Plant Elongation Research Articles

Phenotypic plasticity of sun and shade ecotypes of Stellaria longipes in response to light quality signaling, gibberellins and auxin

Stellaria longipes plant communities (ecotypes) occur in several environmentally distinct habitats along the eastern slopes of southern Alberta's Rocky Mountains. One ecotype occurs in a prairie habitat at ∼1000 m elevation where Stellaria plants grow in an environment in which the light is filtered by taller neighbouring vegetation, i.e. sunlight with a low red to far-red (R/FR) ratio. This ecotype exhibits a high degree of phenotypic plasticity by increasing stem elongation in response to the low R/FR ratio light signal. Another Stellaria ecotype occurs nearby at ∼2400 m elevation in a much cooler alpine habitat, one where plants rarely experience low R/FR ratio shade light. Stem elongation of plants is largely regulated by gibberellins (GAs) and auxin, indole-3-acetic acid (IAA). Shoots of the prairie ecotype plants show increased IAA levels under low R/FR ratio light and they also increase their stem growth in response to applied IAA. The alpine ecotype plants show neither response. Plants from both ecotypes produce high levels of growth-active GA1 under low R/FR ratio light, though they differ appreciably in their catabolism of GA1. The alpine ecotype plants exhibit very high levels of GA8, the inactive product of GA1 metabolism, under both normal and low R/FR ratio light. Alpine origin plants may de-activate GA1 by conversion to GA8 via a constitutively high level of expression of the GA2ox gene, thereby maintaining their dwarf phenotype and exhibiting a reduced phenotypic plasticity in terms of shoot elongation. In contrast, prairie plants exhibit a high degree of phenotypic plasticity, using low R/FR ratio light-mediated changes in GA and IAA concentrations to increase shoot elongation, thereby accessing direct sunlight to optimize photosynthesis. There thus appear to be complex adaptation strategies for the two ecotypes, ones which involve modifications in the homeostasis of endogenous hormones.

Evaluation of phytotoxicity of municipal landfill leachate before and after biological treatment.

In the present study, leachate toxicity of a municipal solid waste landfill located in the Sinos River Valley region (southern Brazil) was evaluated using plant bioassays. Leachate toxicity was assessed by analysis of seed germination and root elongation of lettuce (Lactuca sativa L.) and rocket plant Eruca sativa Mill.) and root elongation of onions Allium cepa L.). Bioassays were performed by exposing the seeds of L. sativa and E. sativa and the roots of A. cepa to raw leachate, treated leachate (biological treatment) and negative control (tap water). The levels of metals detected in both samples of leachate were low, and raw leachate showed high values for ammoniacal nitrogen and total Kjeldahl nitrogen. There is a reduction in the values of several physicochemical parameters, which demonstrates the efficiency of the treatment. Both L. sativa and A. cepa showed a phytotoxic response to landfill leachate, showing reduced root elongation. However, the responses of these two plant species were different. Root elongation was significantly lower in A. cepa exposed to treated leachate, when compared to negative control, but did not show any difference when compared to raw leachate. In L. sativa, seeds exposed to the raw leachate showed significant reduction in root elongation, when compared to treated leachate and negative control. Seed germination showed no difference across the treatments. The results of the study show that plant species respond differently and that municipal solid waste landfill leachate show phytotoxicity, even after biological treatment.

Kinase-mediated orchestration of NADPH oxidase in plant immunity.

Reactive oxygen species (ROS) are important signalling molecules, which participate in multiple physiological processes including immune response, development, cell elongation and hormonal signalling in plants. Plant NADPH oxidase, termed respiratory burst oxidase homologue (RBOH), is frequently studied as a main player for pathogen-responsive ROS burst. Our understanding of the activation mechanism of RBOH after pathogen recognition has increased in recent years. In this review, we focus on kinase-mediated regulatory mechanisms of RBOHs. Calcium-dependent protein kinases (CDPKs) are well known to activate RBOHs by direct phosphorylation. In addition to functions of CDPKs in plants, we also describe the involvement of receptor-like cytoplasmic kinases (RLCKs) and mitogen-activated protein kinases (MAPKs) in fine-tuning RBOH activity at the post-translational and transcriptional levels, respectively.

