Growth Of White Clover Research Articles

Biochar and Deactivated Yeast as Seed Coatings for Restoration: Performance on Alternative Substrates

Seedling establishment is often a critical bottleneck in the revegetation of mine tailings and similar substrates. Biochar and deactivated yeast are potential sustainable materials that could be used in this context as seed coatings to aid in seedling establishment. We conducted a greenhouse study on biochar and deactivated yeast use as seed coatings, assessing germination, establishment, and early growth of white clover (Trifolium repens) and purple prairie clover (Dalea purpurea). Coated seeds were applied to a mine tailing, a coarse granitic sand, and potting soil mix substrates; seedling establishment and growth were monitored over 75 days. Biochar coatings enhanced the seedling establishment of Trifolium, with biochar and biochar plus yeast coatings giving the best results. In some cases, these effects persisted throughout the experiment: biochar coatings resulted in a ~fivefold increase in Trifolium biomass at harvest for plants in the potting soil mix but had neutral effects on sand or tailings. Biochar seed coatings also enhanced Dalea germination in some cases, but the benefits did not persist. Our results indicate that biochar-based seed coatings can have lasting effects on plant growth well beyond germination but also emphasize highly species-specific responses that highlight the need for further study.

Preparation of bacterial fertilizer from biogas residue after anaerobic co-digestion of kitchen waste and residual sludge.

Azotobacter chroococcum and Bacillus subtilis were selected as fermentation strains, and biogas residue after anaerobic digestion of kitchen waste and residual sludge was used as fermentation substrate. A single factor optimization test was used to optimize the solid-state fermentation parameters of biogas residue with the number of viable bacteria and the number of spores as indexes. The results showed that the optimum inoculation conditions involved the following: 55% initial moisture content, 15% initial inoculation amount, 30 ℃, and 1:1 initial inoculation ratio for 13days. Pot experiment showed that the prepared three kinds of bacterial fertilizers could not only effectively promote the growth of white clover, improve the composition of soil nutrients, but also change the structure of soil bacterial community, which is of great significance to the health of soil ecosystem in white clover.

Allelopathic effect of the methanol extract of the weed species-red sorrel (Rumex acetosella L.) on the growth, phytohormone content and antioxidant activity of the cover crop - white clover (Trifolium repens L.)

Allelopathy is a biological process in which one organism releases biochemicals that affect the growth and development of other organisms. The current investigation sought to determine the allelopathic effect of Rumex acetosella on white clover (Trifolium repens) growth and development by using its shoot extract (lower IC50 value) as a foliar treatment. Here, different concentrations (25, 50, 100, and 200 g/L) of shoot extract from Rumex acetosella were used as treatments. With increasing concentrations of shoot extract, the plant growth parameters, chlorophyll and total protein content of Trifolium repens decreased. On the other hand, ROS, such as O2.− and H2O2, and antioxidant enzymes, including SOD, CAT, and POD, increased with increasing shoot extract concentration. A phytohormonal study indicated that increased treatment concentrations increased ABA and SA levels while JA levels were reduced. For the identification of allelochemicals, liquid‒liquid extraction, thin-layer chromatography, and open-column chromatography were conducted using R. acetosella shoot extracts, followed by a seed bioassay on the separated layer. A lower IC50 value was obtained through GC/MS analysis. gammaSitosterol was identified as the most abundant component. The shoot extract of Rumex acetosella has strong allelochemical properties that may significantly impede the growth and development of Trifolium repens. This approach could help to understand the competitive abilities of this weed species and in further research provide an alternate weed management strategy.

Exogenous silicon induces aluminum tolerance in white clover (Trifolium repens) by reducing aluminum uptake and enhancing organic acid secretion.

