Root Growth Of Cress Research Articles

Piper longum L. leaf extracts, a candidate allelopathic plant that suppressed the growth of six test plants, could be a source of potent phytotoxic compounds

Using allelopathic plants, particularly those with growth inhibitory action, has gained significant consideration worldwide because such plants do not have detrimental effects on the environment. Piper longum L. (Piperaceae) is a medicinal plant that has already been documented for its diverse ethnomedicinal uses but not for its phytotoxic action. Therefore, aqueous methanol extracts of P. longum were evaluated for their allelopathic activity at plant biochemistry laboratory, Kagawa University, Kagawa, Japan. The allelopathic efficacy of different concentrations of P. longum leaf extract was investigated against six plant species (alfalfa, cress, lettuce, Italian ryegrass, barnyard grass, and foxtail fescue), and their growth was recorded after 48 h of treatment. The results showed significant inhibition of seedling growth at 0.03 g dry weight (DW) equivalent P. longum extract, and this inhibition was further increased with increasing extract concentration. The maximum inhibitory effect was noted at 0.3 g DW equivalent P. longum extract per mL. The concentrations required for 50% inhibition of shoot and root growth were 0.003–0.070 and 0.003–0.028 g DW equivalent P. longum leaf extract per mL, respectively. The shoot growth of cress, alfalfa, and lettuce, and the root growth of cress, foxtail fescue, and alfalfa were inhibited the most by the P. longum extracts. Thus, these results indicate the potent allelopathic activity of P. longum, which also implies the presence of allelopathic compounds in the P. longum leaf extract.

Allelopathic Activity of Annona reticulata L. Leaf Extracts and Identification of Three Allelopathic Compounds for the Development of Natural Herbicides

Using plant-based allelopathic compounds might be a potent substitute to help mitigate the effects of synthetic herbicides. Annona reticulata L. is often planted for its fruit in residential gardens. This plant is well-documented for its diverse ethnomedicinal uses. However, there is no information in the literature on the allelopathic potential of A. reticulata leaves. Therefore, the allelopathic potential and relevant allelopathic compounds of A. reticulata leaves were investigated in this study. The bioassays were carried out using a completely randomized experimental layout (CRD), and the resulting data were analyzed using one-way ANOVA at p ≤ 0.05. Aqueous methanol extracts of A. reticulata leaves significantly inhibited the growth of three dicots and three monocots (Lepidium sativum L., Medicago sativa L., Lactuca sativa L., Echinochloa crus-galli (L.) P. Beauv., Lolium multiflorum Lam., and Phleum pratense L., respectively). The level of growth inhibition was proportional to the A. reticulata extract concentration. Three compounds were purified through different chromatographic steps, and their structures were determined using spectroscopy and identified as loliolide, 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one, and 3,4-dihydroxyphenylethanol. The 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one had the greatest effect on suppressing cress root growth, while loliolide had the greatest effect on suppressing timothy shoot growth. The values for 50% seedling growth suppression showed that the compound with the maximum inhibitory activity was loliolide, followed by 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one and 3,4-dihydroxyphenylethanol. Therefore, this result suggests that the three compounds might be responsible for the allelopathic effects of A. reticulata leaf extracts, and these compounds have the potential to be used to develop effective bioherbicides.

Allelopathic potential and identification of two allelopathic substances in Eleocharis atropurpurea

Eleocharis atropurpurea is an annual weed and distributed widely in pantropical and subtropical regions. Yet, there have been no studies on the allelopathy of E. atropurpurea. Therefore, we investigated the allelopathic potential of E. atropurpurea to identify allelopathic substances from it. The aqueous methanolic extracts of E. atropurpurea showed an inhibitory effect on the seedling growth of lettuce, rapeseed, barnyard grass and foxtail fescue. Inhibition was species- and concentration-dependent. Two substances, syringaldehyde and acetosyringone, were isolated by using chromatography and using spectroscopy their structures were determined. Syringaldehyde and acetosyringone inhibited the shoot and root growth of cress and barnyard grass at concentrations greater than 3.0 mM except shoot growth of barnyard grass by acetosyringone. Concentration and seedling growth of cress and barnyard grass displayed a negative correlation. The I 50 values of syringaldehyde and acetosyringone for the shoot and root growth of cress were 1.67 and 1.61 mM, and 1.49, and 1.29 mM, respectively, whereas for the shoot and root growth of barnyard grass the values were 4.09 and 2.41 mM, and 4.54 and 1.92 mM, respectively. Therefore, it is suggested that these compounds may contribute to the inhibitory effects of E. atropurpurea.

