Encroachment of Endophyte-infected on Endophyte-free Tall Fescue

Persistence of endophyte-free (E-) tall fescue (Festuca arundinaceaSchreb.)is erratic. Little information exists as to how fast endophyte(Neotyphodium coenophialum)-infected (E+) tall fescue mightencroach on E- tall fescue and whether specific conditions mightinfluence the speed of encroachment. Plots of E+ and E- tallfescue genotypes 7 and 17 were established using a modifiedNelder's design to compare performance of the E+ forms of theplants in pure and mixed communities at different populationdensities. The plots were planted at the USDA Southern PiedmontConservation Research Laboratory in Watkinsville, Georgia, andthe University of Georgia Plant Sciences Farm in Bogart, Georgia.Plants were grown over a 5 year period and dry matter yieldmonitored 1, 3, and 5 years after establishment. Relative crowdingcoefficients were calculated for each to establish trends ofencroachment of the E+ on the E- plants in the mixed communities.Generally, dry matter yields of E+ tall fescue were greaterthan E- tall fescue regardless of whether they were grown inpure or mixed communities. As time progressed, the differencein dry matter yield between E+ and E- tall fescue grown in mixedcommunities was greater than that of the pure communities. Relativecrowding coefficients increased as time progressed. Relativecrowding coefficients at the Watkinsville location were greaterafter 5 years than those at the Plant Sciences Farm. Therefore,site specific conditions exist which affect the competitivenessof E- tall fescue and degree of encroachment by E+ tall fescue.Research is needed to identify which biotic, abiotic and managementvariables exacerbate encroachment of E+ tall fescue to betterdefine the conditions which best suit E- tall fescue.Copyright1998 Annals of Botany Company tall fescue, endophyte,Neotyphodium coenophialum,Festuca arundinacea, competition, population density     

Effect of Ploidy on Quality of Tall Fescue, Italian Ryegrass x Tall Fescue and Tall Fescue x Giant Fescue Hybrids

Selected quality parameters were measured for forage leaf tissuefrom a spaced-plant nursery. The genotypes used were Ky 31 tallfescue and hybrids of Italian ryegrass (Lolium multiflorum Lam.)x tall fescue (Festuca arundinacea Schreb.) and tall fescuex giant fescue [Fescue gigantea (L ) Vill.]. Hybrid ploidy rangedfrom 2n = 28 to 84 chromosomes. Forage quality was characterizedby neutral detergent fibre (NDF), acid detergent fibre (ADF),total soluble carbohydrates (TSC) nutritive value index (NVI),hemicellulose, and in vitro dry matter disappearance (DMD). Quality of tall fescue, as measured by increased DMD, was improvedby hybridization with giant fescue. Improved DMD and NVI correlatedwith lower NDF and ADF in the hybrids. A few hybrids of Italianryegrass x tall fescue (2n = 28) were higher in some qualityparameters than Ky 31. Tall fescue x giant fescue hybrids (2n= 80 to 84), as a group, had significant quality improvementover Ky 31 in higher DMD and NVI and lower NDF and ADF. Whilesome individual hybrids within each group were significantlyhigher in quality, only the 2n = 80 to 84 chromosome group wasconsistently higher than Ky 31. Prediction equations for DMD,NDF, and ADF were established based on solvent extraction withnear-infrared reflectance spectroscopy (NIRS). Linear correlationcoefficients between chemical measurement and NIRS for eachquality parameter were 0–95 or higher. Acid detergent fibre, neutral detergent fibre, dry matter disappearance, hemicellulose, nutritive value index, Festuca arundinacea, Festuca gigantea, Lolium multiflorum     

Does Endophyte Influence Regrowth of Tall Fescue?

