Root DM Research Articles

Root exudate fingerprint of Brachiaria humidicola reveals vanillin as a novel and effective nitrification inhibitor.

Introduction: Biological Nitrification Inhibition (BNI) is defined as the plant-mediated control of soil nitrification via the release of nitrification inhibitors. BNI of Brachiaria humidicola (syn. Urochloa humidicola) has been mainly attributed to root-exuded fusicoccane-type diterpenes, e.g., 3-epi-brachialactone. We hypothesized, however, that BNI of B. humidicola is caused by an assemblage of bioactive secondary metabolites. Methods: B. humidicola root exudates were collected hydroponically, and metabolites were isolated by semi-preparative HPLC. Chemical structures were elucidated by HRMS as well as 1D and 2D NMR spectroscopy. Nitrification inhibiting potential of isolated metabolites was evaluated by a Nitrosomonas europaea based bioassay. Results and discussion: Besides previously described brachialactone isomers and derivatives, five phenol and cinnamic acid derivatives were identified in the root exudates of B. humidicola: 2-hydroxy-3-(hydroxymethyl)benzaldehyde, vanillin, umbelliferone and both trans- and cis-2,6-dimethoxycinnamic acid. Notably, vanillin revealed a substantially higher nitrification inhibiting activity than 3-epi-brachialactone (ED50 ∼ 12.5μg·ml-1, ED80 ∼ 20μg·ml-1), identifying this phenolic aldehyde as novel nitrification inhibitor (NI). Furthermore, vanillin exudation rates were in the same range as 3-epi-brachialactone (1-4μg·h-1·g-1 root DM), suggesting a substantial contribution to the overall inhibitory activity of B. humidicola root exudates. In relation to the verification of the encountered effects within soils and considering the exclusion of any detrimental impact on the soil microbiome, the biosynthetic pathway of vanillin via the precursor phenylalanine and the intermediates p-coumaric acid/ferulic acid (precursors of further phenolic NI) might constitute a promising BNI breeding target. This applies not only to Brachiaria spp., but also to crops in general, owing to the highly conserved nature of these metabolites.

118 Nutrient Cycling Potential from Manure from Heifers Fed Four Bermudagrass Cultivars

Abstract Maintenance of pastures for grazing accounts for $132.50/animal in the United States (23% of operating costs), and pasture nutrient input represents the single greatest influence in productivity per unit area. Cultivar differences in the forage offered to cattle have the potential to manifest differences in digestive efficiency, resulting in different nutrient excretion profiles. The objective of this study was to assess the growth potential and incorporation of N, P, and K into forage material from manure from cattle fed one of four bermudagrass (Cynodon dactylon [L.] Pers.) cultivars. Ruminally fistulated heifers (n = 4) were assigned randomly to one of four bermudagrass cultivars (Coastal, Russell, Tifton 44, or Tifton 85) for four 30-d in vivo periods (21-d adaptation and 9-d collection). On d 23, total fecal collections were subsampled from each heifer. As a hierarchical addition, a controlled greenhouse experiment was conducted for each period [15 pots per period; 5 manure treatments (four bermudagrass diets plus a negative control) × 3 replications]. Manure was added to 4.58 L pots based on stocking rate estimates for Central Alabama (1,110 kg/ha). The pots were seeded with bermudagrass (cv. Giant) as an indicator for forage nutrient uptake. At harvest (d 70), herbage, root, and soil samples were collected. Herbage and root samples were assayed for CP. Soil samples were assayed for pH, N, P, K, Mg, and Ca. Data were analyzed using SAS v. 9.4. There was no effect of manure treatment on herbage (P = 0.88) or root DM yield (P =.00;.54 and.73 g/pot, respectively). Similarly, there was no effect of manure treatment on soil pH (P = 0.18; 5.5), P (P = 0.78; 24.2 kg/ha), or K (P = 0.42;56.7 kg/ha). Results are interpreted to mean that, regardless of the cultivar effects on ruminal digestive dynamics, there is little to no effect of the resulting manure on subsequent forage production and nutrient uptake.

