Impact of Rice Husk Biochar on Drought Stress Tolerance in Perennial Ryegrass (Lolium perenne L.)

Journal of Plant Growth Regulation - In a water shortage crisis, the landscape management of perennial ryegrass, a common lawn grass, is a major challenge. An organic material that can help to...     

Growth of Perennial Ryegrass (Lolium perenne L.) Exposed to a Low Concentration of Sulphur Dioxide

The influence of a low concentration of SO₂ on the growth andsulphur status of perennial ryegrass (Lolium perenne L.) cv.S23 was examined in a system of specially designed growth chambers.For plants grown without additions of sulphate to the soil,erposure to ifitered air containing 50 µg m^–3 SO₂alleviated sulphur deficiency that developed during a sequenceof successive harvests, and gave increased yield. The plantshad higher contents of organic and inorganic sulphur than thosegrown with neither sulphate nor SO₂. Plants grown with addedsulphate showed no signs of sulphur deficiency and althoughexposure to SO₂ increased their sulphur content it had no effecton yield. The coefficient of transpiration (g water transpiredg^–1 dry wt. of shoots) was reduced when plants which otherwisehad an inadequate supply of sulphur were exposed to SO₂; forplants with adequate supplies of sulphate, it was similar whetherthey were grown with or without the addition of SO₂ to the air.The results are discussed in relation to other known reactionsof plants to SO₂.     

Flowering of S. 24 Perennial Ryegrass (Lolium perenne L.) in Short Days at Low Temperature

The flowering of the quantitative long-day plant perennial ryegrass(Lolium perenne L.) in short days (8 h), when grown at low temperature(9/4 °C) and under natural summer daylight, is presentedas evidence for the replacement of specific environmental requirementsfor flowering by alternative stimuli in a grass.     

The Effect of Temperature on Seed Set and Seed Development in Detached Spikelets of Perennial Ryegrass (Lolium perenne L.)

In perennial ryegrass seed yield is low. Pollination, fertilizationand early stages of seed development are critical periods forthe realization of the yield potential. As intact plants aredifficult to handle, we used detached spikelets to study effectsof temperature and genotype on seed set and seed development. Plants of four cultivars were grown in pots. Just prior to flowering,spikelets were detached from the ears and put on water. Afterpollination, various spikelets of each plant were placed atdifferent temperatures (14/14, 17/12 or 20/15°C). Sevendays after pollination the percentage seed set and the lengthof the developing seeds (caryopses) were assessed. Only floretsin the four basal positions were used. For each cultivar an analysis of variance for unbalanced datawas carried out. There were highly significant difference amonggenotypes for seed set and caryopsis length. There was no evidencefor genotypic variation for tolerance to low temperatures. Neithertemperature nor floret position had an effect on seed set. Thecaryopsis length, however, increased with increasing temperatureand basal florets produced longer caryopses than distal florets.The detached spikelets proved to be a useful experimental tool.Copyright1993, 1999 Academic Press Lolium perenne L., perennial ryegrass, seed yield, seed set, detached spikelets culture, temperature, floret position     

The Effects of Light Intensity and External Potassium Level on Root/Shoot Ratio and Rates of Potassium Uptake in Perennial Ryegrass (Lolium perenne L.)

Loliun perenne L. (cv.S. 23) was grown on vermiculite in winterin a heated greenhouse for 8 weeks under factorial combinationsof two potassium regimes (nominally 6 parts/10⁶ and 156 parts/10⁶in Hewitt's solution) and three densities of artificially supplementedvisible radiation flux (36.1, 7.3, and 2.2 W m^–2). Growthand potassium uptake were studied through the calculation ofvarious growth functions from fitted curves. There was little effect of potassium treatment but the experimentalmaterial responded markedly to light. Leaf-area ratio in thethree treatments showed extreme plasticity in increasing from2–3 x 10^–2 through 6 x 10^–2 to 8–9 x10^–2 m² g^–1 as light intensity decreased. Correspondingdecreases in unit leaf rate, however, caused over-all reductionsin relative growth rate. Specific absorption rates for potassium (A_K, dry-weight basis)were strongly reduced at the lower light intensities but alsodisplayed complex ontogenetic drifts. Values of the allometricconstant, k (the ratio of root and shoot relative growth rates),decreased from c. 0.7 at 36.1 W m^–2 through c. 0.3 at7.3 W m^–2 to a value not significantly different fromzero (P < 0.05) at 2.2 W m^–2. In material grown under the two higher light intensities a constantinverse relationship was found between the mass ratio of rootand shoot and the corresponding activity ratio. The resultsconform to this model: Mass ratio = –0.001+45.0 (1/activityratio) where activity ratio is expressed as specific absorptionrate for potassium (in µg g root^–1 h^–1)/unitshoot rate (rate of increase of whole-plant dry weight per unitshoot dry weight, in mg g shoot^–1 h^–1). The implicationsof this relationship are discussed.     

