Comparison Of Roots Research Articles

New insights into the role of the root system of epiphytic bromeliads: comparison of root and leaf trichome functions in acquisition of water and nutrients.

In epiphytic bromeliads, the roots were previously considered to be poorly functional organs in the processes of absorption and metabolization of water and nutrients, while the leaves were considered to always act as protagonists in both functions. More recent discoveries have been changing this old view of the root system. In this review, we address previous ideas regarding the function performed by the roots of epiphytic bromeliads (mere holdfast structures with low physiological activity) and the importance of a reduced or lack of a root system for the emergence of epiphytism. We present indirect and direct evidence that contradicts this older hypothesis. Furthermore, the importance of the root absorptive function mainly for juvenile tankless epiphytic bromeliads and the characteristics of the root absorption process of adult epiphytic tank bromeliads are discussed thoroughly from a physiological perspective. Finally, some factors (species, substrate, environmental conditions) that influence the absorptive capability of the roots of epiphytic tank bromeliads are also be considered, highlighting the importance that the absorptive role of the roots has for the plasticity of bromeliads that live on trees, which is an environment characterized by intermittent availability of water and nutrients. The roots of tank-forming epiphytic bromeliads play important roles in the absorption and metabolization of nutrients and water. The importance of roots is greatest for juvenile tankless bromeliads since the root is the main absorptive organ. In larger plants with a tank, although the leaves become the protagonists in the resource acquisition process, the roots complement the absorptive function of the leaf trichomes, resulting in improved growth of these bromeliad. The physiological and biochemical properties of the processes of absorption and distribution of resources in the tissues appear to differ between absorption by trichomes and roots.

Comparison of root and canal anatomy of taurodont and normal molar teeth: A retrospective cone-beam computed tomography study

ObjectiveTo determine the frequency of taurodontism in maxillary and mandibular molar teeth using cone-beam computed tomography (CBCT) and to compare the differences in root and canal morphologies between taurodont and nontaurodont molars. MethodsCBCT images of 1200 patients were analysed. First, the frequency of taurodontism in maxillary and mandibular molar teeth was calculated. The Shifman and Chanannel taurodontic index was used to diagnose taurodontic teeth. Subsequently, the root and canal morphologies were compared with those of 250 normal teeth randomly selected from each tooth group. P < 0.05 values were considered significant in statistical tests. The chi-square test was used for differences according to sex, age and tooth position. Z-test was used for comparing percentages between independent groups. ResultsThe occurrence rate of taurodontism was 7.78 % and 12.72 % in maxillary first and second molar teeth, respectively, and 1.99 % and 2.41 % in mandibular first and second molar teeth, respectively. Women had more taurodont teeth than men. The frequency of root fusion was greater in taurodont maxillary molars. The percentage of C-shaped roots in taurodont mandibular second molars was significantly higher than in cynodonts (19.15 % and 8.4 %, respectively). ConclusionsTaurodont teeth show wide variations in root and canal morphology. The degree of change in morphology is associated with the severity of taurodontism.

Reciproc Blue, K3XF ve ProTaper Universal Retreatment Nikel-Titanyum Rotary Eğelerinin Kök Kanal Dolgu Materyalini Uzaklaştırma Kabiliyetinin Karşılaştırılması

Reciproc Blue, K3XF ve ProTaper Universal Retreatment Nikel-Titanyum Rotary Eğelerinin Kök Kanal Dolgu Materyalini Uzaklaştırma Kabiliyetinin Karşılaştırılması

Effect of potassium application in drought-stressed tobacco (Nicotiana rustica L.) plants: Comparison of root with foliar application