Exogenous melatonin induces tolerance to drought stress damage in seedlings and soybean plants

Melatonin (ML) is an indolamine that regulates a wide range of physiological processes as growth of roots and shoots, antioxidant enzyme activity, seed germination, photosynthetic efficiency promoting stress tolerance in plants, mitigating the harmful effects of abiotic stress. Effects of pretreatment of soybean (Glycine max (L.) Merr.) seeds with 10, 30, 60 and 90 μM ML were evaluated in seedlings under osmotic stress measuring germination speed index, and root protrusion, growth, and DM. Under osmotic stress, ML increased germination speed index at 10 (239%), 30 (194%) and 60 μM ML (189%); 5th-day root protrusion by 290%, 214%, 185% and 85% (10, 30, 60, and 90 μM ML respectively). The application of 10 (328%), 30 (224%), 60 (265%), 90 μM ML (129%) increased root length, followed by root DM in stressed seedlings. Drought stress reduced photosynthetic efficiency, increased ROS, and reduced antioxidant enzymatic activities in soybean. In a second experiment, well-watered (100% field capacity) (WW) and drought stressed (DS) soybean plants received 30 and 50 μM ML. Melatonin increased rate of CO2 assimilation and net photosynthetic rate at 30 μM ML (WW) in 28% (2 d after application) and 50 μM ML (DS) in 48% (5 d after application). Melatonin increased antioxidant enzymes activity (catalase and peroxidase) in plants under drought stress. The ML application enhanced leaf area in WW plants, however decreased in stressed plants. An increased number of seeds, pod numbers, total seed mass, root DM were observed under WW. Drought stress increased numbers of seeds (27%), pod numbers (33%) and total seeds mass (27%) with 30 μM ML. These results demonstrated that ML mitigated negative effects produced by drought on germination and growth of soybean seedlings, and acted as a drought tolerance inducer, improving yield under stress condition.

Silicon induces changes in the antioxidant system of millet cultivated in drought and salinity

In recent years, benefits of silicon in plants grown under stress conditions have been reported. The objective of the research was to evaluate the response at a physiological and biochemical level of millet (Panicum miliaceum L.) to fertilization with Si under controlled stress conditions during vegetative stage, drought, salinity and the control (without stress). After stress, shoot and root length, DM content, peroxidase (POD) and catalase (CAT) activity, proline, H2O2 and Si content, seed yield and germination percentage were measured. Drought and salinity significantly decreased shoot (24%, 21%) and root (30% in drought) development, weight (36%, 29%) and seed number (30%, 21%) per plant. Application of Si significantly increased seed number (289) and seed weight (1.20 g) in the control plants, increased seed weight (0.83 g) in plants under drought and germination percentage (99%) in plants under salinity. Silicon increased 2.1 times POD activity in drought, 1.4 times in salinity and control plants; CAT activity increased 10.6 times in salinity and 1.7 times in control plants. Silicon decreased 10 times proline levels in plants under drought; in salinity and control, proline content increased 1.3 times with Si and H2O2 levels decreased in these treatments. The Si content in plants fertilized with Si under drought, salinity and control was 6%, 3.54% and 5.45% respectively. In conclusion, Si can improve plant stress tolerance by stimulating POD and CAT activity, and regulating proline levels, allowing it to improve the production and physiological seed.

Dynamics of sugar beet root, crown and leaves mass with regard to plant densities and spring nitrogen fertilization

This study analyzes the dynamics of sugar beet root, crown, and leaves fresh and dry matter (FM and DM, respectively) accumulation per plant and their mass ratio at different plant densities and nitrogen fertilization. The biennial field trials were set as four different planting densities (60,000, 80,000, 100,000 and 140,000 plants ha-1) and three methods of nitrogen application in spring: control – without nitrogen fertilization (N0), presowing only (N1), and presowing with topdressing (N2). Close to the maturation, the mean DM of the whole root, crown, and leaves on September 20, 2014 amounted to 28.8, 7.3 and 4.0 t ha-1, respectively, whereas it amounted to 20.7, 4.1 and 2.3 t ha-1 in 2015, respectively. Moreover, with regard to the plant densities, the highest root DM was at 140,000 and 100,000 (31.6 t ha-1 in 2014 and 22.4 t ha-1 in 2015), compared to the wider plant densities of 80,000 and 60,000 plants ha-1 (22.4 t ha-1 in 2014 and 18.1 t ha-1 in 2015). Nitrogen fertilization positively influenced on dry matter accumulation, but it was different within the years. On September 20, 2014, a presowing fertilization (N1) increased the root DM by 17%, compared to the control, whereas in 2015 the presowing with topdressing (N2) increased the root DM by 30%. The root-to-leaves FM ratio amounted to 1:3.9 on May 30, 2014, whereas it amounted to 1:0.1 on September 20, 2014. The leaves FM was at its largest on June 20, 2015, when the root-to-leaves ratio amounted to 1:1.1, and gradually decreased to 1:0.1 on September 20, 2015.

Effects of Different Growing Media on Yield and Growth Parameters of Potato Minitubers (solanum Tuberosum L.)