Excessive aluminum (Al) in acidic soils is a primary factor that hinders plant growth. The objective of the present study was to investigate the effect and physiological mechanism of exogenous silicon (Si) in alleviating aluminum toxicity. Under hydroponic conditions, 4 mM Al significantly impeded the growth of white clover; however, pretreatments with 1 mM Si mitigated this inhibition, as evidenced by notable changes in growth indicators and physiological parameters. Exogenous silicon notably increased both shoot and root length of white clover and significantly decreased electrolyte leakage (EL) and malondialdehyde (MDA) content compared to aluminum treatments. This positive effect was particularly evident in the roots. Further analysis involving hematoxylin staining, scanning electron microscopy (SEM), and examination of organic acids (OAs) demonstrated that silicon relieved the accumulation of bioactive aluminum and ameliorated damage to root tissues in aluminum-stressed plants. Additionally, energy-dispersive X-ray (EDX) analysis revealed that additional silicon was primarily distributed in the root epidermal and cortical layers, effectively reducing the transport of aluminum and maintaining the balance of exchangeable cations absorption. These findings suggest that gradual silicon deposition in root tissues effectively prevents the absorption of biologically active aluminum, thereby reducing the risk of mineral nutrient deficiencies induced by aluminum stress, promoting organic acids exudation, and compartmentalizing aluminum in the outer layer of root tissues. This mechanism helps white clover alleviate the damage caused by aluminum toxicity.

Allelopathic effect of ragweed (Ambrosia artemisiifolia L.) on seed germination and early seedling growth of barley (Hordeum vulgare L.) and white clover (Trifolium repens L.)

Allelopathy is a unique phenomenon in nature that refers to direct or indirect, positive or negative, impact of one plant (including microorganisms, insects, and herbivores) on another plant through chemical secretions (allelochemicals). Ambrosia artemisiifolia (ragweed) is a well-known invasive plant possessing allelochemicals that have been found to inhibit the growth and development of plants in their immediate environment. This study aimed to determine the allelopathic impact of the aqueous leaf extract isolated from ragweed leaves (concentrated extract, 1:2, 1:4, and 1:8) on seed germination and early seedling growth of barley (Hordeum vulgare L.) and white clover (Trifolium repens L.). The examined aqueous extract of ragweed had a higher inhibitory effect on the germination of white clover seeds compared to barley. The germination of barley seeds was the lowest at the concentrated leaf extract (up to 70%), while the same process in barley seeds was not determined at this concentration. In the other treatments, germination was significantly lower in both examined species compared to the control. Shoot and root growth of both researched species was inhibited in all treatments compared to the control. The obtained results indicate that the aqueous ragweed extract significantly inhibits the growth of roots and shoots of both tested species, which increases the need for more intensive research on this topic.

Soil Application of Sewage Sludge Treated with Clay Minerals or Biochar and Its Effect on Soil Properties and White Clover’s (Trifolium repens L.) Growth and Arbuscular Mycorrhizal Fungal Root Colonization

From the perspective of finding new, more environmental-friendly methods for the stabilization of sewage sludge to be used in agriculture, sludge treated with 15% bentonite, vermiculite or biochar was investigated as a soil amendment for white clover (Trifolium repens L.) growth, by means of a pot experiment. The sludge treatments, which were applied to two soils (an acid and an alkaline soil), in three replications, were the addition of 2% (≈80 Mg ha−1) treated sludge with the clay minerals or biochar, as well as limed or untreated (air-dried) sludge (for comparison reasons). Additional treatments with inorganic fertilization or neither organic nor inorganic fertilization (control) were also included. The application of 2% sludge to both soils significantly increased salinity compared to the control, which remained below harmful levels for sensitive crops, except for the case of untreated sludge. Furthermore, it significantly increased the soil-available macronutrients N, P and K, and micronutrients Cu, Zn (several times, especially in the case of untreated sludge) and B (up to three times) compared with the control. Moreover, the pH of the acid soil was improved, except for the case of limed sludge, where an undesirable pH increase close to 8.5 was observed. Addition of the treated sludge with the clay minerals or biochar and untreated sludge to the acid and alkaline soil significantly increased the aboveground biomass yield of white clover by 117–233% and 114–153%, respectively, compared to the control, whereas limed sludge had no effect. Plant nutrient uptake increased as well. In general, the effect of sludge on soil microbiological properties and arbuscular mycorrhizal fungal root colonization was ambiguous. It was concluded that 2% soil addition of sewage sludge treated with 15% bentonite, vermiculite or biochar could improve soil fertility and enhance plant growth; however, caution is needed with respect to potential risks of soil salinization or Zn and B phytotoxicities.

