Enhancement of seed vigour following insecticide and phenolic elicitor treatment

Thiamethoxam (CGA 293'343) is a novel broad-spectrum neonicotinoid insecticide. It is commercially used as a seed treatment under the trademark Cruiser (CRZ). Although many reports detail its insecticidal, plant-protecting properties, there are minimal reports concerning the effect on seed germination activities which can be key control points of seedling vigour. In this report, we investigated the effect of CRZ, fish protein hydrolysates (FPH; a known elicitor of pentose-phosphate pathway) and the combination of CRZ and FPH (CF) on seed vigour of pea, soybean and corn. Seed vigour was investigated by estimating germination percentage, shoot height, shoot weight, total soluble phenolic content, antioxidant content, G6PDH (glucose-6-phosphate dehydrogenase) activity, and GPX (guaiacol peroxidase) activity. Addition of FPH to CRZ (CF) seemed to have a slightly positive effect on seed vigour, especially, CF and FPH treatment for corn and FPH treatment for pea, suggesting that pre-sowing treatments may cause positive/negative effects on seed vigour, depending on the concentration of treatments. Further research will be needed to determine their effects and the optimal concentration for seed priming.     

Effect of vitamin C and folic acid on seed vigour response and phenolic-linked antioxidant activity

Folic acid and vitamin C were used in the concentration range of 0-500muM as exogenous growth enhancers to stimulate pea (Pisum sativum) seedling vigour. The results suggest that a concentration of 50muM folic acid and 500muM vitamin C were optimum in maximally enhancing seed vigour and potentially seedling performance according to both agronomic and biochemical seed vigour parameters. Results indicated that germination percentage, shoot weight, shoot height, and root length were enhanced in folic acid and vitamin C treated plants compared to control plants. The levels of enhanced phenolic content in response to folic acid and vitamin C treatments were highest on days 8 and 10. Evaluation of critical biochemical parameters indicated that the average glucose-6-phosphate dehydrogenase (G6PDH) activity and proline content in response to treatments were higher than control and correlated to enhanced phenolic content and DPPH-based antioxidant activity. Key enzymes, guaiacol peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) were also higher in response to treatments and correlated to enhanced phenolic content and DPPH-based antioxidant activity. Taken together, these studies support the hypothesis that the proline-linked pentose phosphate pathway stimulates phenolic synthesis and related free-radical scavenging antioxidant activity. Further, this proline-linked pentose phosphate pathway stimulation in response to folic acid and vitamin C was also correlated to antioxidant enzyme response indicated by the stimulation of GPX, SOD, and CAT activities. Therefore, this study indicates the enhancement of seed vigour response by folic acid and vitamin C as reflected in both agronomic and biochemical responses, and this occurred through the stimulation of phenolic-linked antioxidant response that is likely positively modulated through the proline-linked pentose phosphate pathway.     

Effect of hydroxytyrosol‐rich preparations on phenolic‐linked antioxidant activity of seeds

Hydroxytyrosol‐rich extract (HRE) and hydroxytyrosol‐rich olive mill wastewater (HROMW) were used as exogenous growth enhancers to stimulate tomato seedling vigor. The tomato seeds soaking in 10% w/v HROMW or HRE solutions were optimum in maximally enhancing seedling performance according to biochemical seed vigor parameters. Biochemical parameters as the average glucose‐6‐phosphate dehydrogenase (G6PDH) activity in HRE‐treated seeds (915.11 nmoles min^?1 mg^?1 protein) was higher than control (629.58 nmoles min^?1 mg^?1 protein) and correlated with the increased phenolic content (3530 μg g^?1 fw) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH)‐based antioxidant activity (70.60%), respectively. Some key enzymes, guaiacol peroxidase (GPX) (6100.65 nmoles min^?1 mg^?1 protein) and catalase (2.04 μmoles min^?1 mg^?1 protein), were also higher in response to treatments and correlated with enhanced phenolic content and antioxidant activity. This study supports the hypothesis that the exogenous phenolic application stimulates the pentose phosphate pathway through an over‐expression of endogenous phenolic synthesis and an increase in free‐radical scavenging antioxidant activity. Therefore, the current study indicates the enhancement of seed vigor by HRE especially and HROMW as reflected by the stimulation of biochemical responses.     