ABSTRACTSeed potatoes (Solanum tuberosum L.) are increasingly produced by minitubers originated from tissue culture techniques to eliminate the chance of infections by viruses. The aim of this study was to evaluate the suitability of several potting media for minituber production in the greenhouse environment. Six growing media treatments were used in a randomized complete block design with four replications. Treatments included perlite, soil, perlite + vermiculite (1:1 v/v), perlite + peat moss (1:1, v/v), perlite + soil (1:1, v/v), perlite + soil + composted cattle manure (4:3:3 v/v), and perlite + soil + vermicompost (4:3:3v/v). All treatments except treatments that contained composted cattle manure or vermicompost were subjected to daily application of nutrient solution. Growing media were analyzed for a selected number of physical and chemical properties. Tuber yield and yield parameters were determined 75 days after planting. Leaf area, shoots, and root DW and FW and concentrations of N in roots and shoots were measured at tuber bulking stage. The highest value of particle density and bulk density and the lowest value of porosity and EC were obtained for the media that contained Perlite. The greatest value of leaf chlorophyll index throughout the growing period was observed at perlite + soil + composted cattle manure and perlite + soil + vermicompost, likely due to excess availability of N. The maximum contents of N in the shoot root and tubers were observed in perlite + soil + composted cattle manure. Fresh and dry minituber yield and number of minituber per m2 shoot and root FM and DM yield were greater in growing media without soil than the containing Compound with soil. The fertigated perlite + peat moss (1:1, v/v) resulted in the greatest yield among treatments likely due to desirable EC, pH, and porosity. This treatment can be recommended as a suitable media for the production of potato minitubers in greenhouse environment.Abbreviations B: Boron; Ca: Calcium; CEC: Cation exchangeable capacity; Cu: Copper; Db: Bulk density; Dp: Particle density; DM: dry matter; DW: dry weight; EC: Electrical conductivity; Fe: Iron; FW: fresh weight; K: Potassium; LAI: leaf area index; Mg: Magnesium; Mn: Manganese; Mo: Molybdenum; N: Nitrogen; n: Porosity; Na: Sodium; OC: Organic carbon; P: Phosphorus; S: Sulfur; Zn: Zinc.

Effect of carbon source derived from macrophytes on microbial denitrification in constructed wetlands: Role of plant species

Organic matters derived from macrophytes can serve as carbon source in microbial denitrification. In this study, three macrophyte species, namely of macrophytes, Phragmites australis (PA), Acorus calamus (AC), and Scirpus tabernaemontani (ST), were planted in constructed wetlands. The root exudates were extracted, and their effects on microbial denitrification were investigated. Results showed that root exudate release rates were the highest in AC (17.4 μg·g−1 root dry mass [DM]·h−1), followed by ST (15.9 μg·g−1 root DM·h−1) and PA (10.6 μg·g−1 root DM·h−1). The NO3− transformation efficiency was positively correlated to the amount of root exudation (PA: 9.72%, ST: 33.81%, and AC: 37.88%). However, the contributions of root exudation for bacterial denitrification followed the trend PA (54.76%) > ST (53.19%) > AC (29.19%). The copy numbers of NO3−-reducing bacteria gene in PA, ST, and AC were 1.62 × 109, 2.15 × 109, and 2.18 × 109 copies·g−1 soil, which was positively correlated to the root exudation.

Organic matter input influences incidence of root rot caused by Rhizoctonia solani AG8 and microorganisms associated with plant root disease suppression in three Australian agricultural soils

Soil-borne plant root disease caused by Rhizoctonia solani AG8 is prevalent in cereal farming systems worldwide, particularly in semiarid agricultural regions. A controlled environment study was undertaken using three Australian soils to test the hypothesis that OM input from crop roots and residues decreases infection by Rhizoctonia root rot via biologically mediated disease suppression. The specific aim was to determine the relative effect of two different OM inputs (wheat stubble or roots) on (a) abundance (DNA) of the pathogen R. solani AG8 and soil organisms putatively associated with disease suppression, and (b) incidence of Rhizoctonia root rot infection of wheat seedlings (% root infected). An increase in microbial biomass carbon (C) following OM amendment indicated a potential for enhanced general biological disease suppression in all soils. OM inputs also increased the population size (DNA) of certain bacteria and fungi putatively associated with specific suppression for Rhizoctonia root rot, suggesting a C resource-mediated change in microbial functions related to disease suppression. There were no significant changes to measured pathogens with stubble addition. However, OM inputs via root residues and rhizodeposits from living roots increased the populations of R. solani AG8 and Gaeumannomyces graminis var. tritici so that in subsequently planted wheat there was greater incidence of root disease infection and reduced plant shoot and root DM compared with that following OM input as stubble. Differences between soils in terms of plant and soil organism responses to each OM input suggest that abiotic factors modify the development of biological disease suppression and the expression of the disease.

