Effect of salt stress on tomato plant and the role of calcium

Abstract

Salinity is one of the serious abiotic stresses that has adverse effects on plant growth. The aim of this study was to investigate the effect of sodium chloride (NaCl) on germination and growth parameters of tomato plant as well as the role of Ca²⁺as an ameliorating agent. 100?mM NaCl and two concentrations of calcium (5 and 10?mM) were applied to tomato seeds and seedlings. This study was carried out in a Completely Randomized Design (CRD) with a total of six treatments each comprising of three replicates. The application of 100?mM of NaCl delayed the germination time by 27.6%, reduced the seedling length and seedling vigor by 24.33% and germination stress tolerance by 27.6% as compared to control. Salinity also reduced the plant growth (root and shoot length, root fresh and dry weight, shoot fresh and dry weight, membrane stability, relative water content and leaf area), whereas the application of calcium mitigated the negative effects of salinity on germination and growth to a greater extent. With increased calcium concentration, growth and germination increased significantly both alone and in the salt-affected plant. 10?mM calcium showed best results and enhanced the promptness index by 20.7%, seedling length and vigor by 15.1% and GSI by 20.7%. It also improved root fresh and dry weight, shoot fresh and dry weight, relative water content and leaf area. Similarly, 5?mM calcium also increased plant height and membrane stability index. The present study suggests that application of Ca²⁺ enhanced the growth of tomato plant under saline conditions.     

Calcium and humic acid affect seed germination,growth, and nutrient content of tomato (Lycopersicon esculentum L.) seedlings under saline soil conditions

The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg^?1) and calcium (0, 100, 200 and 400 mg kg^?1) were applied to growth media treated with 50 mg NaCl kg^?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg^?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg^?1 Ca²⁺ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.     

Seed priming with sorghum water extract and benzyl amino purine along with surfactant improves germination metabolism and early seedling growth of wheat

The influence of seed priming with sorghum water extract (SWE) and benzyl amino purine (BAP) on germination metabolism and early seedling growth of wheat was evaluated in this study. For priming, wheat seeds were soaked in SWE (5%), BAP (5 mg L^?1) alone and mixed with nonionic surfactant Tween-80 (0.05%). All the seed priming treatments significantly (p ≤ 0.05) improved the germination metabolism and early seedling growth as compared with dry seeds. Seed priming with combination of SWE, BAP and Tween-80 was the most effective treatment in improving the final germination percentage (34%), number of tillers per pot (50%), fresh weight (32%), dry weight (63%), chlorophyll contents (7%) and total phenolic contents (36%) over dry seed control. Similarly, maximum total soluble proteins, total soluble sugars and α-amylase activity were observed from the combined priming with SWE, BAP and Tween-80. Total soluble proteins were maximum in growing seedlings followed by germinating seeds than primed seeds. The germination and growth improvement by priming with SWE was comparable to BAP which makes it a cost-effective natural growth regulator. Combined applications are more effective, which may be due to enzymatic regulation in a synergistic manner.     

腐殖酸对NaCl胁迫下梭梭种子萌发及幼苗生长的影响

[目的] 探究腐殖酸对NaCl胁迫下梭梭种子萌发及幼苗生长的影响,为干旱矿区生态修复提供技术支持。[方法] 设置5个NaCl盐胁迫浓度,5个腐殖酸添加浓度,观测梭梭种子萌发以及幼苗生长指标,分析腐殖酸对梭梭种子萌发及其幼苗生长的耐盐性。[结果] 施用适量腐殖酸能显著提高种子萌发率,缓解梭梭种子萌发过程中的盐胁迫,促进初生根生长,降低盐胁迫对幼苗的伤害。在1.0 mol/L NaCl条件下,腐殖酸为700 mg/kg时缓解效果最好,与对照相比梭梭发芽率、发芽势、根长、幼根鲜质量和幼根干质量分别提高10%,11.12%,1.77 cm,4.84 mg和4.03 mg。[结论] 腐殖酸可作为干旱矿区生态修复中种子萌发和幼苗生长的一种盐渍土调节剂,具有较好的应用潜力。     