Phenolic Compounds and Allelopathic Potential of Fermented and Unfermented Wheat and Corn Straw Extracts

Total phenolic (TPC) and flavonoid (TFC) content, individual phenolic compounds and antioxidant activities of methanol extracts of wheat and corn straw were determined. Germination bioassay was conducted with Abutilon theophrasti Medik. , Asclepias syriaca L., and Chenopodium album L. seed. Samples were fermented by Lactobacillus plantarum and changes in TPC, TFC, antioxidant, and biological activity were investigated. TPC and TFC were significant in both samples and after fermentation their recovery was improved. All samples contain mainly quercetin, cinnamic acid, p‐coumaric acid, and ferulic acid. Fermentation changed the content of phenolic and flavonoid compounds, differently in each case. All tested extracts showed high DPPH activity with IC₅₀ being significantly lower for fermented samples. FRAP activity was also high. Crude straw extracts were overall more effective than fermented ones concerning inhibition of germination and seedlings growth, mainly without statistically significant differences between wheat and corn. Compared with mesotrione, extracts were more effective in germination and seedling growth inhibition of C. album and in seedling growth inhibition of A. theophrasti.     

<Emphasis Type="Italic">Piriformospora indica</Emphasis> Alleviates Salinity by Boosting Redox Poise and Antioxidative Potential of Tomato

More than 20% of irrigated land has been influenced by salt stress, decreasing crop production. In this research, we investigated the effect of different levels of salinity (0, 50, 100 and 150 mM NaCl) and the efficiency of Piriformospora indica on growth, biochemical traits, antioxidative defense system in tomato (Solanum lycopersicum L.). NaCl stress reduced chlorophyll content, height and biomass of plants. Higher level of salinity (150 mM) declined the plant height by 22.65%, total dry weight by 56.44% and total chlorophyll by 44.34%, however, P. indica inoculation raised plant height by 43.47%, dry weight by 69.23% and total chlorophyll content by 48.09%. Salinity stress increased H₂O₂, malondialdehyde (MDA), superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) level in leaves and roots tomato seedlings. However, P. indica inoculation reduced H₂O₂, MDA and superoxide anion and enhanced DPPH compared to non-inoculated plants at all NaCl levels. The total phenol and flavonoids increased with NaCl treatment. On the other hand, the total phenolic and flavonoid increased more in P. indica inoculated plants compared to non-inoculated ones. Moreover, inoculation of P. indica implicated noteworthy improvement of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) activity in tomato upon salinity. Notably, colonization with P. indica significantly improved the content of reduced ascorbic acid (AsA), glutathione (GSH) and redox ratio in the tomato plants under salinity resulting in reduced redox state. Our findings confirmed that salinity had negative effect on tomato seedling; however, P. indica inoculation increased tolerance to salinity by improving the content of phenolic compounds, non-enzymatic antioxidants, and increasing the activity of antioxidant enzymes.     