Lambs Fed Fresh Winter Forage Rape (Brassica napus L.) Emit Less Methane than Those Fed Perennial Ryegrass (Lolium perenne L.), and Possible Mechanisms behind the Difference

The objectives of this study were to examine long-term effects of feeding forage rape (Brassica napus L.) on methane yields (g methane per kg of feed dry matter intake), and to propose mechanisms that may be responsible for lower emissions from lambs fed forage rape compared to perennial ryegrass (Lolium perenne L.). The lambs were fed fresh winter forage rape or ryegrass as their sole diet for 15 weeks. Methane yields were measured using open circuit respiration chambers, and were 22-30% smaller from forage rape than from ryegrass (averages of 13.6 g versus 19.5 g after 7 weeks, and 17.8 g versus 22.9 g after 15 weeks). The difference therefore persisted consistently for at least 3 months. The smaller methane yields from forage rape were not related to nitrate or sulfate in the feed, which might act as alternative electron acceptors, or to the levels of the potential inhibitors glucosinolates and S-methyl L-cysteine sulfoxide. Ruminal microbial communities in forage rape-fed lambs were different from those in ryegrass-fed lambs, with greater proportions of potentially propionate-forming bacteria, and were consistent with less hydrogen and hence less methane being produced during fermentation. The molar proportions of ruminal acetate were smaller and those of propionate were greater in forage rape-fed lambs, consistent with the larger propionate-forming populations and less hydrogen production. Forage rape contained more readily fermentable carbohydrates and less structural carbohydrates than ryegrass, and was more rapidly degraded in the rumen, which might favour this fermentation profile. The ruminal pH was lower in forage rape-fed lambs, which might inhibit methanogenic activity, shifting the rumen fermentation to more propionate and less hydrogen and methane. The significance of these two mechanisms remains to be investigated. The results suggest that forage rape is a potential methane mitigation tool in pastoral-based sheep production systems.     

Synaptonemal complex formation in hybrids of Lolium temulentum x Lolium perenne (L.)

Comparisons were made between two kinds of tetraploids derived from the hybrid Lolium temulentum x L. perenne. One hybrid behaves like an autotetraploid with multivalents at first metaphase of meiosis in pollen mother cells. The other behaves like an allotetraploid, in which pairing at first metaphase is restricted to bivalents comprised of strictly homologous chromosomes. The diploidisation of the latter form is controlled by determinants located on both the normal, A chromosomes and on supernumary B chromosomes. Reconstruction of synaptonemal complexes and their elements, from serial sections through pollen mother cell nuclei examined under the electron microscope, reveals that at zygotene pairing in both forms results in multivalent formation involving non-homologous as well as homologous chromosomes. The mechanism responsible for the diploidisation is, therefore, not based on a restriction of pairing at early meiosis to homologous chromosomes but on a correction or transformation of the multivalent chromosome associations to bivalents subsequent to zygotene. The transformation is not completed until late pachytene. In the multivalent-forming tetraploid a maximum of four chromosomes are associated at first metaphase. Yet configurations of a higher valency are found at zygotene. There is, therefore, a partial transformation of multivalents even in this autotetraploid form which restricts configurations at metaphase I to homologous and homoeologous chromosomes only. In both hybrids some homologous bivalents are not the product of resolution of multivalents but result from two-by-two pairing from the beginning of zygotene.     

Growth of Ryegrass (Lolium perenne L.) Exposed to SO2: I. EFFECTS ON PHOTOSYNTHESIS AND RESPIRATION

The effects of exposure to SO₂ (50 and 400 µg m^–3SO₂) on the growth, photosynthesis, and respiration of perennialryegrass (Lolium perenne L.) cv. S23 were examined in two successivegrowth periods of 29 and 22 d. At the higher concentration ofSO₂, there was some visible injury of the leaves and specificleaf area was reduced, but yield, net photosynthesis, and darkrespiration of the plants were not significantly affected byexposure. The treatment was also without effect on the transpirationcoefficient of the plants and their number of tillers. The plantsexposed to the lower concentration of SO₂ showed no signs ofinjury and did not differ in any of the measured characteristicsfrom plants grown in SO₂-free air. Content of S in the shootsincreased linearly with the concentration of SO₂, the additionalS being found in the sulphate fraction whilst organic S wasunchanged. The results are discussed in relation to earlierfindings that yield of ryegrass exposed to SO₂ may be reducedwithout visible signs of injury.     

