Perenne Seedlings Research Articles

Biometric indicators of growth and development of Lolium perenne and Trifolium repens in terms of recultivation of soil contaminated with petroleum

The aim of the research was to determine the factors defining the growth and development of Lolium perenne and Trifolium repens upon petroleum contamination. The top layer of clay soil contaminated with petroleum products resulting from an oil pipeline failure was collected for the tests. The control was the same type of uncontaminated soil with the addition of, under laboratory conditions, tissue paper. The research was conducted in two stages. The first concerned the germination process and seedlings parameters (Petri dishes). The germination energy ( GE) and the germination capacity ( GC) of seeds were determined. The seedling’s development was also evaluated based on ‘WinRhizo PRO 2009’ software. Then, in the second stage, pot tests were carried out, where the growth and development of species in the first year after sowing were temporarily measured. The parameters studied were the number, height, green and dry masses of the plants. A Gompertz regression model describing seed species germination and number species as time dependent dynamic was applied. The data were analysed statistically using variance analysis (ANOVA) and the PCA (principal component analysis) method. The results of our study indicated that admixture of petroleum into the soil does not seriously affect the development dynamics of Lolium perenne seedlings. The diesel oil contamination mostly affects the germination of the Trifolium repens by a statistically significant increase of the maximum value of germination and increasing the maximum growth rate.

Chitin Deacetylases Are Required for Epichloë festucae Endophytic Cell Wall Remodeling During Establishment of a Mutualistic Symbiotic Interaction with Lolium perenne.

Epichloë festucae forms a mutualistic symbiotic association with Lolium perenne. This biotrophic fungus systemically colonizes the intercellular spaces of aerial tissues to form an endophytic hyphal network and also grows as an epiphyte. However, little is known about the cell wall-remodeling mechanisms required to avoid host defense and maintain intercalary growth within the host. Here, we use a suite of molecular probes to show that the E. festucae cell wall is remodeled by conversion of chitin to chitosan during infection of L. perenne seedlings, as the hyphae switch from free-living to endophytic growth. When hyphae transition from endophytic to epiphytic growth, the cell wall is remodeled from predominantly chitosan to chitin. This conversion from chitin to chitosan is catalyzed by chitin deacetylase. The genome of E. festucae encodes three putative chitin deacetylases, two of which (cdaA and cdaB) are expressed in planta. Deletion of either of these genes results in disruption of fungal intercalary growth in the intercellular spaces of plants infected with these mutants. These results establish that these two genes are required for maintenance of the mutualistic symbiotic interaction between E. festucae and L. perenne.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Labdane-Type Diterpenoids from Leonurus japonicus and Their Plant-Growth Regulatory Activity.

Thirteen new labdane-type diterpenoids 1-6, 9-11, 13, 14, 18, and 19 and seven known ones were isolated from the aerial parts of Leonurus japonicus. Compounds 1-5 represent rare examples of labdane-type diterpenoids, of which compounds 1-4 carry an N-chain linked at C-7 in their B-ring and compound 5 featured an α,β-unsaturated-γ-lactam moiety. The structures and absolute configurations of these new diterpenoids were characterized by a combination of spectroscopic techniques, X-ray crystallography, electronic circular dichroism, and calculated specific rotations. The plant-growth regulatory activity of these compounds on the growth of the roots and shoots of Lactuca sativa and Lolium perenne seedlings were evaluated. Compound 3 showed a broad-spectrum inhibitory activity with the inhibition rates ranging from 60 to 83.5% at a concentration of 200 μg/mL, which were as active as those of glyphosate. Compound 8 had a selective inhibitory activity against the growth of the roots of L. perenne seedlings with an inhibition rate of 81.7%. However, compounds 11 and 16 exhibited significant stimulation effects on the roots of L. sativa with stimulation rates of 59.8 and 65.3%, respectively. In addition, compounds 3 and 8 exhibited inhibitory effects on the germination of L. perenne seeds.