Effect of potassium (K) application through leaves (LA) or roots (RA) was studied in tobacco plants grown under K deficiency and drought stress conditions. Application of K was effective in improving the shoot growth only under drought conditions, whereas root biomass and length responded under both watering regimes. Under drought conditions, photosynthesis and transpiration activities increased upon K application leading to a reduced water use efficiency. Both RA and LA increased the leaf water potential, relative water content and turgor under both well-watered and drought conditions; RA was more effective than LA in the recovery of leaf turgor. Analyses of water relation parameters in different aged leaves showed lower susceptibility of the middle-aged leaves to both K deficiency and drought stresses than the upper and lower leaves; this phenomenon was accompanied by a more conservative control of water loss in the middle-aged leaves. In contrast, proline was accumulated in the young leaves, and K application increased it further. Although various organic osmolytes were accumulated under the combinative effect of K deficiency and drought stress, they did not exceed the amounts found in the control (well-watered +K) plants and were merely a result of the concentration effect. Collectively, our results revealed that the majority of leaf biochemical responses to drought stress are developmentally regulated processes. In addition, the alleviating effect of both RA and LA despite higher water loss indicated that an improved stomatal function upon K application allowed carbohydrates synthesis, thus, enhancing plant growth under water stress.

Comparison of Root Cause Analysis Software for Investigating Patient Safety Incidents

Root Cause Analysis (RCA) has been widely used as a structured approach to investigate patient safety incidents. RCA helps identify what, how, and why something happened, therefore preventing recurrence of incidents. Since many quality tools can be used during RCA, various formats of RCA exist. If RCAs are performed incorrectly or incompletely, they are likely to produce unusable results. To address this issue, RCA software has been developed. The use of RCA software in investigating patient safety incidents may offer several advantages, such as potential reduction in learning time, shortening of the analytic process, facilitation of collection, analysis, and presentation of data and production of meaningful RCA reports. We introduced six healthcare RCA software and compared characteristics. Results from this study will enable the RCA team to choose proper RCA software. Key words: Root cause analysis ㆍ Software ㆍ Patient safety

Uptake and utilization of applied phosphorus in oilseed rape (Brassica napus L. cv. Hayola) plants at vegetative and reproductive stages: Comparison of root with foliar phosphorus application

ABSTRACTIn order to compare plants’ response to phosphorus (P) application through roots and leaves, oilseed rape (Brassica napus L. cv. Hayola) plants were cultivated until vegetative or reproductive stages and were pretreated with an adequate (+P) or low (−P) supply of P. Thereafter, these plants were treated with 0.3 mM P as sodium dihydrogen phosphate (NaH2PO4) either through roots (root application, RA) or leaves (leaf application, LA). Shoot biomass was observed to be suppressed under −P conditions at both stages, whereas root growth was comparatively improved in −P plants at the vegetative stage but not at the reproductive stage. Both RA and LA were able to compensate for the growth of vegetative shoot and roots at both stages; however, LA reduced P and dry matter partitioning into the fruits. At the vegetative stage, recovery of applied P was similar between RA and LA treatments, and was extensive in −P plants compared with the +P ones. At the reproductive stage, in contrast, significantly lower recovery of P was observed likely due to the lower capacity of leaves for P absorption and/or their lower re-translocation ability through the phloem. Data of P utilization efficiency showed that −P plants, at both vegetative and reproductive stages, efficiently use leaf-applied P for biomass production when compared with the +P plants. Activity of acid phosphatase was sharply inhibited by RA in −P plants, whereas it was preferably increased by LA in both +P and −P plants. Results indicated that under P-deficiency conditions, plants had higher ability to utilize foliar-applied P, and in contrast to RA, LA may enable plants for a continuous higher capacity of P uptake from P-deficient soil; however, RA was superior to LA in terms of fruit growth.

Microbiota and Host Nutrition across Plant and Animal Kingdoms.

