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Allelopathic evidence in the Poaceae.

 I. Abstract/Resumen
 II. Introduction
 III. Geographical Distribution and Climatic Requirements
 IV. The Presence of Allelochemicals
 A. Phenolic Acids
 B. Hydroxamic Acids
 C. Alkaloids
 D. Quinones
 V. Mode of Release
 VI. Mechanisms of Action
 VII. Pest Management in Natural and Agricultural Ecosystems
VIII. Implications for Agroecosystems
 IX. Industrial Uses and Future Areas of Research
 X. Literature Cited
 XI. Appendix 1: The Allelopathic Potential of Several Species
 (Maize, Rice, Wheat, Barley, Weeds, etc.) Belonging to
 the Family Poaceae


II. Introduction

The grasses of Gramineae are "ecologically the most dominant and economically by far the most important family in the world" (Heywood, 1978). In human evolution, as well as for grazing mammals like cows or horses, the Gramineae played an essential role. The domestication of the cereals and the ability to store the grains enabled the human civilizations 7000-10,000 years ago to develop higher urban cultures.

The classification of Poaceae (= Gramineae) within the kingdom of plants is as follows, in accordance with Strasburger (1994). They form part of the class Monocotyledonea, belonging to the subclass Liliidae, being part of the superorder Commelinanae, and finally, they are one of the members of the order Poales. This family is very large, with about 8000-9000 species, including species of the greatest economic importance. According to the Food and Agriculture Organization (FAO, 1991, 1992, 1993, 1995, 1998), rice, wheat, and corn are the three most important crops in the world. They are members of this large family, as are fodder species for animals like Lolium spp. or Poa spp. or sugarcane, bamboo, lawns, and some ornamental species. But botanists disagree about the number of subfamilies in the family. Strasburger (1994) divides it into eight subfamilies, using the constitution of the spikelet, the lodicules, the structure of cariopsis, embryo, and plantlet, as well as leaf anatomy, as criteria. The subfamilies are Bambusoideae, Pooideae, Arundineae, Stipeae, Oryzoideae, Eragrostoideae, Panicoideae, and Andropogonoideae.

On the other hand, Watson and Dallwitz (1994) recognize about 10,000 species within 650-753 genera. They divide this family into five subfamilies (with their supertribes): Pooideae (Triticodae, Poodae), Bambusoideae (Oryzodae, Bambusodae), Arundinoideae, Chloridoideae, and Panicoideae (Panicodae, Antropogonoidae).

III. Geographical Distribution and Climatic Requirements

In fact, the Gramineae is a cosmopolitan family, living between the polar circle and the Equator, from the highest mountains down to sea level. Grass species dominate the landscape of steppes, grasslands, and prairies all over the world. Only a few ecological formations lack grasses. The most important cereals--wheat, barley, rye, oat, rice, millet, and corn--are distributed worldwide. Members of the subfamilies Eragrostoideae, Panicoideae, and Andropogonoideae, and some of the Oryzoideae, live in the Tropics. The origin of wheat, barley, rye, and oats is in the near Orient and in the Mediterranean area (fertile half moon). Rice originated in southwestern Asia. In the arid zones of eastern Asia, as well as in India and Africa, the different forms of millet originated. And finally, the place of origin of corn must be in Mexico, as demonstrated by the recent discovery of wild forms (Strasburger, 1994).

Many recent publications demonstrate the evidence of Festuca spp. and Poa spp. in Arctic tundra (Ramesar-Fortner et al., 1995; Zanokha, 1995; Levesque & Svoboda, 1997; Bakker & Loonen-Maarten, 1998; Shirazi et al., 1998). The two native vascular plants from Antarctica, Colobanthus quitensis and Deschampsia antarctica, are also members of this family (McCraw & Day, 1997). Other typical genera from Arctic and subarctic regions are Calarnagrostis (Gwynn-Jones & Johanson, 1996), Dupontia (Wegener & Odasz, 1997; Shirazi et al., 1998), Deschampsia (Steltzer & Bowman, 1998), and A lopecurtts (Wegener & Odasz, 1998). Within the flora of Arctic coastal habitats are species from the genera Deschampsia and Pleuropogon (Rebristaya, 1997).

The high mountain altitudes, another extreme habitat, are also populated by grass species. Some typical grass species of high altitudes are: Agrostis spp. (lslebe, 1993; Frey, 1997), Poa alpina and Dactylis glomerata (Mizianty, 1997; Gauthier & Bedecarrats, 1998); Bromus spp. (Stewart, 1996), bamboo (Sun et al., 1997), and rye (Oram, 1996).

The classification of Watson and Dallwitz (1994) assigns geographical distributions for each subfamily. Accordingly, Pooideae is common in northern and southern temperate and tropical mountains. Bambusoideae is frequent in tropical, warm temperate, mostly forest/woodland and wet places, whereas Arundinoideae is cosmopolitan. Chloridoideae belongs mostly to tropical and subtropical dry climates. Finally, the subfamily Panicoideae lives mainly in the Tropics, extending to temperate zones. The climatic requirements depend on the conditions of the natural habitats to which they are adapted.

IV. The Presence of Allelochemicals

The fact that Poaceae is one of the most important and most widely "used" families in the world is one of the reasons for the extensive research on their allelopathic compounds. The kind and nature of their allelochemicals goes from phenolics to quinones, with a very important diversity in this range. The most clearly identified compounds can be divided into four groups: phenolic acids, hydroxamic acids, alkaloids, and quinones.

A. PHENOLIC ACIDS

The most common phenolic acids are: p-hydroxybenzoic, syringic, vanillic, ferulic, p-coumaric, chlorogenic, caffeic, p-hydroxybenzaldehyde, gallic, protocatechuic, etc., in species like Agropyron repens (Schulz et al., 1994), Avena spp. (Guenzi et al., 1967; Fay & Duke, 1977; Schumacher et al., 1983; Perez & Ormeno-Nunez, 1991a; Wardle et al, 1994), Oryza sativa (Chou eta]., 1981; Alsaadawi et al., 1998), Secale cereale (Wojcik-Wojtkowiak et al., 1990), Sorghum spp. (Nicollier et al., 1983; Weston et al., 1989; Ben-Hammouda et al., 1995a, 1995b), Triticum aestivum (Blum et al., 1992; Alsaadawi et al., 1998; Wu et al., 2001, 2002), and Zea mays (Chou & Patrick, 1976).

