The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

Low phosphorus (LP) limits crop growth and productivity in the majority of arable lands worldwide. Here, we investigated the changes in physiological and biochemical traits of Tibetan wild barleys (Hordeum vulgare L. ssp. spontaneum) XZ99 (LP tolerant), XZ100 (LP sensitive), and cultivated barley ZD9 (moderately LP tolerant) under two phosphorus (P) levels during vegetative stage. These genotypes showed considerable differences in the change of biomass accumulation, root/shoot dry weight ratio, root morphology, organic acid secretion, carbohydrate metabolism, ATPase (Adenosine triphosphatase) activity, P concentration and accumulation under LP in comparison with CK (control) condition. The higher LP tolerance of XZ99 is associated with more developed roots, enhanced sucrose biosynthesis and hydrolysis of carbohydrate metabolism pathway, higher APase (Acid phosphatase) and ATPase activity, and more secretion of citrate and succinate in roots when plants are exposed to LP stress. The results prove the potential of Tibetan wild barley in developing barley cultivars with high tolerance to LP stress and understanding the mechanisms of LP tolerance in plants.     

磷高效型野生大麦根系形态和根系分泌物对低水平植酸态有机磷的响应特征

【目的】 有机磷为土壤磷库的重要组成部分,研究不同磷效率作物对有机磷的利用能力的差异,有助于了解作物高效吸收磷的机理。 【方法】 以磷高效基因型大麦(IS-22-25、IS-22-30)和低效基因型大麦(IS-07-07)为试验材料,植酸钠为有机磷源进行水培试验。设置5个植酸钠浓度(0.1、0.2、0.3、0.4、0.5 mmol/L),使用根系扫描仪分析其根长、根表面积、根体积等形态特征,并测定根系与根系分泌的酸性磷酸酶、植酸酶活性等生理特征。 【结果】 随有机磷浓度降低,磷高效基因型野生大麦总根长、总表面积和总体积呈增加趋势。低有机磷浓度下,磷高效基因型大麦总根长较正常有机磷浓度(0.4 mmol/L)下增加了139.7%~146.0%,直径D＜0.16 mm的根长提高了156.8%~161.5%,且磷高效基因型总根长较低效基因型高8.6%~60.4%。低有机磷浓度下,磷高效基因型根系各参数均显著高于低效基因型。随着有机磷浓度降低,磷高效基因型根总表面积提高了83.5%~117.5%,较低效基因型高14.0%~46.4%;根总体积提高了80.7%~119.3%,较低效基因型高19.6%~150.0%。随着有机磷浓度升高,磷高效基因型根系及其分泌酸性磷酸酶和植酸酶活性显著降低。低有机磷浓度下,磷高效基因型根系酸性磷酸酶和植酸酶活性增加了163.3%~172.2%和98.6%~121.2%,较低效基因型高14.4%~41.2%和23.1%~37.2%;磷高效基因型根系分泌酸性磷酸酶和植酸酶活性增加了157.8%~193.4%和172.4%~183.4%,较低效基因型高20.2%~45.7%和24.7%~51.4%。 【结论】 在低浓度有机磷胁迫下,磷高效基因型通过良好的根系形态,有效扩大了根系对水分和养分的接触空间,为磷高效基因型的快速生长和磷素吸收提供了条件;同时,低浓度有机磷胁迫增强了根系分泌酸性磷酸酶和植酸酶,提高了介质环境中磷素的生物有效性,对有机磷的吸收利用表现出明显优势。     

Growth and physiological characterization of low nitrogen responses in Tibetan wild barley (Hordeum spontaneum) and cultivated barley (Hordeum vulgare)

Development of crop cultivars with high yield under low nitrogen (N) supply is a basic approach for the enhancement of agricultural sustainability. The previous studies showed that Tibetan wild barley shows wider genetic diversity in abiotic stress and poor fertility tolerance. In this study, four barley genotypes (two Tibetan wild and two cultivated), differing in N use efficiency (NUE), were characterized for their growth and physiological responses to low N stress. The genotypes ZD9 (cultivated) and XZ149 (wild) with high NUE performed better in terms of shoot dry weight (DW) and photosynthetic parameters under both low and normal N levels and had higher antioxidative enzyme activities, N concentration, and accumulation in both shoots and roots under low N stress. The current results showed the substantial difference among barley genotypes in low N tolerance and verified the significance of Tibetan wild barley in the genetic improvement of cultivated barley in NUE.     

