Anoxia Tolerance and Sugar Level in Roots and Coleoptiles of Aerobically Germinated Rice

Abstract

The root and coleoptile growth of aerobically germinated rice (Oryza sativa L.) seedlings was suppressed by anoxic stress, but the suppression was more conspicuous in roots than in coleoptiles. In this study, the physiological and metabolic responses of roots to anoxia were compared with those of coleoptiles in aerobically germinated rice seedlings. ATP concentration in the coleoptiles was higher than that in the roots under anoxia. Alcohol dehydrogenase activity and ethanol concentration in the coleoptiles were also higher than in the roots under anoxia, which suggest that ethanolic fermentation may be more active in the coleoptiles than in the roots where glycolysis and ethanolic fermentation are the main source of ATP production. Activity of α-amylase, which mobilized reserved starch in the seeds, was not detected in the roots and coleoptiles of rice seedlings either under aerobic or anoxic conditions. However, α-amylase activity was found in endosperms of the rice seedlings even under anoxia. The α-amylase activity in anoxic endosperms was 64% of that in aerobic endosperms. Sugar concentration in the anoxic coleoptiles was higher than that in the anoxic roots. ATP and ethanol concentrations in the roots and coleoptiles of rice seedlings were correlated well with sugar concentrations in the roots and coleoptiles, which also showed a good correlation with anoxia tolerance of roots and coleoptiles with respect to elongation. These results suggest that the sugar level may be important for the anoxia tolerance of the roots and coleoptiles since the availability of sugar is essential for the operation of ethanolic fermentation leading to ATP production under anoxia, and it may serve to distinguish the anoxia tolerance of the roots and coleoptiles of the rice seedlings.     

水稻出苗顶土动力源研究

在自然条件下,通过设计不同的出苗阻力（覆土深度2 cm、4 cm和6 cm）来测定中胚轴伸长潜力不同的水稻种质的出苗速度、成苗率和芽鞘节及中胚轴的长度,以分析影响水稻种子顶土出苗的动力源。结果表明,水稻种子的出苗动力主要来源于芽鞘节间和中胚轴的伸长。在不同阻力处理条件下,不同种质出苗动力差异较大,其中覆土2 cm的不同种质出苗率相差不明显,与室内发芽率结果比较接近,覆土4 cm和覆土6 cm的两个处理不同种质间出苗率差异明显,长胚轴种质出苗速度快,出苗率高,出苗率与室内发芽率相差不大;而短胚轴种质出苗速度慢,出苗率低,其中春江683的出苗率与室内发芽率相比分别下降了6.5和86.2个百分点。研究表明水稻中胚轴的伸长对覆土较深的种子顶土出苗起到关键作用,长胚轴种质顶土出苗动力来自于芽鞘节与中胚轴的共同作用,出苗动力强;而短胚轴顶土出苗动力主要来源于芽鞘节的伸长,出苗动力较弱。还对通过选育长胚轴直播稻品种解决直播稻易倒伏和出苗差等难题的可能性进行了探讨。     

欧山羊草6Ub染色体附加对小麦萌发期抗旱性的改良作用

为探究欧山羊草U~b染色体附加对普通小麦抗旱性的遗传改良作用,选取2个普通小麦-欧山羊草异附加系(Ae9041和Ae9061,均附加了一对6U~b染色体)和3个普通小麦品种为材料,以聚乙二醇(PEG6000)模拟干旱胁迫,研究了不同小麦材料干旱胁迫后种子发芽势、发芽率、胚芽鞘长度、种子根数、胚根长度、幼苗高度以及贮藏物质利用率等抗旱相关指标的变化。结果表明,干旱胁迫抑制了各供试材料的种子萌发,且胁迫程度越大,抑制越明显。在相同浓度PEG6000处理下,两个异附加系的种子发芽势、发芽率和贮藏物质利用率的表现较为一致,且差异不显著。与耐旱品种晋麦47和节水品种石4185相比,Ae9041和Ae9061的幼苗胚芽鞘长、种子发芽率和贮藏物质利用率在干旱胁迫下均较高。在30%PEG6000胁迫下,Ae9041和Ae9061的种子发芽势、发芽率、幼苗胚芽鞘长、胚根长、幼苗高度均显著高于亲本中国春。由此可见,普通小麦-欧山羊草异附加系种子在干旱胁迫下能迅速吸水并整齐萌发,以发达的根系和较长的胚芽鞘促进幼苗地上部生长,并将胚乳营养快速转运至幼苗中,从而促进其较快地进行形态建成,也说明欧山羊草U~b染色体的附加能够改良小麦萌发期的抗旱性。     