The influence of ecological and environmental factors on theresponse of the mutualistic symbionts Acremonium coenophialum(Morgan-Jones and Gams), and tall fescue ( Festuca arundinacea,Schreb.) has received substantial attention. However, much ofwhat is known about developmental and physiological responseshas been obtained from static or mature canopies and the influenceof defoliation on the symbiota has not been considered in detail.A controlled environment experiment was conducted to assessthe influence of defoliation and endophyte on the regrowth anddevelopment of two tall fescue genotypes and their respectiveendophytes, known to differ in morphology and alkaloid productioncapacity. The response of endophyte infected relative to non-infectedplants was evaluated for measured and calculated parametersfor each defoliation. While the influence of genotype was substantialon virtually all parameters, endophyte interacted with genotypeand defoliation resulting in enhanced plasticity of mutualistsas a response to varying conditions. Endophyte infection influencedleaf mass depending upon genotype, while the relative benefitof endophyte on pseudostem mass was affected by defoliation.Endophyte interacted with genotype to influence relative growthrate and productivity relative to nitrogen concentration whencanopies were clipped, but was less important when canopiesremained uncut. In some instances endophyte gave growth andsize advantage to the host and did not in others. Generalitiesregarding symbiont response to extrinsic factors may be misleading,since responses depend upon the specific mutualism consideredand conditions imposed. Acremonium coenophialum ; Festuca arundinacea ; non-structural carbohydrate; relative growth rate     

Temperature Effects upon Inflorescence and Seed Development in Tall Fescue (Festuca arundinacea Schreb.)

The effects of three temperatures 15, 20, and 25 °C uponinflorescence and seed development in tall fescue (Festuca arundinaceaSchreb) between inflorescence emergence and seed maturity werestudied. Increasing temperature over this range reduced culmlength and the number of florets per spikelet, hastened theonset of anthesis and pollen release, increased relative growth-rateof the florets 9 days after peak anthesis, reduced the periodof seed development and 1000 seed weight No large effects oftemperature upon the percentage of florets setting seed werefound. The practical implications of these results are discussed.     

Importance of host plant species, Neotyphodium endophyte isolate, and alkaloids on feeding by Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae

Three grass host species--tall fescue, Festuca arundinacea Schreber; meadow fescue, Festuca pratensis Hudson; and perennial ryegrass, Lolium perenne L.--each infected with a number of different Neotyphodium endophyte isolates, were investigated for their effects on fall armyworm, Spodoptera frugiperda (J.E. Smith). Alkaloid profiles varied among associations. Choice and no-choice tests comparing feeding and early development of S. frugiperda larvae on endophyte-infected and endophyte-free leaf blade material were performed. Endophyte-mediated resistance to S. frugiperda was greatest in meadow fescue and weakest in tall fescue. Some endophyte isolates, particularly in perennial ryegrass and meadow fescue, had a major effect on feeding and development of S. frugiperda, whereas others had no effect or were only weakly efficacious. In tall fescue, some associations deterred S. frugiperda from feeding in choice tests but had no effect on development, whereas larvae reared on other associations weighed significantly more than control larvae fed endophyte-free grass. It was concluded that the deleterious consequences of endophyte infection were easily masked by other factors in tall fescue. Relative leaf age had no effect on feeding preferences in the three host species. Chemical analysis of herbage from the plants used, and results from a no-choice study using spiked artificial diets, failed to individually implicate any of the major known alkaloids (peramine, lolitrem B, ergovaline, and lolines) in the observed effects on S. frugiperda. Hypotheses explaining these observations, and their impact on creating desirable grass-endophyte associations for use in pastures, are discussed.     

Influence of Endophyte and Water Regime Upon Tall Fescue Accessions. II. Pyrrolizidine and Ergopeptine Alkaloids

