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Summary: Epichloë festucae is an endophytic fungus that forms a symbiotic association with Lolium perenne. Here we analysed how the metabolome of the ryegrass apoplast changed upon infection of this host with sexual and asexual isolates of E. festucae.A metabolite fingerprinting approach was used to analyse the metabolite composition of apoplastic wash fluid from uninfected and infected L. perenne. Metabolites enriched or depleted in one or both of these treatments were identified using a set of interactive tools. A genetic approach in combination with tandem MS was used to identify a novel product of a secondary metabolite gene cluster.Metabolites likely to be present in the apoplast were identified using MarVis in combination with the BioCyc and KEGG databases, and an in‐house Epichloë metabolite database. We were able to identify the known endophyte‐specific metabolites, peramine and epichloëcyclins, as well as a large number of unknown markers.To determine whether these methods can be applied to the identification of novel Epichloë‐derived metabolites, we deleted a gene encoding a NRPS (lgsA) that is highly expressed in planta. Comparative MS analysis of apoplastic wash fluid from wild‐type‐ vs mutant‐infected plants identified a novel Leu/Ile glycoside metabolite present in the former. [ABSTRACT FROM AUTHOR]

The mechanism controlling the use of stored carbon in respiration is poorly understood. Here, we explore if the reliance on stores as respiratory substrate depends on day length. Lolium perenne (perennial ryegrass) was grown in continuous light (275 lmol photons m-2 s-1) or in a 16 : 8 h day : night regime (425 lmol m-2 s-1 during the photoperiod), with the same daily photosynthetic photon flux density (PPFD). Plants in stands were labelled with 13CO2 : 12CO2 for various time intervals. The rates and isotopic signatures of shoot- and root-respired CO2 were measured after labelling, and water-soluble carbohydrates were determined in biomass. The tracer kinetics in respired CO2 was analysed with compartmental models to infer the sizes, half-lives and contributions of respiratory substrate pools. Stores were the main source for respiration in both treatments (c. 60% of all respired carbon). But, continuous light slowed the turnover (+270%) and increased the size (+160%) of the store relative to the 16 : 8 h day : night regime. This effect corresponded with a greatly elevated fructan content. Yet, day length had no effect on sizes and half-lives of other pools serving respiration. We suggest that the residence time of respiratory carbon was strongly influenced by partitioning of carbon to fructan stores. [ABSTRACT FROM AUTHOR]

• The role of fructan in growth and drought-stress responses of perennial ryegrass (Lolium perenne) was investigated in an F2 mapping family that segregates for carbohydrate metabolism. • A quantitative trait locus approach was used to compare the genetic control of traits. • Growth and drought-stress traits were extremely variable within the family. Most traits had high broad-sense heritability. Quantitative trait loci (QTL) were identified for most traits; the maximum number of QTL per trait was four. Between 11% and 75% of total phenotypic variation was explained. Few growth-trait QTL coincided with previously identified fructan QTL. A cluster of drought-trait QTL was close to two previously identified regions of the genome with tiller base fructan QTL in repulsion. • The high sugar parent contributed few alleles that increased ‘reserve-driven’ growth or performance during drought-stress. Correlation of growth and drought-stress traits with fructan content was low and increasing fructan content per se would not appear to improve drought resistance. Complex patterns of carbohydrate partitioning and metabolism within the cell may explain contradictory relationships between carbohydrate content and growth/stress-resistance traits. [ABSTRACT FROM AUTHOR]

• The aim of this work was to disentangle phosphorus status-dependent and -independent effects of arbuscular mycorrhizal fungus (AMF) on leaf morphology and carbon allocation in perennial ryegrass ( Lolium perenne). • To this end, we assessed the P-response function of morphological components in mycorrhizal and nonmycorrhizal plants of similar size. • AMF ( Glomus hoi) stimulated relative P-uptake rate, decreased leaf mass per area (LMA), and increased shoot mass ratio at low P supply. Lower LMA was caused by both decreased tissue density and thickness. Variation in tissue density was almost entirely caused by variations in soluble C, while that in thickness involved structural changes. • All effects of AMF were indistinguishable from those mediated by increases in relative P-uptake rate through higher P-supply rates. Thus the relationships between relative P-uptake rate, leaf morphology and C allocation were identical in mycorrhizal and nonmycorrhizal plants. No evidence was found for AMF effects not mediated by changes in plant P status. [ABSTRACT FROM AUTHOR]

