Utilization of Photosynthates for Growth, Respiration, and Storage in Tops and Roots of Lolium multiflorum

Lolium multiflorum L. was grown in pots in controlled environments. CO₂-exchange rates were continuously measured on two pots during 46 and 52 days, respectively, separating between tops and roots. After 20 days, the plants were entirely defoliated and the plants were then followed during the regrowth period. During the experiment, alternating 2–3 day periods of high and low irradiance were applied. Analogously treated plants were frequently harvested to obtain the distribution of assimilates between tops and roots. From integration of CO₂-exchange rates, diurnal photosynthesis and respiration were obtained, and utilization of assimilates was analysed. The respiration associated with the synthesis of new structural material (growth respiration) was dependent on assimilates originating from both the current and the preceding 24 h diurnal cycles. The amount of new structural material synthesized during the current 24 h diurnal cycle was estimated from the relative contribution of assimilates accumulated from the preceding and the current 24 h and diurnal cycles to growth respiration of the current 24 h. From this approximation, the respiratory components connected to synthesis of new structural material and to maintenance of already established material were found. Growth and maintenance respirations of the tops were alike during the predefoliation and the regrowth periods. For the roots, however, growth respiration was higher and maintenance respiration lower in the regrowth period. The difference between daily integrated CO₂-exchange and the amount converted into new structural material was assumed to be the daily change in assimilates stored. On the first day of a period of high irradiance, the assimilation per unit leaf weight was higher than on the following day of high irradiance, and an accumulation of storage material took place. On the first day of a period of low irradiance, the assimilation per unit leaf weight was lower than on the following day of low irradiance, and there was a depletion of assimilates stored. These effects were most pronounced during the regrowth period, indicating a change in the metabolic sink demand. This indicates a strong feedback mechanism between sources and sinks, in the sense that accumulation of products will inhibit assimilation.     

Influence of Nitrogen Form and Nitrogen Absence on Utilization of Assimilates for Growth and Maintenance in Tops and Roots of Lolium multiflorum

Utilization of assimilates for growth and maintenance of tops and roots of Lolium multiflorum was determined for plants supplied with either nitrate or ammonium. Carbon dioxide exchange rates were measured continuously for tops and roots separately. Three-day periods were applied for two irradiation levels. On the last day of each three-day period no nitrogen was supplied to the two treatments. In the nitrate treatment, the coefficient of utilization for converting assimilates into constructive growth (Y_G) remained unaffected in absence of nitrate. However, in absence of nitrate the maintenance respiration (M) for both tops and roots was only one third of that in presence of nitrate. In the treatment with ammonium the maintenance respiration of the plants was not influenced by the absence of ammonium. However, especially for the tops Y_G increased in absence of ammonium. In both the treatments, growth respiration of the roots was inefficient compared to that of the tops. Only in the case of absence of nitrate, maintenance respiration of the roots was similar to that of the tops.     

Energy, Respiration, and Growth in Plants

The energy relations and heat production during plant growthare analysed in terms of respiration, dry weight, and growth.Wastage respiration and its relationship to this analysis arediscussed The results of microcalorimetric experiments on wheatseedlings are analysed and interpreted.     

多花黑麦草对铝胁迫的生长生理响应

以多花黑麦草(Lolium multiflorum Lam.)为材料,采用盆栽实验法,对其进行不同浓度铝(Al)的胁迫处理(0、100、200、300、400、500 mg/kg),并测定植株胁迫后的各项生长和生理指标。结果显示,Al胁迫会抑制多花黑麦草的生长和生物量的积累,Al~(3+)含量越高,其抑制作用越强。其中,土壤Al~(3+)含量为500 mg/kg时对植物株高和地上部的干重产生显著抑制作用;而当Al~(3+)含量为100 mg/kg时对植物根长和根干重产生显著抑制作用。叶绿素a、叶绿素b和叶绿素总量均随Al~(3+)含量的升高而降低,其中Al~(3+)含量为500 mg/kg时,叶绿素a、叶绿素b分别比对照下降了56.81%和46.57%。地上部和根系中的可溶性糖、游离脯氨酸、MDA含量和SOD活性均随Al~(3+)含量的升高而升高,且上述地上部4个指标均高于根系。     

Growth, Maintenance and Respiration: a Re-interpretation

The traditional view of respiration being due to the processesof growth and maintenance is questioned. A model is proposedin which plant dry matter is divided into three categories:storage material which may be used for growth; non-degradablestructural material which cannot be recycled, and which is consideredto be inert; and degradable structural material which is assigneda rate constant of degradation, and which is considered to bebiologically active. The model has four parameters: two yieldconstants, and two rate constants, and it has been solved forsteady-state exponential growth in continuous daylight, respirationin the dark, and ^l4CO₂ evolution after a pulse label. Analysisof ^l4CO₂ efflux data leads to the complete definition of themodel. The utility and comparative merits of the suggested viewpointof respiration are discussed.     

