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1.
Front Plant Sci ; 10: 818, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31293611

RESUMO

Drought is among the main environmental stressors that reduces wheat production. Nitrogen (N) availability affects plant adaptation to abiotic stress, but the effect of low N (LN) on drought tolerance is unclear. To identify the effect of LN priming on water-deficit stress tolerance in wheat seedlings, we primed cultivar Yangmai158 with 0.25 mM N for 7 days, and then added 20% polyethylene glycol 6000 as a water-deficit treatment for 5 days. The net photosynthetic rate (Pn), plant biomass, and plant growth rate (GR) were significantly reduced under water-deficit conditions; such decreases were less severe in LN-primed (LND) plants than non-primed (CKD) plants. The leaf relative water content (LRWC) decreased under water-deficit conditions, which in turn led to a reduced transpiration rate, stomatal conductance, and intercellular CO2 concentration (C i), causing a stomatal limitation on photosynthesis. LN priming also enhanced root growth, resulting in a higher LRWC and less stomatal limitation in LND plants than CKD plants. PSII quantum efficiency, photochemical quenching, and maximum PSII quantum efficiency were reduced under water-deficit conditions, indicating photoinhibition. However, LN priming increased the electron flux to photorespiration and the Mehler pathway, reducing photoinhibition. In conclusion, LN priming improved the leaf water status and increased alternative electron flux to attenuate photoinhibition, thus alleviating the inhibition of photosynthesis, and growth due to water deficiency.

2.
Front Plant Sci ; 10: 771, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31275335

RESUMO

To develop efficient N management strategies for high wheat NUE and minimizing the environmental impact of N losses under asymmetric warming, 15N micro-plot experiments were conducted to investigate the effects of night-warming during winter (warming by 1.47-1.56°C from tillering to jointing), spring (warming by 1.68-1.82°C from jointing to booting), and winter + spring (warming by 1.53-1.64°C from tillering to booting) on root growth and distribution of winter wheat, the fates of 15N-labeled fertilizer, and their relationships in 2015-2017. The results showed that night-warming increased the recovery of basal 15N and top-dressed 15N, while reduced the residual and loss of basal 15N and top-dressed 15N. The losses decreases of top-dressed 15N were higher than those of basal 15N, indicating that night-warming reduced losses of fertilizer 15N mainly by reducing losses of top-dressed 15N. Moreover, pre-anthesis root dry matter accumulation rate in 0-60 cm soil layer were promoted, resulted in improved root biomass and root/shoot ratio, which favored increasing recovery of fertilizer 15N and reducing losses of fertilizer 15N. Furthermore, residual fertilizer 15N content in 0-100 cm soil layer was reduced, which was associated with improved root weight density in 0-60 cm soil layer, resulted in reduced leaching losses of fertilizer 15N. The path analysis showed that root dry matter distribution in 0-20 cm soil layer was the most important in contributing to reducing losses of total fertilizer 15N compared with other soil layers. Two years data showed that winter and spring night-warming gave better root growth and distribution in 0-20 cm soil layer, resulted in reduced the losses of fertilizer 15N and improved the recovery of fertilizer 15N, while maximizing grain yield of winter wheat, and winter + spring night-warming resulted in higher advantages than winter night-warming and spring night-warming.

3.
Food Chem ; 277: 135-144, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30502129

RESUMO

Nitrogen fertilization regimes significantly affect both grain quality and yield. Wheat plants were subjected to different application timing of topdressed nitrogen at the emergence of the top fifth (TL5), top third (TL3) and top first leaf (TL1), respectively. The iTRAQ (isobaric tag for relative and absolute quantitation) technology was adopted to obtain the complete proteome of wheat flour and to identify the differentially expressed proteins (DEPs) as regulated by nitrogen topdressing timing. Collectively, 591 proteins into 17 functional categories in flour of mature grains were identified. In comparison to TL3, 50 and 63 DEPs were identified in TL5 and TL1, respectively. Nine of the DEPs commonly dependent on nitrogen topdressing timing are the γ-gliadins or high-molecular-weight glutenin subunits. Additionally, delaying nitrogen topdressing modified the grain hardness and allergic protein content. The results suggested that altering nitrogen topdressing timing is a potential strategy for pursuing targeted processing quality of wheat flour.