α-Amylase Activity and Soluble Sugar Supply from Endosperm in Relation to Varietal Differences in Seedling Establishment under Low-Temperature Conditions in Rice (Oryza sativa L.)

Abstract

We examined 𰂱-amylase(EC 3.2.1.1) activity in endosperm in 6 varieties of rice (Oryza sativa L.), which showed different seedling establishment traits in field experiments, using seedlings grown in sterilized agar-bed at 16ºC. At the coleoptile elongation stage and the first leaf elongation stage, there were significant differences in 𰂱-amylase activity among the varieties investigated. However, the varietal difference in 𰂱-amylase activity at the coleoptile elongation stage did not correspond with that in coleoptile growth. Maltose, the immediate product of 𰂱 -amylase activity, accumulated in the endosperm at the coleoptile elongation stage in a greater amount in Fukuhibiki, which has a poor seedling establishment trait, than in Arroz da Terra, which has a superior seedling establishment trait. The concentration of glucose detected in the exudate from the endosperm adjacent to the scutellum at the coleoptile elongation stage was also higher in Fukuhibiki than in Arroz da Terra. The results obtained in sterileagar-bed conditions clearly demonstrated that neither deficiency in 𰂱-amylase activity nor glucose production in the endosperm were responsible for coleoptile growth retardation at 16ºC. Therefore, neither 𰂱-amylase activity nor sugar supply from the endosperm were responsible for the varietal differences seen in the rate of seedling establishment in paddy fields at around 16ºC.     

甜菜种子活力鉴定指标的研究

对不同种子活力的甜菜种子发芽率、发芽势、活力指数、发芽指数、物质效率、贮藏物质运转率以及种子萌发时期酸性磷酸酯酶、脱氢酶活性进行了比较研究,结果表明,高活力种子的发芽势、发芽率、活力指数、物质效率、贮藏物质运转率均大于低活力种子。种子萌发24h后,高活力种子中酸性磷酸酯酶活性大于低活力种子,萌发初期,胚根中的脱氢酶活性也表现为高活力种子大于低活力种子。依据可重复性和可操作性原则,种子贮藏物质运转率、胚根脱氢酶活性可作为鉴定甜菜种子活力大小的可靠生理指标。     

转TrxS基因对啤酒大麦种子贮藏蛋白含量的影响

为探讨导入TrxS基因对大麦籽粒氮代谢的作用,以转TrxS基因啤酒大麦纯合株系为材料,分析了TrxS基因的导入对大麦籽粒蛋白酶活性、醇溶蛋白和谷蛋白含量的影响.结果表明,转基因大麦籽粒的蛋白酶活性增加,发芽第3～5 d转基因大麦种子的蛋白酶活性分别比对照增加42.86%、19.35%和25.76%;发芽第2～4 d醇溶蛋白和谷蛋白的降解平均比对照下降快5.92% 和7.10%.     