B. HYDROXAMIC ACIDS

Several authors identified BOA, DIBOA, DIMBOA, AZOB, DIMBOA-glc, MBOA, CIMBOA, etc. in different species, above all in: Zea mays (Corcuera et al., 1978; Queirolo et al., 1983; Hedin et al., 1993; Friebe et al., 1997), Agropyron repens (Schulz et al. 1994), Tritieum aestivum or Z speltoides (Copaja et al., 1991; Givovich et al., 1994; Contreras & Niemeyer, 1997; Kato-Noguchi et al., 1998; Quader et al., 2001) and Secale cereale (Virtanen et al., 1957; Barnes et al., 1987; Perez & Ormeno-Nunez, 1991b, 1993; Mwaja et al., 1995).

C. ALKALOIDS

Examples of alkaloids include hordenine and gramine, found in Hordeum vulgare (Overland, 1966; Zuniga & Corcuera, 1986; Corcuera et al., 1992; Liu & Lovett, 1993b).

D. QUINONES

The most important and studied quinone is sorgoleone, a compound found in the exudates and extracts of Sorghum bicolor (Einhellig & Souza, 1992; Rasmussen et al., 1992; Einhellig et al., 1993; Nimbal et al., 1996; Gonzalez et al., 1997; Weston & Czarnota, 2001); p-benzoquinones were also identified in this species (Netzly et al., 1988).

V. Mode of Release

The mode of release of the allelopathic compounds and the plant parts where we can find them are not specific (see Appendix 1). So, we can find phenolic acids in the grains, pollen, root exudates, residues, decomposing straw, extracts from different plant parts, soil extracts, etc. The same is true for the hydroxamic acids, the quinones, and the other groups of allelopathic substances detected in the Poaceae.

VI. Mechanisms of Action

When we study the mode of action of the allelochemicals from Poaceae, we can detect that the most studied parameters to see the tolerance of the target plant for the allelopathic substances are rate of germination, speed of germination, radicle length, root and shoot growth, emergence, and plant density. But in recent years, and increasingly, scientists are interested in looking for the exact site of action of the allelochemical in the plant, going to more biochemical and physiological studies. Some examples of that are the effects of Sorghum bicolor found on photosynthesis and oxygen evolution in Pisum sativum and Glycine max (Einhellig et al., 1993) and on mitochondrial respiration in Zea mays (Rasmussen et al., 1992). Another example can be the effects exerted on the chloroplast ATPase from spinach in the presence of extracts of Zea mays (Queirolo et al., 1983).

Gramineae was also studied because of its resistance to aphids, fungi, and algae, producing allelopathic substances to reduce the larval/colonial growth, to stimulate the algae growth, to increase the larval/colonial mortality or to inhibit the reproduction of aphids (Virtanen et al., 1957; Klun et al., 1967; Corcuera et al., 1992; Hedin et al., 1993; Contreras & Niemeyer, 1997; Zwain et al., 1999).

VII. Pest Management in Natural and Agricultural Ecosystems

We cannot forget the economic uses of these plants when we speak about their worldwide role in the pest management. Once more we must remember that the Poaceae include the most important crops in the world for human and animal food. A very interesting goal is biological control of weeds and pests by these extensive crops thanks to the allelopathic effects. Cases were described in pest control for several species (Reed et al., 1972; Corcuera et al., 1992; Givovich et al., 1994; Contreras & Niemeyer, 1997; Zwain et al., 1999). There are references in the literature about the possibility of controlling fungi, bacteria, algae, and aphids with several compounds isolated in exudates or residues from Triticum aestivum (Contreras & Niemeyer, 1997; Zwain et al., 1999), Zea mays (Klun et al., 1967; Corcuera et al., 1978; Wiseman et al., 1992), Imperata cylindrica (Inderjit & Dakshini, 1991), Secale cereale (Virtanen et al., 1957), or Hordeum vulgare (Corcuera et al., 1992). But the most studied allelopathic capacity in Poaceae is weed control by crops and the advantage of the crop rotation for Gramineae species, increasing the yield, vigor, and emergence (Putnam et al., 1983; Einhellig & Rasmussen, 1989; Brecke & Shilling, 1996; Cheema & Khaliq, 2000).

VIII. Implications for Agroecosystems

Soil sickness and self-incompatibility of some crops have led agriculturalists to use rotation of several crops and legumes in the cropping systems to avoid these negative implications. Generally, self-incompatibility is caused by several factors, such as weeds, pests, nutrients, water supply, and toxic substances. It seems difficult to quantify these factors. Rice and oats, especially, are well known to be autotoxic. Wheat is recognized to be self-incompatible, too. Allelopathic substances have been identified (Copaja et al., 1991), but it also could be related to some fungi pests that use the straw and residues of Triticum as host. If these residues remain in the upper part of the soil by mulching or other non-plow techniques, the spores infect the young wheat in the following season. These crops need cropping systems with rotation.

IX. Industrial Uses and Future Areas of Research

Perhaps, in the very near future, the natural herbicides and pesticides obtained from Poaceae can be an alternative for biological control suppressing the indiscriminate use of synthetic compounds. The allelopathic compounds (phenolic and hydroxamic acids) extracted from corn, wheat, or other grasses are in the research lines of biological control for the present and the future.

