rice genotypes that depend on post-anthesis dry matter accumulation and an expanded sink capacity.


Assuntos
Nitrogênio/metabolismo , Oryza/fisiologia , Fotossíntese , Antioxidantes/metabolismo , Biomassa , Grão Comestível , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Solo/química
10.
J Exp Bot ; 69(16): 4033-4045, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-29788146

RESUMO

Understanding the physiological responses of crops to drought is important for ensuring sustained crop productivity under climate change, which is expected to exacerbate the frequency and intensity of periods of drought. Drought responses involve multiple traits, and the correlations between these traits are poorly understood. Using a variety of techniques, we estimated the changes in gas exchange, leaf hydraulic conductance, and leaf turgor in rice (Oryza sativa) in response to both short- and long-term soil drought. We performed a photosynthetic limitation analysis to quantify the contributions of each limiting factor to the resultant overall decrease in photosynthesis during drought. Biomass, leaf area, and leaf width significantly decreased during the 2-week drought treatment, but leaf mass per area and leaf vein density increased. Light-saturated photosynthetic rate declined dramatically during soil drought, mainly due to the decrease in stomatal conductance (gs) and mesophyll conductance (gm). Stomatal modeling suggested that the decline in leaf hydraulic conductance explained most of the decrease in stomatal closure during the drought treatment, and may also trigger the drought-related decrease of stomatal conductance and mesophyll conductance. The results of this study provide insight into the regulation of carbon assimilation under drought conditions.


Assuntos
Oryza/fisiologia , Folhas de Planta/fisiologia , Estômatos de Plantas/fisiologia , Secas
11.
Front Plant Sci ; 9: 172, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29487612

RESUMO

Seed priming is a successful practice to improve crop establishment under adverse environment. However, reduced longevity of primed rice (Oryza sativa L.) seeds during storage limited the adoption of this technique. Present study investigated the effect of temperature, relative air humidity (RH) and oxygen on the longevity of primed rice seeds in a range of 60 days storage. In addition, the biochemical and morphological mechanisms associated with deterioration of primed seeds during storage were explored. Three types of priming treated rice seeds and one non-primed control were stored under (1) low temperature-vacuum (LT-V), (2) room temperature-vacuum (RT-V), (3) room temperature-aerobic-low RH (RT-A-LH) and (4) room temperature-aerobic- high RH (RT-A-HH) for 0, 15, 30, 45, and 60 days. The results showed that storage of seeds under different conditions for 15-60 days did not influence the longevity of non-primed rice seeds. Meanwhile, the viability of primed rice seeds did not reduce when stored under LT-V, RT-V, and RT-A-LH, but was significantly reduced under RT-A-HH. Under vacuum condition, the increases of storage temperature (30°C) did not reduce the longevity of primed seeds. Likewise, the oxygen did not influence the longevity of primed rice seeds stored under low RH. Nevertheless, increase of RH significantly reduced the viability of primed seeds stored for 15-60 days. Reduced starch metabolism, the consumption of starch reserves in rice endosperms, the accumulation of malondialdehyde and the decreases of antioxidant enzyme activities might be associated with the deterioration of primed rice seeds during storage. In conclusion, storage of primed seeds under high RH condition beyond 15 days is deteriorative for germination and growth of rice. The primed rice seeds are recommended to store at vacuum or low RH or low temperature condition to ensure good crop establishment.

12.
Physiol Plant ; 163(1): 45-58, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29055043

RESUMO

Salinity significantly limits leaf photosynthesis but the factors causing the limitation in salt-stressed leaves remain unclear. In the present work, photosynthetic and biochemical traits were investigated in four rice genotypes under two NaCl concentration (0 and 150 mM) to assess the stomatal, mesophyll and biochemical contributions to reduced photosynthetic rate (A) in salt-stressed leaves. Our results indicated that salinity led to a decrease in A, leaf osmotic potential, electron transport rate and CO2 concentrations in the chloroplasts (Cc ) of rice leaves. Decreased A in salt-stressed leaves was mainly attributable to low Cc , which was determined by stomatal and mesophyll conductance. The increased stomatal limitation was mainly related to the low leaf osmotic potential caused by soil salinity. However, the increased mesophyll limitation in salt-stressed leaves was related to both osmotic stress and ion stress. These findings highlight the importance of considering mesophyll conductance when developing salinity-tolerant rice cultivars.


