Tiller Bud Suppression in Reproductive Plants of Lolium multiflorum Lam. Cv. Westerwoldicum

The control of tiller bud growth during reproductive developmentwas investigated in experimental plants ofLolium multiflorumLam. cv. Westerwoldicum that were reduced to a main axis havinga developing but unemerged ear, elongating stem internodes,a series of expanded leaves, slow-growing tiller buds and aroot system. Isolation of the ear by excision of its base, ordecapitation so as to remove the ear together with the upperleaves, promoted the movement of ¹⁴C-assimilates to tiller buds,decapitation being the more effective treatment. Applicationof 0.1 per cent indol–3yl-acetic acid (IAA) to cut tissuesof decapitated plants diverted ¹⁴C-assimilates to upper internodesbut did not reduce import by buds, whereas application of 1.0per cent IAA both diverted labelled assimilates to upper internodesand reduced bud import. Radioactivity from [¹⁴C] IAA appliedto the upper leaves or to the ear base was recovered from budsin very small amounts; larger amounts were recovered from budsfollowing the application of labelled IAA to an elongating internode,especially from the bud at the base of the treated internode.It is suggested that tiller bud suppression may be influencedby the movement of inhibitory levels of auxin into buds fromnearby elongating stem internodes, whose activity in turn maybe controlled by the developing inflorescence and upper leaves.     

Variations in Tiller Dynamics and Morphology in Lolium multiflorum Lam.Vegetative and Reproductive Plants as affected by Differences in Red/Far-Red Irradiation

Lolium multiflorum Lam, plants were grown in a growth room undertwo light sources with red/far-red ratios of 1·62 and0·84 but similar photosynthetically active radiation.In both situations the capacity to produce new tillers and thelight available per tiller decreased with canopy growth. Tilleringwas further reduced by the low red/far-red ratio while lightinterception and plant dry weight were unaffected by this treatment.In both reproductive and vegetative plants under the lower red/far-redratio the time between leaf expansion and the appearance ofa tiller in its axil was increased and the proportion of ‘maturebuds’ that developed was reduced. Irradiation with lowred/far-red advanced the reproductive development and increasedthe number of fertile tillers per plant. It also caused longerleaf sheaths, blades and reproductive shoots. The results suggestthat as canopy density increases the lower light interceptionper tiller and the photomorphogenic effect of low red/far-redratios may reduce the capacity to produce new tillers. Lolium multiflorum, Lam., annual ryegrass, tillering, tiller growth, leaf growth, flowering, light quality.     

The Distribution of Assimilates in Lolium multiflorum Lam. Following Differential Defoliation

In seedling plants of Lolium multiflorum Lam. the tillers weredefoliated but the main shoot was left intact. Radiocarbon as¹⁴CO₂ was supplied to this shoot at different times followingtiller defoliation and the pattern of distribution of labelledassimilates was determined quantitatively. It was found thata greater proportion (approximately 10–20 per cent) ofexported assimilate was translocated to the cut tillers butalthough the proportion supplied to the root system was lessthe total radiocarbon incorporated by the roots was unchanged.This was brought about by a large increase in the export ofradiocarbon fixed by the intact shoot—up to 100 per centfollowing one treatment. These alterations in the organizationof the defoliated plant lead to a greater efficiency in thecarbon economy and are discussed in relation to the stress imposedby defoliation.     

The Interdependence of Tillers in Lolium multiflorum Lam.--a Quantitative Assessment

Experiments were made to determine the extent of reciprocaltransfer of products (derived from the assimilation of ¹⁴CO₂)between various parts of the young vegetative grass plant (Loliummultiflorum Lam.). When individual laminae on different tillerswere supplied with ¹⁴CO₂, 47–64 per cent of the fixedcarbon was exported after 24 h. The principal sinks were theroot system and the shoot or tiller to which the fed leaf wasattached. Other tillers also received significant quantitiesof radiocarbon. When whole tillers were supplied with ¹⁴CO₂the percentage of fixed radiocarbon exported within 24 h rangedfrom 14–31 per cent. Of this, 50–74 per cent wasrecovered from the root system (except in the case of exportfrom the youngest tiller) but exchange of material between tillersalso occurred.A reciprocity diagram is presented and it is concludedthat despite the magnitude of the exchange no tiller showedan over-all net gain or loss. The main shoot and the tillersdiffered in the extent of their carbon exchange and in theirdegree of independence. The oldest daughter tiller of the mainshoot was the most independent and the main shoot most interdependent.     