酚酸物质对红松种子萌发及苗木生长和生理特性的影响

通过室内模拟试验,阐明阔叶红松林中已测得含量较高的3种酚酸物质（苯甲酸、丁香酸和香草酸）对红松种子萌发及苗木生长的影响,为探索阔叶红松林内化感作用机理及解决红松更新障碍问题提供科学依据。采用培养皿培养法及室内盆栽培养法,以红松种子和3年生红松苗为试验对象,设置不同浓度（2、20、200 mg/L）苯甲酸、丁香酸、香草酸处理液,以蒸馏水为对照（CK）,进行红松种子萌发试验及红松苗木生长试验,研究3种酚酸物质对红松种子发芽、苗木生长、光合色素、抗氧化酶活性、膜脂过氧化作用及渗透调节物质的影响。结果表明,（1）不同浓度3种酚酸均抑制红松种子萌发,但酚酸浓度变化仅对红松种子发芽率影响差异显著。（2）3种酚酸对红松苗木生长及物质积累抑制作用显著。浓度变化对红松苗株高及地径影响不显著,对生物量、根干重和茎干重影响显著。（3）针叶叶绿素a、叶绿素b、类胡萝卜素含量变化对酚酸处理反应一致,20 mg/L的3种酚酸均显著抑制光合色素产生,而200 mg/L丁香酸溶液及2 mg/L香草酸溶液均显著促进叶绿素a和类胡萝卜素积累。（4）酚酸处理使红松苗针叶中POD、CAT活性降低,SOD活性增加。针叶中MDA含量显著增加,200 mg/L丁香酸溶液处理组针叶MDA含量高于CK处理组70.51%。（5）不同浓度苯甲酸溶液促进可溶性糖增加,抑制可溶性蛋白增加;不同浓度丁香酸溶液促进可溶性蛋白增加,而不同浓度香草酸溶液抑制可溶性蛋白增加,二者对可溶性糖含量影响受浓度变化影响显著。苯甲酸、丁香酸、香草酸影响红松种子萌发,通过对红松苗光合色素、抗氧化酶活性及渗透调节物质的影响导致其生长受抑制、生物量减少,产生膜脂过氧化伤害。因此,解决阔叶红松林内红松更新障碍问题时,凋落物及土壤中酚酸物质的化感作用不容忽视。     

农杆菌对大麦种子萌发及幼苗生长发育的影响

以大麦品种(系)为主区('云引大麦Ⅰ'、'云引大麦Ⅱ'和'U008'),农杆菌浸种时间为副区(0.5、1.5和2.5 h),农杆菌菌液浓度为副副区(0.5、1.5和2.5 OD),采用再裂区试验研究了农杆菌浸种处理对大麦种子萌发和幼苗生长发育的影响.结果表明:品种、农杆菌菌液浓度、浸种时间对大麦的种子发芽率、幼苗高度、幼苗鲜重、叶绿素含量、丙二醛(MDA)含量影响无显著的互作效应,而对幼苗POD活性的影响存在显著互作效应;随着浸种时间的延长和菌液浓度的增加,各大麦品种(系)的种子发芽率、幼苗高度、幼苗鲜重、叶绿素含量均呈逐渐降低趋势,幼苗MDA含量则逐渐增加,并以'U008'变化幅度最大;在菌液浓度为0～1.5 OD、浸种时间为0～1.5 h范围内,幼苗POD活性随着菌液浓度的增加和浸种时间的延长而增强,超过该范围则均呈下降趋势,并以'U008'下降最为明显.可见,农杆菌处理对大麦种子萌发和幼苗生长发育有抑制作用,并在菌液浓度超过1.5 OD、浸种时间大于1.5 h时达极显著水平,且大麦品种间存在一定差异.     

大豆出苗期和苗期对盐胁迫的响应及耐盐指标评价

比较了4个大豆品种出苗期和苗期的耐盐性,测定150 mmol/L NaCl胁迫下的株高、下胚轴长、侧根数、地上干/鲜重、根干/鲜重、MDA含量、SOD活性、游离Pro含量,并将幼苗移栽到田间生长至成熟。结果表明:出苗期和苗期盐胁迫下4个品种的株高都显著降低、地上干/鲜重和根干/鲜重降低;出苗期胁迫侧根数减少,下胚轴长降低;而苗期胁迫侧根数增加,下胚轴长升高。未胁迫条件下,出苗期和苗期耐盐性强的品种22021-1的MDA含量和SOD活性高于耐盐性弱的品种22293-1。胁迫后,22021-1的MDA含量降低、SOD活性升高,其MDA含量分别比对照低51.03%和21.45%,SOD活性比对照高5.85%和45.77%;22293-1的MDA含量出苗期比对照高58.97%,苗期基本无变化,SOD活性出苗期和苗期升高都不显著。MDA和SOD可以作为大豆耐盐性筛选指标。早期的短时胁迫对不同耐盐性大豆品种的经济产量影响不同。     