Assuntos
Grão Comestível/efeitos dos fármacos , Grão Comestível/metabolismo , Glutens/metabolismo , Dureza/efeitos dos fármacos , Nitrogênio/farmacologia , Farinha/análise , Qualidade dos Alimentos , Folhas de Planta/metabolismo , Proteômica , Fatores de Tempo
4.
Physiol Plant ; 167(2): 159-172, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30430601

RESUMO

No single mechanism can provide an adequate explanation for the inhibition of photosynthesis when plants are supplied with ammonium (NH4 + ) as the sole nitrogen (N) source. We performed a hydroponic experiment using two N sources [5 mM NH4 + and 5 mM nitrate (NO3 - )] to investigate the effects of NH4 + stress on the photosynthetic capacities of two wheat cultivars (NH4 + -sensitive AK58 and NH4 + -tolerant XM25). NH4 + significantly inhibited the growth and light-saturated photosynthesis (Asat ) of both cultivars, but the extent of such inhibition was greater in the NH4 + -sensitive AK58. The CO2 concentration did not limit CO2 assimilation under NH4 + nutrition; though both stomatal and mesophyll conductance were significantly suppressed. Carboxylation efficiency (CE), light-saturated potential rate of electron transport (Jmax ), the quantum efficiency of PSII (ΦPSII ), electron transport rate through PSII [Je(PSII)], and Fv /Fm were significantly reduced by NH4 + . As a result, NH4 + nutrition resulted in a significant increase in the production of hydrogen peroxide (H2 O2 ) and superoxide anion radicals (O2 •- ), but these symptoms were less severe in the NH4 + -tolerant XM25, which had a higher capacity of removing elevated reactive oxygen species (ROS). Thus, NH4 + N sources might decreased electron transport efficiency and increased the production of ROS, exacerbating damage to the electron transport chain, leading to a reduced plant photosynthetic capacity.


Assuntos
Compostos de Amônio/farmacologia , Nitratos/farmacologia , Nitrogênio/metabolismo , Fotossíntese/efeitos dos fármacos , Triticum/fisiologia , Transporte de Elétrons/efeitos dos fármacos , Hidroponia , Plântula/fisiologia , Estresse Fisiológico
5.
BMC Plant Biol ; 18(1): 353, 2018 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-30545290

RESUMO

BACKGROUND: Nitrogen is one basic element of amino acids and grain protein in wheat. In field experiments, wheat plants were subjected to different timing of nitrogen topdressing treatments: at the stages of emergence of the top fifth leaf (TL5), top third leaf (TL3) and top first leaf (TL1) to test the regulatory effects of nitrogen topdressing timing on grain protein quality. The underlying mechanisms were elucidated by clarifying the relationship between proteolysis in vegetative organs and accumulation of amino acids in the endosperm cavity, conversion of amino acids, and storage protein synthesis in endosperm of wheat grain. RESULTS: Delayed nitrogen topdressing up-regulated gene expression related to nitrogen metabolism and protease synthesis in the flag leaf, followed by more free amino acids being transported to both the cavity and the endosperm from 7 days after anthesis (DAA) to 13 DAA in TL1. TL1 enhanced the conversion between free amino acids in endosperm and upregulated the expression of genes encoding high molecular weight (HMW) and low molecular weight (LMW) subunits and protein disulfide isomerases-like (PDIL) proteins, indicating that the synthesis and folding of glutenin were enhanched by delayed nitrogen topdressing. As a consequense, the content of glutenin macropolymers (GMP) and glutenin increased with delaying nitrogen topdressing. CONCLUSIONS: The results highlight the relationship between nitrogen remobilization and final grain protein production and suggest that the nitrogen remobilization processes could be a potential target for improving the quality of wheat grain. Additionally, specific gene expression related to nitrogen topdressing was identified, which conferred more detailed insights into underlying mechanism on the modification protein quality.