Plants and animals each have evolved specialized organs dedicated to nutrient acquisition, and these harbor specific bacterial communities that extend the host's metabolic repertoire. Similar forces driving microbial community establishment in the gut and plant roots include diet/soil-type, host genotype, and immune system as well as microbe-microbe interactions. Here we show that there is no overlap of abundant bacterial taxa between the microbiotas of the mammalian gut and plant roots, whereas taxa overlap does exist between fish gut and plant root communities. A comparison of root and gut microbiota composition in multiple host species belonging to the same evolutionary lineage reveals host phylogenetic signals in both eukaryotic kingdoms. The reasons underlying striking differences in microbiota composition in independently evolved, yet functionally related, organs in plants and animals remain unclear but might include differences in start inoculum and niche-specific factors such as oxygen levels, temperature, pH, and organic carbon availability.

Comparison of root and foliar applications of potassium silicate in potentiating post‐infection defences of melon against powdery mildew

The application of silicon to the roots or leaves reduces the severity of powdery mildew (Podosphaera xanthii) in melon but the latter treatment is less effective. This study compared key biochemical defence responses of melon triggered by P. xanthii after root or foliar treatment with potassium silicate (PS). Treatments consisted of pathogen‐inoculated or mock‐inoculated plants supplied with PS via roots or foliarly, as well as a non‐treated control. The activity of defence enzymes and the concentration of phenolic compounds, lignin and malondialdehyde were determined from leaf samples at different time points after inoculation. Pathogen‐inoculated plants irrigated with PS showed both an accumulation of silicon and primed defence responses in leaves that were not observed in pathogen‐inoculated plants either sprayed with PS or not treated. These responses included the anticipated activity of peroxidase and accumulation of soluble phenols, the activation of chitinase and repression of catalase, and the stronger activation of superoxide dismutase, peroxidase and β‐1,3‐glucanase. Moreover, the lignin concentration increased in response to inoculation, whereas the malondialdehyde concentration decreased. For the foliar treatment, however, only an increase in lignin deposition was observed compared with the control plants. The results show that silicon strongly plays an active role in modulating the defence responses of melon against P. xanthii when supplied to the roots as opposed to the foliage.

Comparison of Root - Crown Lengths and Occlusal Contacts in Patients with Class-III Skeletal Relationship, Anterior Open-bite and High Mandibular Plane Angle

Comparison of Root - Crown Lengths and Occlusal Contacts in Patients with Class-III Skeletal Relationship, Anterior Open-bite and High Mandibular Plane Angle

Aerenchyma formation and increased accumulation of free proline in roots of xerophytic Aloe vera L. cultured in nutrient solutions

Aloe vera L. is a xerophyte with a crassulacean acid metabolism pathway. Due to its importance in traditional medicine, healthcare, cosmetics and food products, aloe production is currently at an accelerated pace worldwide. Field production, however, has been limited by its sensitivity to chilling temperature and also by low yield and low plant quality. To overcome these limitations, this study tested the possibility of aloe cultivation in solution culture in a protected environment. Chinese Aloe or Buyecheng Aloe, both are A. vera, and were grown in four solution media or one of the media at different temperatures and pH levels. Time of primary root appearance and/or root growth was quantified. To identify possible mechanisms underlying aloe adaptation to aquatic stress, Chinese aloe were grown in a developing solution culture system and also in soil for 60 days and microstructure, ultra structure, genomic deoxyribonucleic acid (DNA) profile, free proline and protein contents of Chinese aloe roots adapted to aquatic stress were compared to those grown in soil. Results showed that aloes could be aquatically cultivated even though it is a xerophyte. Nutrient solutions, solution pH and cultivation temperature affected root initiation and root growth. Microstructure and ultra structure comparisons of roots produced in solution to roots grown in soil suggested that aloes adapted to aquatic stress by the formation of aerenchyma. Genomic DNA fragmentation of roots formed in solution showed apparent DNA ladders in the adaptive roots, suggesting that the aerenchyma formation was through programmed cell death. Meanwhile, free proline and protein contents in aquatic roots were significantly higher than those of roots grown in soil. As far as known, this is the first documentation of aerenchyma formation in a succulent crassulacean acid metabolism (CAM) plant for adaptation to aquatic stress. The formation of aerenchyma is structure along the increased of proline accumulation metabolically and could be the mechanisms underlying aloe adaptation to aquatic stress.