Seed Film Coating with Uniconazole Improves Rape Seedling Growth in Relation to Physiological Changes Under Waterlogging Stress

Waterlogging is an important constraint of global production of rape. The effects of seed film coating with 0.0075% uniconazole on the growth and physiology was investigated using seedlings from three varieties of rape (Brassica napus L.) subjected to waterlogging. While seed coating with uniconazole had no significant effect on germination percentage during waterlogging stress, it enhanced root vigour, increased root length, root volume and root dry weight. It also significantly enhanced leaf dry weight and ratio of root to shoot, but induced a significant decrease in shoot height and stem dry weight. Seed film coating with uniconazole also significantly increased the activities of the antioxidant enzymes, POD, CAT and SOD, and soluble sugar concentration during waterlogging. Thus, it suggests that seed film coating with uniconazole at a suitable concentration can improve rape seedling growth and increase seedling establishment during waterlogging.     

水稻幼苗特性与籽粒大小关系的分子检测

水稻 (OryzasativaL .)幼苗特性如叶的发生、叶绿素含量、植株高度等对早期生长是重要的 ,与籽粒大小相联系。以水稻珍汕 97A和明恢 6 3组合的重组自交系群体为材料 ,对 5个幼苗特性性状和籽粒大小进行了数量性状基因定位 (QTL) ,目的在于从遗传水平探求幼苗特性与籽粒大小的内在关系。对叶绿素a、总叶绿素含量、第二片叶长、第三片叶长、幼苗高度、粒重分别检测到 2、1、5、4、4、9个QTLs。结果揭示 4个幼苗特性性状的QTL和 4个籽粒大小的QTL位点分别定位在 4个相似区域 (G35 9_RG5 32、C5 6 7_RG2 36、RZ4 0 3_R1 9和C371_C4 0 5a) ,表明幼苗特性性状与籽粒大小间的紧密关系 ,也显示控制籽粒大小的几个染色体区域对幼苗特性性状没有影响 ,这意味着通过标记辅助选择改良幼苗活力但并不增加粒重是可能的     

9个高羊茅品种初期生长对镉胁迫的响应

用Cd²⁺浓度0（对照）、25、50、75 mg/L分别处理9个高羊茅品种种子,测定供试品种种子发芽势、发芽率、幼苗苗高、根长、鲜重、叶绿素含量、丙二醛含量、质膜透性等8项指标,比较9个品种耐镉性。结果表明:与对照相比,在不同浓度Cd²⁺胁迫下,家园的发芽势和发芽率以及麦哲伦鲜重呈先略上升后下降趋势,其余品种的均呈下降趋势;9个高羊茅品种幼苗根长、苗高、叶绿素含量均呈下降趋势;9个高羊茅品种丙二醛含量和质膜透性均呈上升趋势。对测定的8项指标进行综合评价结果显示:在Cd²⁺25 mg/L胁迫下,9个品种耐Cd²⁺性由强到弱的顺序为热浪>翠碧A>里园2号>缤狗>麦哲伦>家园>宇宙星>回报>爱瑞3号;在Cd²⁺50 mg/L胁迫下,耐Cd²⁺性的顺序为热浪>翠碧A>缤狗>麦哲伦>里园2号>家园>宇宙星>爱瑞3号>回报;在Cd²⁺ 75 mg/L胁迫下,耐Cd²⁺性的顺序为热浪>缤狗>里园2号>翠碧A>家园>麦哲伦>爱瑞3号>宇宙星>回报。所以,在治理Cd²⁺污染土壤时,要根据污染严重程度,合理选用高羊茅品种。     