Alkaloids, along with specific environmental conditions, havebeen associated with both detrimental and beneficial aspectsof endophyte (Acremonium coenophialum Morgan-Jones et Gams)infected tall fescue (Festuca arundinacea Schreb.) associations.Benefits to the plant accrue through reduced herbivory, whereasdetriment to the animal occurs as altered grazing behaviourand reduced productivity. A controlled environment study wasconducted to examine pyrrolizidine and ergopeptine alkaloidconcentration of four tall fescue accessions as influenced byendophyte status and water regime. Endophyte-free plants weredevoid of ergopeptine alkaloid and contained little, if any,pyrrolizidine alkaloid. Leaf blade tissue of endophyte-infectedisolines contained a range of both ergopeptine (256 to 1633ng g^–1) and pyrrolizidine (92 to 450 µg g^–1)alkaloid concentrations. Water deficit generally increased alkaloidconcentration. Alkaloid yield, based upon concentration andtissue d. wt, showed that significant increase in ergopeptineand pyrrolizidine alkaloid in leaf tissue was associated withwater deficit and was due to actual increased synthesis andnot simply decreased phytomass. Leaf and pseudostem (leaf sheathand stem base) tissue alkaloid concentrations indicated differentaccumulation patterns for ergopeptine and pyrrolizidine alkaloids.Ergopeptine alkaloid yield increased in water-stressed pseudostem,whereas pyrrolizidine alkaloid yield decreased in some, butnot all accessions. The range of host genotype/endophyte biotyperesponse offers the possibility to select associations whichproduce few deleterious effects in animals yet maintain highforage productivity and persistence. Festuca arundinacea, Acremonium coenophialum, tall fescue genotypes, water stress, N-formyl and N-acetyl loline, ergovaline     

Production of transgenic tall fescue and red fescue plants by particle bombardment of mature seed-derived highly regenerative tissues

 Highly regenerative tissues of tall fescue and red fescue produced from mature seed-derived embryogenic callus were induced and proliferated on medium containing 2,4-dichlorophenoxyacetic acid (4.5 or 9.0 μM), 6-benzylaminopurine (0, 0.044, 0.44 or 2.2 μM) and cupric sulfate (0.1 or 5.0 μM) under dim-light conditions (10 to 30 μE m^–2 s^–1, 16 h light). Tall fescue tissues were transformed with three plasmids containing the genes for hygromycin phosphotransferase (hpt), phosphinothricin acetyltransferase (bar) and β-glucuronidase (uidA;gus), and red fescue with three plasmids containing hpt, uidA and a synthetic green fluorescent protein gene [sgfp(S65T)]. DNA from T₀ plants of eight independently transformed lines from tall fescue and 11 from red fescue were analyzed by PCR and DNA blot hybridization. The co-expression frequency of all three transgenes [hpt/bar/uidA or hpt/uidA/sgfp(S65T)] in transgenic tall fescue and red fescue plants was 25–27%; for two transgenes [hpt/bar or hpt/uidA for tall fescue and hpt/uidA or hpt/sgfp(S65T) for red fescue], the co-expression frequency was 50–75%. Received: 28 September 1999 / Revision received: 13 March 2000 / Accepted: 16 March 2000     

Thermal Dependence of the Apparent Kmof Glutathione Reductase from Three Wetland Grasses and Maize

The thermal dependence of enzyme kinetic parameters has beenpresented as an indicator of species’ thermal optima andtolerance limits. Previous studies suggest the relationshipbetween temperature and the apparent Michaelis–Mentenconstant (K_m) of an enzyme system can be used to predict wholeplant success at specific temperatures. The apparent K_mfor glutathionereductase (EC 1.6.4.2; GR) (oxidized glutathione as substrate)extracted from leaves of American sloughgrass (Beckmannia syzigachneSteud.), tufted hairgrass (Deschampsia caespitosa L.), tallfescue (Festuca arundinaceae Schreb. ‘Titan’), andmaize (Zea mays L.), was determined over a range of temperatures(1–40 °C). For all species, minimum apparent K_mforGR was observed at 1 °C, and K_mvalues increased as temperatureincreased. The apparent K_mvalues differed among all speciesat the lower temperatures (1–15 °C), but were similarat higher temperatures. The enzyme from tufted hairgrass hadthe lowest apparent K_mat low temperatures (<15 °C), followedin increasing order by American sloughgrass, tall fescue andmaize. Our experimental system failed to reproduce thermal kineticwindow profiles similar to those reported elsewhere. With respectto the enzyme systems reported here, results suggest that thesecool-season grasses can be ranked as more to less eurythermicwithin the temperature range from 1 to 15 °C. Copyright0000 American sloughgrass, Beckmannia syzigachne Steud., tufted hairgrass, Deschampsia caespitosa L., tall fescue, Festuca arundinaceae Schreb. ‘Titan’, Zea mays L., plant competition, temperature stress, kinetics, Michaelis–Menten constant (K_m), glutathione reductase     

Molecular characterisation and interpretation of genetic diversity within globally distributed germplasm collections of tall fescue (Festuca arundinacea Schreb.) and meadow fescue (F. pratensis Huds.)