Evaluation of photosynthetic performance and carbon isotope discrimination in perennial ryegrass (Lolium perenne L.) under allelochemicals stress

Ferulic (FA) and p-hydroxybenzoic acid (pHBA) are commonly found as phenolic compounds (PHC) in many forage and cereal crops. Although the effects of these PHC on seedling growth are relatively explored, not many information is available regarding the phytotoxicity on ecophysiological processes of perennial ryegrass adult plants. The experiment was conducted with the aim to evaluate the phytotoxic potential of PHC on the seedling growth, leaf water relation, chlorophyll fluorescence attributes and carbon isotope discrimination adult plants of perennial ryegrass (Lolium perenne L.). The results clearly indicated that PHC behaved as potent inhibitors of chlorophyll fluorescence yield (Fv/Fm) in leaves of L. perenne and plants showed poor tolerance against allelochemicals stress. Quantum yield (ΦPSII), chlorophyll fluorescence quenching (qP) and non-photochemical quenching (NPQ) were decreased following exposure to FA and pHBA. The portion of absorbed photon energy that was thermally dissipated (D) in L. perenne was decreased. Exposure of the L. perenne seedlings to FA and pHBA stress led to a decrease in fresh/dry weight, relative water content and leaf osmotic potential. Carbon isotope composition ratio (δ13C) was significantly less negative than the control following treatment with FA or pHBA. The results suggested that PHC uptake was a key step for the effectiveness of these secondary metabolites and their phytotoxicity on L. perenne adult plants was mainly due to the alteration of leaf water status accompanied by photosystem II damage. Acquisition of such knowledge may ultimately provide a better understanding about the mode of action of the tested compounds.

Effects of Decomposing Leaf Litter of Eucalyptus grandis on the Growth and Photosynthetic Characteristics of Lolium perenne

The essence of grass growth is a complex system that is driven by light energy. The accumulation of 90% of the dry matter comes from the production of photosynthesis. In this study, we investigated the effect of decomposing leaf litter of Eucalyptus grandis on the growth and photosynthetic characteristics of Lolium perenne by pot experiment. Four treatments with different amounts of leaf litter were designed, including A1 (30 g/pot), A2 (60 g/pot), A3 (90 g/pot) and control (0 g/pot; CK), and the blank experiment groups with distilled fallen leaves were set as the above. The growth indices (including shoot biomass, root biomass and leaf area) were measured, and the photosynthetic characteristics were tested during 9:00-11:00 am on a sunny day. The test results showed that increasing amounts of E grandis leaf litter significantly inhibited the accumulation of shoot and root biomass, growth of leaf area, synthesis of photosynthetic pigments (chlorophyll a, chlorophyll b and cartenoids), photosynthetic rate and gas exchange parameters (Gs, Ci and Tr) of L. perenne seedlings (P A1 > A2 > A3 (P < 0.05). The blank experimental showed that soil chemical and physical properties have not been changed by leaf litter decomposition. This demonstrated that the allelochemicals from E. grandis leaf litter decomposition can negatively affect the photosynthetic capacity and decrease the accumulation of biomass, and eventually inhibit the growth of L. perenne.

Litter‐mediated allelopathic effects of kudzu (Pueraria montana) on Bidens pilosa and Lolium perenne and its persistence in soil

This study investigated the allelopathic effects of kudzu litter on the seed germination and early growth of Bidens pilosa and Lolium perenne. The bioassays, with various concentrations (10, 20, 30, 40, and 50 g L−1) of aqueous kudzu litter leachate, significantly affected the germination percentages and radicle growth of both species. These parameters decreased progressively when the seedlings were exposed to increasing concentrations of leachate. The root and shoot length, dry weight, and chlorophyll concentration of the B. pilosa and L. perenne seedlings also were significantly affected when they were grown in leachate‐amended soil. However, the chlorophyll fluorescence values of the seedlings subjected to different concentrations of aqueous kudzu litter leachate indicated that the mere presence of leachate in the soil was not stressful for the plants. The seedlings of both species were under stressful conditions only when they were grown in the soil that was treated with higher concentrations of leachate (30, 40, or 50 g L−1). A 6 week decomposition study of the kudzu litter in soil was conducted to observe the retention of phenolic content in the soil. The results showed that, although the concentration of dissolved organic carbon decreased with increasing decomposition, the phenolic concentration was not significantly affected when the observation period ended. This suggests that the phytotoxic properties of kudzu litter remain stable in soil systems for a considerable amount of time after incorporation into the soil.