Assuntos
Dióxido de Carbono/metabolismo , Oryza/fisiologia , Fotossíntese/fisiologia , Cloroplastos/fisiologia , Difusão , Células do Mesofilo/fisiologia , Osmose , Folhas de Planta/fisiologia , Estômatos de Plantas/fisiologia , Salinidade , Cloreto de Sódio/metabolismo , Solo/química , Estresse Fisiológico
13.
Front Plant Sci ; 8: 1908, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29167676

RESUMO

Rice production is challenged by the asymmetric increases in day and night temperatures. Efforts are required to improve our understanding of the impact of climate change on rice production. To this end, 2-year experiment was conducted to evaluate the response of mid-season rice growth in the central and southern regions of China to elevated temperatures. Four replicates of four widely planted indica rice cultivars (Huanghuazhan: HHZ; Shanyou63: SY63; Yangliangyou6: YLY6; Liangyoupeijiu: LYPJ) were subjected to four elevated-temperature treatments (control: ambient temperature; NW: night-time warming; DW: daytime warming; AW: all-day warming) generated by an open-top hot-blast system under field conditions. This apparatus causes an ~2°C increase in the rice canopy temperature. Of all the elevated-temperature treatments, AW was the most devastating treatment for all rice cultivars, negatively affecting nearly all of investigated parameters, including grain yield and its components, dry matter accumulation, biomass, and harvest index (HI). The AW treatment decreased the grain yield by 11-35% and 43-78% in 2015 and 2016, respectively. No significant reduction in the grain yield was observed in the DW and NW treatments in 2015. However, the grain yield was decreased in DW and NW treatments by 20-52% and 18-55%, respectively, in 2016. Furthermore, the temperature-driven degradation of pollen viability, the number of pollen grains adhering to the stigma and pollen germination on the stigma caused spikelet sterility and thereby decreased the grain yield. The YLY6 and SY63 cultivars performed better than the HHZ and LYPJ cultivars with respect to grain yield and its components in all elevated-temperature treatments in both years. However, 42.97 and 61.01% reductions still occurred for the SY63 and YLY6 cultivars, respectively, in the AW treatment in 2016. The above results suggested that the elevated temperature may cause a noteworthy reduction in the productions of these widely planted genotypes in central and southern regions of China. To ensure the security of rice production in this region in an expected global warming environment, currently planted varieties will need to be replaced by heat-resistant varieties in the future.

14.
Front Plant Sci ; 8: 1369, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28848573

RESUMO

Remobilisation of non-structural carbohydrates (NSC) from leaves and stems and unloading into developing grains are essential for yield formation of rice. In present study, three recombinant inbred lines of rice, R91, R156 and R201 have been tested for source-flow-sink related attributes determining the nature of NSC accumulation and translocation at two nitrogen levels in the field. Compared to R91 and R156, R201 had lower grain filling percentage, harvest index, and grain yield. Meanwhile, R201 had significantly lower stem NSC translocation during grain filling stage. Grain filling percentage, harvest index, and grain yield showed the consistent trend with stem NSC translocation among the three lines. In comparison with R91 and R156, R201 had similarity in leaf area index, specific leaf weight, stem NSC concentration at heading, biomass, panicles m-2, spikelets per panicle, remobilization capability of assimilation in stems, sink capacity, sink activity, number and cross sectional area of small vascular bundles, greater number and cross sectional area of large vascular bundles, and higher SPAD, suggesting that source, flow, and sink were not the limiting factors for low stem NSC translocation and grain filling percentage of R201. However, R201 had significant higher stem and rachis NSC concentrations at maturity, which implied that unloading in the developing grains might result in low NSC translocation in R201. The results indicate that stem NSC translocation could be beneficial for enhancement of grain yield potential, and poor unloading into caryopsis may be the possible cause of low stem NSC translocation, poor grain filling and yield formation in R201.