Assuntos
Aminoácidos/metabolismo , Grão Comestível/metabolismo , Nitrogênio/metabolismo , Proteínas de Plantas/metabolismo , Triticum/metabolismo , Aminoácidos/análise , Grão Comestível/química , Endosperma/química , Endosperma/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Nitrogênio/administração & dosagem , Folhas de Planta/metabolismo , Reação em Cadeia da Polimerase em Tempo Real
6.
J Exp Bot ; 69(22): 5477-5488, 2018 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-30239847

RESUMO

Studying the response of photosynthesis to low nitrogen (N) and the underlying physiological mechanism can provide a theoretical basis for breeding N-efficient cultivars and optimizing N management. We conducted hydroponic experiments using two wheat (Triticum aestivum) cultivars, Zaoyangmai (low N sensitive) and Yangmai158 (low N tolerant), with either 0.25 mM N as a low N (LN) treatment or 5 mM N as a control. Under LN, a decrease in net photosynthetic rate (Pn) was attributed to reduction in the maximum Rubisco carboxylation rate, which then accelerated a reduction in the maximum ribulose-1,5-bisphosphate regeneration rate, and the reduction in Pn was 5-35% less in Yangmai158 than in Zaoyangmai. Yangmai158 maintained a 10-25% higher Rubisco concentration, especially in the upper leaves, and up-regulated Rubisco activase activity compared with Zaoyangmai to increase the Rubisco activation to sustain Rubisco carboxylation under LN conditions. In addition, Yangmai158 increased electron flux to the photorespiratory carbon oxidation cycle and alternative electron flux to maintain a faster electron transport rate and avoid photodamage. In conclusion, the LN-tolerant cultivar showed enhanced Rubisco activation and sustained electron transport to maintain a greater photosynthetic capacity under LN conditions.


Assuntos
Nitrogênio/deficiência , Fotossíntese , Ribulose-Bifosfato Carboxilase/metabolismo , Triticum/fisiologia , Transporte de Elétrons , Plântula/crescimento & desenvolvimento , Plântula/fisiologia , Triticum/crescimento & desenvolvimento
7.
Plant Physiol Biochem ; 132: 222-228, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30218894

RESUMO

Waterlogging is one of the most common abiotic stress types in wheat production in many rainy areas of the world. Two locally widely grown winter wheat (Triticum aestivum L. cv Yumai 34 and Yangmai 9) were subjected to post-anthesis waterlogging in a pot experiment to investigate the impacts of waterlogging on the starch synthesis and the physiochemical properties. Post-anthesis waterlogging significantly decreased grain weight and affected the content of starch components. Waterlogging down-regulated the activity and expression of genes encoding soluble starch synthase [SSS (EC 2.4.1.21)], while up-regulated those of the granule bound starch synthase I [GBSSI (EC:2.4.1.242)]. This further resulted in decreased amylopectin content and increased amylose content. Waterlogging also caused a reduction in the number of starch granules, while increased the mean diameter of starch granules in mature grains, which was mainly due to an increase in the volume frequency percent of the A-type starch granules. Waterlogging also lowered the peak viscosity and trough viscosity of starch, but did not affect the breakdown viscosity and peak time. We concluded that the modified expressions of the starch synthase encoding genes were responsible for the changed size distribution of starch granules, which finally affected the starch pasting properties of wheat growing under post-anthesis waterlogging conditions.


Assuntos
Sementes/metabolismo , Amido/biossíntese , Amido/química , Triticum/metabolismo , Água , Farinha , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Sintase do Amido/genética , Sintase do Amido/metabolismo , Triticum/enzimologia , Triticum/genética , Viscosidade
8.
Front Plant Sci ; 9: 1137, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30123235

RESUMO

Salicylic acid (SA) can induce plant resistance to biotic and abiotic stresses through cross talk with other signaling molecules, whereas the interaction between hydrogen peroxide (H2O2) and abscisic acid (ABA) in response to SA signal is far from clear. Here, we focused on the roles and interactions of H2O2 and ABA in SA-induced freezing tolerance in wheat plants. Exogenous SA pretreatment significantly induced freezing tolerance of wheat via maintaining relatively higher dark-adapted maximum photosystem II quantum yield, electron transport rates, less cell membrane damage. Exogenous SA induced the accumulation of endogenous H2O2 and ABA. Endogenous H2O2 accumulation in the apoplast was triggered by both cell wall peroxidase and membrane-linked NADPH oxidase. The pharmacological study indicated that pretreatment with dimethylthiourea (H2O2 scavenger) completely abolished SA-induced freezing tolerance and ABA synthesis, while pretreatment with fluridone (ABA biosynthesis inhibitor) reduced H2O2 accumulation by inhibiting NADPH oxidase encoding genes expression and partially counteracted SA-induced freezing tolerance. These findings demonstrate that endogenous H2O2 and ABA signaling may form a positive feedback loop to mediate SA-induced freezing tolerance in wheat.

