The effects of dopamine on root growth and enzyme activity in soybean seedlings

In the present study, we investigated the effects of dopamine, an allelochemical exuded from the velvetbean (Mucuna pruriens L DC. var utilis), on the growth and cell viability of soybean (Glycine max L. Merrill) roots. We analyzed the effects of dopamine on superoxide dismutase, phenylalanine ammonia-lyase and cell wall-bound peroxidase activities as well as its effects on lignin contents in the roots. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), without or with 0.25 to 1.0 mM dopamine, in a growth chamber (25°C, 12L:12D photoperiod, irradiance of 280 μmol m⁻² s⁻¹) for 24 h. In general, the length, fresh weight and dry weight of roots, cell viability, PAL and POD activities decreased, while SOD activities increased after dopamine treatment. The content of lignin was not altered. The data demonstrate the susceptibility of soybean to dopamine and reinforce the role of this catecholamine as a strong allelochemical. The results also suggest that dopamine-induced inhibition in soybean roots is not related to the production of lignin, but may be related to damage caused by reactive oxygen species.     

Nitric oxide affecting root growth,lignification and related enzymes in soybean seedlings

This study analyzed the involvement of nitric oxide (NO) in the root lignification of soybean seedlings. To this end, changes in root cell viability; phenylalanine ammonia-lyase (PAL) and soluble and cell wall bound peroxidase (POD) activities and lignin and hydrogen peroxide (H₂O₂) contents of soybean roots treated with the NO-donor sodium nitroprusside (SNP) and its relationships with root growth were evaluated. Seedlings were cultivated in a nutrient solution supplemented with 5 to 1,000 μM SNP for 24 h. At an extremely low concentration (5 μM), SNP induced root growth and increased lignification and activities of related enzymes (PAL and cell wall-bound POD). At a high concentration (1,000 μM), SNP reduced root growth and lignification (PAL activity and H₂O₂ and lignin contents) and caused a loss of cell viability. Application of potassium ferrocyanide (an analog of SNP that cannot release NO) and PTIO (2-phenyl-4,4,5,5,-tetramethylimidazoleline-1-oxyl-3-oxide, a scavenger of NO) revealed that the inhibitory/stimulatory effects on root lignification may be due to NO itself. These results indicate that NO, depending on its concentration, may act as a stress factor, due to its toxic action, or as a signal molecule, inducing soybean root growth and lignification.     

Peroxidase activity and lignification in soybean root growth-inhibition by juglone

The changes in activities of soluble and cell wall-bound peroxidases and lignin contents in juglone-stressed soybean (Glycine max) seedlings and their relationships with root growth were investigated. Soybean seedlings (3-d-old) were cultivated in nutrient solution supplemented with 0.5 to 25 μM juglone for 24 h. Length and dry mass of roots decreased after 5 to 25 μM juglone treatments. Low juglone concentrations (≤ 1 μM) increased soluble peroxidase activity, while high concentrations (≥ 10 μM) inhibited activities of soluble and cell wall-bound peroxidases. Juglone (≤ 1 μM) did not affect lignin content but highly increased lignification after 5 to 25 μM treatments. Results indicate that lignification may be an important step in root growth reduction of juglone-stressed soybean.     

Cultivar and planting date effects on soybean root growth

To avoid late summer drought, soybean [Gylcine max (L) Merrill] producers in many southern and border states of the USA modify their cropping systems. Options include use of unadapted cultivars and changing planting dates. Because root function is important to plant health and yield, this study was conducted to determine if planting date and soybean cultivar affect root growth and distribution. Seeds of one cultivar from each of four maturity groups (MG III, IV, V, and VI) were sown in mid-April, mid-May, and mid-June in 1992 and 1993 on a Tiptonville silt loam near Portageville, MO. Root observations were performed 30 and 60 days after emergence (DAE) using a minirhizotron system. Cultivars differed for root length density (RLD) only in the 15 to 28 cm depth in 1992 and in the 15 to 28 cm and 29 to 42 cm depths in 1993, but differences were not related to maturity classification of cultivar. Average RLD was 1.02 cm^–3 for MG III and IV cultivars and 1.21 cm cm^–3 for MG V and VI cultivars. Average RLD for the mid-June planting date was 1.65 cm cm^–3 but only 0.73 cm cm^–3 for the mid-April planting date. An increase in RLD between 30 and 60 DAE occurred at all soil depths. For both years, MG V and VI cultivars produced higher yields than the MG III cultivars. Earlier than normal planting dates inhibited early root growth, but did not reduce yield. Cultivars differed only slightly for the rooting characteristics measured in this study. These rooting characteristics may not be important criteria for cultivar selection.Abbreviations MG maturity group - VCR videocassette recorder - DAE days after emergence - RLD root length density - CRLD change in root length density Contribution from the Missouri Agric. Exp. Station Journal Series Number 12, 153Contribution from the Missouri Agric. Exp. Station Journal Series Number 12, 153     