Analysis of Regrowth Patterns and Carbohydrate Levels in Lolium multiflorum Lam.

The regrowth pattern in Lolium multiflorum was analysed in relationto carbohydrate levels and developmental characteristics, usingtwo contrasting populations. Liscate (a natural population collectedin Northern Italy) and the cultivar S 22, the former havingmore erect tillers, longer leaves and a lower rate of leaf appearance.The plants were grown in 16 h photoperiods, at 15/10 °C.NAR was lower in S. 22, but because LAR was higher as a resultof the greater SLA, the RGR was similar in Liscate and S. 22Starch levels were also similar in the two populations, butthe level of WSC was higher in Liscate than in S 22. When thetwo populations were defoliated to the same extent, total leafregrowth and rate of leaf elongation were greater in Liscate,but its tillering was more inhibited. Although the rates ofleaf regrowth were eventually similar in both populations, theywere initially lower in S. 22, leading to a higher total regrowthin Liscate. In both populations, WSC levels in the roots andstubble decreased after defoliation, but starch levels remainedunchanged. During regrowth in the dark, starch levels also decreased,but only when most of the WSC in the stubble was depleted. Lolium multiflorum Lam, Italian ryegrass, relative growth rate, net assimilation rate, leaf area ratio, specific leaf area, leaf weight ratio, carbohydrate     

Pattern and Control of Distribution of 14C-assimilates in Reproductive Plants of Lolium multiflorum Lam. var. Westerwoldicum

The distribution of ¹⁴C-assimilates was examined in reproductiveplants of Lolium multiflorum Lam. var. Westerwoldicum (cv. Tama)from which all emerged tillers had been removed, leaving themain tiller with two expanding leaves, one of them the flagleaf, and two expanded leaves. Export of ¹⁴C from the lowerexpanded leaf was mainly to the tiller in its axil, the steminternode below its node and the roots, whereas the upper expandedleaf supplied predominantly the expanding leaves, the ear, steminternodes, roots and the tiller bud in the axil of the lowerleaf. Defoliation and root-pruning showed that expanding leaveswere able to compete successfully for assimilates, probablythrough the production of substances capable of mobilizing supply.Local application of 1-naphthaleneacetic acid (NAA), gibberellicacid (GA₃) and 6-benzylaminopurine (BAP) to small tiller budsshowed that GA³ and BAP promoted bud growth and ¹⁴C accumulation,but that addition of NAA reduced these effects.     

Water Use Characteristics of Dactylis glomerata L., Lolium perenne L. and L. multiflorum Lam. Plants

Cocksfoot (Dactylis glomerata L.). perennial ryegrass (Loliumperenne L.) and Italian ryegrass (L. multiflorum Lam.) plantswere grown on deep (75–95 cm) columns of soil in glasshousesand growth rooms with and without irrigation. The species inwhich growth declined least rapidly after water had been withheldwere those which transpired most slowly. During early establishmentin the glasshouse cocksfoot transpired least because of slowroot growth. In the growth room, when root systems were deeperand denser, perennial ryegrass transpired least because of lowleaf water conductance. Results are discussed in relation to(a) drought resistance in the three species; (b) breeding forincreased drought resistance through modifying root distributionand leaf water conductance; and (c) the use of isolated soilcolumns in water relations studies. Dactylis glomerata L., Lolium perenne L., Lolium multiflorum Lam., cocksfoot, perennial ryegrass, Italian ryegrass, transpiration, roots, leaf water conductance     

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.): 3. The Leaf Trace System, and Tiller Insertion, in the Adult