Semi‐dominant mutations in the CC‐NB‐LRR‐type R gene, NLS1, lead to constitutive activation of defense responses in rice

In this study, we characterized the semi-dominant mutant nls1-1D (necrotic leaf sheath 1) of rice, which displays spontaneous lesions, specifically on leaf sheaths, with a developmental pattern. nls1-1D plants also exhibited constitutively activated defense responses, including extensive cell death, excess hydrogen peroxide and salicylic acid (SA) accumulation, up-regulated expressions of pathogenesis-related genes, and enhanced resistance to bacterial pathogens. Map-based cloning revealed that NLS1 encodes a typical CC-NB-LRR-type protein in rice. The nls1-1D mutation causes a S367N substitution in the non-conserved region close to the GLPL motif of the NB domain. An adjacent S366T substitution was found in another semi-dominant mutant, nls1-2D, which exhibited the same phenotypes as nls1-1D. Combined analyses of wild-type plants transformed with the mutant NLS1 gene (nls1-1D), NLS1 RNAi and over-expression transgenic lines showed that nls1-2D is allelic to nls1-1D, and both mutations may cause constitutive auto-activation of the NLS1 R protein. Further real-time PCR analysis revealed that NLS1 is expressed constitutively in an age-dependent manner. In addition, because the morphology and constitutive defense responses of nls1-1D were not suppressed by blocking SA or NPR1 transcript accumulation, we suggest that NLS1 mediates both SA and NPR1-independent defense signaling pathways in rice.

A proteomic and phosphoproteomic analysis of Oryza sativa plasma membrane and vacuolar membrane

Proteomic and phosphoproteomic analyses of rice shoot and root tonoplast-enriched and plasma membrane-enriched membrane fractions were carried out to look at tissue-specific expression, and to identify putative regulatory sites of membrane transport proteins. Around 90 unique membrane proteins were identified, which included primary and secondary transporters, ion channels and aquaporins. Primary H(+) pumps from the AHA family showed little isoform specificity in their tissue expression pattern, whereas specific isoforms of the Ca(2+) pump ECA/ACA family were expressed in root and shoot tissues. Several ABC transporters were detected, particularly from the MDR and PDR subfamilies, which often showed expression in either roots or shoots. Ammonium transporters were expressed in root, but not shoot, tissue. Large numbers of sugar transporters were expressed, particularly in green tissue. The occurrence of phosphorylation sites in rice transporters such as AMT1;1 and PIP2;6 agrees with those previously described in other species, pointing to conserved regulatory mechanisms. New phosphosites were found in many transporters, including H(+) pumps and H(+):cation antiporters, often at residues that are well conserved across gene families. Comparison of root and shoot tissue showed that phosphorylation of AMT1;1 and several further transporters may be tissue dependent.

Ray Structure in Root- and Stem-Wood of Larix Decidua: Implications for Root Identification and Function

Differences in ray structure between root- and stem-wood of softwoods can cause confusion in identifying roots using keys based on stem-wood anatomy. Comparison of root- and stem-wood rays of Larix decidua showed root-wood had fewer ray tracheids, taller, wider but shorter ray parenchyma cells, and larger cross-field pits than stem-wood. The implications of these differences are considered in relation to the identification and function of roots.

Fine root biomass, necromass and chemistry during seven years of elevated aluminium concentrations in the soil solution of a middle-aged Picea abies stand