The latest allelopathic studies in this field do more than demonstrate allelopathie action on pests or weeds measuring the germination rate or the seedling growth. In these studies we can appreciate a tendency to identify the compounds responsible for these effects and to know the exact mode and site of action of these allelochemicals in the plant, aphid, fungi, algae, bacteria, etc. And in this direction go the future research lines of allelopathy from Poaceae.
XI. Appendix 1: The Allelopathic Potential of Several Species (Maize,
Rice, Wheat, Barley, Weeds, etc.) Belonging to the Family Poaceae

Allelopathic species Allelochemicals

Agropyron repens L. (root DIBOA, ferulic acid
 exudates)

Agropyron repens L. 5-hydroxy-indole-3-acetic
 acid, 5-hydroxytryptophan

Avena sativa L. (shoot and L-tryptophan
 root extracts)

Avena sativa L. (extracts) Not identified

Avena spp. (root exudates) Scopoletin, vanillic, coumaric,
 p-hydroxybenzoic

Avena spp. (residues) Ferulic, coumaric, syringic,
 vanillic, p-hydroxybenzoic

Avena sativa L. (nonsterile Not identified
 residue extracts)

Bothriochloa pertussa L., Not identified
 Urochloa mosambicensis
 Hack. (aqueous extracts)

Bromus inermis L., Agropyron Not identified
 repens L., Dactylis glom-
 erata L., Festuca elatior
 L., Phleum pratense L.
 (extracts)

Bromus inermis L., Dactylis Not identified
 glomerata L., Lolium per-
 enne L., Festuca pratensis
 L., Poa pratensis L.,
 Phleum pratense L., (root
 leachates)

Bromus inermis L., Dactylis Not identified
 glomerata L., Sorghum bi-
 color L., Phleum pratense
 L., Festuca arundinacea
 L. (extracts)

Buchloe dactyloides p-coumaric, ferulic, gentisic,
 homoveratric, vanillic,
 p-hydroxybenzoic

Cynodon dactylon L. (extracts Not identified
 and root exudates)

Cynodon dactylon L. (resi- Not identified
 dues)

Cynodon dactylon L. and Not identified
 Echinochloa colonum L.
 (individual leaf and root
 leachates and extracts)

Echinochloa crus-galli L. Not identified
 (aqueous extracts)

Festuca arundinacea Schreb. Not identified
 (extracts)

Festuca spp. Not identified

Hordeum vulgare L. (root Hordenine, gramine (alka-
 exudates) loids)

Hordeum vulgare L. (leaves) Gramine (alkaloid)

Hordeum vulgare L. (exu- Not identified
 dates)

Hordezan vulgare L. (extracts) Not identified

Hordeum vulgare L. (extracts) Not identified

Hordeum vulgare L. (straw Not identified
 residues)

Hordeum vulgare L. (residues) Not identified

Hordeum vulgare L. Not identified

Imperata cylindrica L. (leaves Scopolin, scopoletin, chloro-
 and clums extracts) genic acids

Imperata cylindrica L. (aque- Not identified
 ous extracts)

Imperata cylindrica L. (ex- Not identified
 tracts)

Lolium perenne L. (most Not identified
 shoot leachates)

Miscanthus transmorrisonen- Phenolic acids: caffeic, gallic,
 sis (grains, grass leachates p-hydroxybenzoic, ferulic,
 and extracts) m-hydroxybenzoic, etc.

Oryza sativa L. and O. glaber- Not identified
 rima L. (root exudates)

Oryza sativa L (root exudate Not identified
 from early stages)

Oryza sativa L. (decomposing p-hydroxybenzoic, ferulic, p-
 rice straw) coumaric, syringic, vanil-
 lic, o-hydroxyphenylacetic

Oryza sativa L. (seed germi- Not identified
 nation and aqueous ex-
 tracts)

Panicum dichotomiflorum M. Not identified
 (water extracts of dried
 residues)

Pennisetum glaucum L. (root Not identified
 and shoot extracts)

Phalaris minor; Phalaris bra- Not identified
 chystachys

Phleum pratense L. (pollen) Not identified

Poa pratensis L. (decompos- Not identified
 ing roots)

Polypogon monspeliensis L. Phenolic compounds
 (weed straw)

Sasa cernua (rhizosphere soil) p-coumaric, ferulic, vanillic,
 p-hydroxybenzoic, p-h-
 ydroxybenzaldehyde

Secale cereale L. (root exu- DIBOA, DIBOA-glc, BOA
 dates)

Secale cereale L. (exudates) Not identified

Secale cereale L. (root resi- Not identified
 dues, whole plant mulch)

Secale cereale L. (mulch) Phenyllactic and hydroxybu-
 tyric acid

Secale cereale L. (residues) Not identified

Secale cereale L. (residues) Salycilic

Secale cereale L. (residues) Not identified

Secale cereale L. (degradation p-hydroxybenzoic, gallic, va-
 tissues) nillic, protocatechuic, sy-
 ringic, p-coumaric, ferulic,
 benzoic and another not
 identified compound

Secale cereale L. (rye root Not identified
 residue, surface-applied
 residues)

Secale cereale L. (extracts) Hydroxamic acids: (DIBOA,
 BOA, AZOB, Aminophe-
 noxazinone)

Secale cereale L. (aqueous Not identified
 extracts)

Secale cereale L. BOA

Setaria glauca L. (residues) Not identified

Setaria viridis L. Not identified

Sorghum bicolor L. (grain) Not identified

Sorghum bicolor L. (root exu- Sorgoleone (quinone)
 dates)

Sorghum bicolor L. (root exu- Sorgoleone
 date)

Sorghum bicolor L. (root exu- Sorgoleone
 dates)

Sorghum bicolor L. (root exu- Sorgoleone and another
 dates) p-benzoquinonc

Sorghum bicolor L. (extracts) Not identified

Sorghum bicolor L. (extracts) Not identified

Sorghum bicolor L. (extracts) Sorgoleone

Sorghum bicolor L. (extracts p-hydroxybenzoic, vanillic,
 from different plant parts) syringic, p-coumaric,
 ferulic

Sorghum bicolor L. Hydrophobic droplets

Sorghum bicolor L. (root exu- Sorgoleone
 date)

Sorghum bicolor L. (water Not identified
 extract of mature plants)

Sorghum bicolor x Sorghum p-hydroxybenzoic, p-hydrox-
 sudanese hybrid (sudex) ybenzaldehyde acid

Sorghum halepense L. Taxiphyllin, dhurrin,
 p-hydroxybenzaldehyde

Triticum aestivum L. (exu- Aminophenoxazinones
 dates)