Ecological correlates of RAPD DNA diversity of wild barley, Hordeum spontaneum, in the Fertile Crescent

Genetic variability in RAPDs (Randomly Amplified Polymorphic DNA) was studied in 104 genotypes of wild barley, Hordeum spontaneum from 21 populations sampled in Israel, Turkey and Iran, seven population from each country. The band (= loci) frequencies were calculated for each population and correlated with ecogeographical variables. In general, high RAPD genetic diversity indices were associated with stressful environments, either with hot or cold steppes and deserts. Interpopulational genetic distances showed no association with the geographic distance between the populations' provenance. Significant Spearman rank correlations between RAPD band frequencies and ecogeographical parameters of provenance occured. Frequencies of RAPD bands were significantly correlated with the principal component factors of allozymes. The correlation data indirectly suggest that natural selection appears to be the major determinant of both RAPD and allozyme diversities both being correlated with environmental stress.     

Evaluation of aluminum tolerance of three barley cultivars by two short-term screening methods and field experiments

Productivity of cereal crops growing in acid soils of Southern Chile have adversely being affected by acidification and aluminum phytotoxicity. For overcoming such constraints, farmers need to apply heavy amounts of lime and/or use AI-tolerant plants especially with AI-sensitive crops, as barley is. The objectives of this study were to determine the degree of Al tolerance of . three barley cultivars commonly grown in volcanic soils by using two shortterm screening methods and to relate their rankings with field experiments. Additionally, the amounts of citric and malic acids exuded from roots were determined for studying the mechanism involved in Al tolerance. Relative root length (RRL) was the criterion used to evaluate Al tolerance both in nutrient solution and in soil-based culture and yield for field experiments. Results showed a close relationship between the RRL values obtained with the three barley cultivars by applying the two short-term screening methods. Barley yields obtained in field experiments carried out in two soils differing in Al contents agreed well with the ranking observed in the laboratory suggesting that the short-term screening methods could be a useful tool for knowing Al tolerance of cereals habitually cropped in our acidic volcanic soils. Citric and malic acids were detected mainly in the exudates from the most AI-tolerant barley which could indicate a chelation mechanism implied in such a tolerance.     

不同参数评价植物耐铝性的研究

利用相对根伸长率、根尖Al含量和根尖胼胝质含量等三项参数结合苏木精染色法,研究Al胁迫下,各参数在评价植物耐Al性上的地位,以及各参数间的相互关系。结果表明,不同植物和品种间三个参数变异幅度很大,相互间大都达到显著差异水平。各参数以及苏木精染色法在衡量同一植物不同品种间的耐Al性差异时是一致的,衡量不同植物耐Al性时则有所差别。通过相关性分析,确定根尖Al含量和根尖胼胝质含量都可以在一定程度上反映植物或品种间的耐Al性差异,在需要时可以作为替代相对根伸长率或作为补充对植物的耐Al性差异进行评价。     

Difference in response to aluminum among Japanese coniferous species

Seedlings of Chamaecyparis obtusa, Cryptomeria japonica D. Don, and Abies firma Sieb. et Zucco were grown hydroponically for 4 weeks in the presence or absence of aluminum (Al) and with or without reduced pH. Under exposure to AI, root and shoot growth of C. obtusa was enhanced. A. firma showed the same tendency as C. obtusa, though not significantly. Only in C. japonica, growth was reduced with Al, especially shoot growth. In all the species, callose production in the root tips was observed in the presence of Al. A positive correlation was observed between the relative root callose content and relative root growth (r = 0.83), and significant root elongation with AI treatment was observed in all the species. Therefore, it is considered that callose deposition in the root tips of these species may not indicate the Al-induced root cell injury causing root growth inhibition. The highest callose content in the root tip and strong callose fluorescence in the epidermis and zones of cell contact were observed in C. obtusa. Since the Al translocation rate from roots to leaves was the lowest in C. obtusa and since significant growth enhancement was observed in the presence of Al, it is possible that the accumulation of callose in the root epidermis and in the zones of cell contact is related to Al-resistance in C. obtusa.     