Quantitative genetic analysis reveals potential to breed for improved white clover growth in symbiosis with nitrogen-fixing Rhizobium bacteria.

White clover (Trifolium repens) is integral to mixed pastures in New Zealand and temperate agriculture globally. It provides quality feed and a sustainable source of plant-available nitrogen (N) via N-fixation through symbiosis with soil-dwelling Rhizobium bacteria. Improvement of N-fixation in white clover is a route to enhancing sustainability of temperate pasture production. Focussing on seedling growth critical for crop establishment and performance, a population of 120 half-sibling white clover families was assessed with either N-supplementation or N-fixation via inoculation with a commercial Rhizobium strain (TA1). Quantitative genetic analysis identified significant (p < 0.05) family additive genetic variance for Shoot and Root Dry Matter (DM) and Symbiotic Potential (SP), and Root to Shoot ratio. Estimated narrow-sense heritabilities for above-ground symbiotic traits were moderate (0.24–0.33), and the strong (r ≥ 0.97) genetic correlation between Shoot and Root DM indicated strong pleiotropy or close linkage. The moderate (r = 0.47) phenotypic correlation between Shoot DM under symbiosis vs. under N-supplementation suggested plant growth with mineral-N was not a strong predictor of symbiotic performance. At 5% among-family selection pressure, predicted genetic gains per selection cycle of 19 and 17% for symbiotic traits Shoot DM and Shoot SP, respectively, highlighted opportunities for improved early seedling establishment and growth under symbiosis. Single and multi-trait selection methods, including a Smith-Hazel index focussing on an ideotype of high Shoot DM and Shoot SP, showed commonality of top-ranked families among traits. This study provides a platform for proof-of-concept crosses to breed for enhanced seedling growth under Rhizobium symbiosis and is informative for other legume crops.

GROWTH ANALYSIS OF WHITE CLOVER (Trifolium repens L.) AND INDIRECT METHODS TO ESTIMATE ITS FORAGE YIELD

Dry matter (DM) accumulation and its relationship to some indicators of physiological efficiency on white clover (Trifolium repens L.) growth was studied to determine the optimal harvesting time by season. The experiment was carried out at the Colegio the Postgraduados Campus Montecillo, Texcoco, Mexico. Twenty-four plots, each measuring 3.7 X 1.7 m, were used, and distributed in a completely randomized design with eight treatments and three replicates. The treatments consisted of weekly successive cuts during an eight-week sprouting cycle during the middle of each season of the year. The evaluated variables were dry matter accumulation, crop growth rate (CGR), intercepted radiation (IR), and plant height (cm) estimated through the ruler and rising plate meter methods. Most herbage accumulation (p ≤ 0.05) occurred at the eighth week of the spring (2,688 kg DM ha-1). Most CGR (p ≤ 0.05) occurred at the first week of the summer (84 kg DM ha-1 day-1). The largest IR occurred at the sixth and ninth week of the summer (100 %). Maximum height occurred at week eight of the summer (p ≤ 0.05), which was 32 and 23.3 cm for the ruler and the rising plate meter methods, respectively. Dry matter yield increased linearly due to the favorable climatic conditions during spring-summer, where there was a higher intercepted radiation and higher crop growth. The ruler method showed a higher coefficient compared to the ascending plate, so the ruler method for white clover can be recommended.

Assessment of graphene oxide toxicity on the growth and nutrient levels of white clover (Trifolium repens L.)