Growth and N2fixation in Saline and/or Water Stressed Sesbania aculeata Plants in Response to Silicon Application

This study aimed at investigating the effects of silicon (Si) on dry matter yield (DM), N uptake and N2-fixation in Sesbania aculeata grown under water stress and/or salt stress using 15N. Irrigation regime had two levels, well watered (I1) and water stress (I2), and was made either with saline (Salt+) or with non saline water (Salt-). Silicon had positive impacts on DM of sesbania grown under water stress. Only root DM increased as a result of Si addition in well watered plants grown under salt stress or under both stress conditions. Moreover, root/shoot ratio was higher in Si-fed plants, under stresses, than those of non-fertilized plants. N yield significantly increased in salt stressed sesbania plant grown under well watering regime. However, the positive effect of Si in plants subjected to both stresses was only occurred in roots. In addition, Si application enhanced soil (Ndfs), fertilizer (Ndff) and N2-fixation (Ndfa) under salt and/or water stress conditions. The beneficial effect of Si on the amount of Ndfa was more pronounced under stress conditions. In the whole plant, significant effects of Si were obtained in water-stressed, salt-stressed and both water and salt-stressed treatments, where amounts of Ndfa increased by 8, 39 and 39%, respectively, as compared to their controls. Overall, response to Si was expressed more clearly when sesbania plants were subjected to stresses. Silicon may be considered as an important element for the symbiotic performance in legumes by mitigating the adverse effects of abiotic stresses.

Effects of NPK source on the dry matter partitioning in cool season C3-cereals (wheat, rye, barley, and oats) at various growth stages

ABSTRACTDry matter (DM) partitioning into root, leaf, stem, shoot dry weight plant−1 response in four cool season C3-cereals viz. wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.) and oats (Avena sativa L.) was investigated at 30, 60 and 90 days after emergence (DAE) under eight nitrogen, phosphorus and potassium (NPK) sources: S1 = 20-20-20, S2 = 20-27-5, S3 = 7-22-8, S4 = 10-10-10-20S, S5 = 11-15-11, S6 = 31-11-11, S7 = 24-8-16, and S8 = 19-6-12 in pot experiment at Dryland Agriculture Institute, West Texas A&M University, Canyon, Texas, USA during winter 2009-10. A considerable variation in DM partitioning into various plant parts was observed in the four crop species at different growth stages and NPK source. At 30 DAE, 27% of the total DM per plant (TDMPP) was partitioned into roots and 73% into shoots (19% stems + 54% leaf). Only16 % of the TDMPP was partitioned into roots and 84% into shoots (18 % stem + 66 % leaf) at 60 DAE. At 90 DAE, 29% of TDMPP was partitioned into roots and 71 % into shoots (33 % stems + 38 % leaf) at 90 DAE. Percent DM partitioning into stems ranked first (33%) at 90 DAE > at 30 DAE (19%) > at 60 DAE (18 %). With advancement in crops age, DM partitioning into various crop parts increased. The root DM plant−1 (RDMPP) increased from 11.5–722 mg plant−1; stem DM plant−1 (STDMPP) from 8.3–889.0 mg plant−1; leaf DM plant−1 (LDMPP) from 23.1–1031.0 mg plant−1; shoot DM plant−1 (SHDMPP) from 31.3–1921 mg plant−1, and TDMPP increased from 42.9–2693.0 mg plant−1 at 30 and 90 DAE, respectively. Because of the higher N contents in S7 (24:8:16) and S6 (31:11:11) reduced the DM partitioning into various plants parts as well as TDMPP at all three growth stages. The adverse effects of S6 and S7 on DM partitioning was more on oats > rye > wheat > barley. The S4 with 10:10:10 (NPK) and :20S was not toxic at 30 DAE, but at 60 and 90 DAE it became toxic that adversely affected the DM partitioning as well as TDMPP probably may be due its high sulfur (20%) content which lacking in other NPK sources. The DM partitioning to various parts of barley and wheat was more than oats and rye at different growth stages (barley > wheat > rye > oats). Since the DM portioning values were determined on the average of five plants in pot experiment under organic soil at field capacity; in case of field experiments more research is needed on various crop species/varieties under different environmental conditions particularly under moisture stress condition.