铝胁迫下水稻幼苗根尖表面pH和有机酸的动态变化

采用添加pH指示剂溴甲酚紫的琼脂糖凝胶平板技术, 检测了铝胁迫下水稻幼苗根尖表面pH和根尖细胞有机酸含量的动态变化。铝胁迫下, 幼苗根尖表面颜色在处理第1 h、3 h、6 h无明显变化; 而对照处理第1 h时水稻幼苗根尖表面颜色已发生明显变化, 呈浅橙色, 处理第3~6 h幼苗根尖表面变为橙红色。表明在正常条件(pH 4.4)下水稻幼苗根尖表面pH有碱化趋势, 铝胁迫条件下(pH 4.4)水稻幼苗根尖表面pH碱化的趋势被抑制。在测定的铝胁迫水稻幼苗根尖细胞细胞质10种有机酸中, 发现3种有机酸含量的变化趋势不同。草酸含量无明显变化; 柠檬酸含量在铝处理0~3 h内变化不明显, 处理3 h后迅速提高, 处理12 h达最大值后转而下降, 铝胁迫24 h时柠檬酸含量比胁迫12 h时降低16.27%, 差异达显著水平, 胁迫24 h后的柠檬酸含量变化不大但仍高于胁迫6 h的柠檬酸含量; 铝处理3 h后苹果酸含量较胁迫前下降幅度不大, 差异不显著(P>0.05), 3 h后显著下降, 6 h后下降趋势不明显。     

Varietal differences in the growth of rice plants in response to aluminum and silicon

Effects of Al (0–100 μM) and Si (0–2,000 μM) supplied singly or in combination on root growth of different rice varieties were examined under hydroponic conditions. Al addition inhibited root elongation of rice plants, and the inhibition increased with increasing amount of Al in the culture solution. Among 22 indica varieties and among 8 japonica varieties tested, IAC3 and Nakateshinsenbon were relatively tolerant to AI, respectively, whereas IR45 and Norinl were relatively sensitive to AI, respectively. Si exerted a beneficial effect at all levels of Si treatment on indica varieties, whereas Si supply resulted in a slight increase in the root dry weight of japonica varieties only at the highest level (2,000 μM Silo The alleviation of Al inhibition of rice root growth by Si was observed in the combination of Al and Si treatments. Alleviation was more pronounced for all the Si treatments in indica varieties than in japonica varieties, and the alleviation was maximum with 2,000 μM Si in IR45. The alleviation effect by Si was more pronounced in the AI-sensitive varieties than in the AI-tolerant varieties. The application of Si resulted in an increase in the contents of Al and Si in plants, and there was no relationship between the Al content and Al inhibition in plants.     

Genetic diversity in wild barley (Hordeum spontaneum C. Koch) in the Near East: a molecular analysis using Random Amplified Polymorphic DNA (RAPD) markers

We analyzed the genetic diversity in 88 genotypes from 20 populations of wild barley (Hordeum spontaneum C. Koch) from Israel, Turkey and Iran, by randomly amplified polymorphic DNA (RAPD). Twenty two of the 33 primers used yielded scorable products with 1–11 polymorphic bands. No duplicate patterns were found except for four haplotypes.When the total genetic diversity was estimated, 75% of the variation detected was partitioned within the 88 genotypes and 25% among the populations. When variation between countries was assessed, no substantial differences were found, because most of the variation detected (97%) was partioned within the 20 populations and the remainder among countries. The results of this limited survey indicate that the extensive genetic diversity is present in natural stands of wild barley throughout the Fertile Crescent.     