Carbon nanomaterials (CNMs) are novel engineered nanomaterials and have been used widely. Their toxic effects on terrestrial plants in soil matrix require careful investigation. In this study, white clover (Trifolium repens L.) was grown in a potted soil with graphene oxide (GO) at levels of 0.2%, 0.4% and 0.6% and the effects of GO on the growth and nutrient uptake of white clover were evaluated after 50 and 100 days of exposure. GO exposure showed adverse effects on seedling growth, photosynthetic parameters and nutrient uptake in shoots, and the effect was more significant with increasing concentration and exposure time. Compared with the control, GO at the highest level of 0.6% decreased plant height, leaf and stem dry weights, total chlorophyll content and net photosynthetic rate by 43.7%, 45.7%, 43.4%, 32% and 85.7%, respectively, after 100 d of exposure, and N, K, Cu, Zn, Fe, Mo, B, Si contents decreased by 19.5%, 20.1%, 12.6%, 25.0%, 12.9%, 26.0%, 18.9%, 23.0%, respectively. Furthermore, the electrolyte leakage, lipid peroxidation, reactive oxygen species, antioxidant enzyme activities were all increased by GO, especially at high dose and long exposure. These results indicate that GO can suppress plant growth by oxidative stress, photosynthesis inhibition, and nutrient imbalance.

Newly Isolated Paenibacillus monticola sp. nov., a Novel Plant Growth-Promoting Rhizobacteria Strain From High-Altitude Spruce Forests in the Qilian Mountains, China.

Species in the genus Paenibacillus from special habitats have attracted great attention due to their plant growth-promoting traits. A novel plant growth-promoting rhizobacteria (PGPR) species in the genus Paenibacillus was isolated from spruce forest at the height of 3,150 m in the Qilian Mountains, Gansu province, China. The phylogenetic analysis based on 16S rRNA, rpoB, and nifH gene sequences demonstrated that strain LC-T2T was affiliated in the genus Paenibacillus and exhibited the highest sequence similarity with Paenibacillus donghaensis KCTC 13049T (97.4%). Average nucleotide identity (ANIb and ANIm) and digital DNA–DNA hybridization (dDDH) between strain LC-T2T and P. donghaensis KCTC 13049T were 72.6, 83.3, and 21.2%, respectively, indicating their genetic differences at the species level. These differences were further verified by polar lipids profiles, major fatty acid contents, and several distinct physiological characteristics. Meanwhile, the draft genome analysis provided insight into the genetic features to support its plant-associated lifestyle and habitat adaptation. Subsequently, the effects of volatile organic compound (VOC) emitted from strain LC-T2T on the growth of Arabidopsis were evaluated. Application of strain LC-T2T significantly improved root surface area, root projection area, and root fork numbers by 158.3, 158.3, and 241.2%, respectively, compared to control. Also, the effects of LC-T2T on the growth of white clover (Trifolium repens L.) were further assessed by pot experiment. Application of LC-T2T also significantly improved the growth of white clover with root fresh weight increased over three-folds compared to control. Furthermore, the viable bacterial genera of rhizosphere soil were detected in each treatment. The number of genera from LC-T2T-inoculated rhizosphere soil was 1.7-fold higher than that of control, and some isolates were similar to strain LC-T2T, indicating that LC-T2T inoculation was effective in the rhizosphere soil of white clover. Overall, strain LC-T2T should be attributed to a novel PGPR species within the genus Paenibacillus based on phylogenetic relatedness, genotypic features, and phenotypic and inoculation experiment, for which the name Paenibacillus monticola sp. nov. is proposed.

Effects of compost, biochar and ash mixed in till soil cover of mine tailings on plant growth and bioaccumulation of elements: A growing test in a greenhouse