Differences in maize physiological characteristics, nitrogen accumulation, and yield under different cropping patterns and nitrogen levels

Intercropping and N fertilization play an important role in increasing crop yield. In order to further understand the advantage mechanism of intercropping and the effect of increasing N application on the advantage effect of intercropped crop, a field experiment was conducted to investigate the effects of different cropping patterns (i.e. M, maize monoculture; I1, maize-cotton intercrop; I2, maize-soybean intercrop) and N fertilization levels (N1, 100 kg ha-1; N2, 200 kg ha-1; N3, 300 kg ha-1; N4, 400 kg ha-1) on maize (Zea mays L.) Results showed that intercropping and increasing N application could enhance green leaf area per maize plant and chlorophyll content, and differences in green leaf area per plant and chlorophyll content between intercropping and monoculture under N1 were significant. Intercropping and increasing N application could improve maize photosynthetic characters, but their effects would be decreased with increasing N fertilization level. Root bleeding sap rate and root DM of maize were also obviously affected by intercropping and N fertilization, and the differences in root bleeding sap rate and root DM between I2 and M under N1 and N2 were significant. Compared to M, under N1, N2, N3, and N4, I2 increased grain N content by 12.8%, 6.3%, 2.7%, 1.5%, respectively. Intercropping and increasing N application could increase maize yield, and the difference in yield between I2 and M under N1 was significant. All the findings suggest that intercropping and increasing N application can improve maize physiological characters and increase maize root DM, N accumulation and yield, but their effects will be decreased with increasing N fertilization level.

Phosphorus absorption and use efficiency by Lotus spp. under water stress conditions in two soils: A pot experiment

The response to P and water deficiencies of forage Lotus species has not been sufficiently studied in the Andisol and Vertisol soil orders in Chile’s marginal areas. A pot experiment under cover was carried out between October 2007 and March 2008 to study the effects of P and soil water availability (SWA) on DM production, P absorption, and P use efficiency in Lotus spp. The experiment included three Lotus ( L. corniculatus L., L. tenuis Waldst. & Kit. ex Willd., and L. uliginosus Schkuhr) species, two soils (Andisol and Vertisol), two contrasting P levels (low and high), and two SWA levels (10% and 100%). A completely randomized design with a 3 × 2 × 2 × 2 factorial arrangement with four replicates was used. Accumulated shoot and root DM, P absorption and efficiency, and arbuscular mycorrhizal (AM) colonization were measured. Phosphorus absorption was significantly higher in Andisol with 100% SWA and high P in the three species, which was reflected in P efficiency where the species exhibited higher P absorption efficiency (PAE) and P utilization efficiency (PUE) with low P, and mean of the three species with low P and high SWA. When the P level was low, L. uliginosus showed the highest PAE and L. corniculatus exhibited the highest PUE. Phosphorus efficiency was also influenced by AM colonization since on the average mycorrhization in the three species was significantly higher in the low P treatments. Differences existed among species for DM production, response to P, P absorption, PAE, and PUE.

Nitrogen nutrition of Cyperus laevigatus and Phormium tenax: Effects of ammonium versus nitrate on growth, nitrate reductase activity and N uptake kinetics

The effects of inorganic nitrogen (N) nutrition (NH4+, NO3− or both) at equimolar (0.5mM) concentration on growth, biomass allocation, mineral element concentration, N-uptake kinetics and nitrate reductase activity were assessed in hydroponically grown Cyperus laevigatus and Phormium tenax. Both species grew well with both NH4+ and NO3− as the sole N source, but the mean growth rate of C. laevigatus (RGR=0.12d−1) was significantly higher than that of P. tenax (RGR=0.02d−1). However, the RGR of C. laevigatus was higher when supplied with NH4+, either alone or in combination with NO3−, than when supplied with NO3− alone, whereas the RGR of P. tenax was indifferent to nitrogen source. The nitrogen uptake rate of C. laevigatus was generally higher (2–3-fold for NH4+ and 4–14-fold for NO3−) than that of P. tenax in concert with its higher growth rate. Both species had higher uptake capacity and higher affinity for NH4+ than for NO3−. The mean maximum uptake velocity (Vmax) for NH4+ was 99 and 41μmolg−1 root DM h−1 for C. laevigatus and P. tenax, respectively, as opposed to a Vmax for NO3− of 24 and 3.4μmolg−1 root DM h−1 for C. laevigatus and P. tenax, respectively. P. tenax had significantly lower affinities for both NH4+ and NO3− than C. laevigatus indicating that P. tenax are adapted to sites with relatively high N availability, as opposed to C. laevigatus, which via its high-affinity uptake systems can grow at sites with lower N availability. Both shoots and roots of both species had nitrate reductase activity, particularly when plants were fed with NO3−. P. tenax seemed to be more sensitive to NH4+ nutrition than C. laevigatus since tissue concentrations of mineral elements were lower in roots of plants supplied with NH4+. Our results suggest that the indifference to N nutrition provides C. laevigatus and P. tenax with the ability to grow well in periodically inundated areas with fluctuating and variable N sources. However, C. laevigatus may be better adapted than P. tenax to grow in permanently inundated soils with high NH4+ concentrations, whereas P. tenax may be better adapted to grow at high NO3− condition.