The arbuscular mycorrhizal fungus Diversispora spurca ameliorates effects of waterlogging on growth,root system architecture and antioxidant enzyme activities of citrus seedlings

Citrus plants are often exposed to heavy rain and subsequent periods of soil waterlogging which severely restrict tree growth. We assessed the effect of one arbuscular mycorrhizal fungus species (Diversispora spurca) on growth, root system architecture (RSA), and antioxidant enzyme activities of young citrus (Citrus junos) seedlings. Waterlogging for 37 d significantly restricted mycorrhizal colonization but increased the number of entry points and vesicles. Compared with non-mycorrhizal controls, mycorrhizal seedlings had significantly greater plant height, fresh mass, total root and taproot lengths, projected and surface root areas, root volume, and numbers of lst, 2nd and 3rd order lateral roots regardless of waterlogging treatment. D. spurca significantly increased root catalase (CAT) activity in non-stressed seedlings and increased root soluble protein concentration and leaf CAT activity in waterlogged seedlings, thereby inducing lower oxidative damage. These results suggest that D. spurca ameliorates effects of waterlogging on growth, RSA and antioxidant enzyme activities.     

溴甲烷土壤灭菌对大豆苗期根系生长的影响

利用溴甲烷田间土壤灭菌,研究灭菌对正茬、重茬大豆苗期根系生长和产量的影响.试验结果表明,灭菌处理后重茬(连续种植3a)地大豆根系生长良好,根系形态明显改善,总根长、主根长、植株鲜重和根瘤数增加、孢囊线虫孢囊数为0.而灭菌处理后,正茬地大豆根系前期生长受到一定抑制,主根长、总根长、植株鲜重和侧根数有降低的趋势,但随时间推移,抑制幅度降低.溴甲烷处理促进大豆结瘤.灭菌后,重茬大豆与正茬大豆根系生长差异减少.溴甲烷灭菌处理可作为克服大豆连作障碍问题措施之一.     

Ruzigrass root persistence and soybean root growth

Plant and Soil - Cropping systems using forage grasses as cover crops have been effective in soil conservation and nutrient cycling, but root persistence of ruzigrass (Urochloa ruziziensis) is...     

Soybean root growth inhibition and lignification induced by p-coumaric acid

The effects of 0.25–2 mM p-coumaric acid, a phenylpropanoid metabolite with recognized allelopathic properties, were tested on root growth, cell viability, phenylalanine ammonia-lyase (PAL) activities, soluble and cell wall-bound peroxidase (POD) activities, hydrogen peroxide (H₂O₂) level and lignin content and its monomeric composition in soybean (Glycine max (L.) Merr.) roots. At ≥0.25 mM, exogenously supplied p-coumaric acid induced premature cessation of root growth, increased POD activity and lignin content and decreased the H₂O₂ content. At ≥0.5 mM, the allelochemical decreased the cell viability and PAL activity. When applied jointly with PIP (an inhibitor of the cinnamate 4-hydroxylase, C4H), 1 mM p-coumaric acid increased lignin content. In contrast, the application of MDCA (an inhibitor of the 4-coumarate:CoA ligase, 4CL) with p-coumaric acid did not increase lignin content. The lignin monomeric composition of p-coumaric acid-exposed roots revealed a significant increase of p-hydroxyphenyl (H) and guaiacyl (G) units. Taken together, these results suggest that p-coumaric acid's mode of action is entry via the phenylpropanoid pathway, resulting in an increase of H and G lignin monomers that solidify the cell wall and restrict soybean root growth.     

Effects of metalaxyl enantiomers stress on root activity and leaf antioxidant enzyme activities in tobacco seedlings

The objective of this experiment was to study the effects of metalaxyl enantiomers on the activity of roots and antioxidative enzymes in tobacco seedlings. Water culture experiment was conducted to analyze the effects of different concentrations of metalaxyl enantiomers (30 and 10 mg L^?1) on root activity and leaf superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and malondialdehyde (MDA) content of tobacco seedlings. The results showed that metalaxyl significantly inhibited root activity and significantly improved leaf SOD, POD, and CAT activities and MDA content. A better physiological response in tobacco seedlings was observed at 30 mg L^?1 than at 10 mg L^?1 metalaxyl. The stereoselectivity for different enantiomers had no obvious effect on root activity and the leaf POD activity, but it affected significantly the SOD and CAT activities and MDA content. The SOD activity was promoted more by R‐enantiomer than by S‐enantiomer at 30 mg L^?1 metalaxyl, and the same effect was observed on CAT activity from the beginning to the end of the stress period. The MDA content under the stress by R‐enantiomer was higher than that under the stress by S‐enantiomer at 10 mg L^?1 metalaxyl.     