The leaf trace system in the region of congested internodesat the base of Lolium multiflorum is described. A typical major trace in a leaf consists of a collateral bundlehaving a double bundle sheath and incorporating a certain amountof sclerenchyma. As such a leaf trace is followed down intothe stem it increases in diameter, loses the inner (mestome)bundle sheath, and the xylem becomes associated with xylem transfercells. Lower down, the bundle diameter is reduced although nowit has become amphivasal. The internal xylem only is still associatedwith transfer cells. The proximal portions of the bundle aremuch reduced, transfer cells, mestome sheath, and sclerenchymaare lacking and the now insignificant bundle merges with a lowerleaf trace or some other vascular tissue. Such a bundle in thestem may be in direct contact via bridges with other leaf traces,with the nodal plexus, and with the peripheral plexus that surroundsthe inner leaf trace system. In the base of a typical young plant, approximately one-halfof all leaf traces, including all the median veins, join bundlesfrom the next oldest leaf. Approximately one-third join thenodal plexus, and the remainder variously join bundles fromthe same or next but one oldest leaf to join the peripheralplexus. The differentiation of tiller insertions into the pre-existingmain stem system is highly variable. In a very young tillera number of traces were seen to terminate before the main systemwas reached suggesting basipetal differentiation. The actualconnections made by the tiller traces may occur with any nearbyleaf trace, the nodal plexus, or with the peripheral plexus.Later differentiating leaf traces in a tiller join leaf tracesof the tiller itself. Occasional bundles from secondary tillers by-pass the vasculartissue of the primary tiller to join directly with that of theparent plant. Vascular connections between parent and tiller,although very variable, appear to be totally comprehensive froma functional standpoint.     

The Influence of Defoliation on the Distribution of Assimilates in Lolium multiflorum Lam

Autoradiographs were made of plants of Lolium multiflorum Lam.after ¹⁴CO₂ had been fixed by selected leaves. The results showedthat labelled compounds were not translocated to other tillersbut were moved to the whole root system. This pattern of distributionwas changed when all or some of the tillers on the plant weredefoliated. Where a single undefoliated tiller remained, itinitially supplied the cut tillers with ¹⁴C-containing products,thus reintegrating a system of apparently independent tillers.When all the tillers were partially defoliated, labelled compoundswere no longer translocated to the root system. A further experimentsuggested that root reserves were not mobilized for regrowthfollowing defoliation. These results are discussed in termsof the integration of a grass plant in the vegetative state.     

多花黑麦草对不同形态氮的吸收动力学特征研究

采用改进常规耗竭法,比较研究了多花黑麦草(Lolium multiflorum Lam.)对NH₄⁺和NO₃^-吸收动力学特征。结果表明多花黑麦草对NH₄⁺和NO₃^-吸收符合Miehaelis-Menten方程,它对NH₄⁺的亲和力显著大于对NO₃^-的亲和力,但对NH₄⁺和NO₃^-的最大吸收速率差异不显著,说明多花黑麦草偏爱吸收NH₄⁺,在实际污水净化过程中,多花黑麦草具有优先吸收NH₄⁺的趋势,若有足够的停留时间,其对NH₄⁺净化程度会更高些;当吸收系统微生物受抑制时,多花黑麦草对NO₃^-的吸收速率明显降低,亲和力明显提高,可见微生物对吸收体系中氮素的去除有一定促进作用。     

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.) 1. The Young Seedling and Its Variability

The vascular system of the young Italian ryegrass seedling (Loliummultiflorwn Lam.) is very similar to that of oat (Avena) whichhas been described in the past. Early accounts however failto record the distinctive separate course of the xylem and phloemconstituents of the bundles at the coleoptilar node. The ascendingmesocotylar trace is bicollateral. It continues up, in part,into the mid-vein of the first foliage leaf and arches over,joining the bases of the two coleoptilar traces, to become thecollateral scutellar trace. Considerable variation exists from seedling to seedling in thedetails of the vascular pattern. This is coupled with additionalvariation in mesocotyl elongation, extent of the coleoptilarnode, number and location of lateral root primordia and theirmaturation, rate of growth of coleoptile and first foliage leavesand the rate of vascular differentiation within them. Possiblecauses of this variability are discussed and it is noted thatapparently identical plants, selected on a single morphologicalcriterion such as degree of elongation of the coleoptile, maybe expected to differ markedly in other morphological and anatomicalaspects, influencing their performance in physiological experimentation.     