Kinesin-4 Functions in Vesicular Transport on Cortical Microtubules and Regulates Cell Wall Mechanics during Cell Elongation in Plants

In plants, anisotropic cell expansion depends on cortical microtubules that serve as tracks along which macromolecules and vesicles are transported by the motor kinesins of unknown identities. We used cotton (Gossypium hirsutum) fibers that underwent robust elongation to discover kinesins that are involved in cell elongation and found Gh KINESIN-4A expressed abundantly. The motor was detected by immunofluorescence on vesicle-like structures that were associated with cortical microtubules. In Arabidopsis thaliana, the orthologous motor At KINESIN-4A/FRA1, previously implicated in cellulose deposition during secondary growth in fiber cells, was examined by live-cell imaging in cells expressing the fluorescently tagged functional protein. The motor decorated vesicle-like particles that exhibit a linear movement along cortical microtubules with an average velocity of 0.89 μm/min, which was significantly different from those linked to cellulose biosynthesis. We also discovered that At KINESIN-4A/FRA1 and the related At KINESIN-4C play redundant roles in cell wall mechanics, cell elongation, and the axial growth of various vegetative and reproductive organs, as the loss of At KINESIN-4C greatly enhanced the defects caused by a null mutation at the KINESIN-4A/FRA1 locus. The double mutant displayed a lack of cell wall softening at normal stages of rapid cell elongation. Furthermore, enhanced deposition of arabinose-containing carbohydrate was detected in the kinesin-4 mutants. Our findings established a connection between the Kinesin-4-based transport of cargoes containing non-cellulosic components along cortical microtubules and cell wall mechanics and cell elongation in flowering plants.

Flowering of Sugarcane Genotypes under Different Artificial Photoperiod Conditions

Flowering is essential in any breeding programme, particularly in genetic introgression programmes in which flowering synchronism is required. In this work, 16 sugarcane genotypes were evaluated using three different flowering-inductive photoperiod treatments (30 s, 45 s, and 1 min of a daily photoperiod decrease from 12 h 55 of light). Each genotype was planted in 43 L pots (equal proportion of soil, sand, and substrate) with three tillers per pot. Plants with 4 to 6 internodes were placed in a photoperiod facility with three controlled chambers, each chamber containing all 16 genotypes (one treatment per chamber). The temperature range (21°C to 32°C) and humidity were the same for all of the treatments. The flower induction started in September 2010 and ended in April 2011. The plant elongation and flag leaf and inflorescence emergence were recorded and the pollen viability was evaluated by using the iodine staining method. The photoperiod facility provided suitable conditions for flowering, as the plants in the three treatments successfully flowered. The genotypes in the three treatments behaved differently in relation to the date of panicle emergence, with the treatment of 45 s showing better results. The results here presented contribute to synchronise flowering for desired sugarcane crosses, particularly those from introgression programmes between commercial cultivars and species from the Saccharum complex.

Effect of growth retardants on quality production of pot mums

Chrysanthemum or mums (Dendranthema grandiflora) have been grown in gardens for hundreds of years but only in last decade scientists emphasized on making them better plants for home garden, rather than for cut flower industry. Pot mums are versatile, attractive, and can be marketed almost in any size and container type. In order to maintain their height, compactness it is necessary to use plant growth retardants. Plant growth retardants are commonly used to inhibit stem elongation of many ornamental plants. Plant growth retardants act by inhibiting cell division in the sub apical meristem of the shoot. They are commonly used in the production of bedding plants to control plant growth and habit during production and to improve plant appearance and quality during marketing. The type of growth inhibition is, in part, dependent on the concentration of growth retardant applied and species. At low concentrations, growth retardants typically reduce cell elongation, whereas at high concentrations the reduction is increasingly due to a reduced cell division. There are several plant growth retardants like Paclobutrazol, Ancymidol, Sumagic, A-Rest, Daminozide, Cycoceal. Plant growth retardants in ornamental plants are commonly applied to limiting stem elongation and produce more compact, sturdy potted plants without changing developmental patterns or evoke phytotoxic effects. Growth retardants also enhance stress tolerance, green colour of the foliar and postharvest longevity. These growth retardants may be applied as foliar spray, drench at different concentrations according to the variety.