Effects of AG1 and AG2 QTLs on Nonstructural Carbohydrate and Seed Management Options for Rice Seedling Growth and Establishment under Flooding Stress

Rice (Oryza sativa) plants acquired excess photosynthates in the form of nonstructural carbohydrates (NSCs) in their stems and grain. Despite keen interest in rice NSC, the dynamics of NSC accumulation, translocation and re-accumulation have not yet been well investigated. AG1 and AG2 QTLs associated with flooding tolerance through catalyzing starch into soluble sugar in germinating seeds. Here we conducted three experiments, greenhouse and field to lay the groundwork for large-scale diversity studies on grain NSC and some agronomic traits under direct-seeded rice (DSR) system, using elite lines incorporating AG1, AG2 and AG1-AG2 QTLs into the popular varieties PSB Rc82 and Ciherang-Sub1 along with the donors Kho Hlan On (AG1) and Ma-Zhan Red (AG2). In germinating seedlings, soluble sugars increased, while starch concentration decreased gradually especially in the tolerant checks and AG1-AG2 introgression lines under flooded soil. Soluble sugar accumulation in stem started to increase from the vegetative stage and peaked at the panicle initiation stage then gradually decreased towards the maturity stage. But Sub1-AG lines had higher sugar and starch concentrations at different growth stages than other genotypes in wet season 2016 and dry season 2017. Plant survival rate was positively correlated with the stem NSC at the early vegetative stage (21 days after sowing), and stem NSC was positively associated with plant height at different growth stages. Among the tested seeding rate, the most suitable seeding rate, 4 g/m² with shallow burial depth (0.5 cm), resulted in better seedling establishment, relatively higher seedling vigor index and higher leaf area index under flooding in DSR system. Introgression of AG1-AG2 QTLs had no any negative impact on nonstructural carbohydrate, germination rate, and growth and biomass production.     

iTRAQ-Based Proteomics Investigation of Critical Response Proteins in Embryo and Coleoptile During Rice Anaerobic Germination

Direct-seeding of rice has become popular in recent years due to its low cost and convenience, however, hypoxic condition limits seedling establishment. In this study, weedy rice WR04-6 with high germination ability under anaerobic conditions was used as a gene donor, and we successfully improved the seedling establishment rate of rice cultivar Qishanzhan (QSZ) based on selection of a new rice line R42 from the recombinant inbred line population. R42 inherited high anaerobic germination (AG) ability, and was used for isobaric tags for relative and absolute quantitation (iTRAQ)-based comparative proteomic studies with QSZ to further explore the molecular mechanism of AG. A total of 719 differentially abundant proteins (DAPs) were shared by R42 and QSZ responded to AG, and thus defined as common response DAPs. A total of 300 DAPs that responded to AG were only identified from R42, which were defined as tolerance-specific DAPs. The common response and tolerance-specific DAPs had similar biochemical reaction processes and metabolic pathways in response to anoxic stress, however, they involved different proteins. The tolerance-specific DAPs were involved in amino acid metabolism, starch and sucrose metabolism, tricarboxylic acid cycle pathway, ethylene synthesis pathway, cell wall-associated proteins and activity of active oxygen scavenging enzyme. The in silico protein-protein interactions for the top 60 DAPs indicated that tolerance-specific DAPs had relatively independent protein interaction networks in response to an anoxic environment compared with common response DAPs. The results of physiological indicators showed that α-amylase and superoxide dismutase activities of R42 were significantly increased under anoxic conditions compared with aerobic conditions. Multiple lines of evidence from western blot, physiological analysis and quantitative real-time PCR jointly supported the reliability of proteomics data. In summary, our findings deepened the understanding of the molecular mechanism for the rice response to AG.     

Effects of combinational treatment with ethephon and gibberellic acid on rice seedling growth and carbohydrate mobilization in seeds under flooded conditions

ABSTRACT

Early seedling growth, including seedling emergence and vigor, is crucial in direct seeded rice. In this study, we examined the effects of gibberellic acid (GA₃) and ethephon (ET) on the early growth of direct seeded rice, and on α-amylase activity and soluble sugar content in the seeds. Rice seeds were treated with water (control), ET, GA₃, or ET+ GA₃ and were allowed to grow for 21 days. The results showed that ET and GA₃ synergistically improved the lengths of mesocotyl, coleoptile, mesocotyl+ coleoptile, and first leaf. Moderate synergistic effects of ET and GA₃ were detected in the second and third leaves. ET+ GA₃ treatment induced higher α-amylase activities during early post-germination growth, which is consistent with the longer coleoptile, mesocotyl, mesocotyl+ coleoptile, and first leaf. In addition, ET+ GA₃ induced higher α-amylase activity in the seeds, and consequently, higher sucrose and glucose concentrations than other treatments. These results partially explain the regulatory mechanism underlying the synergistic interaction of ET and GA₃ on rice seedling growth in terms of starch and sugar metabolism in the seeds, and this knowledge is expected to facilitate the practical use of ET and GA₃ in direct seeded rice systems.     