Mine closures necessitate vegetation restoration to cover tailings fields and reduce environmental risks. Sole use of forest soil as growth medium provides only low fertility and slow plant growth especially in the harsh boreal climate conditions. This preliminary study examines the feasibility of recyclable waste materials added to forest till soil for improving vegetation success on reclaimed mine tailings. One compost type, three biochar types (Bc1–3) and two ash types (Ash1-2) were studied for physical and chemical properties as well as their effects on the growth and element accumulation of timothy (Phleum pratense L.), white clover (Trifolium repens L.) and Scots pine (Pinus sylvestris L.) during one growing period in a greenhouse. Oxidized surface tailings soil and Ash2 were the finest media components while compost and Ash1 were the coarsest. Tailings soil also had the highest salt contents and electrical conductivity, while in till soil they were at the lowest levels. Timothy and white clover germinated well in moist pure tailings soil but grew poorest in it. White clover grew poorly also in pure till soil. Best biomass growth was in the mixture of till, compost and Bc2 (from sewage sludge and woodchips). Planted pine seedlings grew relatively well in all media during the first growing season but Ash1 (from wood and peat) tended to promote height growth and pure till soil root biomass. In media containing Ash1, pine tissues accumulated B, Ca, Mg, K, Na and S. Elevated As content in tailings soil accumulated in plant shoot tissues slightly; only in the old needles of pine were As levels elevated. The results suggest that till and tailings media with compost added as a nitrogen source can promote adequate plant growth during initial growing seasons. Suitable types of biochar and ash amendments can further expedite plant establishment.

Earthworm (Pheretima guillelmi)-mycorrhizal fungi (Funneliformis mosseae) association mediates rhizosphere responses in white clover

Earthworms and arbuscular mycorrhizal fungi (AMF) are beneficial organisms in the soil and play an important role in improving soil fertility and plant growth. The objective of this study was to analyze the response of single versus dual inoculation of earthworms (Pheretima guillelmi) and AMF (Funneliformis mosseae) on mycorrhizal growth, root morphology, and rhizosphere properties of white clover (Trifolium repens). Addition of earthworms significantly increased the degree of root AMF colonization, while decreased hyphal length and spore number in the soil. Single or dual inoculation of F. mosseae and P. guillelmi significantly increased root traits (total length, area, volume, and average diameter), soil phosphatase activities (acid, neutral, and alkaline), easily extractable and total glomalin-related soil protein content, the percentage of soil water-stable aggregates at the size of 2–4 mm, 1–2 mm and 0.5–1 mm, aggregate stability, Bray-P, and soil organic carbon (SOC) contents. Among them, the dual inoculation further amplified the effect on glomalin production, phosphatase activity, and aggregate stability, but did not show a superposition effect on root improvement, Bray-P, and SOC. Our study, hence, suggested that AMF and earthworms have synergistic roles in elevating rhizosphere properties vis-à-vis agronomic responses of white clover.

Evaluation of Clover Lawns as a Substitute of Common Grass Lawns in Landscape to Reduce the Moving Costs