大气CO2和O3浓度升高对汕优63生长动态、物质生产和氮素吸收的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 大气CO2和O3浓度升高对汕优63生长动态、物质生产和氮素吸收的影响 DOI: 10.5846/stxb201408051557 作者: 作者单位: 扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31371563,31171460,31071359);江苏省高校自然科学重大基础研究项(11KJA210003);江苏高校优秀科技创新团队和江苏省高校优势学科建设工程项目资助 Impact of elevated atmospheric carbon dioxide and ozone concentration on growth dynamic, dry matter production, and nitrogen uptake of hybrid rice Shanyou 63 Author: Affiliation: Xuzhou Institute of Agricultural Sciences of the Xuhuai District of Jiangsu Province,,,,Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University,Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:大气二氧化碳(CO2)和近地层臭氧(O3)浓度升高将极大地改变作物的生长环境,进而影响作物包括主要粮食作物的生产力。利用自然光气体熏蒸平台,设置室外对照(Ambient)、室内对照(CK,实时模拟室外环境)、高浓度CO2(Ambient CO2+200 μmol/mol)、高浓度O3(Ambient O3的1.6倍)、高浓度CO2+O3 5个处理,研究大气组分变化对敏感水稻汕优63生长动态、物质生产及氮素吸收的影响。结果表明,室外对照和室内对照水稻的多数测定指标无显著差异。与CK相比,O3处理使水稻生育中后期株高和分蘖数明显下降,且随时间推移降幅逐渐增加,最大降幅分别达21%和15%,但CO2处理使水稻生育中后期株高和分蘖数明显增加,最大增幅分别为5%和18%,CO2+O3处理使水稻株高最大下降为7%,但对各期分蘖数没有影响。与CK相比,O3处理使水稻成熟期叶片、茎鞘、稻穗和根系生物量大幅下降,使全株总生物量平均下降51%,CO2处理对绿叶和黄叶生物量无显著影响,但使茎鞘、稻穗和根系生物量明显增加,使全株总生物量平均增加37%,CO2+O3处理对各器官和全株生物量均无显著影响。臭氧处理使生物量在叶片中的分配比例显著增加,而CO2处理则表现相反,CO2+O3处理对水稻物质分配的影响小于单独的O3处理。与CK相比,O3处理使水稻抽穗期植株含氮率平均增加29%,吸氮量下降31%,而CO2处理或CO2+O3处理对地上部植株含氮率和吸氮量的影响均未达显著水平。试验结论,近地层臭氧浓度升高使水稻变矮、分蘖减少、生长受抑,但同步增加的二氧化碳浓度可明显缓减甚至抵消臭氧胁迫对汕优63生长发育的负效应。 Abstract:Changes in atmospheric composition will greatly alter future rice production. In this study, a new closed-top chamber was used to investigate the effects of elevated CO2 and O3 on growth, dry matter production, and nitrogen (N) uptake. A three-line indica hybrid rice cultivar, Shanyou 63, was grown under five gas treatments: ambient, CK (realtime simulation of ambient conditions), elevated [O3] (60% higher than the ambient O3 concentration), elevated [CO2] (200 μmol/mol above ambient CO2 concentration), and combined elevation of [CO2+O3]. For most of the measured parameters, there was no statistically significant difference between ambient and CK plants. Relative to the CK, elevated [O3] was significantly related to decreased plant height and tiller number within the middle and late growth stages, with the largest decreases (21% for plant height and 15% for tiller number) detected at the final measurements. Elevated [CO2] showed opposite trends, with the largest ozone-induced increases of 5% and 18% for plant height and tiller number, respectively. Elevated [CO2+O3] decreased plant height (largest reduction: 7%), but did not alter tiller number. Compared with the CK, elevated [O3] greatly decreased the biomass of leaves, stems, panicles, and roots at grain maturity, with 51% reduction recorded for total biomass. Elevated [CO2] did not change the biomass of green and senescent leaves, but increased the biomass of stems, panicles, roots, and thus total biomass (37%). There was no significant effect of elevated [CO2+O3] on total biomass and its components. Dry matter distribution in leaves significantly increased with elevated [O3], while opposite trends were observed with elevated [CO2]. The magnitude of the combined [CO2+O3] effect on dry matter distribution was smaller than that of the solo [O3] treatment. Elevated [O3] increased shoot N concentration by 29%, and it decreased shoot N uptake by 31% at heading stage. Elevated [CO2] and [CO2+O3] had no significant effect on aboveground N concentration and uptake. The above results suggested that the projected increase of surface ozone concentration will inhibit plant elongation, tiller production, and growth of hybrid Shanyou 63. The concurrent increases in [CO2+O3] either ameliorated or negated the detrimental effects of O3 stress on growth and development. 参考文献 相似文献 引证文献