A bioplastic-based seed coating improves seedling growth and reduces production of coated seed dust

Although recently introduced, film-coating of agronomic seeds is now widely accepted in modern agriculture as an effective technology for protecting germinating seeds and seedlings. These experiments explored the possibility of using a bioplastic-based formulation to film-coat corn (maize; Zea mays L.) and canola (Brassica napus L.) seeds, alone and in combination with synthetic pesticides and plant growth-promoting bacteria. The thin bioplastic coat did not affect percent germination or seedling growth. However, incorporating spores of the plant growth-promoting bacterium Bacillus subtilis QST 713 into the bioplastic matrix resulted in a greater elongation of corn and canola seedlings than that of seedlings from untreated seeds. Specifically, stems and roots of seedlings that germinated from corn seeds coated with bioplastic containing spores were 18.0% and 21.4% longer, respectively, than stems and roots from uncoated control seeds. In canola seeds, these values were 19.9% and 20.9% higher for stem and roots, respectively. Incorporating a neonicotinoid insecticide, imidacloprid, and a fungicide, pyraclostrobin, into bioplastic coatings, along with B. subtilis spores, provided results comparable to spores and bioplastic alone. Coated seeds were also evaluated for their potential to generate dust after abrasion testing, using a novel image-based method made possible because seed coatings are typically artificially colored. Abraded seed coat fragments are consequently easily detectable with conventional optical instruments. Corn and canola seeds coated with bioplastic released up to 86.1% and 97.6% less dust during abrasive handling than seeds coated with a commercial seed coating matrix measured by the optical approach described here.     

杂草稻中胚轴伸长动态及其与籽粒淀粉酶活性和可溶性糖含量的关系

采用恒温培养箱,在黑暗条件下进行发芽试验,观察杂草稻中胚轴伸长的动态过程,分析杂草稻中胚轴伸长过程中籽粒淀粉酶活性和可溶性糖含量的变化及相互关系。结果表明,黑暗条件下发芽后1d到3d,杂草稻中胚轴伸长非常慢,发芽后4d到5d中胚轴伸长加快,发芽后7天中胚轴伸长逐渐停止,其最终长度显著长于辽粳294。杂草稻发芽过程中,籽粒α-淀粉酶活性、β-淀粉酶活性和可溶性糖含量均呈逐渐上升趋势。可溶性糖含量与α-淀粉酶活性、β-淀粉酶活性均呈极显著正相关。中胚轴伸长长度与籽粒α-淀粉酶活性、β-淀粉酶活性、可溶性糖含量也均呈极显著正相关。杂草稻发芽初期淀粉酶活性增强,促进了籽粒中淀粉水解为可溶性糖,为中胚轴伸长生长提供了物质和能量基础。     

胡敏酸对苯丙烯酸胁迫下黄瓜种子萌发特性的影响

以黄瓜（Cucumis Sativus L.）种子为材料,研究胡敏酸（Humic Acid,HA）对苯丙烯酸（Cinnamic Acid,CA）胁迫下黄瓜种子萌发的影响及其机理。结果表明： CA对黄瓜种子萌发有明显的抑制作用, 且抑制程度随CA浓度（0.10～1.0 mmol/L）的增加而提高。 CA胁迫下, 黄瓜种子总淀粉酶、 α-淀粉酶、 β-淀粉酶及蛋白酶活性降低, 种子活力、 种子物质消耗率下降,发芽势降低。25 mg/L HA处理可以缓解CA胁迫对种子萌发的抑制作用,表现为发芽势提高,种子活力、α-淀粉酶、β-淀粉酶和蛋白酶活性以及种子物质消耗率提高。     