Triticum aestivum L. (straw) Not identified

Triticum aestivum L. (straw Not identified
 management practices)

Triticum aestivum L. (resi- Not identified
 dues)

Triticum aestivum L. (resi- Not identified
 dues)

Triticum aestivum L. (root DIBOA, DIMBOA
 extracts)

Triticum aestivum L. (aqueous Not identified
 extracts of straw)

Triticum aestivum L. (extract p-hydroxybenzoic, vanillic,
 of residues) syringic, p-coumaric acids

Triticum aestivum L. (soil Phenolic and hydroxamic (6-
 extracts) MBOA) acids

Triticum aestivum L. Hydroxamic acids (DIMBOA,
 DIMBOA-glc)

Trilicmn aestivum L. DIMBOA

Triticum aestivum L. (seed- Multiple compounds
 lings) (p-hyydroxybenzoic,
 vanillic, trans-ferulic
 acids, etc.)

Triticum speltoides L. Not identified

Triticum speltoides L. DIMBOA

Vulpia spp. (residues and Not identified
 aqueous extracts)

Zea mays L. (whorl surface N-O-Me-DIMBOA, 6-MBOA
 waxes)

Zea mays L. (silks) Not identified

Zea mays L. (exudates) Aminophenoxazinones

Zea mays L. (tissues) Hydroxamic acids

Zea mays L. (residues) Phenylacetic, 4-phenylbutyric,
 benzoic

Zea mays L. (nonsterile resi- Not identified
 due extracts)

Zea mays L. (pollen and crude Phenylacetic acid
 pollen extracts)

Zea mays L. (leaf extracts) DIMBOA

Zea mays L. (seedling DIMBOA, MBOA, BOA
 extracts)

Zea mays L. (extracts) DIMBOA

Zea mays L. (extracts) C1-MBOA

Zea mays L. Not identified

Zea mays L. Cyclic hydroxamic acids

Allelopathic species Target species

Agropyron repens L. (root Lepidium sativum, Amaran-
 exudates) thus retroflexus, Brassica
 napus, Lolium perenne,
 Poa annua

Agropyron repens L. Alfalfa, maize, soybean

Avena sativa L. (shoot and Lettuce, cockscomb, cress,
 root extracts) timothy, rice, wheat, oat

Avena sativa L. (extracts) Bromus tectorum L., Descu-
 rainia sophia L., Thlaspi
 arvense L.

Avena spp. (root exudates) Wheat

Avena spp. (residues) ?

Avena sativa L. (nonsterile Zea mays L.
 residue extracts)

Bothriochloa pertussa L., Stylosanthes scabra cv. Seca
 Urochloa mosambicensis
 Hack. (aqueous extracts)

Bromus inermis L., Agropyron Agropyron repens, Bromus in-
 repens L., Dactylis glom- ermis, Dactylis glomerata,
 erata L., Festuca elatior Festuca elatior, Phleum
 L., Phleum pratense L. pratense, Coronilla varia
 (extracts)

Bromus inermis L., Dactylis Bromus inermis, Dactylis
 glomerata L., Lolium per- glomerata, Lolium per-
 enne L., Festuca pratensis enne, Festuca pratensis,
 L., Poa pratensis L., Poa pratensis, Phleum
 Phleum pratense L., (root pratense, Trifolium pra-
 leachates) tense, T. repens

Bromus inermis L., Dactylis Alfalfa
 glomerata L., Sorghum bi-
 color L., Phleum pratense
 L., Festuca arundinacea
 L. (extracts)

Buchloe dactyloides Annual bluegrass and buffalo-
 grass

Cynodon dactylon L. (extracts Cotton, alfalfa
 and root exudates)

Cynodon dactylon L. (resi- Rice
 dues)

Cynodon dactylon L. and Onion, radish, knol-khol
 Echinochloa colonum L.
 (individual leaf and root
 leachates and extracts)

Echinochloa crus-galli L. Cucumber, tomato, radish
 (aqueous extracts)

Festuca arundinacea Schreb. Clover
 (extracts)

Festuca spp. Italian rye grass, alfalfa

Hordeum vulgare L. (root White mustard, tobacco, Stel-
 exudates) laria media, Capsella
 bursa-pastoris

Hordeum vulgare L. (leaves) Schizaphis graminum, Meto-
 polophium dirhodum Rho-
 palosiphum padi,
 R. maidis (aphid)

Hordeum vulgare L. (exu- Eastern black nightshade, yel-
 dates) low foxtail

Hordezan vulgare L. (extracts) Avena spp.

Hordeum vulgare L. (extracts) Bromus tectorum L., Descu-
 rainia sophia L., Thlaspi
 arvense L.

Hordeum vulgare L. (straw Microcystis aeruginosa
 residues)

Hordeum vulgare L. (residues) Amaranthus, Ambrosia, Che-
 nopodium, Portulaca

Hordeum vulgare L. Chenopodium, slim amaranth,
 white mustard

Imperata cylindrica L. (leaves Different crops: maize, sor-
 and clums extracts) ghum, tomato, etc.

Imperata cylindrica L. (aque- Radish, mustard, fenugreek,
 ous extracts) tomato
 Aspergillus

Imperata cylindrica L. (ex- Phalaris minor, Echinochloa
 tracts) colonum

Lolium perenne L. (most Carduus nutans
 shoot leachates)

Miscanthus transmorrisonen- Lettuce, Chinese cabbage, tall
 sis (grains, grass leachates fescue, rye grass
 and extracts)

Oryza sativa L. and O. glaber- Lettuce
 rima L. (root exudates)

Oryza sativa L (root exudate Medicago sativa L., Lepidium
 from early stages) sativum L., Lactuca sativa
 L.