Brassinosteroid improves seed germination and early development of tomato seedling under phenanthrene stress

Polycyclic aromatic hydrocarbons (PAHs) are one of the toxic persistent organic pollutants, have global environmental concern. Seed germination and early seedling development are the initial handicaps for plant establishment in phytoremediation program. Assisted phytoremediation by plant growth regulators may be a potential solution for these problems. Hence, we investigated the effects of seed treatment with various concentrations (0.01, 1.0, 100?nM) of 24-epibrassinolide (EBR) in tomato under graded levels (30, 100, 300???M) of a three-ring PAH namely phenanthrene (PHE). Delayed and decreased seed germination, reduced length and fresh weight (FW) of shoot and root were observed following 10?days of PHE exposure in a dose dependent manner. Chlorophyll fluorescence study suggested a possible photoinhibition and damage to photosynthetic apparatus under PHE exposure. However, seed treatment with EBR improved seed germination and increased length and FW of shoot and root. In addition, EBR remarkably restored the studied chlorophyll fluorescence parameters towards control levels. Different responses in antioxidant enzymes were observed following PHE exposure, while malondialdehyde (MDA) content was increased in a concentration dependent manner. EBR treatment prior to PHE exposure remarkably increased the activities of antioxidant enzymes over PHE alone, but decreased the MDA contents both in shoot and root of young tomato seedlings. Considering all the studied parameters, seed treatment with 1.0?nM EBR was most effective followed by 100 and 0.01?nM for the improvement of germination and seedling growth under PHE stress in tomato.     

芦苇浸提液对虉草种子萌发及幼苗生长生理特性的影响

通过研究不同浓度芦苇浸提液(对照:0;处理1:150g/L;处理2:300g/L)对虉草萌发及幼苗生长影响,揭示了芦苇对虉草化感效应。结果表明:随着芦苇浸提液浓度升高,虉草发芽率、发芽指数、株高、根长以及叶绿素含量显著或极显著下降,各指标相应化感效应指数则显著或极显著上升;超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性和丙二醛(MDA)含量则随芦苇浸提液浓度升高呈不同的升降趋势。所有这些结果显示,随着浸提液浓度升高,芦苇对虉草的化感胁迫效应越来越明显。     

铜胁迫对玉米幼苗生长、叶绿素荧光参数和抗氧化酶活性的影响

本文研究了铜(Cu)胁迫下玉米(Zea mays)幼苗生长、叶绿素含量、叶绿素荧光参数和抗氧化酶活性的变化。研究结果表明, 5~20 μmol.L-1 Cu处理10天明显抑制玉米幼苗根系生长, 并减少玉米幼苗的干物重, 以及增加玉米幼苗地上部和根系含Cu量; 玉米幼苗吸收的Cu大部分积累在根系, 在地上部分布较少。Cu处理还降低玉米叶片的叶绿素含量和Fv/Fm、ETR、qP和qy值。在10天的Cu处理期间, 根系中SOD、POD、CAT和GR活性呈现先上升后下降的趋势。而叶片中的SOD、POD、CAT和GR活性在处理前期不受Cu胁迫的显著影响, 处理后期则因Cu胁迫而增强。实验表明抗氧化酶在抵御过量Cu引起的氧化胁迫中发挥了一定的作用。     