Screening of BC1F1 population (BG 379-2/ IR 07F102 // BG 379-2) of rice (Oryza sativa L.) for submergence tolerance using molecular markers

Rice is susceptible to submergence from germination to early vegetative stage and affects wetland paddy cultivation areas of Sri Lanka is affected by flash floods. There are no submergence tolerant varieties available locally. Therefore, this research was designed to evaluate the BC1F1 population (Bg 379-2/ IR 07F102 // Bg 379-2) morphologically for submergence tolerance and to select polymorphic molecular markers between the donor parents IR07F102 and recurrent parent, Bg 379-2, and to screen and select plants of the BC1F1 population for submergence tolerance using identified molecular markers. The 108 individuals of BC1F1 of rice were morphologically screened for plant lodging, leaf senescence and plant elongation and molecular screening was done by using 5 Rice microsatellites and 1 In Del marker. Out of those, molecular marker, RM464A for SUB1 gene conferring submergence tolerance, was used to screen the BC1F1 population. Five plants were selected as submergence tolerant individuals as they were positive in both morphological and molecular screening. DOI: http://dx.doi.org/10.4038/jas.v9i3.7437 The Journal of Agricultural Sciences, 2014, vol.9, no3: p.147-153

Phosphoproteome and proteome analyses reveal low-phosphate mediated plasticity of root developmental and metabolic regulation in maize (Zea mays L.)

Phosphate (Pi) deficiency has become a significant challenge to worldwide agriculture due to the depletion of accessible rock phosphate that is the major source of cheap Pi fertilizers. Previous research has identified a number of diverse adaptive responses to Pi starvation in the roots of higher plants. In this study, we found that accelerated axile root elongation of Pi-deprived maize plants resulted from enhanced cell proliferation. Comparative phosphoproteome and proteome profiles of maize axile roots were conducted in four stages in response to Pi deficiency by multiplex staining of high-resolution two dimensional gel separated proteins. Pro-Q DPS stained gels revealed that 6% of phosphoprotein spots displayed changes in phosphorylation state following low-Pi treatment. These proteins were involved in a large number of metabolic and cellular pathways including carbon metabolism and signal transduction. Changes in protein abundance of a number of enzymes indicated that low-Pi induced a number of carbon flux modifications in metabolic processes including sucrose breakdown and other downstream sugar metabolic pathways. A few key metabolic enzymes, including sucrose synthase (EC 2.4.1.13) and malate dehydrogenase (EC 1.1.1.37), and several signaling components involved in protein kinase or phosphatase cascades, auxin signaling and 14-3-3 proteins displayed low-Pi responsive changes in phosphorylation state or protein abundance. A variety of key enzymes and signaling components identified as potential targets for phosphorylation provide novel clues for comprehensive understanding of Pi regulation in plants. Protein phosphorylation, coordinating with changes in protein abundance, is required for maize root metabolic regulation and developmental acclimation to Pi starvation.