Allohexaploid tall fescue (Festuca arundinacea Schreb. syn. Lolium arundinaceum [Schreb.] Darbysh.) is an agriculturally important grass cultivated for pasture and turf world-wide. Genetic improvement of tall fescue could benefit from the use of non-domesticated germplasm to diversify breeding populations through the incorporation of novel and superior allele content. However, such potential germplasm must first be characterised, as three major morphotypes (Continental, Mediterranean and rhizomatous) with varying degrees of hybrid interfertility are commonly described within this species. As hexaploid tall fescue is also a member of a polyploid species complex that contains tetraploid, octoploid and decaploid taxa, it is also possible that germplasm collections may have inadvertently sampled some of these sub-species. In this study, 1,040 accessions from the publicly available United States Department of Agriculture tall fescue and meadow fescue germplasm collections were investigated. Sequence of the chloroplast genome-located matK gene and the nuclear ribosomal DNA internal transcribed spacer (rDNA ITS) permitted attribution of accessions to the three previously known morphotypes and also revealed the presence of tall fescue sub-species of varying ploidy levels, as well as other closely related species. The majority of accessions were, however, identified as Continental hexaploid tall fescue. Analysis using 34 simple sequence repeat markers was able to further investigate the level of genetic diversity within each hexaploid tall fescue morphotype group. At least two genetically distinct sub-groups of Continental hexaploid tall fescue were identified which are probably associated with palaeogeographic range expansion of this morphotype. This work has comprehensively characterised a large and complex germplasm collection and has identified genetically diverse accessions which may potentially contribute valuable alleles at agronomic loci for tall fescue cultivar improvement programs.     

A Carbon 14 Study of Metabolism in Tall Fescue Seedlings Acclimating to Growth at Low Temperatures

The youngest fully expanded leaves of young plants of tall fescue(Festuca arundinacea Schreb. cv. S 170) were allowed to assimilate¹⁴CO₂ either (a) at the fifth leaf stage immediately beforetransfer from 17/14?C to 7/4?C (non-acclimated), or (b) aftertransfer from 17/14?C to 7/4?C at the fifth leaf stage, andfurther development in 7/4?C of one or two more leaves (acclimationfor one or two plastochrons). Controls were maintained in 17/14?C and allowed to assimilate ¹⁴CO₂ at the corresponding (fifth,sixth, or seventh) leaf stages. Allocation of 14C amongst sinksand biochemical fractions was analysed during a subsequent periodof growth at 7/4 ?C (cold) or 17/14 ?C (control). Allocationof assimilate to growing parts of the shoot was less than controlsin the non-acclimated plants transferred to the cold and morethan controls in plants acclimated for one plastochron. Afterthe imbalance induced initially by transfer from 17/14?C to7/4 ?C, acclimation for one or two plastochrons brought theallocation amongst sinks and amongst biochemical fates closerto the balance existing in controls. The main shoot and sidetillers differed in the time during acclimation when they becamemore like the controls. The percentage of assimilate in thesoluble carbohydrate fraction of non-acclimated plants and ofplants acclimated for one plastochron, was higher than in controls.The percentage of assimilate in the cell wall fraction was lowerin non-acclimated plants than in controls but the differencefrom controls after two plastochrons acclimation again was less.During the first plastochron after transfer to cold, diversionof assimilate to a reserve pool in sinks could be a factor limitingcell wall synthesis and growth and this limitation may be relievedwhen the reserve pool is ‘full’. Low temperaturereduced the percentage of assimilate in the protein fractionof growing parts of the shoot and the difference was found evenafter two plastochrons acclimation. Key words: Low temperature, metabolism, tall fescue (Festuca arundinacea Schreb. cv. S. 170)     