Phytotoxic Activity and Identification of Phytotoxic Substances from Schumannianthus dichotomus.

The phytotoxic potential of plants and their constituents against other plants is being increasingly investigated as a possible alternative to synthetic herbicides to control weeds in crop fields. In this study, we explored the phytotoxicity and phytotoxic substances of Schumannianthus dichotomus, a perennial wetland shrub native to Bangladesh, India, and Myanmar. Leaf extracts of S. dichotomus exerted strong phytotoxicity against two dicot species, alfalfa and cress, and two monocot species, barnyard grass and Italian ryegrass. A bioassay-driven purification process yielded two phenolic derivatives, syringic acid and methyl syringate. Both constituents significantly inhibited the growth of cress and Italian ryegrass in a concentration-dependent manner. The concentrations required for 50% growth inhibition (I50 value) of the shoot and root growth of cress were 75.8 and 61.3 μM, respectively, for syringic acid, compared with 43.2 and 31.5 μM, respectively, for methyl syringate. Similarly, to suppress the shoot and root growth of Italian rye grass, a greater amount of syringic acid (I50 = 213.7 and 175.9 μM) was needed than methyl syringate (I50 = 140.4 to 130.8 μM). Methyl syringate showed higher phytotoxic potential than syringic acid, and cress showed higher sensitivity to both substances. This study is the first to report on the phytotoxic potential of S. dichotomus and to identify phytotoxic substances from this plant material.

THE INFLUENCE OF HUMIC ACIDS ON THE SOWING QUALITIES OF COCKWEED IN OIL POLLUTION

The stimulating effect of humic acids on the processes of growth and development of cress seeds has been revealed. It has been established that use of humic acids of black alder fen peat most effectively affects the sowing qualities of seeds under conditions of oil pollution (an increase in the germination energy and germination capacity compared to the non-humic acid variant by 38%). The minimal inhibitory effect on shoot growth was observed in the soil with hexadecane (20.8 mm less than the control), the maximum – in the soil with oil (22.5 mm less than the control). Humic acids show a stimulating effect on the growth of cress roots under conditions of pollution with oil hydrocarbons. The root length indicators exceeded the values obtained in the version with the pollutant without the use of humic acids from 6% (oil) to 16% of the control (hexadecane). Based on the data obtained during the vegetation experiments, it can be assumed that the stimulating activity of humic acids is more pronounced in stressful conditions for the organism. The biostimulating effect of humic acids was revealed, which manifested itself in an increase in the length of the hypocotyl and root, and the physiological activity of detoxicants was more effectively detected under conditions of pollution with oil hydrocarbons. According to the results of the vegetative experience on a substrate with hexadecane during the irrigation with humic acids of sphagnum high-moor peat, the maximum values of the test responses were determined, corresponding to the control values ​​obtained on the uncontaminated substrate, or higher than the latter. In the variant with oil, the most pronounced effect was achieved with the introduction of humic acids of reed fen and sphagnum high-moor peat, which confirms the hypothesis about the protective effect of humic acids in pollution conditions, which is determined by the binding ability of humic acids in relation to toxicant and their own biological activity in the relation to plants. It is proved that humic acids of peats make a significant contribution to the natural processes of self-purification, causing immobilization and detoxification of petroleum hydrocarbons, which indicates the prospects of their application in technologies of purification and recultivation of polluted water and soil media.