Introduction Turfgrasses, as one of the important components of urban landscapes, have played a vital role in this regard. Turfgrasses have provided functional, recreational, and aesthetic benefits to urban landscapes. Multiple benefits of turf are well documented such as recreational health, enhanced water infiltration, erosion control, mediation in heat-island effects and reduction in nutrient leaching. But the main problems of turfgrass development are the cost of turfgrass seeds, maintenance costs such as moving, as well as the high water requirement in arid and semi-arid regions. Thus, the reduction of lawn culture in the landscape is one of the decision has taken in parks and green spaces organization of Tehran, Isfahan and even Mashhad. Materials and Methods So the aim of this experiment was to compare three common turfgrasses with two clover varieties as turf replacement to reduce landscape maintenance cost specially moving cost. So, some growth factors of clover lawn: Trifolium repens var. Calway and Trifolium repens var. Pipolina (micro clover) and three turfgrasses of Festuca arundinacea L. and Lolium perenneL. and commercial sport turf mixture (from NAk-Nederland Ltd.) were compared together. This research project was conducted in randomized complete block design with three replications in the research field of the Department of Horticultural Science and Landscape Engineering‚ Agricultural Faculty‚ Ferdowsi University of Mashhad‚ Mashhad‚ Iran, during 2016 and 2017. The site (59o 38′ E and 36o 16 ′ N; elevation 989 m) is located in an arid and semi- arid region with mean annual rainfall 233.8 mm and long term averages of maximum and minimum temperature are 22.5 oC and 9.3 oC‚ respectively. Turfgrass plots were established by directly sowing the seeds in April, 2016. The planting rate of the seedling considering their pure live seeds (PLS) were 45 g.m-2 for Lolium perenne, 34 g.m-2 for Festuca arundinacea, 6.5 g.m-2 for Trifolium repens, 5.5 g.m-2 for micro clover and 39 g.m-2 for commercial mixture of sport turf. The plots were 1 m2 (1m×1m) in size and were prepared after plowing and leveling the soil. The seeds were hand sown and covered with a thin layer of leaf compost and sand. Results and Discussion According to the results in the first evaluation of emergence percentage, Lolium perenne had the highest emergence percentage. But, after 36 days from culture, all plants had 92-98 % coverage which did not have any significant difference among grasses with clover lawns. In terms of density, uniformity and weed density, there was no significant difference between the studied plants. In the other hands, white clover showed the best quality after clipping in both years. At the point of growth index, which have done in this experiment by measuring height and dry weight of clipping, grass lawns had the higher growth index in compered to clover lawn in both years. Festuca arundinacea and Lolium perenne had the highest growth index and white and micro clover had the lowest growth. Also, with air warming, Festuca arundinacea became dominated plant in height and clipping dry weight. In July, Festuca arundinacea produced the highest clipping dry weight by 40 gr.m-2, Lolium perenne (19.52), commercial sport turf (15.68), white clover (6.24) and micro clover (0.36) gr.m-2. Conclusions One of the problems of landscape is reduction of maintenance costs such as moving. So, the low growth of white and micro clover is a positive factor in reduction of the moving costs than turfgrasses. Also, the coverage and proper density of clover lawns are similar to grass lawns and did not have a significant difference with them. The character of low growth can be effective in reduction of irrigation costs in white and micro clover, which requires more research and examination in future. This is a positive point in the white clover and micro clover that do not need to move or cut every months. Almost, clover moving is recommended for removing their flower. Therefore, it is recommended to use white and micro clover as a replacement with less maintenance costs in landscape. Finally, the results of cultivation of grass and clover as monoculture in this study can be used to produce clover-grass mixtures suitable for the climate of our country (arid and semi-arid regions), instead of importing turf mixtures from European countries.

Staphylococcus hominis YJILJH and Staphylococcus epidermidis YJ101 promote the growth of white clover (Trifolium repens L.) by increasing available phosphorus

Phosphorus is critical for the regulation of numerous metabolic processes in plants, and so understanding the mechanisms by which plants acquire phosphorus is important. Phosphate solubilizing bacteria (PSB) are thought to promote the uptake of phosphorus by plants. The effects of PSB YJILJH and YJ101 strains on the growth of white clover (Trifolium repens L.) were investigated through the production of the plant hormone IAA and the change of available phosphorus content in the soil. Two strains of YJILJH and YJ101 were selected from the rhizosphere soil of white clover among rows of apple orchards. Combined with 16S rDNA and next-generation sequencing (NGS), the strains were identified as Staphylococcus hominis and Staphylococcus epidermidis, respectively. The two strains had strong phosphate solubilizing ability, and had solubilization index (SI) values of 4.39 and 3.95, respectively. The dissolved amounts of soy lecithin were 351.2 and 387.3 mg/L in liquid medium, respectively. The amount of Ca3(PO4)2 dissolved reached 506.3 and 789.8 mg/L, respectively. The pot experiment showed that the biomass of white clover after adding the two strains increased by 21.17% and 36.49%, the total phosphorus (TP) content increased by 28.87% and 30.41%, and the soil available phosphorus (AP) content increased by 86.63% and 47.16%, respectively. This study also found that both strains can produce IAA content reaching 55.95 and 54.33 pmol / L in 72 h. In regard to relative gene expression, trpD and trpA genes were expressed in the different treatments, while ipdC was only expressed in Luria-Bertani broth (LB broth) and NBRIP media (+ soy lecithin). It is speculated that the pathway of IAA synthesis by both strains may be related to the tryptophan side chain pathway and the indole-3-pyruvate pathway. The IAA produced by the two bacteria strains is an important reason to promote the growth of white clover and participate in the process of reducing the environmental pH of the growth medium.