γ-氨基丁酸浸种对番茄种子及幼苗耐盐性调节的生理机制

以番茄‘金棚一号’为材料,研究了外源γ-氨基丁酸(GABA)浸种处理对NaCl胁迫下种子萌发及幼苗生长和生理代谢的影响。结果显示:(1)NaCl胁迫显著抑制了番茄种子的萌发和胚根生长,同时导致番茄幼苗体内活性氧(O2.-、H2O2)大量积累,膜脂过氧化程度加重,幼苗叶片光合系统Ⅱ活性显著降低,幼苗的生长受到严重抑制。(2)外源GABA浸种能够显著提高盐胁迫下番茄种子的萌发和胚根的生长,并以10.00mmol.L-1 GABA浸种处理效果最好。(3)外源GABA浸种处理显著提高了NaCl胁迫下番茄幼苗根系和叶片抗氧化酶(SOD、POD和CAT)活性,降低了活性氧(O2.-、H2O2)的产生和膜脂过氧化程度,通过维持较高的光合系统Ⅱ活性,促进了幼苗的生长及生物量积累,但GABA的缓解效应存在较大的浓度差异,其中以10.00mmol.L-1 GABA处理效果较好。研究表明,10.00mmol.L-1 GABA浸种处理能够通过促进番茄种子萌发和幼苗生长来缓解盐胁迫的伤害。     

Anatomy ofZea mays andGlycine max seedlings treated with triazole plant growth regulators

Soil drenches containing 250 μg of paclobutrazol or uniconazol (50 ml of a 17 μM solution) reduced the height of both corn (Zea mays L. cv. How.Sweet It Is) and soybean (Glycine max (L.) Merr. cv. A2) seedlings. With corn, uniconazol was considerably more active than paclobutrazol in reducing height whereas with soybean both compounds had similar dwarfing effects. The compounds increased foliar chlorophyll content and leaf thickness in soybean but had no effect on these parameters in corn. The increase in leaf thickness with soybean was due primarily to an increase in the thickness of the palisade cell layer. Chloroplast size and ultrastructure of both species were unaffected by the compounds. The growth regulators increased root diameter in both corn and soybean because of increased size of cortical parenchyma cells and particularly in soybean because of radial rather than longitudinal growth of the first few layers of the cortical parenchyma.     

NaCl胁迫下海滨锦葵种子萌发和幼苗生长过程的生理特性变化

以1／4 Hoagland溶液为基础培养液,研究了0．5％、1．0%、1．5％、2．0％和2．5％NaCl处理对海滨锦葵[Kostelezkya rirginica（L．）Presl．]种子萌发和幼苗生长的影响,发现随着培养液中NaCl浓度的增加,海滨锦葵种子萌发率逐渐降低;当NaCl浓度达2．5％时种子不萌发,但NaCl胁迫解除后,种子的萌发率水平与对照相当。幼苗在含0．5％～1．0%NaCl的培养液中生长状况良好,叶绿素含量和根系活力明显增高;但当NaCl浓度达1．5％-2．0％时,叶绿素含量和根系活力逐渐下降;与对照相比,NaCl胁迫下幼苗的MDA水平降低。结果表明,NaCl胁迫对海滨锦葵种子萌发和幼苗牛长有一定的影响,但海滨锦葵可通过种子休眠、增加根系活力、降低体内MDA水平来缓解一定的盐害效应．以适应盐胁迫的生长环境．     