Toxic effects of aluminium (Al) on Picea abies (L.) Karst. (Norway spruce) trees are well documented in laboratory-scale experiments, but field-based evidence is scarce. This paper presents results on fine root growth and chemistry from a field manipulation experiment in a P. abies stand that was 45 years old when the experiment started in 1996. Different amounts of dissolved aluminium were added as AlCl3 by means of periodic irrigation during the growing season in the period 1997–2002. Potentially toxic concentrations of Al in the soil solution were obtained. Fine roots were studied from direct cores (1996) and sequential root ingrowth cores (1999, 2001, 2002) in the mineral soil (0–40 cm). We tested two hypotheses: (1) elevated concentration of Al in the root zone leads to significant changes in root biomass, partitioning into fine, coarse, living or dead fractions, and distribution with depth; (2) elevated Al concentration leads to a noticeable uptake of Al and reduced uptake of Ca and Mg; this results in Ca and Mg depletion in roots. Hypothesis 1 was only marginally supported, as just a few significant treatment effects on biomass were found. Hypothesis 2 was supported in part; Al addition led to increased root concentrations of Al in 1999 and 2002 and reduced Mg/Al in 1999. Comparison of roots from subsequent root samplings showed a decrease in Al and S over time. The results illustrated that 7 years of elevated Altot concentrations in the soil solution up to 200 μM are not likely to affect root growth. We also discuss possible improvements of the experimental approach.

POTENTIAL FOR GREENHOUSE AEROPONIC CULTIVATION OF URTICA DIOICA

Resent studies investigating aeroponic cultivation of medicinal plants have provided encouraging results for increasing yields, shortening time to maturity, and improving consistency and overall quality of produce over field production. The goal of the current study was to determine the applicability of aeroponic technology for the cultivation of the traditionally field grown herbaceous medicinal plant Urtica dioica. In addition, we investigated if control of nutrient delivery and repeated harvesting practices could be utilized to increase and direct yield of desired plant parts. Comparison of root and shoot dry weights between treatments revealed; (1) U. dioica cultivated in soil-less medium yielded equal shoot biomass and greater root biomass than aeroponically cultivated plants, (2) potassium and phosphorus ratios within the nutrient solution had no significant impact on yield or biomass allocation, and (3) multiple harvesting of aeroponic roots and shoots yielded greater total biomass of both roots and shoots than a multi-crop replanting strategy. Results suggest aeroponic technology could be a powerful tool for the cultivation U. dioica as well as a variety of other important herbaceous medicinal plants. However, further optimization of the plant growing environment is required to maximize and direct growth.

A comparison of root and stem lodging risks among winter wheat cultivars

Plant characters that determine stem and root lodging were measured on 15 winter wheat cultivars at three UK sites between 2000 and 2002. A model of lodging was used to estimate stem failure wind speeds (resistance to stem lodging) and anchorage failure wind speeds (resistance to root lodging). The degree and type of natural lodging was also recorded in the plots and this correlated well with the stem and anchorage failure wind speeds. Only a weak correlation (R2=0·33) was observed between the stem and anchorage failure wind speeds for the 15 cultivars. This can be explained by the absence of genetic correlation between the plant characters that determine the stem and anchorage strength. There was a significant interaction between type of lodging (stem or root) and cultivar for failure wind speed (P&lt;0·001). This showed that the difference between the resistances for root and stem lodging was not the same for all cultivars. Separate classifications for the stem and root lodging resistance of cultivars are developed that would allow the most appropriate crop management to reduce the risk of both types of lodging. Significant differences were found between cultivars for all lodging-related plant characters (P&lt;0·05). These resulted in the cultivar range of the anchorage failure moment to be 110% of the overall mean. Stem failure moment, shoot and plant base bending moments had ranges of 37–49% of their overall means. Breeders should select for wide, deep root plates and wide stems with a high stem wall failure yield stress for the greatest improvement in lodging resistance.