Photosynthesis and Photorespiration in Lolium multiflorum and Lolium perenne

The response of net photosynthesis to changing light-flux densityby leaves of Lolium multiflorum (S. 22) and L. perenne (S. 321)is more adequately described by current models when a term allowingfor photorespiration is included. The magnitude of this termwas determined from the changes in the slope of the light-responsecurves for net photosynthesis. A pseudo first-order rate-constantfor photorespiration, and a pseudo second-order rate-constantfor photosynthesis calculated by this technique for L. multiflorumwere found to be similar to corresponding parameters calculatedfrom light-compensation-point measurements using a simple modeldescribed by Brown (1969). The relative magnitudes of respirationand photosynthesis at light saturation for both Lolium specieswere similar to reported values for other temperate species(Lake, 1967). Two selection lines of L. perenne (S. 321) with contrastingdry-matter yields were found to have the same parameters forrespiration and photosynthesis.     

Meristem Tip Culture in Lolium multiflorum

Complete plants were regenerated from meristem tips of Loliummultiflorum. Of the three basal culture media used, Murashigeand Skoog's medium gave the best results. Plantlets were produced without exogenous auxins or cytokinins,but 0.2 mg 1^–1 kinetin favoured development. As the mainaim in the development of this technique is the eliminationof viruses, the possibilities of using 2,4.D in the culturemedium and of culturing very small meristem tips for this purposewere considered.     

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.     

Glyphosate resistance in a Chilean Lolium multiflorum

Lolium multiflorum (Italian ryegrass) has recently demonstrated itself to be poorly controlled with glyphosate in cereal crops of South Chile. The concentration of glyphosate necessary to reduce shoot length by 50% (ED50) in seedlings, after eight days of root contact was 7.3-fold in the resistant Vil-1 than in the susceptible (S) biotype. The obtained spray retention values were higher on S than the resistant (Vil-1) biotype. Contact angles measured on the adaxial surface of S and Vil-1 were similar. However, on the abaxial surface contact angles were of 63 degrees on Vil-1 as compared to 42 degrees on S. A greater glyphosate uptake was observed through the abaxial surface of S. Regarding translocation, glyphosate accumulated mainly in the tip of the treated leaf of Vil-1, 24 h after treatment. It was afterwards also well distributed to the rest of the leaves and roots, as in the susceptible biotype. Nevertheless, 14C-glyphosate remained higher in the foliar apex of Vil-1. Hence, resistance to glyphosate by the Vil-1 Lolium multflorum biotype seems to involve a lower uptake through the abaxial leaf surface and a different migration pattern.     

Competitive Al Inhibition of Net Mg Uptake by Intact Lolium multiflorum Roots : I. Kinetics

Aluminum impairs uptake of Mg²⁺, but the mechanisms of this inhibition are not understood. The depletion technique was used to monitor net Mg²⁺ uptake from nutrient solution by intact, 23-day-old plants of ryegrass (Lolium multiflorum Lam., cv Gulf and Wilo). Activities of Mg²⁺ and monomeric Al species in nutrient solution were calculated and used as the basis for expressing the results. The kinetics of net Mg²⁺ absorption was resolved into (a) a transpiration-dependent uptake component, (b) a metabolically mediated, discontinuous saturable component that is Al³⁺ sensitive and p-chloromercuribenzene sulfonic acid (PCMBS) resistant, and (c) a linear, carbonyl cyanide m-chlorophenylhydrazone resistant, Al³⁺ sensitive component that might be a type of facilitated diffusion. Lowering the pH from 6.0 to 4.2 exerted a noncompetitive inhibition of net Mg²⁺ uptake, while aluminum at 6.6 micromolar Al³⁺ activity exerted competitive inhibition of net Mg²⁺ uptake at pH 4.2. The Al³⁺-induced effect was obvious after 30 minutes. Cultivar-specific ability to retain a higher affinity for Mg²⁺ by postulated transport proteins in the presence of Al³⁺ might be one of the mechanisms of differential Al tolerance among ryegrass cultivars.     