Diversity in KCS2 (Ketoacyl-CoA Synthase) of selected plants and its molecular implications: A computational analysis

The majority of calories in human food are derived from plant fatty acids. Besides,plant fatty acids are also a major component of a variety of products useful to human beings such as paints, cosmetics, biofuels, lubricants, detergents and soaps. Ketoacyl-CoA synthase is a key enzyme involved in the fatty acid elongation in plants In this study, we have analyzed the diversity in the KCS2 proteins of a selected plant species. We conclude that though there are extensive similarities in the KCS2 proteins studied with respect to total number of negatively charged residues, total number of positively charged residues, and domain organization, there are notable differences for other features such as extinction coefficients, protein stability, kinase specific phosphorylation sites, number of O-GlcNAc sites, predicted sumoylation sites, residues contributing to nuclear export signal and transmemebrane helices. These differences may have repercussions for the quantitative efficiency of the 3-Ketoacyl-CoA synthase enzyme which catalyzes the condensation of c2 units to acyl coA during the fatty acid elongation process, and its regulation. This paper showcases molecular implications of diversity in KCS2 , which can be used to create a diverse genetic base for engineering KCS 2 genes.

Arabidopsis AtHB7 and AtHB12 evolved divergently to fine tune processes associated with growth and responses to water stress.

BackgroundArabidopsis AtHB7 and AtHB12 transcription factors (TFs) belong to the homeodomain-leucine zipper subfamily I (HD-Zip I) and present 62% amino acid identity. These TFs have been associated with the control of plant development and abiotic stress responses; however, at present it is not completely understood how AtHB7 and AtHB12 regulate these processes.ResultsBy using different expression analysis approaches, we found that AtHB12 is expressed at higher levels during early Arabidopsis thaliana development whereas AtHB7 during later developmental stages. Moreover, by analysing gene expression in single and double Arabidopsis mutants and in transgenic plants ectopically expressing these TFs, we discovered a complex mechanism dependent on the plant developmental stage and in which AtHB7 and AtHB12 affect the expression of each other. Phenotypic analysis of transgenic plants revealed that AtHB12 induces root elongation and leaf development in young plants under standard growth conditions, and seed production in water-stressed plants. In contrast, AtHB7 promotes leaf development, chlorophyll levels and photosynthesis and reduces stomatal conductance in mature plants. Moreover AtHB7 delays senescence processes in standard growth conditions.ConclusionsWe demonstrate that AtHB7 and AtHB12 have overlapping yet specific roles in several processes related to development and water stress responses. The analysis of mutant and transgenic plants indicated that the expression of AtHB7 and AtHB12 is regulated in a coordinated manner, depending on the plant developmental stage and the environmental conditions. The results suggested that AtHB7 and AtHB12 evolved divergently to fine tune processes associated with development and responses to mild water stress.

Light acclimation in submerged macrophytes: The roles of plant elongation, pigmentation and branch orientation differ among Chara species

Light acclimation plays a fundamental role for plant survival. Using an experimental setup where light could only penetrate from above, we studied light acclimation of Chara intermedia and C. contraria, i.e. submerged macroscopic algae which grow in an upright position. Both species produced taller plants at higher light intensities. These results are in contrast to earlier studies which found shorter plants at higher light intensities. This may be explained by light-induced inhibition of shoot-cell elongation. Since Chara shoot-cells point upward, the inhibition can only operate when light reaches plants laterally. We suggest that calcium-encrustation, periphyton-cover and dense neighboring vegetation may reduce lateral light such that plants exposed to such conditions will show increased elongation with increasing light intensity.In contrast to expectations, the uppermost Chara parts had higher chlorophyll a/carotenoid ratios, indicating less light protecting capacity, than the lower parts. This is explained by branches of the uppermost parts generally pointing upward such that they become less light exposed than branches of lower parts, which were less inclined. We found that the more nearly horizontal Chara branches had steeper slopes in their chlorophyll a/carotenoid ratio in relation to light intensity, indicating that the intensity of adjustments in pigmentation depends on branch orientation. C. intermedia adjusted orientation of growing branches to incident light, with branches pointing steeply upward at high light conditions, while C. contraria did not. The combination of branch-orientation and adaptations in pigmentation may give C. intermedia a competitive advantage over C. contraria in high light environments.