9.
Front Plant Sci ; 9: 805, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29951079

RESUMO

Heat stress during grain filling substantially decreases wheat productivity; thus, to ensure food security, heat tolerance in wheat needs to be developed. In this study, we evaluated the effect of heat priming applied during the stem-elongation stage, booting and anthesis, followed by 5 days of severe heat stress (a 7.86°C rise in temperature) during the grain-filling stage on physiological activities and grain yield of winter wheat in pot experiments during the 2015-2017 growing seasons using the winter wheat cultivars Yangmai 18 (a vernal type) and Yannong 19 (a facultative type). Compared with the damage observed in non-primed plants, heat priming during the stem-elongation stage and booting significantly prevented the grain-yield damage caused by heat stress during grain filling. Heat-primed plants displayed higher sucrose contents and sucrose-phosphate activity in leaves and greater above-ground dry matter than non-primed plants. Priming during stem elongation and booting led to increased photosynthetic capacity, stomatal conductance and chlorophyll contents in comparison with non-priming. Improved tolerance to heat stress due to the enhanced activities of antioxidant enzymes superoxide dismutase and peroxidase and reductions in reactive oxygen species and malondialdehyde production was observed in primed plants compared with non-primed plants of both cultivars. The positive effect of heat priming on the response to heat stress during grain filling was more pronounced in plants primed at the booting stage than in those primed at the stem-elongation or anthesis stage. Moreover, the vernal-type Yangmai 18 benefited more from heat priming than did Yannong 19, as evidenced by its higher productivity. We conclude that heat priming during early reproductive-stage growth can improve post-anthesis heat tolerance in winter wheat.

10.
Front Plant Sci ; 9: 327, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29593774

RESUMO

Systemic wound response (SWR), a well-characterized systemic signaling response, plays crucial roles in plant defense responses. Progress in understanding of the SWR in abiotic stress has also been aided by the researchers. However, the function of SWR in freezing stress remains elusive. In this study, we showed that local mild mechanical wounding enhanced freezing tolerance in newly occurred systemic leaves of wheat plants (Triticum aestivum L.). Wounding significantly increased the maximal photochemical efficiency of photosystem II, net photosynthetic rate, and the activities of the antioxidant enzymes under freezing stress. Wounding also alleviated freezing-induced chlorophyll decomposition, electrolyte leakage, water lose, and membrane peroxidation. In addition, wounding-induced freezing stress mitigation was closely associated with the ratio between reduced glutathione (GSH) and oxidized glutathione (GSSG), and the ratio between ascorbate (AsA) and dehydroascorbate (DHA), as well as the contents of total soluble sugars and free amino acids. Importantly, pharmacological study showed that wounding-induced freezing tolerance was substantially arrested by pretreatment of wheat leaves with the scavenger of hydrogen peroxide (H2O2) or the inhibitor of NADPH oxidase (RBOH). These results support the hypothesis that local mechanical wounding-induced SWR in newly occurred leaves is largely attributed to RBOH-dependent H2O2 production, which may subsequently induce freezing tolerance in wheat plants. This mechanism may have a potential application to reduce the yield losses of wheat under late spring freezing conditions. Highlights: In our previous research, we found that local mechanical wounding could induce freezing tolerance in the upper systemic leaves of wheat plants. Surprisingly, in this paper, we further demonstrated that local mechanical wounding could also increase freezing resistance in newly occurred leaves of wheat plants. RBOH mediated H2O2 and ascorbate-glutathione cycle participate in this systemic wound response.