Comparison of root and mycorrhizal characteristics in primary and secondary rainforest on a metamorphic soil in North Queensland, Australia

ABSTRACTRoot biomass, root lengths, and mycorrhizal associations were compared in a series of primary and Acacia-dominated secondary rainforest stands on nutrient-poor, red podzolic soils developed from low grade Palaeozoic metasediments. Five soil cores to 200 mm depth were collected at random locations from each of 20 sites. Ten of these sites were in 20–25 m high closed secondary forest (30–40 y old) dominated by Acacia aulacocarpa and ten sites were located in primary, selectively-logged, rainforest (28–32 m tall). Arbuscular mycorrhizas were the only form of association found in the primary forest sites. Ectomycorrhizas dominated the secondary forest sites although arbuscular mycorrhizas were also present. The primary forest sites had significantly higher root biomass (34.4 ± 17.8 t ha-1) and root length (33,400 ± 3,200 km ha-1) than the secondary forests (11.6 ± 4.6 t ha-1 and 25,200 ± 4,800 km ha-1 respectively), and this was interpreted as a reflection of the greater allocation of biomass to roots necessary to support the greater above ground biomass. The specific root length in the secondary forest (340 ± 119 cm g-1) was twice that of the primary forest (154 ± 65 cm g-1) indicating that the trees in the secondary forests achieved a degree of soil exploration which was comparable to that in the primary forest with less than half the biomass allocation to roots. The dominance of ectomycorrhizas in the secondary forest was associated with the prevalence of Acacia aulacocarpa, and the results cannot be extended to other secondary forests in the region. The implications that the dominant ectomycorrhizal associations have for the patterns of successional development and the patterns of species colonization in these Acaria-dominated secondary forests are discussed.

A comparison of root and shoot competition between spring cereals and Avena fatua L.

Summary: Résumé: ZusammenfassungTwo cultivars of each of three spring cereals (wheat, barley and oats) were grown with Avena fatua in a box experiment, where the effects of root and shoot competition were separated using soil and aerial partitions. Measures of resource complementarity (RYT) and of the relative severity of competition indicated that competition for soil resources, particularly nitrogen, was more severe than competition for aerial resources, i.e. light. When both root and shoot competition occurred, oats and barley were generally more competitive than wheat, but there were significant differences in competitive ability between cultivars of all three cereals. Although competition between cereals and A. fatua occurred predominantly below‐ground, the various cultivars only differed slightly in root competitive ability against weeds. Nitrogen fertilizer did not significantly change the ranking of competitive abilities of the cultivars. Although shoot competition had less effect than root competition, the various cereals differed markedly in shoot competitive ability. The two oat cultivars, and the barley cultivar Egmont, had higher shoot competitive abilities than the two wheat cultivars or the barley cultivar Goldmarker. There was little evidence that differences in shoot competitive ability were due to differences in plant height. Une comparaison de la competition racinaire et aerienne entre les cereales de printemps et Avena fatua L.Deux cultivars de chacune des 3 céréales de printemps (blé, orge et avoine) ont été cultivés avec de l'Avena fatua dans des boites expérimentales ou les effets de la compétition aérienne et ceux de la compétition racinaire étaient séparées en utilisant des partitions de sol et d'air. Des mesures de complémentarité de ressources (RYT) et de la sévérité relative de la competition ont montré que la compétition pour les ressources du sol, en particulier l'azote, était plus forte que la compétition pour les ressources aériennes comme la lumière. Quand à fois on avait une compétition aérienne et racinaire, l'avoine et l'orge étaient généralement plus compétitives que le blé, mais il y avait des différences significatives dans l'aptitude à la compétition entre les cullivars des 3 céréales. Bien que la compétition enlre céréales et A. fatua soit apparue pour la majeure partie sous le sol, les différents cultivars ont seulement légèrement différé dans leur aptitude à la competition contre les adventices. Les engrais azotés n'ont pas changé de façon significative le niveau de la competitivité des cullivars. Bien que la compétition aérienne soit moins forte que la racinaire, les différentes céréales ont exprimé des différences nettes dans leur aptitude à la compétition aérienne. Les 2 avoines et l'orge ‘Egmont’ ont une plus grande capacité de compétition que les 2 blés et l'orge ‘Goldmaker’. II n'est pas ressorti que les différences dans la compétitivé aérienne soient liées à des différences de hauleur de plantes. Konkurrenz im Wurzel‐ und im Sproßbereich zwischen Sommergetreide und Avena fatua L.Je 2 Sorten von Sommerweizen, Sommergerste und Hafer wuchsen mit Avena fatua in einem Topfversuch, wo durch Trennwände die Wirkung der Wurzel‐ und der Sproßkonkurrenz unterschieden werden konnte. Messungen der Nährstoffaufnahme und der relativen Stärke der Konkurrenz zeigten, daß die Konkurrenz um Nährstoffe im Boden, besonders Stickstoff, heftiger war als die Konkurrenz im Sproßbereich, z. B. um Licht. Lag sowohl Wurzel‐ wie Sproßkonkurrenz vor, waren Hafer und Gerste allgemein konkurrenzstärker als Weizen, aber es gab bei allen 3 Getreidearten signifikante Unterschiede zwischen den Sorten. Obwohl die Konkurrenz zwischen den Getreiden und A. fatua vor allem im Wurzelbereich lag, unterschieden sich die verschiedenen Sorten da in ihrer Konkurrenzkraft nur wenig, was auch durch Stickstoffdüngung nicht signifikant geändert werden konnte. Trotz der geringeren Bedeutung der Konkurrenz im Sproßbereich unterschieden sich die Getreidearten hier in ihrer Konkurrenzkraft deutlich: Die beiden Hafersorten und die Gerstensorte ‘Egmont’übertrafen hierin die beiden Weizensorten oder die Gerstensorte ‘Goldmaker’. Es gab keine Hinweise darauf, daß die Unterschiede der Konkurrenzkraft im Sproßbereich auf die Halmlänge zurückzuführen sei.