Response to Selection for Dark Respiration Rate of Mature Leaves in Lolium perenne and its Effects on Growth of Young Plants and Simulated Swards

Selections for slow and for fast rate of dark respiration ofmature leaves were made from within Lolium perenne cv. S23.Selected parents were pair-crossed to provide 15 F₁ familieswith slow respiration and 15 with fast. Dark respiration was inherited and families with contrastingrates were subjected to sequentially harvested growth analysesfrom the third leaf stage to that of 95 per cent light interceptionin a growth room. Seven periods of regrowth of simulated swardsof the families were then recorded. During development of theprimary canopy, growth of the selections did not differ untilthe final harvest interval. At this stage slow respiration familieshad faster (P < 0.05) net assimilation rate and greater plantdry weight (P < 0.05) and leaf area index (P < 0.05) thanthe fast respiration group. Relative growth rate followed thesame trend. In the swards after each regrowth dry matter yieldof the slow respiration group was greater than that of the fast. In another experiment, simulated swards of six slow respirationfamilies yielded more than swards of six fast respiration familiesover sequential regrowth periods in a glasshouse from May toNovember: S23 was intermediate. Differences were most duringAugust and September. Crop growth rate at each harvest correlated(P < 0.05 or P < 0.01) with previously determined leafrespiration at 25 °C. Leaf protein levels in August weaklycorrelated (r = +0.57, P < 0.05) with respiration rate perunit dry weight but there was a significant residual negativecorrelation (r = –0.67, P < 0.05) between the rateper unit protein and growth at that time. Results are discussedin relation to the concept of ‘maintenance-relàted’respiration. Lolium perenne L., perennial ryegrass, respiration, maintenance respiration, relative growth rate, leaf area ratio     

Development of novel microsatellite markers for the grassland species Lolium multiflorum,Lolium perenne and Festuca pratensis

Twelve microsatellite markers were isolated from Lolium multiflorum. Allelic variability and cross‐species amplification were assessed on 16 individuals of each of the three grassland species L. multiflorum, Lolium perenne and Festuca pratensis. Cross‐species amplification success was 100% for L. perenne and 83% for F. pratensis. The number of alleles detected ranged from one to 14 with an average of 3.4. While three microsatellite loci were polymorphic in all three species, one marker produced species‐specific alleles in all three species. These microsatellite markers provide a valuable tool for population genetic studies within and among species of the Festuca–Lolium complex.     

Rapid Shedding of Roots from Azolla filiculoides Plants in Response to Inhibitors of Respiration

Chemicals that are known to be inhibitors of respiration, namely,sodium azide, sodium cyanide, DNP, CCCP and DCCD, caused sheddingof roots of Azolla filiculoides plants. Complete shedding ofroots of more than 10 mm in length occurred when Azolla plantswere treated with sodium azide, DNP or CCCP at concentrationsabove 50µM, 30µM and 20µM, respectively. Theshedding in response to sodium azide, DNP and CCCP was veryrapid and was complete within 5–20 min. Microscopic studies revealed the presence of large cells atthe outer surface of the base of roots that were about to beshed. The tested-chemicals caused the expansion, rounding upand separation of these cells, probably via the rapid absorptionof water, with resultant shedding of roots. When detached roots were immersed in a solution of sodium azide,DNP or CCCP, the large cells expanded and rounded up. Thesecells were gradually separated from the roots. However, theseparation of the cells caused by DNP was inhibited by the presenceof various buffers at acidic pH. By contrast, buffers at neutralpH greatly facilitated the separation of cells irrespectiveof whether DNP was present or absent. The results suggest that the separation of cells involves anincrease in the pH of the external solution in the vicinityof the large cells. A change in ion fluxes of the large cells,which accompanies an increase in pH of the external solution,may cause the rapid absorption of water by the cells and resultin the expansion and separation of the cells. (Received June 15, 1993; Accepted October 25, 1993)     

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.     