CULTIVATION OF CHRYSANTHEMUM WITHOUT SUBSTRATE

In The Netherlands there are 700 hectares of cut flowers in soil. Recent studies have shown that mineral fertilizers used can seep into the subsoil and eventually cause high levels of nitrogen and phosphate in the surrounding environment. Therefore the goal of this experiment was to find a system for the year-round production of cut chrysanthemum in recirculating water without run-off into the subsoil. Prior to planting the unrooted cuttings of chrysanthemum ‘Euro Speedy’ were pre-treated by placing them for 4 days in a waterbed kept at 26°C, under 95% RH and 600 ppm CO2 under long day conditions in a greenhouse in The Netherlands. After rooting three batches of 2,500 rooted plants were planted in the period August 2010 to November 2011 onto three systems: Deep flow waterbed; aeroponic and peat in aluminium cassettes. The elongation of the plants during the long day period, the number of leaves, weight and length at final harvest were recorded. Additionally the composition and EC of the nutrient solution and the oxygen content of the solution were measured. The deep flow waterbed and the aeroponic systems were found to produce constant good quality stems (1 g fresh weight per cm stem). Aeration of the deep flow waterbed system gave 10% more fresh weight per stem. Water use, plant density, air and nutrient levels are evaluated in relation to the systems. The prospect for such a system in a commercial setting is discussed.

Overexpression of miR172 suppresses the brassinosteroid signaling defects of bak1 in Arabidopsis

BRI1-Associated Receptor Kinase 1 (BAK1) is a leucine-rich repeat serine/threonine receptor-like kinase (LRR-RLK) that is involved in multiple developmental pathways, such as brassinosteroid (BR) signaling, plant immunity and cell death control in plants. Because the roundish and compact rosette leaves of bak1 mutant plants are characteristic phenotypes for deficient BR signaling, we screened genetic suppressors of bak1 according to changes in leaf shape to identify new components that may be involved in BAK1-mediated BR signaling using the activation-tagging method. Here, we report bak1-SUP1, which exhibited longer and narrower rosette leaves and an increased BR sensitivity compared with those of bak1. Analyses of the T-DNA insertional site and the gene expression that was affected by the T-DNA insertion revealed that a microRNA, namely, miR172, over-accumulates in bak1-SUP1. Detailed phenotypic analyses of bak1-SUP1 and a single mutant in which the bak1 mutation was segregated out (miR172-D) revealed that the overexpression of miR172 promotes leaf length elongation in adult plants and increases the root and hypocotyl growth during the seedling stage compared with that of wild type plants. Taken together with its increased BR sensitivity, these results suggest that miR172 regulates vegetative growth patterns by modulating BR sensitivity as well as by the previously identified developmental phase transition.

Impact of Antimicrobial Compounds on Etiolation Caused byXanthomonas translucensand on Turf Quality of Creeping Bentgrass Putting-Green Turf