The earthworm Lumbricus terrestris favours the establishment of Lolium perenne over Agrostis capillaris seedlings through seed consumption and burial

We studied the effects of the anecic earthworm Lumbricus terrestris L. on seed germination of two plant species to understand the mechanisms underlying earthworm–seed interactions. We set up microcosms with seeds of Lolium perenne L. (large seeds) and Agrostis capillaris L. (small seeds), in a loam based compost, with and without earthworms. We buried seeds at three depths and recorded their germination, we also examined to what depth earthworms buried seeds, and we studied seed viability after transit through the gut of earthworms. Earthworms dramatically reduced the numbers of A. capillaris seeds germinating, but did not modify the germination of L. perenne seeds. Earthworms did, however, increase the biomass of L. perenne seedlings. When we buried the seeds, those from A. capillaris rarely germinated when they were placed below 7 cm, unlike L. perenne seeds. Earthworms buried the seeds of L. perenne to a depth of 15 cm. Passage of seeds through the gut of earthworms had a detrimental effect on A. capillaris seed viability, while L. perenne seeds remained unaffected. While our results show that earthworm activity can strongly influence grass seed germination and plant establishment in microcosm experiments, further work is needed to asses the implications of earthworm–seed interactions for vegetation dynamics in the field.

Effects of elevated CO 2 concentration on rhizodeposition from Lolium perenne grown on soil exposed to 9 years of CO 2 enrichment

The effects of enriched CO 2 atmosphere on partitioning of recently assimilated carbon were investigated in a plant-soil-microorganism system in which Lolium perenne seedlings were planted into cores inserted into the resident soil within a sward that had been treated with elevated CO 2 for 9 consecutive years, under two N fertilisation levels (Swiss FACE experiment). The planted cores were excavated from the ambient (35 Pa pCO 2) and enriched (60 Pa pCO 2) rings at two dates, in spring and autumn, during the growing season. The cores were brought back to the laboratory for 14C labelling of shoots in order to trace the transfer of recently assimilated C both within the plant and to the soil and microbial biomass. At the spring sampling, high N supply stimulated shoot and total dry matter production. Consistently, high N enhanced the allocation of recently fixed C to shoots, and reduced it to belowground compartments. Elevated CO 2 had no consequences for DM or the pattern of C allocation. At the autumn sampling, at high N plot, yield of L. perenne was stimulated by elevated CO 2. Consistently, 14C was preferentially allocated aboveground and, consequently belowground recent C allocation was depressed and rhizodeposition reduced. At both experimental periods, total soil C content was similar in all treatments, providing no evidence for soil carbon sequestration in the Swiss Free Air CO 2 Enrichment experiment (FACE) after 9 years of enrichment. Recently assimilated C and soil C were mineralised faster in soils from enriched rings, suggesting a CO 2-induced shift in the microbial biomass characteristics (structure, diversity, activity) and/or in the quality of the root-released organic compounds.

Glomus intraradices Enhances Growth and Gas Exchange of Lolium perenne Seedlings in Petroleum-contaminated Soil

Arbuscular mycorhizal fungi (AMF) have been used in phytoremediation and can increase tolerance and growth of plants in contaminated environments. However, little is known about the influence AMF on plant growth to organic contaminants in soils. A greenhouse experiment was conducted to study the response of seedlings of annual ryegrass (Lolium perenne L.) var. Passerel Plus inoculated with Glomus intraradices Schenck &amp; Smith in soil contaminated with sweet Arabian median crude oil. Inoculated (AMF) and non-inoculated (Non-AMF) plants were established in an pasteurized and artificially contaminated sandy loam soil with 0; 3000; 15,000; or 45,000 mg of petroleum kg-1 soil (n = 20). Plants were inoculated with 500 spores of G. intraradices (Mycorise® ASP, PremierTech Biotechnologies, Canada). After 90 days, plant growth of AMF or Non-AMF plants, was drastically affected at all petroleum concentrations. However, G. intraradices enhanced plant growth, chlorophyll content, and gas exchange of plants grown at 3,000 mg kg-1 compared to Non-AMF plants. Total leaf area, chlorophyll, and net photosynthesis were also higher (+380%, +63%, and +81%, respectively) at this concentration. Water use efficiency (net photosynthesis/stomatal conductance) of AMF-plants was three times greater than Non-AMF at 3,000 mg·kg-1. At concentrations of 15,000 and 45,000 mg kg-1 AMF did not have effect, but colonization was observed (11.8% and 18.6%, respectively). These values of colonization were significantly lower than those observed in AMF-plants at 0 (42.5%) and 3,000 mg·kg-1 (55.6%). Studies are currently being conducted to understand the physiological role of AMF on plants exposed to organic contaminants.