NADH‐dependent nitrate reductase from two‐row barley roots: Purification, characteristics and comparison with leaf enzyme

NADH‐nitrate reductase (EC 1.6.6.1) was purified 800‐fold from roots of two‐row barley (Hordeum vulgare L. cv. Daisen‐gold) by a combination of Blue Sepharose and zinc‐chelate affinity chromatographies followed by gel filtration on TSK‐gel (G3000SW). The specific activity of the purified enzyme was 6.2 μmol nitrite produced (mg protein)−1 min−1 at 30°C.Besides the reduction of nitrate by NADH, the root enzyme, like leaf nitrate reductase, also catalyzed the partial activities NADH‐cytochrome c reductase, NADH‐ferricyanide reductase, reduced methyl viologen nitrate reductase and FMNH2‐nitrate reductase. Its molecular weight was estimated to be about 200 kDa, which is somewhat smaller than that for the leaf enzyme. A comparison of root and leaf nitrate reductases shows physiologically similar or identical properties with respect to pH optimum, requirements of electron donor, acceptor, and FAD, apparent Km for nitrate, NADH and FAD, pH tolerance, thermal stability and response to inorganic orthophosphate. Phosphate activated root nitrate reductase at high concentration of nitrate, but was inhibitory at low concentrations, resulting in increases in apparent Km for nitrate as well as Vmax whereas it did not alter the Km for NADH.

Comparison of root‐ and shoot‐acting growth retardants on a grass/clover sward

SummaryThe effects of six grass growth retardants, maleic hydrazide (±2,4‐D), mefluidide, paclobutrazol, EL500 and a mixture of mefluidide with paclobutrazol on a grass/clover sward were compared over a 3‐year period. Maleic hydrazide, which is the most commonly used retardant, gave poor levels of growth control except when used with 2,4‐D. Greatest growth suppression, a 38% reduction in dry matter production from May to July, was obtained from a mixture of mefluidide and paclobutrazol. Differences were observed between the effects of the shoot‐acting retardants, maleic hydrazide and mefluidide and the root‐acting retardants, paclobutrazol and EL500. Shoot‐acting retardants were less effective in wet weather and lasted for a shorter period than root‐acting retardants. They also increased compensatory growth after a period of growth suppression, and increased the proportion of clover in the sward.