Etiolation is an abnormal elongation and chlorosis of turfgrass plants that has become problematic in recent years, and bacteria have been implicated as causal agents. The frequent reports of etiolation are of concern to turfgrass managers, since management practices for bacterial diseases in turf are not well developed. The purpose of this research trial was to evaluate fungicides and nonregistered antibiotics for management of etiolation in creeping bentgrass turf. This 2-year field study evaluated oxytetracycline, streptomycin sulfate, acibenzolar-S-methyl + chlorothalonil (ASM + C), potassium phosphite (PPP), hydrogen dioxide, fosetyl-Al [pigmented (FAP) and nonpigmented (FA)], and copper + mancozeb for their effects on etiolation caused by Xanthomonas translucens on creeping bentgrass putting-green turf. Reductions in etiolation severity were observed with oxytetracycline treatment in both years and with ASM + C in the second year of study. While ASM + C did not reduce etiolation in the first year, turf quality with ASM + C alone and in combination with PPP was superior to all other treatments in both years. While PPP and FAP did not reduce etiolation, turf quality of these plots was often better than the control. Both antibiotics in addition to copper + mancozeb had phytotoxicity that reduced turf quality. Preventative applications of ASM + C were the most effective in reducing etiolation of creeping bentgrass while maintaining turf quality.

Transcription ofST2AEncoding A Sulfotransferase Family Protein That Is Involved in Jasmonic Acid Metabolism Is Controlled According to the Circadian Clock- and PIF4/PIF5-Mediated External Coincidence Mechanism inArabidopsis thaliana

Plant elongation growth on a day-to-day basis is enhanced under specific photoperiod and temperature conditions. Circadian clock is involved in the temperature adaptive photoperiodic control of plant architecture, including hypocotyl elongation in Arabidopsis thaliana. In this regulation, phytochrome interacting transcriptional factors, PIF4 and PIF5, are activated at the end of night under short photoperiod or high temperature conditions, due to the coincidence between internal (circadian rhythm of the transcripts) and external (length of dark period) time cues. It is previously found that biosynthesis or metabolism of phytohormones including auxin, and their signal transduction-related genes are downstream targets of circadian clock and PIF4/PIF5 mediated external coincidence mechanism. Brassinosteroid and gibberellic acid played a positive role in the hypocotyl elongation of seedlings under light and dark cycle conditions. On the other hand, cytokinin and jasmonic acid played an opposite role. In this study, diurnal expression profile of a gene encoding a sulfotransferase family protein that is involved in the jasmonic acid metabolism, ST2A, was examined. It was found that transcription of ST2A is induced at the end of night under LD/22 °C and SD/28 °C conditions according to the external coincidence mechanism. The results of this study support the idea that the circadian clock orchestrates a variety of hormone-signaling pathways to regulate the photoperiod and temperature-dependent morphogenesis in A. thaliana.

Phytotoxicity assessment of γ-Fe2O3 nanoparticles on root elongation and growth of rice plant

This study was conducted to determine the phytotoxicity of 6 nm γ-Fe2O3 nanoparticles (IONPs) in terms of root elongation and the physiological performance of rice plants. Rice seeds (Oryza sativa L. var. Koshihikari) exposed to IONPs at 500, 1,000 and 2,000 mg/L, had a significantly higher root elongation than the control and its bulk counterparts (IOBKs), indicating that the effect can be nanospecific. In a 14-week greenhouse pot experiment, the CO2 assimilation rate in IOBK and IONP-treated pots (500 and 1,000 mg/pot) decreased over time, with the decline (maximum 42.5 %) being less pronounced for IONPs, indicating that the effect cannot be inferred from the toxicity of nanoscale size iron oxide. Excessive adsorption of IONPs onto soil colloids with subsequent low water extractable iron was responsible for the unremarkable phytotoxic nature of IONPs in the rice plants. Amendment of IONPs coated with 20 mmol citric acid (IONPs-Cit) significantly diminished the CO2 assimilation rate and the decrease was similar to its bulk counterpart (IOBKs-Cit). However, maximum shoot growth inhibition (37 %) was associated with the application of IOBKs-Cit. It was concluded that massive accumulations of Fe plaque on the root surfaces of IOBKs-Cit treatments due to a decline in the pH of rhizoplane soils compared to the IONPs-Cit treatments were responsible for the remarkable shoot growth reduction. This study provided evidence of the phytotoxicity of γ-Fe2O3 nanoparticles, demonstrating the lower toxicity of nanosized iron oxide compared to a microsized preparation under reductive conditions.