Oryza sativa L. (decomposing Rice
 rice straw)

Oryza sativa L. (seed germi- Monochoria vaginalisvar.
 nation and aqueous ex- plantaginea
 tracts)

Panicum dichotomiflorum M. Corn, soybean
 (water extracts of dried
 residues)

Pennisetum glaucum L. (root Pearl millet
 and shoot extracts)

Phalaris minor; Phalaris bra- Wheat
 chystachys

Phleum pratense L. (pollen) Elytrigia repens, Agropyron
 repens, Agrostis stoloni-
 fera, Bromus inermis,
 Danthonia compressa, Poa
 compressa, P. pratensis

Poa pratensis L. (decompos- Alopecurus pratensis, Dactylis
 ing roots) glomerata, Phleum prat-
 ense, Festuca pratensis

Polypogon monspeliensis L. Radish, cluster bean
 (weed straw)

Sasa cernua (rhizosphere soil) Lettuce, green amaranth, timo-
 thy, barnyard grass, barley,
 wheat

Secale cereale L. (root exu- Wild oats
 dates)

Secale cereale L. (exudates) Eastern black nightshade,
 yellow foxtail

Secale cereale L. (root resi- Sicklepod
 dues, whole plant mulch)

Secale cereale L. (mulch) Redroot pigweed, common
 lambsquarters, common
 ragweed

Secale cereale L. (residues) Ambrosia artemisiifolia, Ama-
 ranthus retroflexus, Portu-
 laca oleracea, Setaria
 lutescens, S. viridis

Secale cereale L. (residues) Lettuce

Secale cereale L. (residues) Lettuce

Secale cereale L. (degradation Rye
 tissues)

Secale cereale L. (rye root Barnyard grass
 residue, surface-applied
 residues)

Secale cereale L. (extracts) Barnyard grass, garden cress,
 cucumber, snap bean,
 large crabgrass, prosomil-
 let, tomato lettuce, redroot
 pigweed

Secale cereale L. (aqueous Lettuce, lambsquarters
 extracts)

Secale cereale L. Fusarium

Setaria glauca L. (residues) Soybean, corn

Setaria viridis L. Soybean, maize, sorghum

Sorghum bicolor L. (grain) Setaria, Polygonum, Kochia,
 Lactuca, Solanum, Ambro-
 sia, Amaranthus, Convol-
 vulus, Physalis

Sorghum bicolor L. (root exu- Abutilon, Datura, Digitaria,
 dates) Amaranthus, Echinochloa

Sorghum bicolor L. (root exu- Pisum sativum, Glycine max
 date)

Sorghum bicolor L. (root exu- Soybean, corn
 dates)

Sorghum bicolor L. (root exu- Witchweed
 dates)

Sorghum bicolor L. (extracts) Redroot pigweed

Sorghum bicolor L. (extracts) Avena spp.

Sorghum bicolor L. (extracts) Spinach, redroot pigweed,
 potato

Sorghum bicolor L. (extracts Wheat
 from different plant parts)

Sorghum bicolor L. Lettuce

Sorghum bicolor L. (root exu- Amaranthus retroflexus L.
 date) (thylakoids)

Sorghum bicolor L. (water Weeds of wheat crops
 extract of mature plants)

Sorghum bicolor x Sorghum Tomato, garden cress, foxtail
 sudanese hybrid (sudex) millet, barnyard grass

Sorghum halepense L. Tomato, radish

Triticum aestivum L. (exu- Barnyard grass
 dates)

Triticum aestivum L. (straw) Ipomoea hederacea, Abutilon
 theophrasti, Sesbania exal-
 tata, Senna obtusifolia,
 Echinochloa crus-galli

Triticum aestivum L. (straw Sorghum, pearlmillet, maize,
 management practices) clusterbean, cowpea

Triticum aestivum L. (resi- Amaranthus, Ambrosia, Che-
 dues) nopodium, Portulaca

Triticum aestivum L. (resi- Anabaena cylindrica, Nostoc
 dues) musicorum (algae)

Triticum aestivum L. (root Wild oat
 extracts)

Triticum aestivum L. (aqueous Carpet weed, pigweed, sun-
 extracts of straw) berry, barnyard grass,
 crowfoot grass

Triticum aestivum L. (extract Rice
 of residues)

Triticum aestivum L. (soil Crimson clover, ivy-leaved
 extracts) morning glory

Triticum aestivum L. Schizaphis graminum, Meto-
 polophium dirhodum, Rho-
 palosiphum padi, R. mai-
 dis, Sitobion avenae
 R. maidis, Sitobion avenae

Trilicmn aestivum L. Wheat

Triticum aestivum L. (seed- Lolium rigidum Gaud.
 lings)

Triticum speltoides L. Wild oats, Indian hedge mus-
 tard

Triticum speltoides L. Lactuca sativa, Avena spp.

Vulpia spp. (residues and Wheat, barley, lupins
 aqueous extracts)

Zea mays L. (whorl surface Diatraea grandiosella Dyar
 waxes) (southwestern corn borer)

Zea mays L. (silks) Larvae of the corn earworm,
 Helicoverpa zea

Zea mays L. (exudates) Barnyard grass

Zea mays L. (tissues) Ostrinia nubilalis (European
 corn borer)

Zea mays L. (residues) Lettuce

Zea mays L. (nonsterile resi- Zea mays L.
 due extracts)

Zea mays L. (pollen and crude Amaranthus leucocarpus,
 pollen extracts) Echinochloa crus-galli

Zea mays L. (leaf extracts) Spinach

Zea mays L. (seedling Oats
 extracts)

Zea mays L. (extracts) Erwinia spp.