UV-B and PAR in a grass (Lolium perenne L.) canopy

The penetration of natural and artificial UV-B_BE (Biologically Effective UV-B, Caldwell 1971) and PAR (400–700 nm) in a grass canopy with increasing LAI was followed during 2 months. Overall, the transmission of UV-B_BE sunlight is significantly higher than of PAR sunlight. This is mainly due to the higher proportion of diffuse light in the UV-B. Under cloudy conditions no difference between UV-B_BE and PAR could be found. Sun angle and intensity of the radiation were less important in determining the penetration of light. Artificial light penetrates much more through the canopy, resulting in higher irradiation levels in the lower part of the canopy, but a lower UV-B_BE/PAR ratio (since UV-B transmittance of the leaves is lower). The UV-B_BE/PAR ratio reaching the leaves was influenced by LAI, sun angle, percent diffuse light and leaf angle. The large differences in UV-B_BE/PAR ratio per unit leaf area under natural and artificial light conditions are important in understanding the influence of UV-B on plants.     

Relationships between Root Temperature and the Transport of Ammonium and Nitrate Ions by Italian and Perennial Ryegrass (Lolium multiflorum and Lolium perenne)

At root temperature below 14 C the absorption of ¹⁵N from NH₄⁺ greatly exceeded that from NO₂⁻ by tillers of Lolium multiflorum and Lolium perenne under conditions where pH, external concentration, plant N status, and pretreatment temperature were varied. There was a marked increase in the temperature sensitivity of NO₃⁻ transport below 14 C, irrespective of the temperature at which plants were grown previously. A marked increase in the temperature sensitivity was also seen for NH₄⁺ transport, but this occurred at the lower temperature of 10 C. Pretreatment of roots at 8 C lowered this still further to 5 C. Above and below these transition temperatures the Q₁₀ values for NO₃⁻ and NH₄⁺ transport were similar. Thus, the increased absorption of NH₄⁺ relative to NO₃⁻ at low temperatures seems to be related primarily to the difference in transition temperatures.     

Olivine Weathering in Soil, and Its Effects on Growth and Nutrient Uptake in Ryegrass (Lolium perenne L.): A Pot Experiment

Mineral carbonation of basic silicate minerals regulates atmospheric CO(2) on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natural CO(2) sequestration ('enhanced weathering'). While agriculture may offer an existing infrastructure, weathering rate and impacts on soil and plant are largely unknown. Our objectives were to assess weathering of olivine in soil, and its effects on plant growth and nutrient uptake. In a pot experiment with perennial ryegrass (Lolium perenne L.), weathering during 32 weeks was inferred from bioavailability of magnesium (Mg) in soil and plant. Olivine doses were equivalent to 1630 (OLIV1), 8150, 40700 and 204000 (OLIV4) kg ha(-1). Alternatively, the soluble Mg salt kieserite was applied for reference. Olivine increased plant growth (+15.6%) and plant K concentration (+16.5%) in OLIV4. At all doses, olivine increased bioavailability of Mg and Ni in soil, as well as uptake of Mg, Si and Ni in plants. Olivine suppressed Ca uptake. Weathering estimated from a Mg balance was equivalent to 240 kg ha(-1) (14.8% of dose, OLIV1) to 2240 kg ha(-1) (1.1%, OLIV4). This corresponds to gross CO(2) sequestration of 290 to 2690 kg ha(-1) (29 10(3) to 269 10(3) kg km(-2).) Alternatively, weathering estimated from similarity with kieserite treatments ranged from 13% to 58% for OLIV1. The Olsen model for olivine carbonation predicted 4.0% to 9.0% weathering for our case, independent of olivine dose. Our % values observed at high doses were smaller than this, suggesting negative feedbacks in soil. Yet, weathering appears fast enough to support the 'enhanced weathering' concept. In agriculture, olivine doses must remain within limits to avoid imbalances in plant nutrition, notably at low Ca availability; and to avoid Ni accumulation in soil and crop.     

Gene-associated single nucleotide polymorphism discovery in perennial ryegrass (Lolium perenne L.)