The Effects of Plant Density on Shoot and Leaf Lamina Angles in Lolium multiflorum and Paspalum dilatatum

The effects of plant density on shoot and leaf lamina zenithangles (i e the angles with respect to the vertical) were investigatedin Lolium multiflorum and Paspalum dilatatum plants grown inpots either outdoors or in a glasshouse Tillers appeared abovethe ligule of their subtending leaf with a small zenith anglebut, in plants grown at low densities, gradually adopted a morehorizontal position In plants grown at high densities this gradualincrease in shoot zenith angle with age was strongly reducedThe average shoot zenith angle at a given time was lower (ie tillers were more erect) at high, compared to low plant densitiesShoot number per plant and average shoot zenith angle per plantwere directly related In P dilatatum plants the leaf lamina remained nearly horizontalat any plant density This observation indicates that the movementof the leaf lamina, pivoting at the point of attachment to theleaf sheath, compensated the movement of the shoot, pivotingat the base of the leaf sheath-tube Shoot angle responses to plant density would place leaf laminaeat different heights within the canopy, affecting their abilityto compete for light and their susceptibility to wind impactand herbivore grazing Foliage architecture, Lolium multiflorum Lam, Paspalum dilatatum Poir, plant density, neighbour effects, shoot angle, leaf angle     

Chromosome pairing in tetraploid hybrids between Lolium perenne and L. multiflorum

Summary Chromosome association at first meiotic metaphase in tetraploid hybrids between Lolium perenne and L. multiflorum was compared with that in autotetraploid L. perenne. The hybrids were found to have significantly higher levels of bivalent frequency, and lower levels of multivalent and chiasma frequency. A significant increase in multivalent frequency with increasing chiasma formation was found in both groups, but the increase was much less in the hybrids. These differences in chromosome associations between the two groups must therefore reflect differences in chiasma distribution and it is suggested that the results indicate a significant degree of preferential bivalent pairing in the hybrids.     

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.) 4. The Peripheral Plexus, and Nodal Root Insertion

The interconnecting system of leaf traces constitutes only afraction of the vascular tissue found in the base of a ryegrassstem. The tillers and nodal roots have their insertion in thiscongested region of the plant in addition to the majority ofthe leaf traces. Study of the attachment of nodal roots revealsthe extensive differentiation of vascular tissue in a perforatedcylinder surrounding the inner leaf trace system—the peripheralplexus. This plexus consists of two components, the diffuse bundlesorientated along the stem axis, and interconnected with theroot girdles orientated around the stem axis. The peripheralplexus which is bounded externally by a mestome sheath, makesnumerous contacts with the leaf trace system within it, bothdirectly and via the nodal plexi, and receives the vascularattachment of all the nodal roots. It appears in the stem atabout the same time as adjacent nodal roots, and differentiatesfrom meristematic tissue totally independently of the leaf tracesystem. The diffuse bundles themselves apparently differentiateacropetally in this meristematic tissue and are augmented bybranches from leaf traces and the nodal plexi. The integrated vascular systems of leaf, stem, and root at thebase of the grass plant, bounded by a mestome sheath, must allowtotal intercommunication between all organs. Nearly all tissuewithin the mestome sheath is vascular in nature and it is intothis vascular tissue that the leaf traces associated with transfercells are inserted.     

Silica in the Mesophyll Cell Walls of Italian Rye Grass (Lolium multiflorum Lam. cv. RvP)

Isolated cell envelopes from the leaf mesophyll of Italian ryegrass were examined in a transmission electron microscope equippedwith an energy-dispersive X-ray spectrometer. Silicon was detectedin these walls at an estimated concentration of 1–2 percent. Samples were also subjected to a range of techniques,for the removal of organic matter, which confirmed the presenceof silica throughout the cell walls. Lolium multiflorum Lam, Italian rye grass, cell walls, silica, electron microscopy, X-ray microanalysis     

The Effect of Sulphur Dioxide on the Growth of Lolium perenne L., Lolium multiflorum Lam., Dactylis glomerata L., and Phleum pratense L.