White Clover

The document provides information on white clover, a cool-season legume that acts like an annual in Florida. It discusses the superior feed value of white clover-grass mixtures, recommended varieties, establishment practices, management recommendations for grazing, irrigation, reseeding, summer live-over, and fall regrowth. The document also addresses factors affecting white clover growth, such as nematodes, viral diseases, drainage ditches, and irrigation availability. It emphasizes careful site selection for successful white clover cultivation.

Nitrogen uptake and growth of white clover inoculated with indigenous and exotic Rhizobium strains

Little information is available on investigating the effectiveness of indigenous and exotic rhizobia in enhancing nitrogen uptake and growth of white clover. This study aimed to evaluate the nitrogen fixation effectiveness of native rhizobia isolated from white clover grown in Taiwan as compared to an exotic strain, Rhizobium leguminosarum bv. trifolii BCRC 14266. Indigenous rhizobia were isolated from nodules in roots of white clover, and 16S rRNA gene sequences were used to identify their taxonomy. To compare the symbiotic effectiveness of indigenous and exotic rhizobia, white clover plants were inoculated respectively with two indigenous isolates (CHB 1120 and CHB 1121), BCRC 14266, and a non-inoculated control. Based on 16S rRNA gene sequences, CHB 1120 and CHB 1121 could be identified as Rhizobium species. Compared with the non-inoculated control and BCRC 14266, CHB 1120 and CHB 1121 significantly increased the dry weight of shoots and roots at 75 days after planting (DAP). Additionally, CHB 1120 and CHB 1121 significantly enhanced the amount of chlorophyll present in leaves estimated by SPAD readings, increasing nitrogen contents in shoots by 38.1 and 49.2%, respectively. In comparison with BCRC 14266, CHB 1120 and CHB 1121 significantly increased the nodule number and nitrogenase activity at both 45 and 75 DAP. In conclusion, the two indigenous strains significantly outperform the exotic strain and non-inoculated control in promoting nitrogen uptake and growth of white clover.

Indole-3-acetic acid improves drought tolerance of white clover via activating auxin, abscisic acid and jasmonic acid related genes and inhibiting senescence genes

BackgroundAuxin may have a positive effect on plants under drought stress. White clover is widely cultivated and often prone to water shortages. In the present study, we investigated the effects of exogenous indole − 3-acetic acid (IAA) on growth and physiological changes of white clover under drought stress condition. The contents of endogenous IAA and other hormones including ABA, CTK, JA, GA, IAA, and SA were assayed. Moreover, expressions of auxin-responsive genes, drought-responsive genes and leaf senescence-associated genes were detected in response to exogenous IAA.ResultsCompared to control, drought stress alone significantly diminished stem dry weigh, relative water content (RWC) and total chlorophyll content (Chl). Exogenous IAA treatment significantly increased RWC and Chl, whereas L-AOPP treatment drastically decreased stem dry weight, RWC and Chl under drought stress condition. Additionally, exogenous IAA treatment significantly increased ABA content and JA content, up-regulated expression of auxin responsive genes (GH3.1, GH3.9, IAA8), drought stress responsive genes (bZIP11, DREB2, MYB14, MYB48, WRKY2, WRKY56, WRKY108715 and RD22), and down-regulated expressions of auxin-responding genes (GH3.3, GH3.6, IAA27) and leaf senescence genes (SAG101 and SAG102) in the presence of PEG. Contrarily, L-AOPP treatment significantly reduced contents of ABA, GA3 and JA, down-regulated expressions of GH3.1, GH3.9, IAA8, bZIP11, DREB2, MYB14, MYB48, WRKY2, WRKY56, WRKY108715, ERD and RD22, and up-regulated SAG101 and SAG102.ConclusionsExogenous IAA improved drought tolerance of white clover possibly due to endogenous plant hormone concentration changes and modulation of genes involving in drought stress response and leaf senescence. These results provided useful information to understand mechanisms of IAA improved drought tolerance in white clover.