综合形态与叶片叶绿素含量的番茄壮苗指数筛选

为建立最佳的番茄秧苗壮苗指数,提高秧苗评判的准确度,该文以四叶一心番茄秧苗为研究对象,在测定11项秧苗指标的基础上,利用模糊综合评判法建立番茄秧苗综合评价指数,使用主成分分析进行指标筛选并组合构成多个番茄壮苗指数,通过综合评价指数与壮苗指数的相关分析筛选出适宜的壮苗指数并验证。结果表明:对300株样本进行统计分析,番茄秧苗综合评价指数为0.26～0.79,可全面概括秧苗的整体素质,能客观、准确地评价秧苗健壮程度;通过秧苗单一指标的主成分分析将各指标划分为形态指标、色素指标和株高3个主成分,表明秧苗的质量必须从形态、叶绿素含量和株高这3方面进行评价。从主成分中各选一种指标进行完全随机排列组合成25种壮苗指数,并筛选出与综合评价指数相关性较高且具有代表性的4种壮苗指数;并用3种不同品种番茄秧苗对其进行稳定性验证,其中壮苗指数"(总叶绿素/株高)?全株干质量"与综合评价指数相关性最大为0.797且极显著(P0.01),稳定性好、代表性强,可作为衡量番茄秧苗素质的推荐壮苗指数。以番茄秧苗的综合评价指数为分级依据,根据推荐壮苗指数将秧苗质量分为3个等级(等级Ⅰ(壮苗指数≥0.065)为优质苗,等级Ⅱ(壮苗指数:0.030～0.065)为合格苗,等级Ⅲ(壮苗指数≤0.030)为弱苗(幼苗或老苗)),各等级间差异显著,可以作为较好的判别指标。该研究表明可为番茄育苗生产提供参考,也可为其他蔬菜秧苗评判提供参考。     

腐植酸对番茄苗期氮素代谢的影响

腐植酸对肥料具有改性增效的作用,以番茄为供试材料,研究腐植酸增效剂不同添加量对番茄苗期生长及氮素代谢酶活性的影响,为腐植酸的开发应用提供参考依据。采用砂培试验方法,设置了向霍格兰营养液分别加入腐植酸增效剂0(HA0),1(HA1),2(HA2),5(HA3),10(HA4) mL/L处理。培养30天后,测定番茄的生长指标、植株养分含量、硝酸还原酶活性、谷氨酰胺合成酶和谷氨酸脱氢酶活性。添加适量腐植酸增效剂能促进番茄苗期生长,HA3处理番茄根系干重比HA0提高了31.68%,HA1处理番茄地上部干重最大。添加腐植酸可以提高番茄苗期叶片叶绿素含量,HA3处理番茄苗期叶片叶绿素总量和类胡萝卜素含量最高,分别比HA0提高了17.11%,24.04%。添加适量腐植酸增效剂能增加番茄苗期根系和地上部对氮素的吸收,HA3处理的番茄根系、地上部及总氮素积累量比HA0分别提高了30.61%,20.24%,21.54%。添加腐植酸增效剂可以调控番茄根系和叶片氮素代谢过程,提高了氮素代谢酶活性,与HA0相比,HA4处理根系硝酸还原酶活性最大,HA3处理根系谷氨酰胺合成酶活性最高,HA2处理根系谷氨酸脱氢酶的活性最大;HA3处理番茄苗期叶片中硝酸还原酶、谷氨酰胺合成酶和谷氨酸脱氢酶活性最大,与HA0处理相比分别提高了38.27%,64.54%,106.63%。添加腐植酸增效剂可以促进番茄苗期的生长和对氮素的吸收,提高氮素代谢酶活性,处理中以在营养液中添加5 mL/L腐植酸增效剂效果最佳,腐植酸增效剂添加量低于5 mL/L时,对番茄苗期的生长及氮素代谢具有明显的促进作用。     

~(60)Coγ辐射对野牛草干种子的刺激生长效应

用不同剂量(25～300Gy)60Coγ射线辐射野牛草干种子,对辐射后干种子的发芽情况和幼苗的性状进行了室内和田间观测,结果表明:辐射可促进干种子萌发,特别是100Gy辐射剂量可明显提高种子的发芽率;对田间出苗率,幼苗的根长、高度而言,150Gy是其临界点;辐照剂量在100Gy以下对幼苗的茎叶和根系鲜重有促进作用;因而,从实验结果中我们初步确定促进野牛草种子萌发适宜的辐射剂量为100～150Gy。     