15.
Sci Rep ; 7(1): 4878, 2017 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-28687785

RESUMO

Poor crop establishment of direct-seeded rice (DSR) is one of the major constraints to wide adoption of DSR, particularly in areas prone to flooding after sowing or where fields are not level. Seed pelleting is an effective, practical and facile technique to enhance crop establishment under unfavorable environmental conditions. To evaluate the effects of seed pelleting on rice germination, seedling growth and associated metabolic events under waterlogging stress, various seed pelleting treatments including formulae, pelleting times (the weight ratio of pelleting agents: rice seeds = 1:1~7:1 (w/w) and CaO2 contents were tested in series of experiments. Naked seeds were maintained for comparison as a control. Pelleting treatments with CaO2 significantly increased seed germination and seedling growth of DSR under waterlogging conditions compared with pelleted seeds without CaO2 and naked seeds. The optimum weight ratios of CaO2 to dry seeds were found to be in the range of 0.6:1-1:1 based on seed germination and seedling growth performance under waterlogging conditions. Under waterlogging conditions, high seed germination percentage and vigorous seedling growth of DSR due to seed pelleting with CaO2 was associated with an increase in α-amylase activity, but decrease in alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) activities in pelleted seeds.


Assuntos
Agricultura/métodos , Germinação , Oryza/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Peróxidos/metabolismo
16.
Sci Rep ; 7(1): 5782, 2017 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-28720786

RESUMO

The photosynthetic, biochemical, and anatomical traits of accumulation and replication of chloroplasts (arc) mutants of Arabidopsis thaliana were investigated to study the effects of chloroplast size and number on photosynthesis. Chloroplasts were found to be significantly larger, and the chloroplast surface area exposed to intercellular air spaces (S c) significantly lower in the mutants than in their wild-types. The decreased S c and increase cytoplasm thickness in the mutants resulted in a lower mesophyll conductance (g m) and a consequently lower chloroplast CO2 concentration (C c). There were no significant differences between the mutants and their wild-types in maximal carboxylation rate (V cmax), maximal electron transport (J cmax), and leaf soluble proteins. Leaf nitrogen (N) and Rubisco content were similar in both Wassilewskija (Ws) wild-type (Ws-WT) and the Ws mutant (arc 8), whereas they were slightly higher in Columbia (Col) wild-type (Col-WT) than the Col mutant (arc 12). The photosynthetic rate (A) and photosynthetic N use efficiency (PNUE) were significantly lower in the mutants than their wild-types. The mutants showed similar A/C c responses as their wild-type counterparts, but A at given C c was higher in Col and its mutant than in Ws and its mutant. From these results, we conclude that decreases in g m and C c are crucial to the reduction in A in arc mutants.


Assuntos
Arabidopsis/genética , Cloroplastos/genética , Mutação , Fotossíntese/genética , Arabidopsis/metabolismo , Dióxido de Carbono/metabolismo , Cloroplastos/metabolismo , Luz , Microscopia Eletrônica de Transmissão , Nitrogênio/metabolismo , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/ultraestrutura
17.
Front Plant Sci ; 8: 945, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28634485

RESUMO

Nitrogen is one of the most important elements for plants and is closely related to photosynthesis. High temperature stress significantly inhibits photosynthesis under both steady-state and flecked irradiance. However, it is not known whether nitrogen can affect the decrease in photosynthesis caused by high temperature, especially under flecked irradiance. In the present study, a pot experiment was conducted under two nitrogen (N) supplies with rice plants, and the steady-state and dynamic photosynthesis rates were measured under 28 and 40°C. High temperature significantly increased leaf hydraulic conductance (Kleaf) under high N supply (HN) but not under low N supply (LN). The increased Kleaf maintained a constant leaf water potential (Ψleaf) and steady-state stomatal conductance (gs,sat) under HN, while the Ψleaf and gs,sat significantly decreased under high temperature in LN conditions. This resulted in a more severe decrease in steady-state photosynthesis (Asat) under high temperature in the LN conditions. After shifting from low to high light, high temperature significantly delayed the recovery of photosynthesis, which resulted in more carbon loss under flecked irradiance. These effects were obtained under HN to a lesser extent than under LN supply. Therefore, it is concluded that nitrogen can alleviate the inhibition of photosynthesis caused by high temperature stress under both steady-state and flecked irradiance.