First Report of a Labyrinthula sp. Causing Rapid Blight Disease of Rough Bluegrass and Perennial Ryegrass.

A Labyrinthula sp. was isolated from symptomatic rough bluegrass (Poa trivialis L.) and perennial ryegrass (Lolium perenne L.) from a golf course in Arizona. Initial symptoms were a water-soaked appearance and rapid collapse of small patches of turf foliage. The affected turf died, and patches coalesced to form large dead areas after several weeks. The symptoms were those of the disease recently termed "rapid blight" for which the causal agent has not been identified (1). Rapid blight was first observed in southern California in 1995 and has become increasingly problematic in 10 other states on several cool-season turfgrasses (1). In Arizona, it is associated with high salinity irrigation water. In microscopic examinations of symptomatic P. trivialis and L. perenne leaf tissue from November 2002 to February 2003, fusiform or spindle-shaped vegetative cells (4 to 5 × 15 to 20 μm) were observed in leaf cells. These cells are consistently associated with rapid blight (1) and are typical in size and shape of those described for Labyrinthula spp. (3,4). The fusiform cells were cultured in 1% horse serum water agar medium made with irrigation water (electrical conductivity [EC] = 3.5 to 4.0 dS/m) from a golf course in central Arizona with rapid blight. The cells readily formed colonies on this medium and exhibited gliding motility along a network of hyaline slime filaments as previously described for the genus Labyrinthula (3,4). Koch's postulates were fulfilled by inoculating P. trivialis and L. perenne seedlings with Labyrinthula sp. isolated from naturally infested P. trivialis in two experiments. The grasses were started from seed and grown as a lawn in containers in the laboratory. Both experiments were repeated once. In the first experiment, infested autoclaved leaf pieces of P. trivialis were used as inoculum. Inoculated leaf pieces were placed within each of several bundles of 4 to 6 leaves and held loosely in place with a 0.5-cm wide ring of tygon tubing. Seedlings were irrigated with sterilized irrigation water from the golf course (EC = 4.0 dS/m). In the second experiment, agar discs from Labyrinthula sp. colonies on 1% horse serum agar were used as inoculum by placing the agar discs in contact with leaves. Seedlings were irrigated with sterile tap water adjusted to 4.0 dS/m using synthetic sea salt (Instant Ocean, Aquarium Systems, Inc., Mentor, OH) Leaf tissue of all inoculated seedlings became water soaked within 3 to 7 days and collapsed within 10 days in both experiments. Fusiform cells were observed in inoculated leaf tissue cells, and the Labyrinthula sp. was reisolated from 100% of selected symptomatic seedlings. Control seedlings treated with noninfested leaf pieces or sterile agar pieces did not develop symptoms, and no fusiform cells were isolated from the leaf tissue. Labyrinthula spp. are usually associated with marine systems (3). Labyrinthula zosterae D. Porter & Muehlst. has been identified as the causal agent in a marine grass wasting disease (2), but to our knowledge, no Labyrinthula spp. have been described as pathogens of terrestrial plants.