Potential of Trichoderma spp. as consistent plant growth stimulators

In a series of repeated trials, six Trichoderma spp. strains, applied as a dried powder from a liquid fermentation in molasses/yeast medium, proved to be consistent at promoting the growth of lettuce (Latuca sativa L.) seedlings grown in a peat-sand potting compost in the glasshouse. Strains WT, 92, 20, and 75 at 0.75% or 1% w:w concentrations increased shoot dry weight by up to 26%, although WT did inhibit germination. For example, after 4 days only 13% of seeds sown in WT 1% w:w treated compost had germinated, whereas in other treatments germination was consistently greater than 32%. WT increased shoot fresh and dry weights by 14.3 g and 0.6 g per pot, respectively, without affecting the root dry weights, to give concomitant increases in shoot: root ratios of fresh and dry weight. The potential use of these Trichoderma spp. strains for plant growth promotion is discussed.     

二氧化碳施肥对番茄幼苗生长与养分吸收利用的影响

Exposing tomato seedlings to elevated CO2 concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO2 on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO2 (360 or 720 μL L-1), and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age),and the seedling vigor index (seedling vigor index = stem thickness/(plant height × total plant dry weight) increased with the elevated CO2, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO2 did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO2 treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO2 concentrations.     

Alleviation of noxious effects of cattle ranch composts on wheat seed germination by inoculation with Azospirillum spp.

Two commonly-used composts from dairy cow manure that are used to improve poor structure and fertility of desert soils have inhibitory effects on wheat seed germination, probably as a result of their high levels of humic acids. Inoculation of wheat seeds with two species of the plant growth-promoting bacteria Azospirillum brasilense Cd and A. lipoferum JA4 (separately) prior to sowing in these amended soils improved germination, similar to the natural level of germination of seeds in desert soil without compost amendment. Both compost amendments increased height of wheat seedlings in the range of 20–25%, increased shoot dry weight by 15–19%, but severely decreased (51–54% less) root dry weight. Inoculation of wheat seeds with A. brasilense Cd, but not with A. lipoferum JA4, significantly increased plant growth parameters (height, shoot and root dry weight) over control plants grown in soil-compost mixtures. This bacterial species could survive for a period of 20 days in compost humic acid solution, could increase its population when the humic acids served as the sole carbon source, and may change the composition of humic acids in which it grows. We suggest that inoculation with A. brasilense may alleviate noxious effects on germinating seeds caused by compost application by possibly transforming the composition of humic acids in the compost.     

Seed priming in nanoparticles of water treatment residual can increase the germination and growth of cucumber seedling under salinity stress

Abstract

A laboratory experiment was carried out to evaluate the impact of the nanoparticles of water treatment residuals (nWTRs) and salt stress on germination and growth parameters of cucumber seedling. The interaction between three nWTRs treatments (0, 500, and 1000 mgL^?1) nWTRs and five saline solution (fresh water: sea water) treatments had 0.70, 2, 3, 6, and 11?dSm^?1 were studied. The results revealed that increasing salinity levels significantly reduced the percentage of germination (GP) for the primed seeds treated in fresh water and nWTRs. The GP reduction was higher in seeds primed in fresh water compared to which primed in nWTRs. Salt stress negatively affected radicle length of cucumber seedling for both priming treatments. However, this impact was more pronounced for the primed seeds treated in fresh water than which treated in nWTRs at high salinity stress. Priming in nWTRs significantly decreased the root radius of cucumber seedlings, and the1000 mgL^?1 priming treatment obtained a lowest value of radicle radius. Increasing salt concentration in culture medium reduced total biomass of cucumber seedling, however for the primed seeds treated in nWTRs, the total biomass was increased in comparison with which treated in fresh water. Salt tolerance and vigor indices were significantly (p?<?0.01) affected by salinity levels, nWTRs treatments and their interaction. It can be concluded that nWTRs are ameliorating materials for plant growth under salt stress conditions.     