酸雨胁迫对大豆萌发种子糖代谢影响初探

为探索酸雨影响大豆种子萌发机理,采用模拟酸雨处理大豆种子,研究酸雨对大豆萌发种子糖代谢的影响。结果表明:大豆种子的可溶性糖、还原性糖、蔗糖及淀粉含量,α-淀粉酶和淀粉酶活性均在pH2.0酸雨胁迫下受到抑制而降至最低,4种碳水化合物含量随酸雨胁迫强度的减弱呈上升趋势,α-淀粉酶对酸雨胁迫的敏感性低于淀粉酶,大豆萌发种子糖代谢对酸雨胁迫有较强适应。     

Germination response of endophytic Festuca rubra seeds in the presence of arsenic

Epichloë fungal endophytes colonize the intercellular space of aerial organs of their plant hosts without causing symptoms. These symbionts are known to improve the performance of their host grasses in some situations of biotic and abiotic stress, leading to the suggestion that they can be used to improve grass tolerance to contaminants. The grass Festuca rubra is a host of the endophyte Epichloë festucae. We used two half‐sib lines of F. rubra, each line composed of infected (E+) or endophyte‐free (E?) seeds, to study the effect of varying levels of arsenic (6, 12, 25, and 50 mg L^?1), and of the endophyte in seed germination and radicle growth. The results showed that seed germination was not significantly affected by arsenic (As) levels lower than 25 mg L^?1, indicating that this grass has a relatively high tolerance of As at the germination stage. The decrease in germination observed at 25 and 50 mg L^?1 was due to increased seed mortality and to the reversible inhibition of the germination of viable seeds caused by As. The presence of the endophyte did not change the germination response to arsenic of one line, but affected negatively the germination of the other line. In contrast to the process of germination, radicles of E+ seeds of both lines were longer than those of endophyte‐free seeds. The results of this work indicate that Epichloë endophytes can affect the performance of some F. rubra genotypes when As is present in the soil.     

Evaluation on Sixty-eight Rice Germplasms in Cold Tolerance at Germination Stage

Sixty-eight rice germplasms were used for cold tolerance evaluation at the germination stage in laboratory. Seeds of rice germplasms germinated at three different temperatures containing low temperature (constant 13°C for 28 days), alternative temperature (a temperature cycle of 12 h at 20°C and 12 h at 23°C for 14 days) and control (constant 26°C for 7 days). Analysis of variance revealed that temperature had a significant effect on germination rate, coleoptile length and radicle length. Germination rate was strongly affected by the low temperature and alternative treatments. Stress of low temperature at the germination stage on the tested rice germplasms caused a reduction in final germination rate and the lengths of coleoptile and radicle. The normal and healthy seeds began to germinate within 36 h after imbibition and germination were completed on the 7th day in the control, but delayed under the low and alternative temperature treatments. The low and alternative temperature treatments delayed the growth of coleoptile and radicle compared to the control, and the average lengths of coleoptile and radicule were strongly inhibited with the decreasing temperature in all of the tested germplasms. Taichung, a semi-dwarf, low amylose content and early maturing rice variety, showed a significantly higher germination rate at the three temperature treatments and its coleoptile length was significantly higher than other germplasms.     

Sprouted Sorghum Extract Elicits Coleoptile Emergence,Enhances Shoot and Root Acclimatization,and Maintains Genetic Fidelity in indica Rice