Selected populations of Lolium perenne have previously been shown to have contrasting rates of mature leaf dark respiration and yield. Plants were now grown in high-and in low-density stands. We were able to reproduce the differences in yield for the high-density-grown plants. However the low-density-grown plants did not different in yield and so the correlation between respiration and yield is no apparent. It is concluded that the difference in respiration rate is not the most important factor determining yield with these populations. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of osmotic stress on metabolism of NO3- in Lolium perenne L. cv. Réveille, plants were exposed to NaCl or polyethylene glycol 6000 in the culture medium. Four-week-old plants were kept in the dark for 36 h in order to decrease nitrate reductase activity (NRA). Afterwards, they were placed in a greenhouse for 27 h under continuous illumination with a nutrient solution containing 1 mM 14NH4 16NO3. To induce osmotic stress, the solution wits supplemented with either NaCl or PEG 6000 to give an osmotic potential of --0.335 MPa in the medium. Osmotic adjustment in PEG treated plants was strongly limited, because PEG could not be absorbed. Over 7(1 not of the osmoregulation in NaCI treated plants resulted from chloride uptake. Compared to control plants, PEG 6000 treatment decreased absorption (by 40%) and reduction (by 60%) of NO3- in the leaves, leading to NO3- storage in the vacuolar pool. In contrast, addition of NaCI in the medium did not significantly affect either uptake or reduction of NO3-. The proportion of NO3- translocated to the leaves was unaffected by osmotic stress and represented about 76% of consumed NO3-. Nitrate reductase activity, measured in vivo with exogenously supplied NO3-, was not significantly different between treatments. Compared to reduction of P15NO3 in control plants, it appeared that reduction of NO3- in leaves of PEG-treated plants was not limited by enzyme activity or by the amount of reducing power. Availability of NO3- at the site of reduction therefore seems to be limiting when PEG 6000 is added to the medium. [ABSTRACT FROM AUTHOR]

Changes in carbohydrate content and composition of ryegrass (Lolium perenne L.) cv. Réveille field-grown in Normandy were investigated from May 1987 to May 1988. During the winter period, the concentrations of high DP (degree of polymerization) fructan were the lowest whilst those of ethanol-soluble carbohydrates were the highest. Ethanol-soluble carbohydrates also accounted for most of the non-structural carbohydrates of four cultivars of Lolium perenne field-grown in central France in January 1989. The accumulation of osmotically active carbohydrates during winter leads only to a small depression of freezing point and consequently, these sugars cannot be considered as efficient cryoprotectants in ryegrass. [ABSTRACT FROM AUTHOR]

Pure stands of Trifolium repens L. N.Z. Huia and Lolium perenne L. S32 and mixtures of various densities and frequencies were treated with sulphuric acid solutions of pH 2.5, 3.5 and 5.6. The species yield was recorded over live sequential harvests. Multifactorial response equations were used to describe the behavior of the species yield as a function of acidity and the density of both species. Predictions, made through these models, showed that the response of yield of these species to simulated acid rain treatments varied greatly depending on the planting density, the time of harvesting and on whether the plants were growing in monoculture or in mixture. This suggests that it is not sufficient to consider the effects of experimentally applied acid rain on single individuals or low density stands, since the results obtained will not reflect the response in a close canopy sward. [ABSTRACT FROM AUTHOR]

Three experiments using soil-grown Lolium perenne plants were performed in order to investigate the effects of a gradually increasing drought stress on the death of root cells and the growth of lateral roots. Water potentials of -2 to -10 MPa caused death of the root cortex, but death of root tips occurred only at soil water potentials below -10 MPa. Low soil water potentials promoted lateral root initiation and elongation, the total length of lateral roots being between three and five times that of control plants. On rewetting severely droughted plants, root growth continued by elongation of existing, previously initiated, lateral roots. [ABSTRACT FROM AUTHOR]

Monocultures of Lolium perenne were grown at high densities under various shade regimes to investigate the effects of shade on self-thinning. Unshaded populations conformed to the minus 3/2 power law when dead matter was taken into account in the calculation of mean weight per plant. In a plot of live weight per plant, populations reached a common minus 3/2 line but then deflected from it. Adherence to the minus 3/2 power law is a characteristic of shoots but not of whole plants of L. perenne. Populations increased in shoot:root ratio as they developed so that the thinning line for shoot plus root weight per plant was shallower than the thinning line for shoot weight per plant. Shoot: root ratios were generally higher in shaded than in unshaded populations. Tiller weights and numbers in experimental populations of L. perenne also conformed to the minus 3/2 power law. Populations grown in deep shade thinned along a line of slope minus 1 when sown at 'low' densities but those sown at very high densities underwent an initial period of thinning along a slope of minus 3/2, followed by a switch to a slope of minus 1. Populations at intermediate levels of shade showed a decrease in the intercept of the thinning line with increasing shade but no change in gradient. A schematic diagram is presented to help explain the effects of shade on self-thinning. [ABSTRACT FROM AUTHOR]