Some effects of nitrate and light intensity on soybean root growth and development

A field experiment was conducted to determine the effects of light intensity and nitrate nutrition on soybean (Glycine max (L) Merr.) root growth and development. Relative growth rates, total, root and nodule dry weights, and the rates of increase in the number of roots indicated that nitrogen fixation limited growth relative to that achieved with nitrate and that the response to nitrate increases with light intensity and varies with plant age. Nitrate increased with rate of taproot extension but light intensity had no effect.     

活性铝对小麦根生长及酶活性的影响

利用铝形态分布与环境pH的相关性,通过改变染毒液pH条件,研究了不同浓度活性铝对小麦根生长、蛋白质含量及酸性磷酸酶活性的影响,并探讨了不同形态活性铝植物毒性的差异.本实验染毒液中总铝浓度设置为0(CK)、25(T₁)和75μmol·L^-1(T₂)3组,各组pH分别调至4.0、4.5、5.0和5.5.结果表明,微量Al_a与Al_b对小麦根生长均具有抑制作用.但随染毒液中活性铝组分的改变,小麦根蛋白质含量和酸性磷酸酶活性显现相反变化趋势:T₁和T₂组在pH4.0,活性铝主要成分为Al_a时(Al_a浓度高于活性铝浓度的90%),小麦根细胞蛋白质含量显著下降,酸性磷酸酶活性显著上升;T₁和T₂组在pH5.0,Al_a浓度降低至与Al_b浓度接近,且Al_a和Al_b浓度均低于10μmol·L^-1时,根细胞蛋白质含量显著上升,酸性磷酸酶活性显著下降.     

Cell wall peroxidase activity,hydrogen peroxide level and NaCl-inhibited root growth of rice seedlings

The changes in cell-wall peroxidase (POD) activity and H₂O₂ level in roots of NaCl-stressed rice seedlings and their correlation with root growth were investigated. Increasing concentrations of NaCl from 50 to 150 mM progressively reduced root growth and increased ionically bound cell-wall POD activity. NaCl had no effect on covalently bound cell-wall POD activities. The reduction of root growth by NaCl is closely correlated with the increase in H₂O₂ level. Exogenous H₂O₂ was found to inhibit root growth of rice seedlings. Since ammonium and proline accumulation are associated with root growth inhibition caused by NaCl, we determined the effects of NH₄Cl or proline on root growth, cell-wall POD activity and H₂O₂level in roots. External application of NH₄Cl or proline markedly inhibited root growth, increased cell-wall POD activity and increased H₂O₂ level in roots of rice seedlings in the absence of NaCl. An increase in cell-wall POD activity and H₂O₂ level preceded inhibition of root growth caused by NaCl, NH₄Cl or proline. NaCl or proline treatment also increased NADH-POD and diamine oxidase (DAO) activities in roots of rice seedlings, suggesting that NADH-POD and DAO contribute to the H₂O₂ generation in the cell wall of NaCl- or proline-treated roots. NH₄Cl treatment increased NADH-POD activity but had no effect on DAO activity, suggesting that NADH-POD but not DAO is responsible for H₂O₂ generation in cell wall of NH₄Cl-treated roots.     

Low temperature acclimation of root fatty acid composition, leaf water potential, gas exchange and growth of soybean seedlings