Effect of Moringa Extract on Growth and Yield of Maize and Common Beans

An evaluation on the potential benefit of using Moringa oleifera leaf extract as a growth hormone on common beans (Phaseolus vulgaris) and maize (Zea mays) was done. Trials were carried out in the greenhouse and field. In the greenhouse, five treatments were used: control (M0, only water applied), second control (ME, only ethanol applied), moringa extract (in 80% ethanol) applied (on leaves) once at 2 weeks from emergence (M1), moringa extract applied at 2 and 4 weeks from emergence (M2), and moringa extract applied every 2 weeks to maturity from two weeks from germination (M3). The same treatments were adopted in the field except ME, which was considered unnecessary after observing the results of the greenhouse experiment. Results showed that moringa extract increased growth and yield of beans in both greenhouse and field, and of maize in the field. However, the extract showed no significant effect on DM yield, root DM or plant height of maize in the greenhouse. The highest DM and root weight, height and crop yields in greenhouse and field experiments for beans, and for maize in the field only, were obtained at M3. The study recommends the application of extract at M3.

Effects of water and nitrogen supply on growth, water-use efficiency and mucilage yield of isabgol (Plantago ovata Forsk)

A two-way factorial experiment based on a randomized complete design (RCD) with four replications was used to compare four levels of N supply including control (N 0 ), 60(N 60 ), 120(N 120 ) and 180(N 180 ) mg N per Kg soil and four different water supply including 100(I 100 ), 80(I 80 ), 60(I 60 ) and 40(I 40 ) % FC on growth, water-use efficiency and mucilage yield of isabgol. Under I 40 , higher N addition led to a significant decrease in root and shoot DM. N addition increased root and shoot biomass especially in I 80 treatment followed by I 60 . The highest (1.71 g plant -1 ) and the lowest (0.42 g plant -1 ) seed yield of isabgol observed in I 100 at N 120 and I 40 at N 120, respectively. The concentration of soluble sugar increased with N supply at I 100 and I 40 . Water stress led to an increase in proline levels, particularly in the N supply treatments. The addition of N tended to reduce the positive effect of water stress on proline content. Seed water use efficiency (WUEg) of isabgol decreased with the increase in drought stress. N supply significantly increased WUEg from N 0 to N 120 with no significant differences between N 60 and N 120 and then significantly decreased by supplying N 180 . Mucillage water use efficiency (WUEm) is also increased linear in all watering regime at all N supply.

Impact of phosphorus mineral source (Al–P or Fe–P) and pH on cluster-root formation and carboxylate exudation in Lupinus albus L.

Lupinus albus L. were grown in rhizoboxes containing a soil amended with sparingly available Fe–P or Al–P (100 μg P g−1 soil/resin mixture). Root halves of individual plants were supplied with nutrient solution (minus P) buffered at either pH 5.5 or 7.5, to assess whether the source of mineral-bound P and/or pH influence cluster-root growth and carboxylate exudation. The P-amended soil was mixed 3:1 (w/w) with anion-exchange resins to allow rapid fixation of carboxylates. Treatments lasted 10 weeks. Forty percent and 30% of the root mass developed as cluster roots in plants grown on Fe–P and Al–P respectively, but cluster-root growth was the same on root-halves grown at pH 5.5 or 7.5. Mineral-bound P source (Al– or Fe–P) had no influence on the types of carboxylates measured in soil associated with cluster roots—citrate (and trace amounts of malate and fumarate) was the only major carboxylate detected. The [citrate] in the rhizosphere of cluster roots decreased with increased shoot P status (suggesting a systemic effect) and also, only for plants grown on Al–P, with decreased pH in the root environment (suggesting a local effect). In a separate experiment using anion exchange resins pre-loaded with malate or citrate, we measured malate (50%) and citrate (79%) recovery after 30 days in soil. We therefore, also conclude that measurements of [citrate] and [malate] at the root surface may be underestimated and would be greater than the 40- and 1.6-μmol g−1 root DM, respectively estimated by us and others because of decomposition of carboxylates around roots prior to sampling.