11.
Sci Rep ; 8(1): 4615, 2018 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-29545536

RESUMO

Defining the metabolic strategies used by wheat to tolerate and recover from drought events will be important for ensuring yield stability in the future, but studies addressing this critical research topic are limited. To this end, the current study quantified the physiological, biochemical, and agronomic responses of a drought tolerant and drought sensitive cultivar to periods of water deficit and recovery. Drought stress caused a reversible decline in leaf water relations, membrane stability, and photosynthetic activity, leading to increased reactive oxygen species (ROS) generation, lipid peroxidation and membrane injury. Plants exhibited osmotic adjustment through the accumulation of soluble sugars, proline, and free amino acids and increased enzymatic and non-enzymatic antioxidant activities. After re-watering, leaf water potential, membrane stability, photosynthetic processes, ROS generation, anti-oxidative activities, lipid peroxidation, and osmotic potential completely recovered for moderately stressed plants and did not fully recover in severely stressed plants. Higher photosynthetic rates during drought and rapid recovery after re-watering produced less-pronounced yield declines in the tolerant cultivar than the sensitive cultivar. These results suggested that the plant's ability to maintain functions during drought and to rapidly recover after re-watering during vegetative periods are important for determining final productivity in wheat.


Assuntos
Adaptação Fisiológica , Secas , Fotossíntese , Folhas de Planta/fisiologia , Estresse Fisiológico , Triticum/fisiologia , Antioxidantes/metabolismo , Peroxidação de Lipídeos , Espécies Reativas de Oxigênio/metabolismo , Triticum/crescimento & desenvolvimento
12.
Front Plant Sci ; 9: 261, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29545817

RESUMO

Drought is the major abiotic stress that decreases plant water status, inhibits photosynthesis, induces oxidative stress, restricts growth and finally lead to the reduction of wheat yield. It has been proven that drought priming during vegetative growth stage could enhance tolerance to drought stress at grain filling in wheat. However, whether drought priming imposed at grain filling in parental plants could induce drought tolerance in the offspring is not known. In this study, drought priming was successively applied in the first, the second and the third generation of wheat to obtain the plants of T1 (primed for one generation), T2 (primed for two generations), T3 (primed for three generations). The differently primed plants were then subjected to drought stress during grain filling in the fourth generation. Under drought stress, the parentally primed (T1D, T2D, T3D) plants, disregarding the number of generations, showed higher grain yield, leaf photosynthetic rate and antioxidant capacity as well as lower [Formula: see text] release rate and contents of H2O2 and MDA than the non-primed (T0D) plants, suggesting that drought priming induced the transgenerational stress tolerance to drought stress. Moreover, the parentally primed plants showed higher leaf water status, which may result from the higher contents of proline and glycine betaine, and higher activities of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and betaine aldehyde dehydrogenase (BADH), compared with the non-primed plants under drought stress. In addition, there was no significant difference among three generations under drought, and the drought priming in parental generations did not affect the grain yield of the offspring plants under control condition. Collectively, the enhanced accumulation of proline and glycine betaine in the parentally primed plants could have played critical roles in parental priming induced tolerance to drought stress. This research provided a potential approach to improve drought tolerance of offspring plants by priming parental plants.

13.
Funct Plant Biol ; 45(8): 840-853, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32291066

RESUMO

Excess N input results in low N use efficiency and environmental crisis, so nitrogenous fertiliser applications must be reduced. However, this can lead to low-N stress. Previous studies on low N have not explored the unique adjustment strategy to N deficiency in the short term, which is important for developing long-term N deficiency tolerance. In this case, two wheat (Triticum aestivum L.) cultivars with different tolerances to low N, Zaoyangmai (sensitive) and Yangmai158 (tolerant), were exposed to 0.25mM N as a N-deficient condition with 5.0mM N as a control. Under long-term N-deficient conditions, a significant decrease in Rubisco content resulted in decreased Rubisco activity and net photosynthetic rate (Pn) in both cultivars. However, the NO3-:soluble protein ratio decreased, and nitrate reductase and glutamine synthetase activity increased under short-term N deficiency, especially in Yangmai158. As a result, Rubisco content was not decreased in Yangmai158, while total N content decreased significantly. Moreover, increased Rubisco activase activity promoted Rubisco activation under short-term N deficiency. In sequence, Rubisco activity and Pn improved under short-term N deficiency. In conclusion, N deficiency-tolerant cultivars can efficiently assimilate N to Rubisco and enhance Rubisco activation to improve photosynthetic capabilities under short-term N deficiency conditions.