The high growth-stimulating effect of plant extract has urged the plant biotechnologists to use natural supplements in the culture media instead of synthetic phytohormones. We advocated the effect of sprouted sorghum extract(SSE) on emergence, in vitro acclimatization, and genetic fidelity in coleoptile derived callus of indica rice variety ADT36. The use of SSE with Murashige Skoog medium efficiently acclimatized the root and shoot apical systems. A higher mat and seminal roots(3.4 g biomass) with an efficient shoot primordium elongation were observed with an increase in the concentration of SSE. Seeds treated with SSE medium showed higher germination and earlier coleoptile maturation about 48 h compared to untreated seeds, and there was a higher expression of e EF-1α with an increase in coleoptile length. B5 medium was effective on inducing embryogenic and nodular callus from 3-day-old coleoptile with 3.0 mg/L 2,4-dichlorophenoxyacetic acid and further proliferated effectively with 0.8 mg/L kinetin with a fresh weight of 180 mg. Highly significant regeneration was observed with combination of 2.5 mg/L 6-benzylamino purine and 3.0 mg/L α-naphthaleneacetic acid. The metabolic and genetic profiles of in vitro and directly cultivated plants were the same, examined through Fourier-transform infrared spectroscopy, random amplified polymorphic DNA(RAPD), inter-simple sequence repeat(ISSR) and R-ISSR(combination of RAPD and ISSR) markers, respectively, and thus confirming the significant efficacy of the SSE incorporated medium. Disarmed T-DNA was transformed to coleoptile derived callus through Agrobacterium tumefaciens LBA4404 and confirmed by GUS assay. The T-DNA integration was confirmed by DNA blot analysis using DNA from transient GUS-expressed explants. Thus, SSE can be used as a natural and organic supplement for organogenesis and efficient acclimatizations of shoot and root apical meristems in regenerated plants.     

尿素对玉米种子发芽的影响

试验结果表明,尿素可降低玉米种子发芽率,低活力种子所受的影响更显著。种子发芽过程中根茎的生长速度受尿素的影响而显著减慢,而以根的生长所受影响更大,发芽后期,幼根生长进一步减慢并逐步腐烂,从而降低出苗率。尿素使玉米种子的蛋白酶活性增加,使淀粉酶活性显著下降,酶活动平衡受到破坏。本试验这些不良影响是尿素本身的作用,而并非是缩二脲的毒害作用。     

Sucrose Metabolism for the Development of Seminal Root in Maize Seedlings

Abstract

The objective of this study was to elucidate the roles of sugar in the formation of root systems. Several parts of theseminal root were investigated to determine their sucrose, glucose and fructose contents, and the activity and the in situ localization of the activities of two kinds of metabolic enzymes, invertase and sucrose synthase, whichhydrolyze sucrose. The sucrose, glucose and fructose concentrations in the 0-1 cm section from the root apex were three to five times those in the other sections. The invertase and sucrose synthase activities were also higher in the apical section. The in situ localization of invertase activity was detected in the cell elongation zone of the seminal root using histochemical method. The sucrose synthase activity was detected in the cell elongation zone of the seminal root and the root apices of lateral roots. These results suggested that sucrose is transported to the root elongation zone and the surrounding tissue of the lateral root primordia, and is cleaved into glucose, fructose, and UDP-glucose by invertase or sucrose synthase. This suggested that sucrose contributes to root formation by serving as the energy source, the carbon source for cell wall synthesis, and as a compatible solute for cell elongation.     

壳聚糖对花生种子萌发过程中某些生理活性的影响

研究不同浓度的壳聚糖处理花生种子 ,对种子发芽势、发芽率、脂肪酶活性、GA3和IAA含量的影响。结果表明 ,用浓度为 7.5mg/mL的壳聚糖溶液处理花生种子 ,其发芽势、发芽率分别比对照提高了 1 4.4%和4.5 % ,脂肪酶活性比对照提高 1 62 % ,GA3、IAA含量分别比对照增加 80 .0 %和 60 .3 %。     

大型水浴式集中催芽器与恒温催芽箱催芽效果对比试验

为实现100%集中催芽,以大型水浴式集中催芽器与恒温催芽箱对比,二者在相同催芽时间内相差不大;大型集中催芽器催芽后在空气温度内堆温出芽效果较好,与恒温催芽箱早生率差35.8%,晚生率多35%。大型水浴式集中催芽器可提高催芽效率,每次可催30 t种子,可完成400 hm2的育苗任务,10 d可催出200 t种子;节省人工,节约资金;突出了统一供种的模式,为实现集约化、工厂化育苗、供苗奠定了坚实的基础。