Zea mays L. (extracts) Oats, timothy, crabgrass, rye-
 grass, cockscomb, cress,
 lettuce

Zea mays L. Chenopodium album

Zea mays L. Rhopalosiphum maidis F.
 (corn leaf aphid)

Allelopathic species Mode of action

Agropyron repens L. (root Inhibition of root length and
 exudates) seedling development;
 stimulation of growth
 (some concentrations of
 DIBOA)

Agropyron repens L. Inhibition of seedling growth

Avena sativa L. (shoot and Inhibition of germination and
 root extracts) growth of roots and hypo-
 cotyls

Avena sativa L. (extracts) Substantial reductions in ger-
 mination and seedling
 growth

Avena spp. (root exudates) Inhibition of shoot and root
 growth

Avena spp. (residues) Inhibition of growth

Avena sativa L. (nonsterile Inhibition of seed germina-
 residue extracts) tion, radicle, secondary
 root lengths

Bothriochloa pertussa L., Inhibition of germination (B.
 Urochloa mosambicensis pertusa) and root length
 Hack. (aqueous extracts)

Bromus inermis L., Agropyron Inhibition of germination and
 repens L., Dactylis glom- radicle lengths
 erata L., Festuca elatior
 L., Phleum pratense L.
 (extracts)

Bromus inermis L., Dactylis Inhibition of seed germination
 glomerata L., Lolium per- (B. inermis, P. pratensis,
 enne L., Festuca pratensis T. repens, T. pratense)
 L., Poa pratensis L.,
 Phleum pratense L., (root
 leachates)

Bromus inermis L., Dactylis Effects on germination, seed-
 glomerata L., Sorghum bi- ling length, weight
 color L., Phleum pratense
 L., Festuca arundinacea
 L. (extracts)

Buchloe dactyloides Inhibition of root growth and
 reduction of establishment;
 autotoxic

Cynodon dactylon L. (extracts Inhibition of growth and/or
 and root exudates) germination

Cynodon dactylon L. (resi- Reduction of leaf number, leaf
 dues) area per plant, leaf total
 chlorophyll content, leaf
 nitrate reductase activity

Cynodon dactylon L. and Inhibition of germination
 Echinochloa colonum L. and/or shoot and root
 (individual leaf and root length
 leachates and extracts)

Echinochloa crus-galli L. Effect on seedling growth and
 (aqueous extracts) seed germination

Festuca arundinacea Schreb. Increased seedling shoot
 (extracts) length and decreased of
 root length; reduction of
 root-hair length and root-
 hair density

Festuca spp. Inhibition of seed germination
 and seedling growth

Hordeum vulgare L. (root Reduction of radicle length;
 exudates) reduction in health and
 vigor

Hordeum vulgare L. (leaves) Resistance to aphids; de-
 creased survival, feeding
 and reproduction of
 aphids

Hordeum vulgare L. (exu- Suppression of the emergence
 dates)

Hordezan vulgare L. (extracts) Inhibition of germination in
 wild oats

Hordeum vulgare L. (extracts) Substantial reductions in ger-
 mination and seedling
 growth

Hordeum vulgare L. (straw Antialgal activity
 residues)

Hordeum vulgare L. (residues) Inhibition of weed densities

Hordeum vulgare L. Inhibition of germination
 and/or radicle lengths

Imperata cylindrica L. (leaves Inhibition of growth
 and clums extracts)

Imperata cylindrica L. (aque- Inhibition of germination,
 ous extracts) root, and shoot length and
 fresh and dry weight; re-
 duction in the number of
 fungal colonies

Imperata cylindrica L. (ex- Inhibition of germination
 tracts)

Lolium perenne L. (most Inhibitions of radicle length
 shoot leachates) and shoot and root growth

Miscanthus transmorrisonen- Inhibition of radicle growth
 sis (grains, grass leachates
 and extracts)

Oryza sativa L. and O. glaber- Inhibitory activity
 rima L. (root exudates)

Oryza sativa L (root exudate Inhibition of gross th of root,
 from early stages) shoot, and fresh mass in
 alfalfa, cress, and lettuce
 seedlings

Oryza sativa L. (decomposing Autotoxicity (inhibition of
 rice straw) rice growth)

Oryza sativa L. (seed germi- Stimulation of seed germina-
 nation and aqueous ex- tion; inhibition of radicle
 tracts) elongation

Panicum dichotomiflorum M. Inhibition of radicle elonga-
 (water extracts of dried tion (corn) and hypocotyl
 residues) growth (soybean)

Pennisetum glaucum L. (root Autotoxic: inhibition of rate
 and shoot extracts) germination, root length,
 shoot length, etc.

Phalaris minor; Phalaris bra- Reduction of grain yield
 chystachys

Phleum pratense L. (pollen) Inhibition of the germination
 of pollen and reduction of
 seed set

Poa pratensis L. (decompos- Inhibition of seed germination
 ing roots) and initial development;
 reduction of root length

Polypogon monspeliensis L. Inhibition of root growth and
 (weed straw) shoot growth (radish)

Sasa cernua (rhizosphere soil) Inhibition of seed germination,
 seedling growth, length of
 aerial part and root

Secale cereale L. (root exu- Inhibition of root and coleop-
 dates) tile growth

Secale cereale L. (exudates) Suppression of emergence

Secale cereale L. (root resi- Inhibition of biomass and
 dues, whole plant mulch) weed growth

Secale cereale L. (mulch) Inhibition of growth

Secale cereale L. (residues) Inhibition of germination

Secale cereale L. (residues) Inhibition of growth

Secale cereale L. (residues) Inhibition of germination,
 growth, and vigor

Secale cereale L. (degradation Inhibition of length of seed-
 tissues) ling roots

Secale cereale L. (rye root Inhibition of seedling growth;
 residue, surface-applied reduction in the number of
 residues) leaves; reduction of emer-
 gence and height

Secale cereale L. (extracts) Inhibition of root and shoot
 growth; inhibition of radi-
 cle elongation

Secale cereale L. (aqueous Inhibition of calluses and radi-
 extracts) cle growth

Secale cereale L. Chemical resistance of rye to
 the infection

Setaria glauca L. (residues) Inhibition of shoot and root
 growth and nutrient uptake

Setaria viridis L. Inhibition of growth

Sorghum bicolor L. (grain) Suppression of weed abun-
 dance

Sorghum bicolor L. (root exu- Inhibition of growth
 dates)

Sorghum bicolor L. (root exu- Inhibition of photosynthesis
 date) and oxygen evolution

Sorghum bicolor L. (root exu- Inhibition of mitochondrial
 dates) respiration

Sorghum bicolor L. (root exu- Stimulation of germination
 dates)

Sorghum bicolor L. (extracts) Inhibition of growth

Sorghum bicolor L. (extracts) Stimulation of germination
 in wild oats

Sorghum bicolor L. (extracts) Inhibition of photosynthetic
 electron transport

Sorghum bicolor L. (extracts Inhibition of radicle growth
 from different plant parts)