14.
Front Plant Sci ; 8: 1284, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28769973

RESUMO

Mechanical wounding is a common stress caused by herbivores or manual and natural manipulations, whereas its roles in acclimation response to a wide spectrum of abiotic stresses remain unclear. The present work showed that local mechanical wounding enhanced freezing tolerance in untreated systemic leaves of wheat plants (Triticum aestivum L.), and meanwhile the signal molecules hydrogen peroxide (H2O2) and nitric oxide (NO) were accumulated systemically. Pharmacological study showed that wounding-induced NO synthesis was substantially arrested by pretreatment with scavengers of reactive oxygen species and an inhibitor of NADPH oxidase (respiratory burst oxidase homolog, RBOH). On the contrary, wounding-induced H2O2 accumulation was not sensitive to NO synthetic inhibitors or scavenger, indicating that H2O2 acts upstream of NO in wounding signal transduction pathways. Cytochemical and vascular tissues localizations approved that RBOH-dependent H2O2 acts as long-distance signal in wounding response. Transcriptome analysis revealed that 279 genes were up-regulated in plants treated with wounding and freezing, but not in plants treated with freezing alone. Importantly, freezing- and wounding-induced genes were significantly enriched in the categories of "photosynthesis" and "signaling." These results strongly supported that primary mechanical wounding can induce freezing tolerance in wheat through the systemic accumulation of NO and H2O2, and further modifications in photosystem and antioxidant system.

15.
Front Plant Sci ; 8: 992, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28659943

RESUMO

The diurnal and seasonal temperature rising patterns "asymmetric warming," plays an important role in crop distribution and productivity. Asymmetric warming during the early growth periods of winter wheat (Triticum aestivum L.) profoundly affects vegetative growth and post-anthesis grain productivity, but the underlying physiological mechanism is still unclear. We conducted field experiments from 2012 to 2014 using two wheat cultivars, namely, Yangmai-13 (vernal type) and Yannong-19 (semi-winter type), to investigate the influences of night-warming during the winter (warming by 1.56-1.67°C from tillering to jointing) or during the spring (warming by 1.78-1.92°C from jointing to booting) on post-anthesis physiological activities and grain-filling processes. Both night-warming treatments enhanced the source activity by increasing flag leaf area, chlorophyll content, and photosynthetic capability in both cultivars compared with those of the control. The night-warming treatments caused an increase in the antioxidant activities of superoxide dismutase (SOD), peroxidase, and catalase (CAT) in the flag leaves of both cultivars, while ROS contents such as superoxide anion radical ([Formula: see text]) and hydrogen peroxide (H2O2) decreased. Moreover, the expression levels of Rubisco activase B (RcaB), major chlorophyll a/b-binding protein (Cab), chloroplast Cu/Zn superoxide dismutase (Cu/Zn-SOD), mitochondrial manganese superoxide dismutase (Mn-SOD), and CAT genes were upregulated at anthesis and were associated with higher photosynthetic capacity and antioxidant activities. Furthermore, night-warming improved sink activities by increasing the concentrations of grain indole-3-acetic acid and cytokinins as well as the sucrose synthase activity for both cultivars. Winter night-warming showed greater potential for improving source strength and grain filling, with consistent performance in both cultivars compared with that of spring night-warming. We concluded form these results that night-warming can improve source and sink capacities in winter wheat, and winter night-warming has greater advantages in this respect than does spring warming.

16.
Planta ; 246(3): 509-524, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28526982

RESUMO

MAIN CONCLUSION: Drought stress during grain filling is the most yield-damaging to wheat. Pre-drought priming facilitated the wheat plants to sustain grain development against the post-anthesis drought stress by modulating the levels of growth hormones. Post-anthesis drought stress substantially reduces grain yield in wheat (Triticum aestivum L.) due to impaired grain development associated with imbalanced levels of growth hormones. To investigate whether pre-drought priming could sustain grain development in wheat by regulating favorable levels of growth hormones under post-anthesis drought conditions, the plants of a drought-sensitive (Yangmai-16) and drought-tolerant (Luhan-7) wheat cultivar were exposed to a moderate drought stress during tillering (Feekes 2 stage) for priming, and then, a subsequent severe drought stress was applied from 7 to 14 days after anthesis. The results showed that drought-stressed plants of both cultivars showed a decline in flag leaf water potential, chlorophyll contents, photosynthetic rate, grain size initiation, and grain filling as compared to well-watered plants; however, decline in these traits was less in pre-drought primed (PD) plants than in nonprimed (ND) plants. Under drought stress, the PD plants regulated higher concentrations of zeatin and zeatin riboside, indole-3-acetic acid, gibberellins, and lower abscisic acid content in grains, resulting in higher endosperm cell division and expansion, grain size initiation, grain-filling rate and duration, and finally higher grain dry weights as compared to ND plants. The PD plants of both cultivars showed higher potential to tolerate the post-anthesis drought stress, but more effect was displayed by drought-tolerant cultivar. From the achieved results, it was concluded that pre-drought priming facilitated the wheat plants to sustain higher grain development and yield against the most yield-damaging post-anthesis drought stress by modulating the levels of growth hormones.