Tall fescue EST-SSR markers with transferability across several grass species

Tall fescue (Festuca arundinacea Schreb.) is a major cool season forage and turf grass in the temperate regions of the world. It is also a close relative of other important forage and turf grasses, including meadow fescue and the cultivated ryegrass species. Until now, no SSR markers have been developed from the tall fescue genome. We designed 157 EST-SSR primer pairs from tall fescue ESTs and tested them on 11 genotypes representing seven grass species. Nearly 92% of the primer pairs produced characteristic simple sequence repeat (SSR) bands in at least one species. A large proportion of the primer pairs produced clear reproducible bands in other grass species, with most success in the close taxonomic relatives of tall fescue. A high level of marker polymorphism was observed in the outcrossing species tall fescue and ryegrass (66%). The marker polymorphism in the self-pollinated species rice and wheat was low (43% and 38%, respectively). These SSR markers were useful in the evaluation of genetic relationships among the Festuca and Lolium species. Sequencing of selected PCR bands revealed that the nucleotide sequences of the forage grass genotypes were highly conserved. The two cereal species, particularly rice, had significantly different nucleotide sequences compared to the forage grasses. Our results indicate that the tall fescue EST-SSR markers are valuable genetic markers for the Festuca and Lolium genera. These are also potentially useful markers for comparative genomics among several grass species.Electronic Supplementary Material Supplementary material is available for this article at .     

The Effects of Nitrogen Fertilization and the Growing Season on Photosynthesis of Field-grown Tall Fescue (Festuca arundinacea Schreb.) Canopies

Canopy gross photosynthesis of tall fescue receiving three tofour rates of N fertilization was studied under field conditionsduring three contrasting growing seasons. Under non-limitingN growing conditions, the growing seasons did not have a significanteffect on the maximum canopy gross photosynthesis (canopy grossphotosynthesis at saturating PAR) and the maximum light yield(quantum efficiency of the canopy at low PAR). In the absenceof N fertilization and for a similar LAI, the values of themaximum canopy gross photosynthesis were approximately equalto 70% of those obtained under non-limiting N conditions. Thisresponse of the tall fescue canopy to N concentration is muchsmaller than that reported at the leaf level. The reductionin canopy photosynthetic capacity with no N applied comparedto non-limiting N conditions is much less than the reductionobserved previously in above-ground dry matter accumulation.The effect of N fertilization on above-ground dry matter accumulationis due primarily to changes in C partitioning and the resultingfaster leaf area development and greater light interceptionrather than the effect of N on the canopy photosynthetic capacityper se .Copyright 1993, 1999 Academic Press Festuca arundinacea Schreb., photosynthesis, nitrogen, grass, carbon     

Estimation of Potential Tiller Production and Site Usage During Tall Fescue Canopy Development

Tiller appearance in tall fescue (Festuca arundinacea Schreb.)occurs in an orderly, predictable manner with the potentialfor a high degree of synchronization among tillers on a givenplant. Estimates of potential cumulative tiller production (Tmax)are made for synchronous (Tmax_lx = 2^Lx+1 – 1, where Lxis the axil number of the youngest leaf on the main stem whichbears an emerged tiller) and non-synchronous (Tmax₁ = 2^L–NLAT–1,where L is the number of leaves on the main stem and NLAT thenumber of leaves above the youngest primary tiller at its appearance)conditions. A method for determining the degree of synchronizationand an equation for estimating site usage are also presented.Early in seedling development, site usage of a tall fescue populationwith high tillering capacity was near 90%, and tillering wasregulated largely by rate of tiller site formation. As the canopydeveloped the phyllochron (time between successive leaf appearances)and NLAT increased, slowing the rate of tiller production intemporal terms and in relation to leaf appearance, respectively.Beyond 45 d after planting, site usage decreased rapidly, furtherreducing tiller production. High tiller production appearedto be associated with synchronized tiller appearance, with alack of synchrony being associated with decreased site usage.Tillers formed in prophyll axils were less likely to be in synchronywith other tillers and frequently failed to appear. In contrastwith branching in dicotyledons, apical dominance appears toplay a minor role in regulating tillering in tall fescue Tillerproduction initially appears to proceed at near maximum ratesthen is down-regulated during later development by longer phyllochrons,slower rate of tiller elongation and reduced site usage. Festuca arundinaceaSchreb., tall fescue, tiller production, leaf appearance, site usage, leaf elongation rate, synchronization, phyllochron, canopy development     