In six experiments Lolium perenne L. and Plantago lanceolata L. were grown together in pots. Two experiments also included L. perenne alone, P. lanceolata alone, or L. perenne + Trifolium repens L. In five of the experiments prior sterilization of the soil followed by reinoculation was used to obtain two treatments, one having plants infected with vesicular-arbuscular mycorrhiza, the other non-mycorrhizal. The shoots of some plants in each pot ('donors') were injected with 32P. After a week these shoots were removed, and after a further week the remaining plants ('receivers') were harvested and their 32P content determined. In all experiments and species-combinations there was some 32P transfer to the shoots of both mycorrhizal and non-mycorrhizal receiver plants. The amount of transfer in mycorrhizal treatments was 2 to 8-fold greater than in non-mycorrhizal treatments, except in one experiment where mycorrhizal infection was very low. There was no clear difference between the different species combinations in the amount by which phosphorus transfer was enhanced by mycorrhizas. These results show that mycorrhizas can increase phosphorus transport between plants, but do not show whether there is direct transport from one root to another via interconnecting hyphae or whether the phosphorus must leave the donor root before being taken up by mycorrhizal hyphae. [ABSTRACT FROM AUTHOR]

Using a buried slide technique, hyphal connections are shown to exist between different roots on one plant, Lolium perenne L., and also between two roots of different species L. perenne and Plantago lanceolata L. These two species are commonly found together in permanent pasture. [ABSTRACT FROM AUTHOR]

Lolium perenne L. cv. S23 was grown in Perspex chambers situated out of doors and ventilated with clean air or controlled levels of sulphur dioxide (SO2). Fumigations were carried out with [SO2] ranging from 43 to 423 μg m-3 for periods up to 194 days under both summer and winter conditions. Concentrations as low as 43 μg m-3 for 173 days in winter and 106 μg m-3 for 194 days in summer could produce reductions in shoot dry wt but, in some experiments, similar or higher concentrations had no effect on growth. This difficulty in obtaining a clear dose/response relationship is possibly due to an interaction of environmental factors with the effects of the pollutants. In some of the experiments, growth was reduced in the absence of any detectable symptoms whereas, in other cases, the fumigated plants became chlorotic. There was some evidence for chronic SO2 injury being more severe on young plants. SO2 acted primarily through a depression in net assimilation rate. No clear correlation was found between either chlorophyll content or total sulphur content of the fumigated plants and a reduction in any of the growth parameters investigated. The results are discussed in relation to those of other workers and their relevance to conditions in the field in the United Kingdom. [ABSTRACT FROM AUTHOR]

Many cytogenetic abnormalities are described from Festuca-Lolium hybrids. Some have not been reported before, notably extra spindles in meiotic interphase and second telophase, and the formation of secondary cells from syncytes. Many of the abnormalities prevent the formation of normal gametes and thus contribute to the sterility of the species. Previous work, however, has shown that this is largely due to genic imbalance in the hybrids. [ABSTRACT FROM AUTHOR]

A mutation of a gene (discovered in Festuca pratensis Huds, and designated sid) confers indefinite greenness on senescing leaves. Via intergeneric hybrids with Lolium multiflorum L. and Lolium perenne L., the mutant gene (sidy) has been introgressed into a range of Lolium backgrounds. Using genomic in situ hybridization we have identified segments carrying sidy in recombinant chromosomes of Lolium-Festuca introgression lines. We also used L. perenne lines segregating 1:1 for the staygreen character to tag the gene with molecular markers. In two mapping populations a total of 84 genotypes were screened with isoenzymes, RAPD primers, RFLP probes and AFLP primer pairs. Over 180 polymorphic loci were identified, representing 10 linkage groups spanning 600 cM. Two AFLP markers are linked to sid at 4.6 and 14.9 cM, close enough to be usable for marker-assisted selection. Introgression of sidy into Lolium temulentum L. resulted in the production of near-isogenic inbreeding lines suitable for comparative studies of gene expression. Using a variation of the method of representational difference analysis a very small number of cDNAs have been identified as promising candidates for sid, or genes directly regulated by sid. [ABSTRACT FROM AUTHOR]

This study investigated the mechanisms which control the partitioning between roots and shoots in plants subjects to changes in environment. Two types of analyses were used: firstly, an examination of the cost and revenue associated with investment in different plant parts, and secondly, a test of the principle of functional equilibrium between roots and shoots, i.e. whether root dry matter × root specific activity balances shoot dry matter × shoot specific activity. Measurements were made on individual plants of Lolium perenne in sunlit controlled environments, grown from germination to canopy closure under optimal nitrogen supply. At the final harvest, increased air temperature (+4 °C above ambient) reduced whole-plant dry matter by 12% relatie to the control, whereas elevated CO2 mole fraction (700 μmol mol-1) led to a 38% gain. The combined treatment yielded an intermediate result (+19%). Plants grown at +4 °C maintained balanced activity between roots and shoots in young plants to compensate for a strong negative effect of higher temperature on root specific activity, which suggests that plants conserve balanced activity by adjusting dry matter partitioning. The extra cost involved with the adjustment at +4 °C significantly enhanced the cost: revenue ration of plant investment. IN ambient temperature, the balance between roots and shoots departed from equilibrium, slightely at ambient but substantially at elevated CO2: the plants accumulated excess carbon relative to nitrogen, and this imbalance increased with plant age. At elevated CO2, the cost: revenue ratio increased in young plants but this was later reversed owing to loss of root and shoot functioning observed in the different treatments are discussed in the light of whole plant performance. [ABSTRACT FROM AUTHOR]