Assuntos
Reguladores de Crescimento de Planta/fisiologia , Sementes/crescimento & desenvolvimento , Triticum/fisiologia , Divisão Celular , Clorofila/análise , Desidratação , Secas , Endosperma/citologia , Fotossíntese , Folhas de Planta/química , Folhas de Planta/fisiologia , Triticum/crescimento & desenvolvimento , Água/metabolismo
17.
Plant Physiol Biochem ; 108: 447-455, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27569412

RESUMO

Because soil acidification accompanies ammonium (NH4+) stress, the tolerance of higher plants to ammonium is associated with their adaptation to root medium acidification. However, the underlying mechanisms of this adaptation have not been fully elucidated. The objective of this study was thus to elucidate the effect of rhizosphere pH on NH4+ tolerance in different winter wheat cultivars (Triticum aestivum L.). Hydroponic experiments were carried out on two wheat cultivars: AK58 (an NH4+-sensitive cultivar) and XM25 (an NH4+-tolerant cultivar). Four pH levels resembling acidified (4.0, 5.0, 6.0 and 7.0) were tested and 5 mM NH4+ nitrogen (AN) was used as a stress treatment, with 5 mM nitrate nitrogen used as a control. The addition of AN led to a severe reduction in biomass and an increase in free NH4+, amino acids, and the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in the shoots and roots of the two wheat cultivars. Further decreases in growth medium pH led to further increases in free NH4+, but decreases in total amino acids and the activities of GS and NADH-dependent glutamate synthase (NADH-GDH). However, there was less of an increase in free NH4+ and less of a reduction in the activities of GS and NADH-GDH in the cultivar XM25 compared with AK58. In addition, total soluble sugar content and the root-to-shoot soluble sugar ratio were also decreased by AN treatment, except in the shoots of XM25. Decreasing pH resulted in lower root-to-shoot soluble sugar ratios with greater reductions in the AK58 cultivar. These results indicate that wheat growth was inhibited significantly by the addition of NH4+ combined with low pH. Low medium pH reduced the capacity for nitrogen assimilation and interrupted carbohydrate transport between the shoot and root. The NH4+-tolerant cultivar XM25 was better adapted to low rhizosphere pH due to its increased capacity for assimilating NH4+ efficiently and thereby avoiding toxic levels of intracellular NH4+ at low medium pH.


Assuntos
Adaptação Fisiológica , Compostos de Amônio/farmacologia , Rizosfera , Plântula/fisiologia , Triticum/fisiologia , Aminoácidos/metabolismo , Compostos de Amônio/farmacocinética , Biomassa , Glutamato Desidrogenase/metabolismo , Glutamato-Amônia Ligase/metabolismo , Concentração de Íons de Hidrogênio , Hidroponia/métodos , Monossacarídeos/análise , Monossacarídeos/metabolismo , NAD/metabolismo , Nitrogênio/metabolismo , Plântula/efeitos dos fármacos , Estresse Fisiológico , Triticum/efeitos dos fármacos
18.
PLoS One ; 11(8): e0160997, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27512992