Grass Leaf Elongation Rate as a Function of Developmental Stage and Temperature: Morphological Analysis and Modelling

Elongation of successive leaves was measured following defoliationof tall fescue plants in controlled environments. Measurementswere made under constant temperatures of 24 °C and 14 °C,and after temperature changes from 24 to 14 °C andvice versa.A morphological analysis of the growing leaf was made from thetime it was 1 mm long until it was fully elongated. The timeelapsed from initiation until the leaf was 1 mm long was estimated.Young leaves less than 1.5 mm long elongated slowly at a constantleaf elongation rate (LER). By extrapolating this LER back toleaf initiation from the apex it was calculated that elongationlasted 42.5 d at 24 °C and 51 d at 14 °C. Lengths ofthe division zone (DZ) and the extension-only zone (E-OZ) increasedto a maximum and then decreased during leaf development. Temperaturechange had an immediate effect on LER but the response varieddepending on the direction of the temperature change. To describethese different features, an empirical model of DZ and E-OZwas designed. Its five parameters were optimized at constanttemperature. The model was then used to simulate the LER ofplants subjected to temperature changes. Instant and lastingeffects of the initial temperature on mean LER in plants transferredfrom 14 to 24 °C andvice versawere well simulated. It wasconcluded that the major reason for differences was due to thegrowth stage (DZ and E-OZ lengths) at which the changes occurredat both temperatures.Copyright 1999 Annals of Botany Company Festuca arundinaceaSchreb., tall fescue, growth zone, division zone.     

Effects of Increasing Water Stress on Simulated Swards of Festuca arundinacea Schreb under Wind Tunnel Conditions

The effects of increasing water stress on water relations, leafconductance, leaf extension and leaf rolling of Festuca arundinaceain sward (I m²) were investigated under wind tunnel conditions.The plants were grown in a container 60 cm deep and the experimentwas conducted over a 36 d period. Upon cessation of watering(day 11), leaf extension and conductance were affected. Within8 d, the onset of leaf rolling helped to reduce transpirationand to maintain leaf water potential. Nocturnal recovery of turgor potential helped in maintainingleaf extension at a moderate level and in the final 5 d waterand osmotic potentials dropped sharply as leaf rolling becamemore acute and leaf extension stopped. The grass combines various morphological and physiological mechanismsto prevent water losses and maintain growth. Festuca arundinacea, tall fescue, wind tunnel, water stress, water potential, osmotic potential, conductance, leaf rolling, leaf extension     

Atmospheric vapor pressure deficit is critical in predicting growth response of “cool-season” grass <Emphasis Type="Italic">Festuca arundinacea</Emphasis> to temperature change

There is a lack of information on plant response to multifactor environmental variability including the interactive response to temperature and atmospheric humidity. These two factors are almost always confounded because saturated vapor pressure increases exponentially with temperature, and vapor pressure deficit (VPD) could have a large impact on plant growth. In this study using climate controlled mini-greenhouses, we examined the interacting influence of temperature and VPD on long-term growth of tall fescue (Festuca arundinacea Schreb), a cool season grass. From past studies it was expected that growth of tall fescue would decline with warmer temperatures over the range of 18.5–27°C, but growth actually increased markedly with increasing temperature when VPD was held constant. In contrast, growth declined in experiments where tall fescue was exposed to increasing VPD and temperature was held constant at 21°C. The inhibited growth appears to be in response to a maximum transpiration rate that can be supported by the tall fescue plants. The sensitivity to VPD indicates that if VPD remains stable in future climates as it has in the past, growth of tall fescue could well be stimulated rather than decreased by global warming in temperate climate zones.     