Phytotoxic activity of crop residues from Burdock and an active substance

Problems related to weed management such as outbreaks of herbicide-resistant weeds have recently increased. An interesting approach to such problems is to use plant materials with phytotoxic activity. Burdock (Arctium lappa L.) is a biennial herb belonging to Asteraceae and is cultivated in several countries. The present study investigated the phytotoxic activity of burdock and its active substances. Extracts of both burdock leaves and roots inhibited the shoot and root growth of cress and barnyard grass, where the level of inhibition increased with increasing extract concentration. The leaf extracts had 2.0–2.5 times higher activity than the root extracts. Bioassay-guided separations of the leaf extracts led to isolation of a phytotoxic substance, onopordopicrin. Onopordopicrin significantly inhibited the shoot and root growth of cress and barnyard grass. The concentrations of the substance required for 50% growth inhibition were 0.27 and 0.26 mM for cress shoots and roots, respectively, and 1.86 and 0.35 mM for barnyard grass shoots and roots, respectively. The present results suggest that burdock leaves have high phytotoxic activity and onopordopicrin may play a major role in the activity. Burdock leaves may be a good resource for weed management.

Phytotoxic potential of Chrysopogon aciculatus (Retz.) Trin. (Poaceae)

The creeping weed, Chrysopogon aciculatus (Retz.) Trin., is widely known for its use as folk medicine, while its phytotoxic potential has not been examined. Therefore, we carried out an investigation into the phytotoxic potential of C. aciculatus to identify phytotoxic substances. C. aciculatus extracts showed inhibitory effects on shoot and root growth of cress, lettuce, rapeseed, and Italian ryegrass. Inhibition was both species‐dependent and concentration‐dependent. Two substances, (9S,10E,12Z)‐9‐hydroxyoctadeca‐10,12‐dienoic acid (9‐HO‐ODDEA) and rhizopycnin A, were isolated using chromatographies and characterized by spectral analysis. 9‐HO‐ODDEA retarded shoot and root growth of cress at concentrations higher than 1.0 and 0.3 mM, respectively, while on cress seedling by rhizopycnin A, the inhibition began from 1.0 mM. The concentrations needed for 50% inhibition of the shoot and root growth of test plants ranged from 1.71–2.31, and 0.71–0.72 mM for 9‐HO‐ODDEA and rhizopycnin A, respectively. These results indicate that these substances may contribute, to a certain extent, to the phytotoxic activity of C. aciculatus.

Plant Growth Inhibitory Activity of the Extracts of Acmella oleracea and its Growth Inhibitory Substances

Aqueous methanol extracts of Acmella oleracea inhibited the growth of roots and shoots of cress ( Lepidum sativum), lettuce ( Lactuca sativa), Italian ryegrass ( Lolium multiflorum), and barnyard grass ( Echinochloa crus-galli) with the extract concentration-dependent manner. The extracts were then purified and 2 growth inhibitory substances were isolated and identified by spectral data as ( E,E)-2,4-undecadien-8,10-diynoic acid isobutylamide (compound 1) and nona-(2 Z)-en-6,8-diynoic acid 2-phenylethylamide (compound 2). Compound 1 inhibited the growth of cress roots and shoots at concentrations greater than 0.3 mM and that of barnyard grass root at concentrations greater than 0.03 mM. Compound 2 inhibited the growth of cress shoots and barnyard grass roots at concentrations greater than 1 mM. The inhibition on the seedling growth indicates that both compounds had growth inhibitory activity and may contribute to the inhibitory effect of A. oleracea extracts. This is the first report of having growth inhibitory activity of compounds 1 and 2 on plants.

Isolation and identification of a phytotoxic substance in kiwifruit leaves

The yield of kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] often decreases after 20 years of cultivation. Replanted young kiwifruit plants cannot grow well in fields where aged trees were previously cultivated. Phytotoxicity is considered one possible reason for this problem. However, allelopathic or phytotoxic substances from kiwifruit have not been reported. This study aimed to isolate and identify potentially allelopathic active substances in kiwifruit leaves. Extracts from kiwifruit leaves inhibited the growth of cress, suggesting that kiwifruit leaf extracts may contain growth-inhibitory substances. The extracts were then purified using a silica-gel column, Sephadex LH-20 column, ODS cartridge, and HPLC. The inhibitory activity of all fractions obtained in each purification step was determined by the cress bioassay. Quercitrin was finally isolated and identified as a growth-inhibitory substance. This substance inhibited cress root growth by more than 50% of control at 3 mM. The aglycone of quercitrin, quercetin, did not significantly inhibit cress growth. Quercitrin may work as an allelopathic substance and cause the kiwifruit replant problem. Further study is in progress to investigate the influence of kiwifruit leaf extracts and these flavonoids on kiwifruit seedlings.