Forum

In a recent Forum article, Tibbett (2000) argued that mycorrhizal symbionts are more important than root proliferation for the exploitation of nutrient-rich zones or ‘patches’ in soil. There is little doubt that mycorrhizal fungi can enhance nutrient capture for their host. Both ecto- and ericoid mycorrhizal fungi can access nutrients (e.g. organic N) that would otherwise be unavailable to the plant, and through enzymatic production may enhance organic matter degradation. But this paper addresses the role of arbuscular mycorrhizas (AMs) in patch exploitation, as AMs are the most common of mycorrhizal associations, occurring in two-thirds of all land plant species. Tibbett’s case for mycorrhizas competing better than roots for nutrients needs critical examination. He stated that ‘we may come to perceive the role of roots, in terms of acquiring nutrients from organic patches, as relatively inert structures from which symbiotic organs, that can better compete with the wider microbiota are dispatched.’ Thus fungal, not root, proliferation would be expected. In support of this view, Tibbett (2000) cited experiments where root proliferation took a long time to occur in complex organic patches of a high C : N ratio. Other studies however, reveal that: • Plant N capture from N-rich patches of lower C : N ratio (<4) can be substantial (45–54%) even if root proliferation occurs only after c. 25 days (Hodge, Robinson & Fitter 2000). • Mycorrhizal colonization had little effect on the root foraging responses of seven co-occurring herbaceous species, and only one (Oxalis acetosella) showed a nutritional benefit from colonization (Farley & Fitter 1999). • Root responses are demonstrably more important for plant N capture than those of AM fungi. Lolium perenne seedlings supplied with l-lysine patches had the same slight (<20%) AM colonization that did not vary among treatments nor differ from controls (Hodge et al. 1999a). By contrast, roots responded strongly to the treatments. Duke et al. (1994) concluded that ‘increased plant root proliferation and uptake capacity are likely to be more important for the exploitation of temporary nutrient pulses or patches than is increased mycorrhizal activity.’ In contrast, Tibbett (2000) stated that ‘current emphasis on plant roots may have over estimated their significance in patch exploitation.’ Which view is correct? It is not yet possible to give a definitive answer. More experiments must be carried out on the ecology of AM fungi, in particular on the role of the external mycelium, before we can determine their importance in patch exploitation and their influence on root proliferation. Furthermore, AM fungi are multifunctional, and it cannot be assumed that all will necessarily enhance nutrient capture equally. Meanwhile, it should be remembered that the context in which roots proliferate may be as important as the response itself, for example, proliferation is relatively unimportant for nitrate capture by isolated individuals, but is important when individuals compete for nitrate (Hodge et al. 1999b). This context dependency may also apply to AM fungi. For example, inoculation of Plantago lanceolata seedlings with an AM fungus did not increase N capture from an organic patch, but it did increase root production, most pronouncedly within the patch zone (Hodge et al. 2000). Had the plants been grown in competition, however, the AM-related increase in root production may have enhanced their N capture. Root proliferation in N-rich patches would still give a plant a competitive advantage over its neighbours, whatever their mycorrhizal status.

Characterisation and microbial utilisation of exudate material from the rhizosphere of Lolium perenne grown under CO 2 enrichment

The effects of elevated atmospheric CO 2 concentration on alterations, both qualitatively and quantitatively, of exuded compounds from the roots of Lolium perenne seedlings were investigated by growing plants in a sterilised sand microcosm unit. In addition, the effect of CO 2 treatment on carbon substrate utilisation of microbial populations extracted from the rhizosphere of L. perenne seedlings grown in soil microcosm units was examined and alterations on microbial activity and diversity assessed using a commercially-available redox-based sole C source utilisation test (Biolog®) including additional exudate compounds. Both types of microcosm units (sand and soil) were maintained at specific growth conditions under two CO 2 regimes (450 and 720 μmol mol −1). Growth of L. perenne seedlings from both types of microcosm units was enhanced under elevated atmospheric CO 2 although the root-to-shoot ratios were not significantly altered, indicating no gross change in dry matter partitioning. Cumulative total organic carbon (TOC) release in the exudate material over the duration of the experiment was significantly ( P≤0.05) higher from ambient-grown seedlings despite a significant ( P≤0.05) increase in the dry weight of roots of the elevated CO 2 grown seedlings as determined at harvest. Over the individual sampling periods TOC release was significantly ( P≤0.05) higher from elevated CO 2 grown seedlings on only one occasion (21 d). Qualitative differences, measured between d 1–6 and 14–18, also occurred with elevated CO 2 treatment decreasing the amount of phenolic acids and total sugars at the latter sampling period compared to ambient CO 2 seedlings. Total numbers of bacteria were significantly ( P≤0.05) decreased under elevated CO 2 although culturable numbers significantly ( P≤0.05) increased. This increase in culturable microorganisms may explain the faster carbon source utilisation rates of the elevated CO 2 treatment. No change in morphotypes of microbial colonies were observed suggesting a quantitative difference due to elevated CO 2 treatment only.