Effects of humic acids and herbicides,and their combinations on the growth of tomato seedlings in hydroponics

The morphology and length of roots and shoots of tomato (Lycopersicon esculentum Mill.) seedlings grown on a nutrient medium for fourteen days in a controlled environment chamber were apparently not affected, whereas the dry matter content of roots was significantly enhanced when 200 mg L^?1 of humic acid (HA) isolated from either a non-amended soil or a sewage-sludge-amended soil was present in the nutrient medium. In contrast, the HA-like fraction isolated directly from the sewage sludge caused, under the same conditions, extensive alterations of tomato morphology and a significant reduction of the length and dry weight of both shoots and roots. The presence in the nutrient medium of the herbicides alachlor or imazethapyr at concentrations of 1 and 0.01 mg L^?1, respectively, caused a marked decrease of tomato root and shoot length and dry weight. Differently, the herbicide rimsulfuron at a concentration of 0.01 mg L^?1 produced a slight decrease in shoot and root length and a slight increase in their dry weight. A combination of 200 mg L^?1 soil HA and each of the herbicides alachlor, rimsulfuron and imazethapyr at concentrations of 1, 0.01 and 0.01 mg L^?1, respectively, in the nutrient medium attenuated the growth depression of tomato shoots and roots observed in the presence of the herbicide alone. However, the simultaneous presence of sewage sludge HA and any herbicide in the nutrient solution caused negative synergistic effects on tomato growth. The volume of nutrient solution and the amount of electrolytes taken up by tomato plants during the growth experiments correlated highly significantly with the total plant dry weight. Tomato seedlings induced a pH decrease in the nutrient medium in all treatments except in those where sludge-HA was present, either alone or in combination with any herbicide.     

纳米氧化镁促进番茄植株生长的机理

  【目的】  探讨具有抗菌作用剂量的纳米氧化镁 (MgONPs) 对番茄早期生长发育的影响，并明确其被吸收和在植株体内的运输特性，为MgONPs在植物营养和病害防控领域的应用提供理论依据。  【方法】  以番茄为模式植物，利用MgONPs (50～250 μg/mL) 处理番茄种子和幼苗，测定种子萌发率、MgONPs处理幼苗30天后的植株生物量、植物组织细胞形态、叶绿素含量和相对含水量等指标，并用电感耦合等离子发射光谱仪和透射电子显微镜 (TEM) 测定植株对MgONPs的吸收状况。  【结果】  50～250 μg/mL的MgONPs对番茄种子的发芽无抑制作用，而对番茄幼苗生长具有显著的促进作用，其中250 μg/mL剂量作用最显著；此剂量处理后的番茄根长、根干重、地上部分干重和径围分别为20.33 cm、0.11 g、0.20 g、1.65 cm，对照分别为15.63 cm、0.03 g、0.15 g和1.16 cm；番茄叶绿素含量提高了47.37%，相对含水量提高了13.14%。且MgONPs促进了镁元素的吸收，MgONPs处理后番茄叶片中的镁含量较清水组提高了35.16%；透射电子显微镜 (TEM) 照片发现，MgONPs处理后叶片叶绿体周围有纳米颗粒的聚集；扫描电子显微镜 (SEM) 照片和石蜡切片观察证实，MgONPs未破坏番茄植株的组织和细胞形态，明确了在一定浓度下MgONPs对番茄植物细胞无毒副影响。  【结论】  MgONPs在土壤中的分散程度虽然不如在去离子水中，但是依然表现出对番茄生长的显著促进作用，且对种子发芽和幼苗生长无任何不利影响。施入土壤后，MgONPs能被番茄根系吸收，通过维管束系统向上运输至叶片中，从而显著增加叶绿素含量和相对含水量，最终促进了幼苗的生长和干物质积累。在本试验条件下，高浓度 (250 μg/mL) 的MgONPs促进番茄生长的效果好于低浓度。     

Earthworm-Processed Organic Wastes as Components Of Horticultural Potting Media for Growing Marigold and Vegetable Seedlings

We germinated and grew tomato, pepper, lettuce, and marigold seedlings in a standard commercial soilless plant growth medium (Metro-Mix 360), and in coir/perlite and peat/perlite-based container media substituted with 10% or 20%, by volume, of vermicompost derived from pig manure or food wastes. Half of the treatments were watered with liquid inorganic fertilizer while the other half received only water. Germination rates of tomato, pepper, lettuce, and marigold seeds in the coir/perlite mixture did not differ significantly from that in Metro-Mix 360. However, the germination rate of tomato, pepper and lettuce seedlings was very low in the peat/perlite mixture. Substituting some of the peat/perlite mixtures with equal amounts of vermicomposts, particularly pig manure vermicompost, enhanced germination rates greatly, making it comparable to that in the commercial medium (Metro-Mix 360). Pepper, lettuce, and marigold seedlings grown in Metro-Mix 360, which already contains a starter nutrient fertilizer in its formulation, had greater root and shoot dry weights than those grown in the control media (coir/perlite mix and peat/perlite mix). Substituting coir/perlite and peat/perlite mixtures with 10% or 20% of either vermicompost enhanced the growth of seedlings significantly, resulting in an overall plant growth as good as and sometimes better than that in Metro-Mix 360. When the plants were provided daily with a complete fertilizer solution, marigold seedlings in peat-based substrate with 20% pig waste vermicompost, and lettuce seedlings in both coir and peat-based substrates, mixed with 20% food wastes vermicompost, produced greater shoot dry weights than those grown in the commercial potting medium. The growth enhancements tended to be greater in peat/perlite-based mixes than in coir/perlite-based mixes, more so with the addition of pig manure vermicompost than with food waste vermicompost. Earthworm-processed pig manure and food wastes would be suitable materials for inclusion into the formulation of soilless potting media, since substitution of these media with relatively low concentrations of vermicomposts can promote plant growth.     