Abstract Root fatty acid composition, photosynthesis, leaf water potentials, stomatal resistances, leaf specific weights, and root: shoot ratios of soybean were measured in two temperature regimes. Groups of soybean plants were grown in controlled chambers of the Duke University Phytotron under two thermoperiods. One group of the plants was grown from seed for 3 weeks in either 29/23°C or 17/11°C thermoperiods, and another group was grown for 2 weeks in 29/23°C and then transferred to the 17/11°C thermoperiod where it remained for 8 days. Broccoli was also grown in either 29/23°C or 17/11°C thermoperiods. Soybean roots contained more unsaturated fatty acids than broccoli roots, although broccoli roots showed a larger increase in unsaturation than soybean roots with decreased temperature. The fatty acid unsaturation in the roots of soybean began to increase rapidly after the temperature regime was changed. The increase was in the new roots produced in the cold regime rather than in the pre-existing roots. The soybean leaf water and osmotic potentials decreased about 0.4 MPa, beginning one day after the transfer from 29/23°C to 17/11°C, but recovered significantly after 8 d. Plants grown at 17/11 °C had lower rates of photosynthesis and adaxial stomatal resistances, but higher root: shoot ratios and specific leaf weights compared to plants grown at 29/23°C. Plants grown and maintained at 29/23°C showed a steady increase in photosynthetic rates over the 8-d experimental period, whether rates were measured in 1 mol m^?3 or 9 mol m^?3 oxygen. Plants transferred to 17/11°C however maintained constant rates of photosynthesis at 1 mol m^?3 O₂, whereas at 9 mol m^?3 rates declined for 2 d then were constant for the remaining 6 d of the experimental period. These results suggest that changes in membrane fatty acid unsaturation is an important aspect of plant acclimation to chilling temperatures in terms of maintaining root permeability and water uptake. However, the degree of unsaturation is not a good indicator of differences in chilling tolerance among species. The apparent acclimation of photorespiration to a constant percentage of photosynthesis suggests a role of photorespiration in the plant.     

Isoflavonoids in root and hypocotyl of soybean seedlings (Glycine max,Fabaceae)

Isoflavonoids, some of which are highly fluorescent, are produced by soybean [Glycine max (L.) Merr.] and serve as chemical signals for certain aspects of nitrogen fixation and microbial resistance. This study was conducted to determine whether soybean mutants with nonfluorescent roots contained abnormal concentrations of isoflavonoids. Isoflavonoids were extracted from the root and hypocotyl of 4-d-old wild-type soybean seedlings (cv. Hark) having fluorescent roots and from four nonallelic mutant, near isogenic lines of Hark having nonfluorescent roots. In addition, isoflavonoids were extracted from the root and hypocotyl of 4-d-old seedlings of near isogenic lines of Hark harboring two pairs of the mutant alleles for nonfluorescent roots. Malonyl daidzin, daidzin, malonyl genistin, and genistein were the most abundant isoflavonoids extracted from either the root or hypocotyl of seedlings with either fluorescent or nonfluorescent roots. Extracted malonyl daidzin, malonyl genistin, and malonyl glycitin decomposed readily, yielding daidzin, genistin, and glycitin, respectively. The concentrations of malonyl genistin and genistein, two highly fluorescent compounds, were similar in both fluorescent and nonfluorescent roots. Thus, root fluorescence was not correlated with abundance per se of fluorescent isoflavonoids in roots. In addition, the abundance of isoflavonoids extractable from the hypocotyl did not correlate with root fluorescence.     

根系在凋落物层生长对凋落叶分解及酶活性的影响

根系向凋落物层生长是森林生态系统存在的普遍现象,研究根系存在对凋落物分解的影响对理解森林生态系统的养分物质循环具有重要意义.在福建三明市楠木和格氏栲林进行1年的凋落叶分解试验,设置有根处理和无根处理(对照),研究根系生长对凋落叶分解速率、养分释放和酶活性的影响.结果表明:在分解360 d后,有根处理楠木和格氏栲凋落叶干...     

Variety specific relationships between effects of rhizobacteria on root exudation,growth and nutrient uptake of soybean

Aims

It has been increasingly recognized that only distal lower order roots turn over actively within the <2 mm fine root system of trees. This study aimed to estimate fine root production and turnover rate based on lower order fine roots and their relations to soil variables in mangroves.

Methods

We conducted sequential coring in five natural mangrove forests at Dongzhai Bay, China. Annual fine root production and turnover rate were calculated based on the seasonal variations of the biomass and necromass of lower order roots or the whole fine root system.

Results

Annual fine root production and turnover rate ranged between 571 and 2838 g m^?2 and 1.46–5.96 yr^?1, respectively, estimated with lower order roots, and they were increased by 0–30 % and reduced by 13–48 %, respectively, estimated with the whole fine root system. Annual fine root production was 1–3.5 times higher than aboveground litter production and was positively related to soil carbon, nitrogen and phosphorus concentrations. Fine root turnover rate was negatively related to soil salinity.

Conclusions

Mangrove fine root turnover plays a more important role than aboveground litter production in soil C accumulation. Sites with higher soil nutrients and lower salinity favor fine root production and turnover, and thus favor soil C accumulation.