야생화초지 혼파조합을 위한 몇 가지 잔디형 및 야생화 초종의 초기생육과 개화특성에 관한 연구

본 연구는 야생화 초지조성을 위한 잔디형 목초 및 야생화초종의 선정과 혼파조합구성에 대한 기초자료를 탐색하고자 몇 가지 잔디형 목초와 야생화초종을 공시하여 초기생육, 경엽 및 근중, 건물수량, 개화특성 및 기호성 등을 비교분석하였다. 공시초종은 잔디형 목초 5종{Kentucky bluegrass(Midnight), tall fescue(Millennium), perennial ryegrass(Palmer III), redtop(Barricuda) 및 creeping bentgrass(Crenshaw)}과 야생화 11종{Chrysanthemum leucanthemum L., Coreopsis lanceolata L., Rudbeckia bicolor Nutt., Dianthus chinensis L., Chrysanthemum lindicum L., Lotus corniculatus var. Japonicus Regel, Veronica linariaefolia Pallas, Aster koraiensis Nakai., Chrysanthemum zanadskii var. latilobum(Maxim.) Kitamura, Lythrum anceps Makino 및 Iris nertschinskia. Lodd}을 공시하였으며, 충남대학교 농과대학 초지시험포장에서 2005년 1월부터 2006년 12월까지 수행하였다. 공시된 잔디형 목초 중에서 상대적으로 야생화와 혼파가능성이 큰 초종은 Kentucky bluegrass이었으며, Kentucky bluegrass에 비하여 상대적으로 초기생육이 왕성하고 경엽과 근중이 높아 야생화초지를 조성하는 데 유리할 것으로 보이는 야생화는 Chrysanthemum leucanthemum L., Lotus corniculatus var. Japonicus Regel, Chrysanthemum zawadskii var. latilobum (Maxim) Kitamura 및 Lythrum anceps Makino 등으로 조사되었다. 이들 야생화는 꽃색, 개화시기 및 개화지속기간 등이 서로 중복되지 않았으며 가축에 의한 기호성도 대체적으로 양호한 결과를 보였다. 따라서 야생화초지의 조성을 위해서는 잔디형 목초는 야생화와의 경합력이 낮은 초종을, 반대로 야생화는 경합에서 유리한 초종을 선발하되 개화특성이 서로 다른 야생화를 다양화하여 혼파조합을 구성하는 것이 중요하다고 판단된다. The purpose of this study was to compared the early growth pattern, stem, leaf and root weight, DM yield, flowering characteristics and preference for selection of turf type grasses and wild flower species in mixtures combination for wildflower pasture. The experimental design included five species of turf grasses and 11 species of wildflower : turf type grass species{Kentucky bluegrass(Midnight), tall fescue(Millennium), perennial ryegrass(Palmer III), redtop(Barricuda) and creeping bentgrass(Crenshaw)}, wildflower species {Chrysanthemum leucanthemum L. Coreopsis lanceolata L., Rudbeckia bicolor Nutt.., Dianthus chinensis L., Chrysanthemum lindicum L., Lotus corniculatus var. Japonicus Regel, Veronica linariaefolia Pallas, Aster koraiensis Nakai., Chrysanthemum zanadskii var. latilobum (Maxim.) Kitamura, Lythrum anceps Makino and Iris pallassi var. chinensis Lodd}. The field trials were carried out on the experimental pasture plots of Chungnam National University from January 2005 to December 2006. The appropriate species of turf grass which have a mixture possibility with wildflower are thought to be Kentucky bluegrass. Compared with Kentucky bluegrass, on the other hand, species such as Chrysanthemum leucanthemum L., Lotus corniculatus var. Japonicus Regel, Chrysanthemum zanadskii var. latilobum Maxim.) Kitamura and Lythrum anceps Makino have shown advantageous aspects of fast early growth pattern and highly weights of stem, leaf and root. Futhermore, these wild flowers were in harmony and no overlap on flower color, flowering periods and flowering longevity, and highly preference by Korean native goats. For the establishment of wildflower pasture in Korea, therefore, it is important to select the appropriate species of turf glasses, which have a weak competition against wild flowers, and then to make mixture combination of those turf glasses with the various wild flowers which have a strong competition against turf glasses but have a different anthesis characteristics among themselves.