Responses of ryegrass, white clover, soil plant primary macronutrients and microbial abundance to application of anaerobic digestates, cattle slurry and inorganic N-fertiliser

This study compared the fertiliser effects of different types of liquid anaerobic digestates on the growth of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), and on soil's primary plant macronutrients and microbial abundance. A factorial design with seven fertilisers and one control (five liquid anaerobic digestates, undigested cattle slurry, calcium ammonium nitrate (CAN) 27% N, and no fertiliser) and four plant schemes (monocultures of perennial ryegrass and white clover, a mix of both, and bare soil) were tested. Plant (forage yield, leaf area index (LAI), canopy height and root mass) and soil (concentrations of total N, Morgan's extracted P and K) responses were measured, as well as soil bacterial/archaeal (16S) and fungal (18S) gene copy numbers (GCN). Digestates and cattle slurry with different chemical compositions, when balanced in terms of the quantity of dry matter applied, had comparable forage yield responses (p > 0.05), with higher yields than CAN mostly observed in ryegrass and mixed vegetation (p < 0.05). The presence of white clover contributed to higher soil N (p < 0.05). Soil available P was increased by biofertiliser applications (p < 0.05). Soil available K was influenced by the interaction between biofertiliser and type of plant (p < 0.05), with ryegrass/mixed swards showing lower K concentrations than white clover and bare soil. Soil bacterial (16S) GCN responded to the interaction between fertiliser/vegetation (p < 0.05), while archaeal (16S) and fungal (18S) GCN only to the type of vegetation (p < 0.05). The application of anaerobic digestates showed low direct impacts on the microbial GCN of the soil, mostly influenced by type of vegetation. The biofertilisers showed comparable performances and effects, despite substantial differences between their chemical compositions, indicating a possible complex matrix of interactions between fertiliser-plant-soil-environment.

English

Glyphosate, 2,4-D, imazethapyr and paraquat + diuron were studied in greenhouse experiments at four application rates in order to evaluate their effects on white clover (Trifolium repens L.) growth and aerial shoot injury at three different phenological stages. Herbicide-induced foliar injury on white clover ranged from no symptoms to early chlorosis, leaf necrosis, stunted growth and death depending on herbicide rate and white clover phenological stage. Imazethapyr showed the highest selectivity at the three-leaf trifoliate stage. Seedlings treated with glyphosate at 1080 g a.i. ha-1, however, were dead at 21 days after application (DAA). White clover herbicide tolerance increased with plant age, and selectivity was found to be affected as herbicide rate increased. Paraquat + diuron caused the highest levels of white clover phytotoxicity and plant death. The herbicides studied showed potential to be used as selective products on white clover depending on their rates, as well as the timing of their application onto white clover depending furthermore, on the specificity weeds infesting white clover fields. Key words: Glyphosate, 2,4-D, Paraquat + diuron, Imazethapyr, Trifolium repens.

Alleviation of Drought Stress in White Clover after Inoculation with Arbuscular Mycorrhizal Fungi

White clover is extremely susceptive to drought stress (DS), while it is not clear whether arbuscular mycorrhizal fungi (AMF) enhance drought tolerance of the plant. This study was carried out to evaluate effects of two AMF species, Funneliformis mosseae and Paraglomus occultum, on flavonoid, soluble protein, proline, and nutrient uptake in roots of white clover under well-watered (WW) and DS conditions. Root colonization by F. mosseae and P. occultum was heavily decreased by 7-week DS treatment. Mycorrhizal plants showed considerably greater biomass production in shoot, root, and total (shoot+root) than non-mycorrhizal plants, irrespective of soil water status. AMF inoculation led to significantly higher root soluble protein and proline accumulation under WW and DS and root flavonoid level under DS, regardless of AMF species. Root N, P, K and Cu concentrations were dramatically increased by mycorrhization under WW and DS, and root Ca, Mg, Fe, and Mn levels were significantly higher in AMF plants than in non-AMF plants under WW. It concluded that AMF strongly enhanced plant growth and drought tolerance of white clover by greater nutrient absorption and protective substances (soluble protein, proline, and flavonoid) accumulation.