RESUMO

Most of the studies about NH4+ stress mechanism simply address the effects of free NH4+, failing to recognize the changed nitrogen assimilation products. The objective of this study was to elucidate the effects of glutamate on root growth under high ammonium (NH4+) conditions in winter wheat (Triticum aestivum L.). Hydroponic experiments were conducted using two wheat cultivars, AK58 (NH4+-sensitive) and Xumai25 (NH4+-tolerant) with either 5 mM NH4+ nitrogen (AN) as stress treatment or 5 mM nitrate (NO3-) nitrogen as control. To evaluate the effects of NH4+-assimilation products on plant growth, 1 µM L-methionine sulfoximine (MSO) (an inhibitor of glutamine synthetase (GS)) and 1 mM glutamates (a primary N assimilation product) were added to the solutions, respectively. The AN significantly reduced plant biomass, total root length, surface area and root volume in both cultivars, but less effect was observed in Xumai25. The inhibition effects were alleviated by the application of MSO but strengthened by the application of glutamate. The AN increased the activities of GS, glutamate dehydrogenase (GDH) in both cultivars, resulting in higher glutamate contents. However, its contents were decreased by the application of MSO. Compared to AK58, Xumai25 showed lower glutamate contents due to its higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). With the indole-3-acetic acid (IAA) contents decreasing in roots, the ratio of shoot to root in IAA was increased, and further increased by the application of glutamate, and reduced by the application of MSO, but the ratio was lower in Xumai25. Meanwhile, the total soluble sugar contents and its root to shoot ratio also showed similar trends. These results indicate that the NH4+-tolerant cultivar has a greater transamination ability to prevent glutamate over-accumulation to maintain higher IAA transport ability, and consequently promoted soluble sugar transport to roots, further maintaining root growth.


Assuntos
Compostos de Amônio/farmacologia , Glutamato Desidrogenase/antagonistas & inibidores , Glutamato-Amônia Ligase/antagonistas & inibidores , Ácido Glutâmico/farmacologia , Raízes de Plantas/crescimento & desenvolvimento , Triticum/crescimento & desenvolvimento , Alanina Transaminase/metabolismo , Aminação , Aspartato Aminotransferases/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/efeitos dos fármacos , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Triticum/efeitos dos fármacos
19.
Front Plant Sci ; 7: 942, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27446169

RESUMO

The distribution patterns of total protein and protein components in different layers of wheat grain were investigated using the pearling technique, and the sources of different protein components and pearling fractions were identified using (15)N isotope tracing methods. It was found that N absorbed from jointing to anthesis (JA) and remobilized to the grain after anthesis was the principal source of grain N, especially in the outer layer. For albumin and globulin, the amount of N absorbed during different stages all showed a decreasing trend from the surface layer to the center part. Whereas, for globulin and glutenin, the N absorbed after anthesis accounted for the main part indicating that for storage protein, the utilization of N assimilated after anthesis is greater than that of the stored N assimilated before anthesis. It is concluded that manipulation of the N application rate during different growth stages could be an effective approach to modulate the distribution of protein fractions in pearled grains for specific end-uses.

20.
Front Plant Sci ; 7: 981, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27446197

RESUMO

Efficient nitrogen (N) nutrition has the potential to alleviate drought stress in crops by maintaining metabolic activities even at low tissue water potential. This study was aimed to understand the potential of N to minimize the effects of drought stress applied/occur during tillering (Feekes stage 2) and jointing (Feekes stage 6) growth stages of wheat by observing the regulations and limitations of physiological activities, crop growth rate during drought periods as well as final grain yields at maturity. In present study, pot cultured plants of a wheat cultivar Yangmai-16 were exposed to three water levels [severe stress at 35-40% field capacity (FC), moderate stress at 55-60% FC and well-watered at 75-80% FC] under two N rates (0.24 g and 0.16 g/kg soil). The results showed that the plants under severe drought stress accompanied by low N exhibited highly downregulated photosynthesis, and chlorophyll (Chl) fluorescence during the drought stress periods, and showed an accelerated grain filling rate with shortened grain filling duration (GFD) at post-anthesis, and reduced grain yields. Severe drought-stressed plants especially at jointing, exhibited lower Chl and Rubisco contents, lower efficiency of photosystem II and greater grain yield reductions. In contrast, drought-stressed plants under higher N showed tolerance to drought stress by maintaining higher leaf water potential, Chl and Rubisco content; lower lipid peroxidation associated with higher superoxide dismutase and ascorbate peroxidase activities during drought periods. The plants under higher N showed delayed senescence, increased GFD and lower grain yield reductions. The results of the study suggested that higher N nutrition contributed to drought tolerance in wheat by maintaining higher photosynthetic activities and antioxidative defense system during vegetative growth periods.

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