铝胁迫下大豆根系脱落酸累积与柠檬酸分泌的关系研究

为探讨铝(Al)胁迫条件下脱落酸(ABA)调控植物根系有机酸分泌的机制,进行了ABA与Al诱导大豆根系柠檬酸分泌的关系试验。结果表明:1)外源ABA和ABA合成抑制剂fluridone分别提高和降低了Al诱导的大豆根尖ABA含量的增加,但对根系柠檬酸分泌量均无影响,ABA对根系内源柠檬酸含量和柠檬酸合成酶的活性也没有影响;2)分根试验表明,与Al直接接触的根部(Part A)内源ABA含量发生变化,且有柠檬酸的分泌,而不与Al直接接触的根部(Part B)内源ABA含量也发生变化,但没有柠檬酸分泌;3)Al胁迫下,大豆耐Al基因型柠檬酸分泌量远高于敏感基因型,但二者的内源ABA含量却没有差异;4)30μmol AlCl3处理,在0~12 h柠檬酸分泌速率和内源ABA含量随Al处理时间增加而增加,去除Al胁迫时(12~18 h),柠檬酸分泌速率继续增加,但内源ABA含量则迅速下降。综合以上结果,推测ABA不是通过提高Al诱导柠檬酸分泌来调控大豆耐Al性。     

Evaluation of grain yield indices in hexaploid wheat genotypes in response to drought stress

Drought stress limits crop production in the world. Therefore, employing high-yielding cultivars tolerant to drought is an effective approach to reduce its detrimental effects. To identify drought-tolerant genotypes, 36 wheat genotypes were evaluated during the 2010–2011 and 2011–2012 growth seasons. A field experiment was conducted in a split-plot design with two irrigation treatments (100% field capacity (FC) until harvest and no irrigation after anthesis) as main plots in three replications and genotypes as subplots. Grain yield, its components and drought tolerance indices were measured. Results showed a significant reduction in yield and its components under drought conditions. Grain yield had significant positive correlations with stress tolerance index (STI), mean productivity (MP) index and geometric mean productivity (GMP), while it was negatively correlated with stress susceptibility index (SSI) and tolerance index (TOL) under stress condition. These results indicated that superior genotypes could be selected based on high values of STI, MP and GMP and low value of SSI. The results were validated by principal component analysis (PCA) as it showed genotypes with high PC1 and low PC2 were more desirable. Based on the results, genotypes number 8, 11, 17, 30, 34 and 35 were recognized as suitable for both conditions.     

The effect of cobalt stress on growth and physiological traits and its association with cobalt accumulation in barley genotypes differing in cobalt tolerance

Cobalt (Co) is beneficial for legume plants and not an essential element for most plants. There is no sufficient information about the effect of Co stress on barley growth. The current experiment was carried out to investigate the effects of different Co levels (25, 50, 75, and 100 µM) on growth and physiological traits of three barley genotypes (B325, J36, and B340) differing in Co tolerance. The results showed that Co stress inhibited plant growth, decreased chlorophyll content and photosynthetic rate, and enhanced oxidative stress. However, the effects differed among genotypes, with B325 and B340 being the most and the least affected, respectively. Co stress caused decrease and increase of manganese (Mn) and phosphorus (P) concentrations in both roots and shoots, respectively; iron (Fe) concentration had little change in shoots and a significant decrease in roots. The current results showed a close association of Co tolerance and its accumulation in plant tissues.     

Effects of freeze and cold stress on certain physiological and biochemical traits in sensitive and tolerant barley (Hordeum vulgare) genotypes