18.
Front Plant Sci ; 8: 371, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28367158

RESUMO

Cytokinins (CTKs) regulate panicle size and mediate heat tolerance in crops. To investigate the effect of high temperature on panicle CTK expression and the role of such expression in panicle differentiation in rice, four rice varieties (Nagina22, N22; Huanghuazhan, HHZ; Liangyoupeijiu, LYPJ; and Shanyou63, SY63) were grown under normal conditions and subjected to three high temperature treatments and one control treatment in temperature-controlled greenhouses for 15 days during the early reproductive stage. The high temperature treatments significantly reduced panicle CTK abundance in heat-susceptible LYPJ, HHZ, and N22 varieties, which showed fewer spikelets per panicle in comparison with control plants. Exogenous 6-benzylaminopurine application mitigated the effect of heat injury on the number of spikelets per panicle. The high temperature treatments significantly decreased the xylem sap flow rate and CTK transportation rate, but enhanced cytokinin oxidase/dehydrogenase (CKX) activity in heat-susceptible varieties. In comparison with the heat-susceptible varieties, heat-tolerant variety SY63 showed less reduction in panicle CTK abundance, an enhanced xylem sap flow rate, an improved CTK transport rate, and stable CKX activity under the high temperature treatments. Enzymes involved in CTK synthesis (isopentenyltransferase, LONELY GUY, and cytochrome P450 monooxygenase) were inhibited by the high temperature treatments. Heat-induced changes in CTK transportation from root to shoot through xylem sap flow and panicle CTK degradation via CKX were closely associated with the effects of heat on panicle CTK abundance and panicle size. Heat-tolerant variety SY63 showed stable panicle size under the high temperature treatments because of enhanced transport of root-derived CTKs and stable panicle CKX activity. Our results provide insight into rice heat tolerance that will facilitate the development of rice varieties with tolerance to high temperature.

19.
Sci Rep ; 7: 38982, 2017 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-28079051

RESUMO

Information on maximum grain yield and its attributes are limited for double-season rice crop grown under the subtropical environment. This study was conducted to examine key characteristics associated with high yielding double-season rice crop through a comparison between an integrated crop management (ICM) and farmers' practice (FP). Field experiments were conducted in the early and late seasons in the subtropical environment of Wuxue County, Hubei Province, China in 2013 and 2014. On average, grain yield in ICM was 13.5% higher than that in FP. A maximum grain yield of 9.40 and 10.53 t ha-1 was achieved under ICM in the early- and late-season rice, respectively. Yield improvement of double-season rice with ICM was achieved with the combined effects of increased plant density and optimized nutrient management. Yield gain of ICM resulted from a combination of increases in sink size due to more panicle number per unit area and biomass production, further supported by the increased leaf area index, leaf area duration, radiation use efficiency, crop growth rate, and total nitrogen uptake compared with FP. Further enhancement in the yield potential of double-season rice should focus on increasing crop growth rate and biomass production through improved and integrated crop management practices.


Assuntos
Agricultura/métodos , Grão Comestível/crescimento & desenvolvimento , Oryza/crescimento & desenvolvimento , China , Humanos
20.
Artigo em Inglês | MEDLINE | ID: mdl-26678834

RESUMO

The complete nucleotide sequence of Pinus tabuliformis chloroplast genome (cpDNA) was carried out using Illumina Hiseq 2500. The genome is 119 646 bp in length, and the overall base composition of H-strand is 30.6% for A, 19.3% for C, 19.2% for G and 30.9% for T. There are 116 genes in the cpDNA, including 74 protein-coding genes, four ribosomal RNA genes (four rRNA species), and 36 transfer RNA genes (20 tRNA species). Phylogenetic analyses of P. tabuliformis and other 12 species belonging to Pinales were carried out using MEGA 6.0 with Neighbor-Joining methods. The sequences of P. tabuliformis were clustered in subfamily Pinaceae.


Assuntos
Cloroplastos/genética , Genoma de Cloroplastos , Pinus/genética , Composição de Bases , China , DNA de Cloroplastos/química , DNA de Cloroplastos/isolamento & purificação , DNA de Cloroplastos/metabolismo , Fases de Leitura Aberta/genética , Filogenia , Pinus/classificação , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA Ribossômico/química , RNA Ribossômico/genética , RNA de Transferência/química , RNA de Transferência/genética , Análise de Sequência de DNA
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