硝基苯酚胁迫下外源褪黑素对水稻幼苗生长及生理特性的影响

采用液体培养实验方法,研究硝基苯酚胁迫对水稻(Oryza sativa L.)幼苗生长、抗氧化特性、光系统Ⅱ(PSⅡ)光合特性的影响,以及添加外源褪黑素对缓解硝基苯酚胁迫的作用。结果显示,随着硝基苯酚胁迫浓度的升高,水稻幼苗株高、根长、地下部干重、地上部干重、全株干重和叶片PSⅡ实际光化学效率[Y(Ⅱ)]、光化学淬灭系数(q P)、PSⅡ电子传递速率(ETR)、叶绿素含量均有所下降,而叶片非光化学淬灭系数(qN、NPQ)上升;同时,根系活性氧[过氧化氢(H_2O_2)和超氧阴离子(O·-2)]积累量、抗氧化酶[超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)]活性,以及渗透调节物质(可溶性蛋白和可溶性糖)含量呈先升高后降低的趋势。在非硝基苯酚胁迫下,与对照组相比,添加外源褪黑素显著提高了幼苗地下部干重、根系可溶性糖含量和SOD活性、叶片PSⅡ光化学效率和叶绿素含量。与单独添加硝基苯酚处理相比,硝基苯酚+褪黑素复合处理显著缓解了硝基苯酚胁迫对幼苗生长、叶片PSⅡ光化学效率和叶绿素合成的抑制作用;降低了根系活性氧水平、抗氧化酶活性和渗透调节物质含量。研究结果表明添加外源褪黑素能够显著缓解硝基苯酚胁迫对水稻幼苗生长、根系活性氧水平、抗氧化酶活性、叶片PSⅡ光化学效率及叶绿素合成的不良影响,提高水稻幼苗对硝基苯酚胁迫的适应性。     

The Effects of Priming and Ageing on Seed Vigour in Tomato

A comparison was made of the effects of seed priming or ageingtreatments on the performance of tomato (Lycopersicon esculentumMill. cv. UC204C) seeds according to a number of indices ofseed vigour. A single lot of tomato seeds was primed in 120mol m^–3 K2HPO4 + 150 mol m^–3 KNO₃ for 5 d at 20?C, or aged at 13% moisture content (dry weight basis) and 50?C for 6 d. Germination percentage (>98%) was unaffectedby priming and reduced to 85% by ageing. X-ray photographs andlongitudinal sections revealed the formation of free space surroundingthe embryo in dry primed seeds, which was not evident in controlor aged seeds. Priming increased the rate of germination atall temperatures above the base temperature (T_b), while ageingdecreased it. T_b was unaffected by priming and only slightlyincreased by ageing. The variation in individual times to germinationwas approximately doubled in both primed and aged seed comparedto the control, based upon the slopes of probit germinationpercentage versus log thermal time curves. Root growth aftergermination tests and seedling growth in both greenhouse andfield tests were not influenced by either priming or ageing.The conductivity test was found to be unreliable as a vigourtest for tomato seeds. The results identify several indiceswhich can be used to quantify seed vigour in tomato. They alsoillustrate that seed priming can enhance seed performance accordingto some criteria, while having no effect or decreasing qualityaccording to other criteria. Seed vigour can apparently be separatedinto various components which can be independently influencedby seed enhancement treatments. Key words: Tomato, seed germination rate, seed priming, seed vigour     

Allelopathic Effects,Physiological Responses and Phenolic Compounds in Litter Extracts of Juniperus rigidaSieb. et Zucc.

The allelopathic effects of Juniperus rigida litter aqueous extract (LE) on wheat and Pinus tabuliformis were studied, as well as the physiological responses to the extract. High concentration LE (0.10 g Dw/ml) significantly inhibited the seed germination and seedling growth in receptor plants. The chlorophyll content and root activity in the wheat seedlings were reduced significantly across all treatments; however, those were more prominently reduced at high concentration (0.10 g Dw/ml) but received little stimulation at low concentration (0.025 g Dw/ml) in P. tabuliformis. The content of malonaldehyde (MDA) increased with increasing concentrations of LE, except at 0.025 g Dw/ml. Activities of antioxidant enzymes (POD, CAT and SOD) in receptor plants were all significantly inhibited at high concentrations but stimulated at low concentrations. These results demonstrate that the aqueous extract from J. rigida litter has allelopathic potential. Various phenolic compounds were identified in litter aqueous extract and litter ethanol extract by HPLC. The phenolic compound content in the aqueous extract was significantly lower than that in the ethanol extract. Chlorogenic acid and podophyllotoxin were the predominant phenolic compounds in both types of litter extracts. These findings suggest that the seed germination and seedling growth of P. tabuliformis and wheat would be inhibited when planted near large amounts J. rigida litter.