Competitive Al Inhibition of Net Mg Uptake by Intact Lolium multiflorum Roots : II. Plant Age Effects

Rhizotoxicity of Al is more pronounced in younger plants. Effects of Al on nutrient uptake by plants of different age are poorly understood. The depletion technique was used to monitor net Mg²⁺ uptake from nutrient solutions by intact 15- and 35-day-old plants of two ryegrass (Lolium multiflorum Lam.) cultivars. Lowering the pH from 6.0 to 4.2 decreased the maximum net ion influx without affecting K_m. Aluminum at 6.6 micromolar Al³⁺ activity increased K_m indicating competitive inhibition. The effects of pH and 6.6 micromolar Al³⁺ on net Mg²⁺ uptake were much larger in 15- than in 35-day-old plants. Aluminum at 26 micromolar Al³⁺ activity competitively inhibited net Mg²⁺ uptake by 35-day-old plants, while causing time- and external Mg²⁺ activity-dependent net Mg²⁺ efflux from 15-day-old plants. The equilibrium constant (K_i) of a reversible combination of postulated plasmalemma Mg²⁺ transporter and Al³⁺ was calculated to be 2 and 5 micromolar Al³⁺ activity for 15-day-old plants of Wilo and Gulf ryegrass, respectively, and 21 micromolar Al³⁺ activity for 35-day-old plants of both cultivars. The Al³⁺-mediated increase in K_m was larger for 15-day-old plants of the Al-sensitive cultivar `Wilo' than of the more Al-tolerant cultivar `Gulf,' while Al³⁺ affected 35-day-old plants of both cultivars to the same extent.     

Tillering Responses of Lolium multiflorum Plants to Changes of Red/Far-Red Ratio Typical of Sparse Canopies

Casal, J. J., Sáchez, R. A. and Deregibus, V. A. 1987.Tillering responses of Lolium multiflorum plants to changesof red/far-red ratio typical of sparse canopies.—J. exp.Bot. 38: 1432–1439. Plants of Lolium multiflorum were grown either in growth roomsunder radiation sources providing equivalent PAR but differentR/FR ratios between 0·46 and 2·36, or under sunlightsupplemented with a series of small fluence rates of FR throughoutthe photoperiod. In both kinds of experiments a reduction oftillering was found along with small depressions of R/FR ratiobelow the values typical of sunlight. In this range both thesquare-root-transformed rate of tillering and the site-fillingrate were linearly related to the estimated phytochrome photo-equilibriaand the slope was very steep under conditions that allowed hightillering rates. The addition of low fluence rates of red lightat the base of the shoots raised tillering of plants exposedto low R/FR ratios to the level of plants grown under high R/FRratios in spite of the ratios received by the rest of the plant.Moreover, irradiation of plant bases with intermediate-low R/FRratios reduced tillering indicating that this would be one siteof perception. These results show a high sensitivity to changesof R/FR ratio typical of different degrees of shade in sparsecanopies. This suggests that by monitoring these changes Loliummultiflorum plants would be able to perceive an anticipatedsignal of impending competition in growing canopies.     

多花黑麦草对啤酒废水净化功能的研究

1 引言 利用水生高等植物净化污水,国内外已有很多报道,1992年丁树荣等首先利用人工基质无土栽培多花黑麦草(Lolium multiflorum Lam.)净化缫丝废水获得成功,是利用陆生植物于高等水生植物净化塘中以净化有机污水的首例,并提出了解决在亚热带和温带冬季低温地区,利用高等水生植物净化污水时冬季不能有效运转难题的新途径,而作者于1987—     

The dynamics of aneuploidy in an induced tetraploid population of Lolium multiflorum x Lolium perenne

Summary Populations of induced polyploids invariably contain a substantial proportion of aneuploid individuals. A model is described which can predict the level of aneuploidy in successive generations of a closed population of Lolium tetraploids. The results demonstrate clearly that the proportion of aneuploid individuals increases sharply for two to three generations and then stabilizes at a level determined by the gametic output of the euploid plants. A change in the gametic output of aneuploid individuals has a relatively small effect on the final level of aneuploidy reached.     

A Method for in Vitro Storage of Lolium multiflorum Lam

A means of storing Lolium multiflorum Lam. stock plants in vitrohas been developed over a period of three years. Variousexplantsand cultureconditions were examined. Shoot tips 0.3–0.9mm long were found to be best for establishing storage culturesbecause they gave a high yield of plantlets in culture and importantpathogens are eliminated. For sub-culturing, after each annualcycle of storage at 2–4 °C, shoot tips, tiller buds,tiller bases and nodes can be used. Tiller buds were most abundantand best for increasing the number of stored plantlets whennecessary. There was no advantage of including an auxin in theculture medium for shoot tips and Murashige and Skoog's mediumwith 0.2 mg l^–1 kinetin has been adopted for initiating,sub-culturing and storing cultures. The optimum temperaturerange for regenerating plantlets was 20–25 °C. Lightwas necessary for a high rate of plantlet regeneration and lightquality and intensity affected their growth. Lolium multiflorum Lam., ryegrass, storage in vitro, tissue culture