Two allelopathic substances from Paspalum commersonii Lam.

ABSTRACTPaspalum commersonii (Poaceae) is a herbaceous perennial weed distributed in the tropics and subtropics regions and grows mainly in the moist, or even flooded soil. It often appears in the rice field as a competitive weed and difficult to manage. Its strong competitive nature indicates possible allelopathic potential of P. commersonii. However, no studies have been found yet on the allelopathic activity of P. commersonii. Thus, we investigated the allelopathic potential of this weed and determined its allelopathic substances. Aqueous methanol extracts of P. commersonii showed concentration-dependent inhibitory activity on the seedling growth of cress, alfalfa, rapeseed, lettuce, barnyard grass, foxtail fescue, Italian ryegrass, and timothy. Two substances were isolated through bioassay-guided fractionation and their structures were determined through spectral data as dehydrovomifoliol and loliolide. Dehydrovomifoliol and loliolide started inhibiting the shoot and root growth of cress at concentrations greater than 3 and 0.03 mM, respectively. The concentrations required for 50% inhibition (I50) of cress shoot and root growth were 3.34 and >3.50 mM for dehydrovomifoliol and 0.04 and 0.05 mM for loliolide, respectively. These results indicate that both substances may affect the inhibitory activity of P. commersonii.

Phytotoxicity and Chemical Characterization of Compost Derived from Pig Slurry Solid Fraction for Organic Pellet Production

The phytotoxicity of four different composts obtained from pig slurry solid fraction composted by itself (SSFC) and mixed with sawdust (SC), woodchips (WCC) and wheat straw (WSC) was tested with bioassay methods. For each compost type, the effect of water extracts of compost on seed germination and primary root growth of cress (Lepidium Sativum L.) was investigated. Composts were also chemically analysed for total nitrogen, ammonium, electrical conductivity and heavy metal (Cu and Zn). The chemicals were correlated to phytotoxicity indices. The mean values of the germination index (GI) obtained were 160.7, 187.9, 200.9 and 264.4 for WSC, WCC, SC and SSFC, respectively. Growth index (GrI) ranged from the 229.4%, the highest value, for SSFC, followed by 201.9% for SC, and 193.1% for WCC, to the lowest value, 121.4%, for WSC. Electrical conductivity showed a significant and negative correlation with relative seed germination at the 50% and 75% concentrations. A strong positive correlation was found for water-extractable Cu with relative root growth and germination index at the 10% concentration. Water-extractable Zn showed a significant positive correlation with relative root growth and GI at the 10% concentration. These results highlighted that the four composts could be used for organic pellet production and subsequently distributed as a soil amendment with positive effects on seed germination and plant growth (GI > 80%).

Myrislignan, a Growth Inhibitor from the Roots of Citronella grass

A phytotoxic compound was isolated from the root extracts of Cymbopogon nardus by bioassay-guided purification and characterized to be myrislignan. Myrislignan significantly inhibited seedling growth of cress at a concentration greater than 100 μM (p < 0.05). The concentrations required for 50% growth inhibition of myrislignan on hypocotyl and root growth of cress were 429 μM and 517 μM, respectively. The inhibition on seedling growth indicated that myrislignan had a phytotoxic activity and may contribute to the phytotoxic effect of C. nardus.

Influence of platinum ions on the germination and seedling root growth of diff erent plant species

For several decades an increase of platinum in the environment was recorded. This is connected with the release of platinum from automobile catalytic converters and pharmaceutical industries. In the conducted experiments the effect of various forms and concentrations of platinum on the germination and roots growth of different plants (oat, garden cress and tomato) was investigated. Two separate experiments were performed with lower (experiment 1 st : 1, 5 and 10 mg/L ) and higher (experiment 2 nd : 10, 20 and 40 mg/L ) [Pt(NH 3 ) 4 ](NO 3 ) 2 or PtCl 4 dosages. There was no significant effect of dose and form of platinum on the germination of seeds (experiment 1 st and 2 nd ). The effect of platinum containing substances dose on root growth of young seedlings was observed during experiment, dependent on the species of tested plants. The root length of oat plants was similar in all treatments in experiment 1 st . The shortest tomato roots were observed in the case of a 10 mg/L of PtCl 4 , it was statistically shorter than the control plants (treated with water) as well. The roots of the tomato treated with [Pt(NH 3 ) 4 ](NO 3 ) 2 were the same length as observed for the control sample. The garden cress root growth was not affected by [Pt(NH 3 ) 4 ](NO 3 ) 2 , but a solution containing Pt 4+ stimulated the root growth. The roots of tomato and oat treated with [Pt(NH 3 ) 4 ](NO 3 ) 2 had similar length as the control plants in contrast to the far shorter roots treated with PtCl 4 (experiment 2 nd ). Moreover, the treatment with [Pt(NH 3 ) 4 ](NO 3 ) 2 stimulated the growth of garden cress roots compared to the control, while only the lowest dose of PtCl 4 stimulated the root growth.