育苗基质添加腐植酸促进番茄穴盘苗生长改善生理特性

【目的】以番茄为材料,研究穴盘育苗基质中腐植酸添加对幼苗生长及硝酸还原酶活性、光合参数等的影响,为培育优质壮苗和腐植酸的应用提供参考依据。【方法】番茄育苗基质以草炭、蛭石、珍珠岩按体积比4:3:2配成,其中腐植酸含量为54.5 g/L（约11.85%）,播种前在基质中分别添加折合纯腐植酸0（CK）、10 g/L（T1）、20 g/L（T2）、30 g/L（T3）、40 g/L（T4）,共5个处理,每处理3次重复,每个重复3个穴盘。待植株长到5叶1心（子叶展开后29~31天）时测定番茄幼苗的生长指标、根系活力、硝酸还原酶活性、光合色素含量、光合参数和叶绿素荧光参数。【结果】T1、T2、T3处理均显著提高了番茄幼苗的株高、茎粗,对番茄幼苗根干重的提高幅度大于地上部干重;T1、T2处理显著提高了根冠比和壮苗指数,T3处理与CK差异不显著;各生长指标均以T2处理表现最好,T4处理最差。T1、T2、T3处理显著提高了根系活力和硝酸还原酶活性,而T4处理二者明显降低。基质中适当提高腐植酸含量,可提高番茄幼苗叶片各种光合色素含量,但腐植酸含量过高,则会降低各光合色素含量。T1、T2、T3处理的Pn、Gs、Ci均显著高于CK,均以T2处理最高,T4处理的Pn、Gs显著低于CK,但其Ci高于CK;Tr表现为CK最高,随腐植酸添加量的增加,逐渐降低。T1、T2处理的Fo、NPQ均低于CK,且以T2处理的最低,T3、T4处理的均高于CK,且以T4处理的最高;各处理的Fv/Fm和ΦPSⅡ的大小顺序均为T2 > T1 > CK > T3 > T4,其中T1、T2处理显著高于CK,T3、T4处理则显著低于CK。【结论】番茄育苗基质中腐植酸在已含有54.5 g/L的基础上以添加20 g/L能够更好地促进番茄穴盘苗生长,改善其生理活动,对培育壮苗有更好的效果。     

Effect of fly ash extract on growth and development of corn and soybean seedlings

Different concentrations of aqueous extract of fly ash were prepared by soaking air dried fly ash and mixing thoroughly with an electric blender. Extracts were then applied to the seeds of corn (Zea mays L.) and soybean (Glycine max L.) after being filtered through a Whatman No. 42 filter paper. Fly ash extract in the lower concentration range of 0.5 to 1.0% (W/V) had no significant effect on germination and seedling growth of each of the two crops. Higher concentrations of fly ash extracts, however, had deleterious effects on the percentage of germination, viability, number of roots, shoot and root length, fresh weight and dry weight of seedlings of both the crops. The elemental concentrations in shoot and root systems of control seedlings of corn and soybean were found to be the same, whereas in the extract treated corn and soybean seedlings, a relatively high elemental concentration was found in roots as compared to shoots.     