Potential of nine multipurpose tree species to reduce saline groundwater tables in the lower Amu Darya River region of Uzbekistan

This paper evaluates the potential of nine multipurpose tree species for afforestation of degraded land in the Khorezm region, Central Asia, particularly their suitability for biodrainage i.e., lowering the elevated groundwater table through the transpirative capacity of plantations. For this purpose water use (WU), water use effi- ciency (WUE) and tree physiological factors influencing transpiration were assessed during two consecutive years. Mean daily leaf transpiration differed significantly among the species and ran- ged during the seasons from 4.5-5.2 mmol m -2 s -1 for Prunus armeniaca L. to 4.5-10 mmol -2 s -1 for Elaeagnus angustifolia L. WU differences were triggered by species physiological features such as capability of water uptake by roots. Transpiration rates and the length of fine roots correlated highly (r = 0.7). Correlations of leaf transpiration rates with leaf area were weaker (r = 0.6). No correla- tions were found between salt content in plants and water uptake under conditions of slight-to- moderate rootzone soil salinity. Values of WUE per root and shoot DM were similar averaging, respectively, 0.2 and 0.3 g DM g -1 water for two- year-old trees, and decreased with age. In addition to WU characteristics, also salinity tolerance, growth rate and the ability to produce fodder and fuelwood must be considered during species selection. Regarding these features, the N-fixing E. angustifolia ranked the highest, combining high WU, fast growth and production of nutritious feed. Examined Populus spp. and Ulmus pumila L. ranked lower but still represented potential candidates for biodrainage purposes. Typical fruit species in the region such as P. armeniaca and Morus alba, showed low biodrainage potential.

Kura Clover Early Growth Is Comparable to That of White Clover When Not Nitrogen Limited

ABSTRACT Kura clover (Trifolium ambiguum M.B.) is a forage legume whose use is currently restricted by establishment difficulties. In this study, we evaluated the effects of rhizobial strain selection and nitrogen (N)-supply on early growth of Kura clover. There were eight treatments in total: non-inoculated, non-N-fertilized Kura clover; Kura clover fertilized or not with N-fertilizer and inoculated with either a commercial rhizobial strain (UMR6015) or a new rhizobial strain (CT1-2); non-inoculated, non-N-fertilized white clover (Trifolium repens L.); and white clover inoculated with rhizobial strain UMR6906 fertilized or not with N-fertilizer. Plants were collected every two weeks starting on the fourth week after seeding for a total of four harvests. Total dry matter (TDM), foliage DM (FDM), and root DM (RDM), plant height, and leaf and nodule number were recorded at each sampling; percent N, total N, and leaf area were determined 10 weeks after seeding. All inoculated Kura clover plants supplied with inorganic N produced similar TDM and FDM, but greater RDM than similarly treated white clover. Kura clover inoculated with CT1-2 also produced TDM and FDM similar to that of inoculated non-N-fertilized white clover, which was not the case with UMR6015. Kura clover produced significantly fewer leaves than white clover; however, it had greater individual leaf weight. Kura clover plants inoculated with UMR6015 produced 140% more nodules than those inoculated with CT1-2 or than white clover; however, most were small and ineffective. Total N content of non-N-fertilized Kura clover plants inoculated with CT1-2 was 70% greater than those inoculated with UMR6015, and similar to that of inoculated non-N-fertilized white clover plants, suggesting similar N2 fixation levels. Results demonstrate that the use of UMR6015 may not maximize Kura clover early growth in N-limited environments. If not N-limited, Kura clover early FDM and TDM accumulation is comparable to that of white clover.

Isolation and identification of an EPS-producing Rhizobium strain from arid soil (Algeria): characterization of its EPS and the effect of inoculation on wheat rhizosphere soil structure

The production of exopolysaccharides (EPSs) by bacterial populations in the rhizosphere has been demonstrated to contribute to water and nutrient uptake by plant roots through the modification of the physical properties of rhizosphere soil. We report here the characterization of a new EPS produced by a bacterial strain (KYGT207) isolated from an arid soil in southern Algeria (Gassi Touil), and the effect of inoculation of this strain on soil physical properties in the rhizosphere of Triticum durum L. Strain KYGT207 was assigned to the genus Rhizobium by 16S ribosomal DNA sequencing and belongs to a new species closely related to Rhizobium sullae. The EPS produced by this strain was found to be composed of glucose (Glc), galactose (Gal), and mannuronic acid (ManA) in a molar ratio of 2:1:1. The primary structure of the EPS was determined by sugar analysis, 1D and 2D NMR spectroscopy, consisting of a tetrasaccharide repeating unit with the following original structure: [Display omitted] . A rheological analysis showed that this EPS could be considered as a thickening agent with polyelectrolyte properties. Inoculation of wheat plantlets with strain KYGT207 caused significant promotion of plant growth (+85% for shoot dry mass and +56% for root dry mass), a significant increase in root-adhering soil (RAS) dry mass (dm) per root dm (RAS/RT) up to 137%, and in RAS aggregate water stability. We demonstrate that EPS-producing bacteria were present in sandy soils subjected to water stress and that EPS-producing Rhizobium populations play an important role in the rhizosphere through their contribution to soil aggregation.