The Role of Temperature in the Growth and Flowering of Geophytes.

Among several naturally occurring environmental factors, temperature is considered to play a predominant role in controlling proper growth and flowering in geophytes. Most of them require a “warm-cold-warm” sequence to complete their annual cycle. The temperature optima for flower meristem induction and the early stages of floral organogenesis vary between nine and 25 °C, followed, in the autumn, by a several-week period of lower temperature (4–9 °C), which enables stem elongation and anthesis. The absence of low temperature treatment leads to slow shoot growth in spring and severe flowering disorders. Numerous studies have shown that the effects of the temperature surrounding the underground organs during the autumn-winter period can lead to important physiological changes in plants, but the mechanism that underlies the relationship between cold treatment and growth is still unclear. In this mini-review, we describe experimental data concerning the temperature requirements for flower initiation and development, shoot elongation, aboveground growth and anthesis in bulbous plants. The physiological processes that occur during autumn-winter periods in bulbs (water status, hormonal balance, respiration, carbohydrate mobilization) and how these changes might provoke disorders in stem elongation and flowering are examined. A model describing the relationship between the cold requirement, auxin and gibberellin interactions and the growth response is proposed.

Comparing Anthracene and Fluorene Degradation in Anthracene and Fluorene-Contaminated Soil by Single and Mixed Plant Cultivation

The ability of three plant species (sweet corn, cucumber, and winged bean) to remediate soil spiked with 138.9 and 95.9 mg of anthracene and fluorene per kg of dry soil, respectively, by single and double plant co-cultivation was investigated. After 15 and 30 days of transplantation, plant elongation, plant weight, chlorophyll content, and the content of each PAH in soil and plant tissues were determined. Based on PAH removal and plant health, winged bean was the most effective plant for phytoremediation when grown alone; percentage of fluorene and anthracene remaining in the rhizospheric soil after 30 days were 7.8% and 24.2%, respectively. The most effective combination of plants for phytoremediation was corn and winged bean; on day 30, amounts of fluorene and anthracene remaining in the winged bean rhizospheric soil were 3.4% and 14.3%, respectively; amounts of fluorene and anthracene remaining in the sweet corn rhizospheric soil were 4.1% and 8.8%, respectively. Co-cultivation of sweet corn and cucumber could remove fluorene to a higher extent than anthracene from soil within 15 days, but these plants did not survive and died before day 30. The amounts of fluorene remaining in the rhizospheric soil of corn and cucumber were only 14% and 17.3%, respectively, on day 15. No PAHs were detected in plant tissues. This suggests that phytostimulation of microbial degradation in the rhizosphere was most likely the mechanism by which the PAHs were removed from the spiked soil. The results show that co-cultivation of plants has merit in the phytoremediation of PAH-spiked soil.

Overexpression of the Galega orientalis gibberellin receptor improves biomass production in transgenic tobacco

Gibberellins (GAs) are well-known phytohormones that contribute to a wide range of plant growth and development functions including stem elongation and leaf expansion. GA receptors perceive GA and transmit signals to activate GA-regulated reactions. In this study, a GA receptor gene with homology to other leguminous plants was isolated from Galega orientalis and termed GoGID. The 1732-bp full-length GoGID gene included an open reading frame of 1035 bp encoding a peptide of 344 amino acids. Sequence analysis indicated that GoGID shares conserved HGGS motif and active amino acid sites (Ser-Asp-Val/IIe) that are essential for maintaining it GA-binding activity. GoGID mRNA expression was more abundant in leaves than in roots or stems and could be up-regulated by the exogenous hormones. Overexpression of GoGID in transgenic tobacco plants promoted plant elongation and improved biomass production. These results suggested that GoGID functions as a GA receptor to alter GA-mediated signaling. GoGID may have a role in genetic engineering for the improvement of forage crops.