Sorghum bicolor L. Inhibition of root elongation

Sorghum bicolor L. (root exu- Affinity to the D1 protein of
 date) the PSII complex (poten-
 tial PSII inhibitor)

Sorghum bicolor L. (water Control up to 35-49% of
 extract of mature plants) weeds; increase of wheat
 yield by 10-21%

Sorghum bicolor x Sorghum Alteration of radicle length
 sudanese hybrid (sudex)

Sorghum halepense L. Effects on seedling growth

Triticum aestivum L. (exu- Inhibition of radicle elonga-
 dates) tion

Triticum aestivum L. (straw) Inhibition of germination

Triticum aestivum L. (straw Effects on germination, seed-
 management practices) ling growth, plant stand,
 plant height, leaf area in-
 dex, dry matter, yield

Triticum aestivum L. (resi- Inhibition of weed densities
 dues)

Triticum aestivum L. (resi- Stimulation of growth of al-
 dues) gae; inhibition of rate of
 biological nitrogen fixa-
 tion

Triticum aestivum L. (root Inhibition of growth
 extracts)

Triticum aestivum L. (aqueous Stimulation of gemination
 extracts of straw) (carpet weed, barnyard
 grass, crowfoot grass) and
 growth; inhibition of germi-
 nation (pigweed, sunberry)

Triticum aestivum L. (extract Reduction of growth of root,
 of residues) shoot and whole rice plant

Triticum aestivum L. (soil Effects on gemination and
 extracts) radicle and hypocotyl
 length

Triticum aestivum L. Resistance to aphids; de-
 creased survival, feeding
 and reproduction of aphids

Trilicmn aestivum L. Yield and disease resistance

Triticum aestivum L. (seed- Inhibition of ryegrass root
 lings) growth

Triticum speltoides L. Effects on radicle lengths

Triticum speltoides L. Inhibition of root growth of
 lettuce and wild oats

Vulpia spp. (residues and Inhibition of radicle elonga-
 aqueous extracts) tion, coleoptile growth,
 and seed germination

Zea mays L. (whorl surface Inhibition of larval growth
 waxes)

Zea mays L. (silks) Silks of popcorn collection
 produced corn earworm
 larvae equal to or smaller
 than larvae on silk of the
 resistant standard

Zea mays L. (exudates) Inhibition of radicle elonga-
 tion

Zea mays L. (tissues) Increasing of larval mortality;
 slower development;
 smaller individuals

Zea mays L. (residues) Inhibition of growth

Zea mays L. (nonsterile resi- Inhibition of seed germination,
 due extracts) coleoptile lengths, secon-
 dary root lengths

Zea mays L. (pollen and crude Inhibition of seed germination
 pollen extracts) and radicle growth

Zea mays L. (leaf extracts) Inhibition of ATPase from
 chloroplasts

Zea mays L. (seedling Inhibition (DIMBOA) and/or
 extracts) stimulation (BOA, MBOA
 some concentrations) of
 the [H.sup.+]-ATPase activity
 plasma membrane

Zea mays L. (extracts) Inhibition of soft rotting bac-
 teria

Zea mays L. (extracts) Growth inhibition of roots
 and shoots

Zea mays L. Growth of seedling

Zea mays L. Influence on the resistance of
 corn to aphids

Allelopathic species Source

Agropyron repens L. (root Schulz et al., 1994
 exudates)

Agropyron repens L. Hagin, 1989

Avena sativa L. (shoot and Kato-Noguchi et at., 1994a,
 root extracts) 1994b

Avena sativa L. (extracts) Moyer & Huang, 1997

Avena spp. (root exudates) Fay & Duke, 1977; Schuma-
 cher et al., 1983; Perez &
 Ormeno-Nunez, 1991a;
 Wardle et al., 1994

Avena spp. (residues) Guenzi & McCalla, 1966;
 Guenzi et al., 1967

Avena sativa L. (nonsterile Martin et al., 1990
 residue extracts)

Bothriochloa pertussa L., Hu & Jones, 1997
 Urochloa mosambicensis
 Hack. (aqueous extracts)

Bromus inermis L., Agropyron Stowe, 1979
 repens L., Dactylis glom-
 erata L., Festuca elatior
 L., Phleum pratense L.
 (extracts)

Bromus inermis L., Dactylis Wanda & Lipinska, 1997
 glomerata L., Lolium per-
 enne L., Festuca pratensis
 L., Poa pratensis L.,
 Phleum pratense L., (root
 leachates)

Bromus inermis L., Dactylis Chung & Miller, 1995
 glomerata L., Sorghum bi-
 color L., Phleum pratense
 L., Festuca arundinacea
 L. (extracts)

Buchloe dactyloides Wu et al., 1998

Cynodon dactylon L. (extracts Abdul-Rahman & Al-Naib,
 and root exudates) 1986; Abdul-Rahman &
 Habib,1986

Cynodon dactylon L. (resi- Kalita et al., 1999
 dues)

Cynodon dactylon L. and Challa & Ravindra, 1998
 Echinochloa colonum L.
 (individual leaf and root
 leachates and extracts)

Echinochloa crus-galli L. Piskorz, 1998a, 1998b
 (aqueous extracts)

Festuca arundinacea Schreb. Springer, 1996
 (extracts)

Festuca spp. Smith & Martin, 1994

Hordeum vulgare L. (root Overland, 1966; Liu & Lovett,
 exudates) 1993b

Hordeum vulgare L. (leaves) Zuniga & Corcuera, 1986;
 Corcuera ct al., 1992

Hordeum vulgare L. (exu- Creamer et al., 1996
 dates)

Hordezan vulgare L. (extracts) Jones et al., 1999

Hordeum vulgare L. (extracts) Moyer & Huang, 1997

Hordeum vulgare L. (straw Pillinger et al., 1994
 residues)

Hordeum vulgare L. (residues) Putnam et al., 1983

Hordeum vulgare L. Went et al., 1952; Liu &
 Lovett, 1990, 1993a

Imperata cylindrica L. (leaves Eussen, 1979; Hussain &
 and clums extracts) Abidi, 1991