     

Nitrite in the root zone and its effects on ion uptake and growth of wheat seedlings

The immediate and posteffects of various concentrations of NaNO₂ on ion uptake of wheat ( Triticum aestivum L. cv. GK Öthalom) seedlings were studied at different pH values. Without pretreatment, the higher the concentration of NaNO₂ the greater was the decrease in uptake of K⁺ into the roots, both at pH 4 and pH 6. At pH 6 but not at pH 4 the reverse was true when the seedlings were pretreated with NaNO₂. Due to the high Na⁺ content of the roots, an effect of Na⁺ in this process cannot be excluded. Nitrite was taken up by the roots more rapidly than nitrate. Nitrite at 0.1 m M in the medium induced the development of an uptake system for both NO⁻₂ and NO⁻₃ in wheat roots. At higher concentrations pretreatment with NO⁻₂ decreased NO⁻₃ uptake by the roots, but NO₃ did not inhibit the uptake of NO₂. The toxic effect of NO⁻₂ was strongly pH dependent. Lower pH of the external solution led to an increased inhibition by NO⁻₂ of both ion uptake and growth of seedlings. The inhibitory effect of NO⁻₂ differed considerably for roots and shoots. The roots and especially the root hairs were particularly sensitive to NO⁻₂ treatment.     

Comparative effects of NaCl and polyethylene glycol on root distribution,growth, and stomatal conductance of sour orange seedlings

An experiment was conducted to study sour orange (Citrus aurantium L.) seedling root density, distribution, and morphological development under NaCl and polyethylene glycol (PEG) stresses in relation to shoot growth and stomatal conductance. Plants were treated with 2 stress levels (– 0.12 and – 0.24 MPa) of NaCl and PEG 4000 for 7 months. Root observation chambers were used to monitor root growth and distribution under stressed and non-stressed conditions. Seedlings receiving NaCl or PEG treatments produced fewer roots and shallower root systems with 46 to 65% of the roots occurring in the top portion of the soil. Fibrous root weight per unit length was increased by 24 to 30% by PEG but was not significantly increased by NaCl.Root growth rate usually alternated with shoot growth in a 2-month cycle. This alternating pattern was not shifted by NaCl and PEG stresses. In all NaCl and PEG treatments, growth was depressed and stomatal conductance was reduced. Compared to controls, plants that received NaCl or PEG had smaller shoot and root dry weights, fewer leaves, shorter height, and fewer roots. Sodium chloride usually caused less damage than PEG to sour orange seedlings suggesting that NaCl and PEG acted through different mechanisms.Florida Agricultural Experiment Station Journal Series No. 9941.     

Effect of vanadium on the growth of soybean seedlings

Pot experiments were conducted in a glasshouse to investigate the effects of vanadium (V) on the growth of soybean seedlings in two soils. As the concentration of V added to the fluvo-aquic soil (Fluvaqents) exceeded 30 mg V kg^-1 soil, the dry matter yields of shoots and roots were significantly decreased (>1%LSD), and the leaves of soybean seedlings turned yellow and withered and the roots were short and beginning to rot. In the red earth (Oxisols), no marked stunting was observed (<5% LSD), even when the concentration of V added to the soil was as high as 75 mg V kg^-1. As the concentrations of vanadium in soybean seedling were closely related to the concentration of soluble vanadium in soil solutions at pH 5–9 in the soil equilibrium solution, the fluvo-aquic soil had lower adsorption capacity for V than the red earth, there was much higher concentration of soluble V in the soil solution, so the symptom of V toxicity appearing in the plants grown on fluvo-aquic soil was easily observed. In addition, the ratio of the total Mo to the total V in shoots decreased slightly with increase of concentration of V added to soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Control of wheat root growth. The effects of excision on growth,wall rheology and root anatomy

Excision and subsequent incubation of the apices (1 cm) of wheat (Triticum aestivum L.) seedling roots in simple media severely reduced elongation from 28 mm·(24 h)^-1 in intact roots to a maximum of 2 mm·(24 h)^-1 in excised roots. The reduction in growth was accompanied by a loss of cell turgor in the growing zone but was correlated with a hardening of the cell walls in this region. Rheological properties were measured as percent extensibility (both plastic and elastic) using a tensiometer, and as instantaneous volumetric elastic modulus ( _i) using the pressure probe. Excision decreased plastic and elastic properties with a half-time of some 60 min. Plastic extension was reduced from 2.5% to 0.9% and elastic from 4.8% to 2.6% for an 8-g load. By contrast, _i was increased by excision. The observed reduction in root elongation rate was accompained by a reduction in mature cell length from 240 m to 40 m and a shortening of the zone of cell expansion.Symbol _i instantaneous volumetric elastic modulus