An experiment was performed as a split-plot design based on a randomized complete block (RCB) with three replicates. The aim was to explore physiological traits, catalase (CAT) and peroxidase (POD) activity associated with cold and freeze stress in four barley genotypes (two stress-tolerant genotypes and two sensitive genotypes). The genotypes were regarded as sub-plots and five temperature levels (namely 20, 4, 0, ?4, ?8°C) as main plots. The results revealed that the hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content increased through freeze and cold stress from 20 to 4°C. This increase was more in the sensitive genotypes than in the tolerant ones. Subsequent to the increase in lipid peroxidation, the membrane stability index (MSI) decreased, thereby increasing the electrolyte leakage. The sensitive genotypes demonstrated greater reduction in the studied parameters. Upon the increase in the H₂O₂ content, the antioxidant enzymes CAT and POD also increased in order to collect and prevent H₂O₂ from damaging the cell and the plant. Compared with the sensitive ones, the tolerant genotypes indicated more increase in the enzymes. The H₂O₂ and MDA content decreased from ?4 to ?8°C, which could be due to intracellular freezing in the sensitive genotypes, but due to the detoxifying of the antioxidant enzymes in the tolerant genotypes. Compared with the POD content, the increase in the CAT content through cold stress was more, which could mean that it was possibly CAT which acted as the main inhibitor of H₂O₂ in cold stress in the barley plant.     

耐盐和非耐盐大麦幼苗叶片抗氧化及抗坏血酸–谷胱甘肽循环系统对 NaCl 胁迫的反应差异

【目的】研究NaCl胁迫下,耐盐和非耐盐品系大麦幼苗叶片抗氧化系统及抗坏血酸–谷胱甘肽循环的反应差异。【方法】以耐盐品系12pj-118和非耐盐品系12pj-045为材料进行了水培试验。营养液中设定了6个NaCl浓度:0、100、200、300、400、500 mmol/L。在大麦苗生长至3叶1心时,取样分析测定叶片中活性氧代谢、抗氧化酶活性以及抗坏血酸–谷胱甘肽循环变化。【结果】随着NaCl胁迫的增加,2个品系的O_2~-产生速率、H_2O_2含量和MDA含量均逐渐增加,耐盐品系12pj-118的增幅均小于非耐盐品系12pj-045;SOD、POD、CAT、APX、GR活性、As A含量、GSH含量和As A/DHA比值均呈先上升后下降的趋势。12pj-118的SOD、POD、CAT活性在各NaCl浓度胁迫下的增幅大于12pj-045,降幅小于12pj-045;12pj-118的APX、GR活性在同一盐浓度胁迫下的增幅均大于非耐盐品系12pj-045,降幅小于12pj-045;在各NaCl浓度下,12pj-118的As A含量和As A/DHA比值较对照增幅均大于12pj-045;GSH/GSSG比值呈波状变化,12pj-118在较高NaCl浓度下,仍能够维持较高的GSH含量和GSH/GSSG比值。显示12pj-118较12pj-045有较强的耐盐性。【结论】耐盐和非耐盐品系大麦叶片抗氧化及抗坏血酸–谷胱甘肽循环系统在NaCl胁迫下的反应不同。在一定范围内,随着盐胁迫增强,耐盐品系12pj-118叶片SOD、POD、CAT、APX和GR活性、As A和GSH含量增幅均大于非耐盐品系12pj-045,降幅小于12pj-045,表明叶片抗氧化及抗坏血酸–谷胱甘肽循环系统与大麦幼苗抗盐性密切相关。     

Monitoring the photosystem II behavior of wild and cultivated barley in response to progressive water stress and rehydration using OJIP chlorophyll a fluorescence transient

To study the effects of progressive drought stress on photosystem II behavior of wild type (Spantaneum) and cultivated barley (Morocco), different levels of soil water availability, including control, moderate, mild, and severe water stress (70%, 50%, 30%, and 10% water holding capacity of soil, respectively) and rehydration were used. Polyphasic OJIP fluorescence transient of Morocco plants exhibited a considerable increase in fluorescence intensity at O, J, and I steps under mild and severe stress relative to slight increase in wild barley. Values of fluorescence parameters and quantum efficiencies, including minimal fluorescence, relative variable fluorescence at phase J and I, maximal quantum yield of photosystem II (PSII), performance index, electron transport yield, and excitation transfer efficiency were influenced by water stress in both genotypes. These parameters were significantly less affected in wild type barley by progressive drought stress compared to Morocco. After re-watering, both genotypes were able to restore from severe drought in most of the traits. Based on our findings, highly correlated values of relative water content (RWC) and independent JIP-test parameters (P < 0.01) indicate that the chlorophyll a fluorescence induction technique is sensitive to plant water status and performance index represent an accurate and reliable indicator for early stress detection and also explore plant vitality under water stress.     