Organ-specific-active allelopathic substance in red pine needles

An organ-specific-growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as 1-mono(16-hydroxyhexadecanoyl)glycerol. This substance inhibited root growth of cress (Lepidium sativum L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv) seedlings at concentrations greater than 0.01 and 0.03 μM, respectively. The concentrations required for 50 % growth inhibition on roots of cress and barnyard grass were 0.16 and 3.4 μM, respectively. However, the inhibitory activity of the substance on shoots of cress and barnyard grass was very weak. The endogenous concentration of 1-mono(16-hydroxyhexadecanoyl)glycerol in the pine needles was 4.6 μmol kg−1. Two related compounds, 1-monohexadecanoylglycerol and 16-hydroxyhexadecanlic acid had no activity up to 1,000 μM on cress roots and shoots. The effectiveness of 1-mono(16-hydroxyhexadecanoyl)glycerol on root growth inhibition and the occurrence of 1-mono(16-hydroxyhexadecanoyl)glycerol in pine needles suggest the substance may play an important role in the allelopathy of red pine. Root-specific-growth-inhibition by the substance may be one of the strategies for red pine to compete with neighboring plants for nutrients and space because root growth of competitive plants may be very important for their whole plant development.

Allelopathy of the moss Rhynchostegium pallidifolium and 3-hydroxy-β-ionone

The moss Rhynchostegium pallidifolium (Mitt.) A. Jaeger, which often forms large pure colonies on soils and rocks, inhibited the hypocotyls and root growth of cress (Lepidium sativum L.) seedlings when R. pallidifolium and cress were incubated to-gether on agar medium. The inhibition of cress was greater at the close position from the moss than at the far position from the moss. 3-Hydroxy-β-ionone was found in the medium and concentration of 3-hydroxy-β-ionone in the medium was greater at the close position than at the far position from R. pallidifolium, suggesting that R. pallidifolium may secrete 3-hydroxy-β-ionone into the medium. Exogenously ap-plied 3-hydroxy-β-ionone inhibited the growth of hypocotyls and roots of cress at con¬cen¬tra¬tions greater than 1 and 3 μM, respectively. Considering the growth inhibi-tory activity and concentrations found in the medium, 3-hydroxy-β-ionone was esti-mated to be able to cause 46 - 64 % of the observed growth inhibition of cress hypo-cotyls and roots by R. pallidifolium. Therefore, 3-hydroxy-β-ionone may play an important role in the allelopathic activity of R. pallidifolium and may help competi-tion with neighboring plants resulting in the formation of pure colonies.

Reduction of compost phytotoxicity during the process of decomposition

Hog manure from windrows composted at different operating strategies was used in a bioassay to determine phytotoxicity. Twelve windows that differed in composting strategies (i.e. turning frequency and moisture content adjustment) were built. The effects of hog manure water extracts on seed germination and primary root growth of cress ( Lepidum sativum L.) was measured. The germination index (GI, a product of relative seed germination and root elongation) was related to the chemical characteristics (electrical conductivity, nitrogen compounds, C:N ratio, heavy metals and humification parameters) of the hog manure. The water-extractable chemical properties of the hog manure that showed the highest negative correlation with GI were extractable Cu, extractable Zn and NH 4 + N , demonstrating that these chemical compounds gradually decrease during composting due to transformation to other compounds and immobilization effects. A GI > 80 (an indicator of the disappearance of phytotoxicity) was reached when the concentrations of NH 4 + –N, extractable Cu, and extractable Zn were ⩽ 2 g kg −1, ⩽ 15 mg kg −1, and ⩽ 15 mg kg −1, respectively. Multiple regression analysis revealed that NH 4 + –N was the most important factors affecting the phytotoxicity of the hog manure. Composting strategies employed affected the speed of composting, time of maturation, and disappearance of phytotoxicity. The disappearance of phytotoxicity corresponded with the time of maturation of the hog manure. If optimum composting conditions (windrows turned every 4 d with weekly moisture adjustment to 60%) are met, phytotoxicity disappears within 56 d.