Imperata cylindrica L. (aque- Inderjit & Dakshini, 1991
 ous extracts)

Imperata cylindrica L. (ex- Tripathi & Vaishya, 1997
 tracts)

Lolium perenne L. (most Wardle et al., 1996
 shoot leachates)

Miscanthus transmorrisonen- Chou & Lee, 1991
 sis (grains, grass leachates
 and extracts)

Oryza sativa L. and O. glaber- Fujii, 1994
 rima L. (root exudates)

Oryza sativa L (root exudate Kato-Noguchi & Ino, 2001
 from early stages)

Oryza sativa L. (decomposing Chou & Lin, 1976; Chou et
 rice straw) al., 1981

Oryza sativa L. (seed germi- Kawaguchi et al., 1997a,
 nation and aqueous ex- 1997b
 tracts)

Panicum dichotomiflorum M. Bhowmik & Doll, 1982
 (water extracts of dried
 residues)

Pennisetum glaucum L. (root Saxena et al., 1996
 and shoot extracts)

Phalaris minor; Phalaris bra- Afentouli & Eleftherohorinos,
 chystachys 1996

Phleum pratense L. (pollen) Murphy & Aarssen, 1995a,
 1995b, 1995c, 1996

Poa pratensis L. (decompos- Lipinska & Harkot, 1998
 ing roots)

Polypogon monspeliensis L. Inderjit & Dakshini, 1995
 (weed straw)

Sasa cernua (rhizosphere soil) Li et al., 1992

Secale cereale L. (root exu- Perez & Ormeno-Nunez,
 dates) 1991b, 1993

Secale cereale L. (exudates) Creamer et al., 1996

Secale cereale L. (root resi- Brecke & Shilling, 1996
 dues, whole plant mulch)

Secale cereale L. (mulch) Shilling et al., 1985

Secale cereale L. (residues) Putnam et al., 1983

Secale cereale L. (residues) Chou & Patrick, 1976

Secale cereale L. (residues) Souza, 1996

Secale cereale L. (degradation Wojcik-Wojtkowiak et al.,
 tissues) 1990

Secale cereale L. (rye root Hoffman et al., 1996a, 1996b
 residue, surface-applied
 residues)

Secale cereale L. (extracts) Barnes et al., 1987; Chase et
 al., 1991; Gagliardo &
 Chilton, 1992; Mwaja et
 al., 1995

Secale cereale L. (aqueous Vicol & Dobrota, 1994
 extracts)

Secale cereale L. Virtanen et al., 1957

Setaria glauca L. (residues) Bhowmik & Doll, 1982, 1984

Setaria viridis L. Bhowmik & Doll, 1982

Sorghum bicolor L. (grain) Einhellig & Rasmussen, 1989

Sorghum bicolor L. (root exu- Einhellig & Souza, 1992
 dates)

Sorghum bicolor L. (root exu- Einhellig et al., 1993
 date)

Sorghum bicolor L. (root exu- Rasmussen et al., 1992
 dates)

Sorghum bicolor L. (root exu- Netzly et al., 1988
 dates)

Sorghum bicolor L. (extracts) Alsaadawi et al., 1986

Sorghum bicolor L. (extracts) Jones et al., 1999

Sorghum bicolor L. (extracts) Nimbal el al., 1996; Gonzalez
 et al., 1997

Sorghum bicolor L. (extracts Ben-Hammouda et al., 1995a
 from different plant parts) 1995b

Sorghum bicolor L. Netzly & Butler, 1986

Sorghum bicolor L. (root exu- Weston & Czarnota, 2001
 date)

Sorghum bicolor L. (water Cheema & Khaliq, 2000
 extract of mature plants)

Sorghum bicolor x Sorghum Weston et al., 1989
 sudanese hybrid (sudex)

Sorghum halepense L. Nicollier et al., 1983

Triticum aestivum L. (exu- Kumar et al., 1993
 dates)

Triticum aestivum L. (straw) Steinsiek et al., 1982

Triticum aestivum L. (straw Narwal et al., 1997
 management practices)

Triticum aestivum L. (resi- Putnam et al., 1983
 dues)

Triticum aestivum L. (resi- Zwain et al., 1999
 dues)

Triticum aestivum L. (root Perez & Ormeno-Nunez,
 extracts) 1991b

Triticum aestivum L. (aqueous Narwal & Sarmah, 1996
 extracts of straw)

Triticum aestivum L. (extract Alsaadawi et al., 1998
 of residues)

Triticum aestivum L. (soil Blum et al., 1992
 extracts)

Triticum aestivum L. Corcuera et al., 1992; Givo-
 vich et al., 1994; Contreras
 & Niemeyer, 1997

Trilicmn aestivum L. Copaja et al., 1991

Triticum aestivum L. (seed- Wu et al., 2001, 2002
 lings)

Triticum speltoides L. Abdul & Adkins, 1998

Triticum speltoides L. Quader et al., 2001

Vulpia spp. (residues and An et al., 1996, 1997a, 1997b;
 aqueous extracts) Pratley, 1996

Zea mays L. (whorl surface Hedin et al., 1993
 waxes)

Zea mays L. (silks) Wiseman et al., 1992

Zea mays L. (exudates) Kumar et al., 1993

Zea mays L. (tissues) Klun et al., 1967; Reed et al.,
 1972

Zea mays L. (residues) Chou & Patrick, 1976

Zea mays L. (nonsterile resi- Martin et al., 1990
 due extracts)

Zea mays L. (pollen and crude Anaya et al., 1992
 pollen extracts)

Zea mays L. (leaf extracts) Queirolo et al., 1983

Zea mays L. (seedling Friebe et al., 1997
 extracts)

Zea mays L. (extracts) Corcuera et al., 1978

Zea mays L. (extracts) Kato-Noguchi et al., 1998

Zea mays L. Dzubenko & Petrenko, 1971

Zea mays L. Beck et al., 1983


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A. M. SANCHEZ-MOREIRAS, O. A. WEISS, AND M. J. REIGOSA-ROGER

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