磁化等离子体处理大豆种子的生物学效应

利用不同剂量的磁化等离子体处理晋豆20种子,分析被处理种子发芽率、幼苗生长、呼吸与能量的代谢以及同功酶谱的变化,为探讨磁化等离子体对种子的作用机理提供依据。结果表明,经不同剂量磁化等离子体处理后,种子的发芽率和幼苗的根长、干重没有显著变化;2.0～3.0A处理组苗高、鲜重比对照分别增加17.8%～26.9%和12.70%～17.08%;2.0A处理侧根数比对照显著增加,增幅为11.8%。当处理剂量为2.5A时,根系活力提高60.9%,叶片和根系的呼吸速率分别提高43.68%和38.92%,ATP含量分别提高37.79%和47.68%。磁化等离子体处理大豆种子后幼苗同工酶谱没有特异性条带的产生,但POD和酯酶同工酶的活性得到了普遍提高,其中2.5A处理后POD活性最高。综合分析指标表明2.5A的磁化等离子体处理对刺激种子活力、促进种子发芽和幼苗生长效果最佳。     

Seed priming improves growth of nursery seedlings and yield of transplanted rice

Abstract

An attempt to improve the performance of rice (Oryza sativa L.) nursery seedlings through seed priming and its effect on the yield after transplantation was made in a field trial. Priming tools employed during the investigation include pre-germination, hydropriming for 48 h, osmohardening with KCl and CaCl₂ (ψs-1.25 MPa) for 24 h, vitamin priming with 10 ppm ascorbic acid for 48 h and seed hardening for 24 h. All the priming techniques resulted in improved germination speed and spread, seedling fresh and dry weight, root and shoot length, number of secondary roots, seedling nitrogen, total sugars and α-amylase activity. Osmohardening with CaCl₂ resulted in the best performance as indicated by improved germination speed and spread, seedling vigour and starch metabolism, followed by hardening and osmohardening with KCl. However, improved starch metabolism in coarse rice was observed in osmohardening with KCl. Higher K and Ca contents were observed in seeds osmohardened with KCl and CaCl₂, respectively. Maximum straw and kernel yield and harvest index were recorded from osmohardening with CaCl₂ in fine and osmohardening with KCl in coarse rice. Increased number of secondary roots and α-amylase activity were accompanied with increased seedling nitrogen and reducing sugars, respectively.     

Protection of tomato seed germination from the inhibitory effect of 2,4,5-trichlorophenoxyacetic acid by inoculation of soil with Burkholderia cepacia AC1100

The effect of 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) on the germination and seedling vigor of different crop seeds was tested. Seeds of rice, maize, sorghum, finger millet, and horse gram were comparatively more tolerant to the chemical with no marked effect up to a concentration of 200 mg 2,4,5-T L(-)(1) as tested by the filter paper method. Tomato and brinjal (egg plant) were highly susceptible. Even at 5 and 10 mg 2,4,5-T L(-)(1), marked reduction in the germination and seedling vigor of tomato and egg plant, respectively, was observed. At 20 and 30 mg L(-)(1), the germination of tomato and egg plant seeds, respectively, were completely inhibited on filter paper, whereas the inhibitory concentrations in soil was 40 mg 2,4,5-T kg(-)(1) soil. Several abnormalities were observed in the chemically affected seedlings. Protease activity of the seeds germinating in the presence of the chemical was drastically reduced. Bioremediation of the chemically contaminated soil with Burkholderia cepacia AC1100, by inoculation of the soil 7 days before sowing the seeds, completely protected the seeds, resulting in normal germination and an improved seedling vigor.     

Humic substances can modulate the allelopathic potential of caffeic, ferulic, and salicylic acids for seedlings of lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum Mill.)

The capacity of a leonardite humic acid (LHA), a soil humic acid (SHA), and a soil fulvic acid (SFA) in modulating the allelopathic potential of caffeic acid (CA), ferulic acid (FA), and salicylic acid (SA) on seedlings of lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum Mill.) was investigated. Lettuce showed a sensitivity greater than that of tomato to CA, FA, and SA phytotoxicity, which was significantly reduced or even suppressed in the presence of SHA or SFA, especially at the highest dose, but not LHA. In general, SFA was slightly more active than SHA, and the efficiency of the action depended on their concentration, the plant species and the organ examined, and the allelochemical. The daily measured residual concentration of CA and FA decreased drastically and that of SA slightly in the presence of germinating seeds of lettuce, which were thus able to absorb and/or enhance the degradation of CA and FA. The adsorption capacity of SHA for the three allelochemicals was small and decreased in the order FA > CA > SA, thus suggesting that adsorption could be a relevant mechanism, but not the only one, involved in the "antiallelopathic" action.