Osmotic stress and silicon act additively in enhancing pathogen resistance in barley against barley powdery mildew

Osmotic stress as well as silicon (Si) improve the resistance of barley (Hordeum vulgare cv. Ingrid) against barley powdery mildew (Blumeria graminis f. sp. hordei Speer). Nothing is known about interactions, particularly whether Si is necessary for pathogen resistance induced by osmotic stress. In this paper, we show that Si nutrition was not necessary for osmotic‐stress‐induced pathogen resistance. Si‐mediated resistance could, however, be enhanced by osmotic stress and vice versa. Even at maximum Si‐mediated resistance, further enhancement of pathogen resistance by osmotic stress was possible. The fungus was controlled by the formation of effective papillae in both treatments. The combined effect of Si and osmotic stress was as strong as the calculated addition of the Si and the osmotic‐stress effect. Our data clearly show that the effect of osmotic stress and Si is not competitive but additive. A synergistic action of both treatments cannot be supported by our data. It is assumed that the basal pathogen resistance of barley is enhanced by Si due to strengthening of papillae in addition to the increased formation of effective papillae induced by osmotic stress. Therefore, the addition of Si increases pathogen resistance equally at all investigated NaCl concentrations. A function of Si in pathogen defense exceeding the strengthening of papillae is not supported by our data.     

Root cation exchange capacity of cotton cultivars in relation to aluminum toxicity

Root cation exchange capacity (CEC) was analyzed for four cotton cultivars (Pima S‐5, Stoneville 825, Deltapine 41 and Auburn 56) within tvo species (Gossypium barbadense and G. hirsutum) grown in control (O Al) and Al (1.5 mg/l) solution. Pima S‐5, a G. barbadense variety, had significantly (P < 0.10) lower root CEC than G. hirsutum cultivars in control (O Al) solution. Root CEC of Stoneville 825 was numerically but not significantly lower than Auburn 56 and Deltapine Al in control solution. Root CEC was significantly reduced in all cultivars when grown in Al solution. Compared to controls, Pima S‐5 and Stoneville 825 had either numerically or significantly less reduction in root CEC than Auburn 56 or Deltapine 41 in Al solution. Aluminum content of roots after CEC analysis was numerically greater in the former cultivars than the latter.

The lower root CEC of Pima S‐5 and Stoneville 825 in non‐toxic conditions could provide an initially greater Al tolerance when roots grow into marginally Al toxic soil. Under sustained, Al toxic conditions, root CEC becomes altered and is more of an indirect indicator of root growth as affected by as yet undetermined Al tolerance mechanism(s).

The steady‐state technique to determine root CEC virtually eliminated the inherent problems of CO. effects on pH and titrating to an end point in a specific period of time in a dynamic system.     

野生大豆根系形态对局部磷供应的响应及其对磷吸收的贡献

通过土柱试验模拟局部供磷,定量评价了磷局部供应对野生大豆根系形态参数的影响以及这些根形态参数对植株磷吸收的贡献.磷局部供应明显改变了野生大豆的根形态,使总根长增加了80.5％,比根长增加了32.6％,根表面积扩大了70.7％,根直径减小了27.6％,植株对磷的吸收增加了43.2％,地上干重增加了72.0％;在所有的根形态参数中,总根长、根表面积和比根长对野生大豆植株磷吸收具有较大贡献,其中尤以比根长对植株磷吸收贡献最大,即在根长增加的同时,根直径减小能够明显提高野大豆根系对磷的吸收.结果表明,野生大豆对局部磷供应表现出高度的根系形态可塑性,通过局部养分供应优化根系空间分布和定向调控根系生长能显著提高植物对异质性土壤磷资源的获取能力.