Molecular genetic marker development in perennial ryegrass has largely been dependent on anonymous sequence variation. The availability of a large-scale EST resource permits the development of functionally-associated genetic markers based on SNP variation in candidate genes. Genic SNP loci and associated haplotypes are suitable for implementation in molecular breeding of outbreeding forage species. Strategies for in vitro SNP discovery through amplicon cloning and sequencing have been designed and implemented. Putative SNPs were identified within and between the parents of the F₁(NA₆ × AU₆) genetic mapping family and were validated among progeny individuals. Proof-of-concept for the process was obtained using the drought tolerance-associated LpASRa2 gene. SNP haplotype structures were determined and correlated with predicted amino acid changes. Gene-length LD was evaluated across diverse germplasm collections. A survey of SNP variation across 100 candidate genes revealed a high frequency of SNP incidence (c. 1 per 54 bp), with similar proportions in exons and introns. A proportion (c. 50%) of the validated genic SNPs were assigned to the F₁(NA₆ × AU₆) genetic map, showing high levels of coincidence with previously mapped RFLP loci. The perennial ryegrass SNP resource will enable genetic map integration, detailed LD studies and selection of superior allele content during varietal development.     

Growth of Ryegrass (Lolium perenne L.) Exposed to SO2: III. EFFECTS ON FREE AND STORAGE CARBOHYDRATE CONCENTRATIONS

Exposure of ryegrass (Lolium perenne L.) cv. S23 to 0, 50, and400 µg m^–3 SO₂ for an initial 29 d (first harvest),and for an additional 22 d period of regrowth (second harvest),resulted in distinct alterations in carbohydrate metabolismat each harvest. At the first harvest, exposure to 50 µgm^–3 increased concentrations of free and total carbohydrates,whereas exposure to 400 µg m^–3 resulted in concentrationshardly different from those in control plants. At both SO₂ concentrations,more assimilate was retained as free carbohydrate rather thanas storage carbohydrate. Comparison of assimilate distributionat the end of the light, and at the end of the dark period atthe first harvest led to the conclusion that light-mediatedmetabolism is more sensitive to SO₂ exposure than dark metabolism,and that assimilate distribution might be controlled by at leasttwo processes exhibiting different SO₂ sensitivities.     

Isolation of viable egg cells of perennial ryegrass (Lolium perenne L.)

Summary Isolation of viable egg cells of perennial ryegrass (Lolium perenne L.) has been accomplished. After an enzyme incubation, ovules disintegrated into loose cells upon mechanical manipulation. The egg cells could be identified between the bulk of sporophytic cells derived from the macerated ovules. The morphology of the isolated egg cell corresponds to the morphology of the egg cell in situ and is comparable to the morphology of egg cells of other monocotyledons and angiosperms. Two hours after isolation the egg cells were still viable. The protocol proved reproducible and the yield was determined at 10%.     

Models for mesophyll cell arrangement in leaves of ryegrass (Lolium perenne L.)

Summary Three models for mesophyll cell arrangement in leaves of Lolium perenne L. are described. It is shown that mesophyll cells may be represented as spheres packed in a tetragonal lattice. The need to quantify mesophyll cell arrangement is discussed in relation to leaf photosynthesis.The variation on measurements of some anatomical features of leaves is examined and discussed.     

Photosynthetic and Photorespiratory Carbon Metabolism in Mesophyll Protoplasts and Chloroplasts Isolated from Isogenic Diploid and Tetraploid Cultivars of Ryegrass (Lolium perenne L.)

Photosynthetic ¹⁴CO₂ fixation, [¹⁴C]glycolate formation, and the decarboxylation of [1-¹⁴C]glycolate and [1-¹⁴C]glycine by leaf mesophyll protoplasts isolated from isogenic diploid and tetraploid cultivars of ryegrass (Lolium perenne L.) were examined. The per cent O₂ inhibition of photosynthesis in protoplasts from the tetraploid cultivar was less than that of the diploid line at both 21 and 49% O₂. Kinetic studies revealed that the K_m (CO₂) for photosynthesis by the diploid protoplasts was about twice that of the tetraploid line. In contrast, the K_i (O₂) for protoplast photosynthesis was similar in both cultivars, as was the potential for oxidizing glycolate and glycine to CO₂ via the photorespiratory carbon oxidation cycle. Although the maximal rates of glycolate accumulation by the isolated protoplasts in the presence of 21% O₂ and a glycolate oxidase inhibitor were similar in the two cultivars, the percentage of total fixed ¹⁴C entering the [¹⁴C]glycolate pool and the ratio of the rate of [¹⁴C]glycolate formation to ¹⁴CO₂ fixation at 21% O₂ and low pCO₂ were about two times greater in protoplasts and intact chloroplasts isolated from the diploid line compared to the tetraploid. These results fully support the recent observation that a doubling of ploidy in various ryegrass cultivars reduced the K_m (CO₂) of purified ribulose bisphosphate carboxylase-oxygenase by about one-half without affecting the K_i (O₂) (Garrett 1978 Nature 274: 913-915).