Cold acclimation of forage grasses in relation to pink snow mould (Microdochium nivale) resistance

The aim of our work is to investigate the changes in phenolic level, PAL activity and heat production rate induced during pre-hardening at 12°C and cold acclimation at 2°C of the forage grasses Festulolium, meadow fescue, tall fescue and Italian ryegrass in relation to their resistance to snow mould caused by Microdochium nivale. Meadow fescue and tall fescue were most resistant to M. nivale infection, while Italian ryegrass demonstrated the least resistance to this fungus inoculation. Festulolium, meadow fescue and tall fescue responded similarly to low temperature, while Italian ryegrass demonstrated considerable disturbance of energy balance and lower phenolic concentration, which could explain a higher susceptibility of the latter species to infection by M. nivale. The enhanced level of phenolic compounds, probably utilised for cell wall lignification as well as equilibrium of the metabolic activity observed in meadow fescue and tall fescue, is very important for both cold and pathogen-resistance mechanisms. The studied Festulolium cultivar ‘Felopa’, a hybrid of the Lolium multiflorum and Festuca pratensis genomes, was characterised by changes in biochemical parameters similar to the resistant meadow fescue and tall fescue.     

The Effects of Nitrogen Fertilization and the Growing Season on Carbon Partitioning in a Sward of Tall Fescue (Festuca arundinacea Schreb)

The effect of N fertilization on the relative carbon partitioningto the roots of tall fescue (Festuca arundinacea Schreb ), grownunder field conditions, was studied with a ¹⁴C-labelling techniqueon three regrowths representing contrasting growing seasonsUnder non-limiting N growing conditions, the relative carbonpartitioning to the roots averaged 17.0, 15 8, and 11 1% inthe summer, autumn, and spring regrowths, respectively The relativecarbon partitioning to the roots increased during the summerand autumn regrowths but decreased during the spring regrowthIn the absence of N fertilization, the relative carbon partitioningto the roots averaged 31 3, 26 5, and 26 7 in the summer, autumn,and spring regrowths, respectively The results were interpretedin terms of a functional equilibrium between the shoots andthe roots It was concluded that, for a dense canopy of a perennialgrass growing under fluctuating conditions of solar radiationand temperature, the relative growth of the roots compared tothe relative growth of the total biomass is primarily a functionof the shoot biomass Festuca arundinacea Schreb, carbon, partitioning, nitrogen, root growth, fertilization, grass     

Changes in Dry Matter, Carbohydrate and Seed Yield Resulting from Lodging in Three Temperate Grass Species

The adverse effect of lodging on grass seed yield may be attributed,in part, to assimilate limitation during the seed filling period.This investigation examined plant dry matter assimilate partitioningand seed yield as affected by lodging in three species thatare closely related but phenotypically different: tall fescue(Festuca arundinacea Schreber.), Italian ryegrass (Lolium multiflorumLam.), and perennial ryegrass (L. perenne L.). Studies wereperformed in field plots at Corvallis, Oregon, USA. Seed yieldcomponents (seed number per inflorescence, seed yield per inflorescence,and single seed mass) and leaf, stem (lower, middle, and peduncle)and seed inflorescence dry mass were measured just prior toanthesis to seed maturity. Dry mass and water soluble carbohydrates(WSC) were determined for shoot components. The reduction indry mass and WSC in leaves and stem components following anthesiswas often greater in lodged plants compared to upright plants.The relatively low seed yield depression in lodged tall fescuesuggested a higher compensation potential for partitioning reserveassimilate from leaves and stems to support seed growth anddevelopment. This potential does not appear to be present tothe same degree in Italian ryegrass and to an even lesser extentin perennial ryegrass. These findings suggest that the potentialto compensate for reduced assimilate supply during the periodof high assimilate demand by seeds may be attributed, in part,to the total assimilate reserve accumulated prior to photoassimilatereduction caused by the lodged condition. Copyright 2000 Annalsof Botany Company Tall fescue, Festuca arundinacea Schreber., Italian ryegrass, Lolium multiflorum Lam., perennial ryegrass, L. perenne L., assimilate partitioning, source–sink