Effects of photon flux density on carbon partitioning and rhizosphere carbon flow ofLolium perenne

The distribution and partitioning of dry matter and photoassimilate of Lolium perenne was investigated under two light regimes providing photosynthetically active radiation of 350 /imo m 2 s~1 (low light treatment) or 1000 //mol m 2 s~1 (high light treatment). Plants were grown at specific growth conditions in either soil or sand microcosm units to follow the subsequent release of carbon into the rhizosphere and its consequent incorporation into the microbial biomass (soil system) or recovery as exudates (sand system). The distribution of recent assimilate between the plant and root released carbon pools was determined using 14C02 pulse-chase methodology at both light treatments and for both sand- and soil-grown seedlings. A significant (P<0.05) increase in partitioning of Relabel below-ground occurred for both soil- and sandgrown seedlings at the increased light treatment. Incorporation of recent assimilate into the microbial biomass, however, was unaltered by light treatment. Total plant biomass of L. perenne seedlings grown in the sand microcosm unit was unaffected by light treatment, but differences in partitioning of biomass did occur resulting in an increased root-to-shoot ratio under high light. Soil-grown L. perenne seedlings showed a large (81%) and significant (P< 0.001) increase in shoot biomass under high light with a consequent decrease in root-to-shoot ratio. Specific leaf area was altered in the soil grown plants only, where it decreased under high light. Total organic carbon (TOC) content of the recovered exudate material was measured throughout the 14 d experimental period and during the 14C-chase period. Comparison of plant C budgets using these two measurements is discussed.

Ultrastructural evidence of damage to leaf stromal protein four hours after treatment with paraquat

An ultrastructural investigation of paraquat-treated leaf tissue of Lolium perenne seedlings using negative staining techniques alongside conventional ultrathin sectioning methods revealed extensive damage to the Rubisco molecules after only 4 h in light. The early involvement of hydroxyl radicals in chloroplast stroma destruction is discussed

The effect of copper on Lolium perenne seedlings

The present study looks at the effects of copper on perenial ryegrass seedlings that have been grown in hydroponic solutions and the uptake of some essential elements.

The use of experimental design and response surfaces in a study of the influence of copper, arsenic and chromium on Lolium perenne seedlings

The present investigation uses response surface methodology (RSM) in the study of the effects of Cu, As and Cr on Lolium perenne seedlings and reports the interactions that may occur between these elements.

Uptake of selenium, tellurium and interaction with some essential metals (Mn, Fe, Cu and Zn) by Lolium perenne

Two experiments involving the growth of Lolium perenne seedlings were carried out by adding Se(VI) (as sodium selenate) or Te(VI) (as telluric acid) to the nutrient solutions and the plants allowed to grow for a further period of time. Se and Te concentrations in the shoots follow closely the level of Se or Te supplied in the nutrient solution. The uptake of Se and Te by shoots is higher thanin the corresponding root samples. Se and Te reduce the dry weight of both shoots and roots of this particular species. The significant effects of Se and Te which were observed on the uptake of some essential metals (Mn, Fe, Cu and Zn) into the roots did not extend to the shoots.

Paraquat tolerant and susceptible perennial ryegrasses: effects of paraquat treatment on carbon dioxide uptake and ultrastructure of photosynthetic cells

Abstract. Paraquat treatment of susceptible Lolium perenne seedlings (cultivar Kent Indigenous) rapidly inhibited CO2 uptake and after 1 h chloroplasts exhibited abnormal fusions of the thylakoid membranes. Further ultrastructural changes occurred within the chloroplasts until 8 h after treatment, when cytoplasmic damage also became evident. The localization of primary damage within the chloroplast differs from previous reports of paraquat toxicity in other species. Paraquat treatment of tolerant L. perenne seedlings (line PRP IX) resulted in little change in CO2 uptake and ultrastructural effects were generally confined to the gradual development of deposits in the chloroplast stroma. These observations are discussed in relation to the mechanism of action of the herbicide and the proposed mechanism of paraquat tolerance in L. perenne.

Competition between Lolium perenne and Poa trivialis during establishment

AbstractThree experiments were carried out in boxes to determine the response of L. perenne seedlings to competition from P. trivialis seedlings at different densities and ages and when the proportions of the two species were varied according to the replacement principle. Tiller numbers per plant were significantly reduced by P. trivialis at densities commonly found in the field. Prior establishment of P. trivialis caused disproportionate damage to L perenne tillering and the early removal of such plants resulted in yield benefits to L. perenne. When sown together, P. trivialis was shown to be competitive towards L. perenne during the first 4 weeks of establishment but during the next 4 weeks, although competition was still occurring between the two species to the detriment of Poa, relative productivity (but not total productivity) was marginally greater in the mixture. The need for early herbicide treatment to prevent interspecific competition between graminaceous species during establishment is discussed.