Isolation and Structure Elucidation of a Potent Growth Inhibitor, Helian, from Blue Light-Illuminated Sunflower (Helianthus annuus) Hypocotyls

A potent growth inhibitor was isolated from blue light-illuminated sunflower (Helianthus annuus) hypocotyls and identified as 8-β-D-glucopyranosyloxy)-3-hydroxy-1,9,14-pentadecatriene-4,6-diyne (1, designated helian) from analysis of its 1 H and 13 C NMR spectra, and HRFABMS. Helian 1 showed plant growth-inhibitory activity at concentrations higher than 2.6 x 10 -6 mol/L for the cress root growth test. The amount of helian was higher in the illuminated halves than in the shaded ones in phototropically stimulated sunflower hypocotyls. These results suggest that this new potent growth inhibitor, helian, may play an important role on phototropism of sunflower hypocotyls.

Isolation and Identification of an Allelochemical Exuded from Germinating Pea (Pisum sativum) Seeds.

ChemInformVolume 36, Issue 26 Natural Products Isolation and Identification of an Allelochemical Exuded from Germinating Pea (Pisum sativum) Seeds. Keiko Higashinakasu, Keiko Higashinakasu Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorKosumi Yamada, Kosumi Yamada Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorHideyuki Shigemori, Hideyuki Shigemori Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorKoji Hasegawa, Koji Hasegawa Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this author Keiko Higashinakasu, Keiko Higashinakasu Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorKosumi Yamada, Kosumi Yamada Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorHideyuki Shigemori, Hideyuki Shigemori Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this authorKoji Hasegawa, Koji Hasegawa Grad. Sch. Life Environ. Sci., Univ. Tsukuba, Tsukuba, Ibaraki 305, JapanSearch for more papers by this author First published: 31 May 2005 https://doi.org/10.1002/chin.200526143Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume36, Issue26June 28, 2005 RelatedInformation

Isolation and Identification of an Allelochemical Exuded from Germinating Pea (Pisum sativum) Seeds

When pea seeds were cultured in a Petri dish together with cress seeds, the hypocotyl and root growth of cress was significantly inhibited, whereas the epicotyl growth of pea was promoted. These results suggest that the growth of each seeds is either inhibited or promoted with allelochemical(s) exuded from each seeds during seed germination. An allelochemical, which showed a growth-inhibiting activity against cress seeds, was isolated from the exudates of germinating pea seeds. It was identified as 6a-hydroxy-3-methoxy-8,9-methylenedioxy peterocarpan (pisatin) based on its 'H NMR spectrum. The endogenous pisatin level (22 mg/L) in the exudates from germinating pea seeds seems to be a good agreement with the exogenous concentration (>3 mg/L) of pisatin required to inhibit the hypocotyl and root growth of cress. These results suggest that pisatin may play an important role in the allelopathy of pea seeds during germination.

Growth inhibitory alkaloids from mesquite ( Prosopis juliflora (Sw.) DC.) leaves

Plant growth inhibitory alkaloids were isolated from the extract of mesquite [ Prosopis juliflora (Sw.) DC.] leaves. Their chemical structures were established by ESI-MS, 1H and 13C NMR spectra analysis. The I 50 value (concentration required for 50% inhibition of control) for root growth of cress ( Lepidium sativum L.) seedlings was 400 μM for 3⁗-oxo-juliprosopine, 500 μM for secojuliprosopinal, and 100 μM for a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine, respectively. On the other hand, the minimum concentration exhibiting inhibitory effect on shoot growth of cress seedlings was 10 μM for 3⁗-oxo-juliprosopine, 100 μM for secojuliprosopinal, and 1 μM for a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine, respectively. Among these compounds, a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine exhibited the strongest inhibitory effect on the growth of cress seedlings.