Lockyer, D. R. 1985. The effect of sulphur dioxide on the growthof Lolium perenne L., Lolium multiflorum Lam., Dactylis glomerataL., and Phleum pratense L.?J. exp. Bot. 36: 1851-1859. Fouragriculturally important grasses, Lolium perenne L., Loliummultiflorum Lam., Dactylis glomerata L. and Phleum pratenseL. were exposed to sulphur dioxide (SO₂) in a system of exposurechambers. The plants were exposed for a total of 43 d to meanconcentrations of SO₂ in the air of 0,87 or 448 (µg m^–3and herbage was harvested twice. All four grasses showed chloroticlesions after exposure to the highest concentration of SO₂.The effect of SO₂ on the yield of herbage was statisticallysignificant only at the second harvest and at the highest concentration;the dry weights of shoots of D. glomerata and L. perenne werereduced by 33% and 16% respectively. Significant effects ofSO₂ were also found on the 'transpiration coefficients' measuredfor D. glomerata and P. pratense. The grasses differed in theiruptake of sulphur from the atmosphere but this was not relatedto their sensitivity to SO₂. Total–S concentration inthe shoots of L. perenne, L. multiflorum and D. glomerata increasedalmost linearly in response to increasing SO₂ concentration;with P. pratense only the highest SO₂ concentration raised total-Sabove the level in control plants. These increases were almostentirely due to the accumulation of sulphate–S. Key words: Sulphur diozide, Lolium perenne, Lolium multiflorum, Dactylis glomerata, Phleum pratense     

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.) 2. Development of the Seedling Axis to Maturity

The vascular system present in a grass seedling axis persistsin a functional state at the base of a maturing plant, but undergoesa number of modifications. Two strands of phloem, accompanied by some internal xylem, differentiatein association with the bicollateral mesocotyl trace at rightangles to the existing phloem, resulting in a tetrarch bundle.Lateral seminal roots are themselves tetrarch and the vascularinsertion of a seminal root on to the mesocotyl is a distinctivethree-dimensional feature. At the base of the mesocotyl thetetrarch bundle merges with the tetrarch bundle of the primaryseminal root via a transition zone. The four phloem poles uniteand then diverge again; the central xylem strand splits intothree and then reunites, the two tissues being intimately interlockedby this rearrangement. The additional vascular tissue of the mesocotyl extends up intothe coleoptilar node and becomes involved in the vascular attachmentof nodal roots at this point. Additional vascular tissue continuesto differentiate in the periphery of the maturing stem and ishere termed the ‘peripheral plexus’. In the seedling, the xylem of the ‘bridge’ linkingthe mesocotyl trace with the scutellar trace is associated withxylem transfer cells and also contains tracheids with distinctive,thin-barred scalariform thickening. These transfer cells disappearas the plant matures but numerous tracheids with thin-barredscalariform thickening are then to be found. The possible significanceof transfer cells in the coleoptilar node is discussed.     

Effects of a localized supply of nitrate on NO3 - uptake rate and growth of roots in Lolium multiflorum Lam.

Roots of higher plants are usually exposed to varying spatial and temporal changes in concentrations of soil mineral nitrogen. A split root system was used to see how Lolium multiflorum Lam. roots adapt to such variations to cope with their N requirements. Plants were grown in hydroponic culture with their root system split in two spatially separated compartments allowing them to be fed with or without KNO₃. Net NO₃ ^- uptake, ¹⁵NO₃ ^- influx and root growth were studied in relation to time. Within less than 24 h following deprivation of KNO₃ to half the roots, the influx in NO₃ ^- fed roots was observed to increase (about 200% of the influx measured in plant uniformly NO₃ ^- supplied control plant) thereby compensating the whole plant for the lack of uptake by the N deprived roots. Due to the large NO₃ ^- concentrations in the roots, the NO₃ ^- efflux was also increased so that the net uptake rate increased only slightly (35% maximum) compared with the values obtained for control plants uniformly supplied with NO₃ ^-. This increase in net NO₃ ^- uptake rate was not sufficient to compensate the deficit in N uptake rate of the NO₃ ^- deprived split root in the short term. Over a longer period (>1 wk), root growth of the part of the root system locally supplied with NO₃ ^- was stimulated. An increase in root growth was mainly responsable for the greater uptake of nitrate in Lolium multiflorum so that it was able to fully compensate the deficit in N uptake rate of the NO₃ ^- deprived split root.