Affect Root Morphology Research Articles

Differential responses to Cd stress induced by exogenous application of Cu, Zn or Ca in the medicinal plant Catharanthus roseus

Cd(II) is one of the most widespread and toxic heavy metals and seriously threatens plant growth, furthermore negatively affecting human health. For survival from this metal stress, plants always fight with Cd(II) toxicity by themselves or using other external factors. The effects of second metals copper (Cu(II)), zinc (Zn(II)) and calcium (Ca(II)) on the Cd(II)-affected root morphology, Cd(II) translocation and metabolic responses in Catharanthus roseus were investigated under hydroponic conditions. We found that the Cd-stressed plants displayed the browning and rot root symptom, excess H2O2 content, lipid peroxidation and Cd(II) accumulation in plants. However, the supplement with second metals largely alleviated Cd-induced toxicity, including browning and rot roots, oxidative stress and internal Cd(II) accumulation. The amended effects at metabolic and transcriptional levels involved in different second metals share either common or divergent strategies. They commonly repressed Cd uptake and promoted Cd(II) translocation from roots to shoots with divergent mechanisms. High Zn(II) could activate MTs expression in roots, while Cu(II) or Ca(II) did not under Cd(II) stress condition. The presence of Ca(II) under Cd stress condition largely initiated occurrence of lateral roots. We then grouped a metabolic diagram integrating terpenoid indole alkaloid (TIA) accumulation and TIA pathway gene expression to elucidate the metabolic response of C. roseus to Cd(II) alone or combined with second metals. The treatment with 100 Cd(II) alone largely promoted accumulation of vinblastine, vindoline, catharanthine and loganin, whereas depressed or little changed the expression levels of genes detected here, compared to 0 Cd(II) control. In the presence of Cd(II), the supplement with second metals displayed specific effect on different alkaloid. Among them, the metal Ca(II) is especially beneficial for serpentine accumulation, Zn(II) mainly promoted tabersonine production. However, the addition of Cu(II) commonly depressed accumulation of most alkaloids detected here. Generally, we presented different mechanisms by which the second metals used to alleviate Cd (II) toxicity. This plant has potential application in phytoremediation of Cd(II), due to relatively substantial accumulation of biomass, as well as secondary metabolites TIAs used as pharmaceutical materials when facing Cd stress.

Arbuscular mycorrhizae modify winter wheat root morphology and alleviate phosphorus deficit stress

Arbuscular mycorrhizal (AM) root colonization is known to have beneficial effects on plant growth especially under phosphorus (P) deficit conditions. The objectives of present study were: (i) to quantify changes in early wheat root development of AM-inoculated (AMI) and AM-free (AMF) roots under limited P availability; (ii) to assess possible mitigating effect of AM inoculation on photochemical efficiency under P deficit stress. AMI (inoculated with Rhizophagus irregularis) and AMF wheat plants were grown for 20 days in low (1 μmol/L) and high (50 μmol/L)P treatments. AM inoculation affected root morphology and shoot P concentration in low P treatment. AM inoculation alleviated reduction of the total root length in low P treatment, mainly due to an increase of fine roots length(< 0.5 mm). Contrastingly, shoot dry weight was reduced by AM inoculation in low P treatment. P deficiency decreased photochemical efficiency of wheat plants. However, due to increased sink capacity and facilitated nutrient concentrations AM inoculation alleviates phosphorus deficit stress and increased photochemical efficiency.

Influence of biochar and nitrogen on fine root morphology, physiology, and chemistry of Acer mono

Fine roots play an important role in the overall functions of individual plants. Previous studies showed that fertilization and available soil resources have a notably profound effect on fine root, but there is lack of study centered on how fine root morphology, physiology, and chemistry respond to biochar with N additions. Different levels of biochar (0, 10, 15, and 20 g) and N (0, 2, 4 and 6 g) were applied to Acer mono seedling plants in a field nursery. The root system morphology and root chemistry and physiology were evaluated in line with root length, root diameter, SRL, N and N: C and root respiration. Biochar and N significantly affected root morphology, chemistry and root respiration. Morphological, chemical and physiological parameters were found to be at their maximum with 20 g biochar and 6 g N; however, no significant effect was noted on fourth- and fifth-order roots. Furthermore, a significant increase in root respiration was recognized with the increase in root tissue N concentration and the negative relationship of root respiration with higher branch order. Thus, overall, study parameters indicate that biochar and nitrogen positively influence the Acer mono fine root, and therefore should be used to improve fine root health.

Nitrogen addition enhanced water uptake by affecting fine root morphology and coarse root anatomy of Chinese pine seedlings

Global nitrogen (N) deposition can affect root morphology, anatomy and thus the water uptake by trees. The variation in uptake with the induced changes in root morphology and anatomy, however, is not clear. We grew seedlings of Pinus tabuliformis for two years across an N gradient (0–12 g N m−2 y−1) and analysed the associated changes between the root hydraulic conductance (RHC) and the morphology and anatomy of different root orders. (1) The RHC increased with N addition and reached the peak at 9 g N m−2 y−1. (2) The number, length, biomass and mycorrhizal colonization rates of the fine roots (first two order roots) decreased with N addition. (3) The stele diameter and tracheid diameter of the coarse roots (third and higher root orders) increased with N addition. (4) Decreasing root quantity and increasing physiological activity (i.e. RHC and respiration rates) induced by N addition may be a trade-off between root morphology and physiology plastic. The morphological, anatomical and physiological responses of the different root orders to N addition increased the water uptake, transport, and whole-seedling growth. These heterogeneous responses should be incorporated into models of root uptake and growth in forest ecosystems.

Growth and antioxidant defense responses of wheat seedlings to di-n-butyl phthalate and di (2-ethylhexyl) phthalate stress

Phthalate acid esters (PAEs) are vital environmental hormone-like chemicals that are noxious to plants, animals, and human beings. In this study, the influences of di-n-butyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) on the seed germination, root morphology, and various physiological changes of wheat seedlings were investigated by analyzing superoxide anion (O2−) accumulation, antioxidant enzyme activity, and lipid peroxidation. DBP and DEHP were found to obviously inhibit germination only at high concentrations, but significantly affected root morphology even at lower concentrations. Their toxic effects were the most severe on root elongation, followed by shoot elongation, and were the least severe on germination rate, indicating that root elongation was the best index for evaluating DBP and DEHP eco-toxicity. DBP and DEHP also enhanced O2− and malondialdehyde levels and membrane permeability, as well as produced changes in the antioxidant status and PAE content in the stem and leaf (combined tissues, hereafter shoot) and root tissues. The activities of superoxide dismutase, catalase, and peroxidase increased at low and medium DBP and DEHP concentrations, but declined at high PAE concentrations. These results indicated that PAEs could exert oxidative damage in the early development stage of wheat, particularly at higher concentrations. DBP and DEHP accumulation was higher in the roots than in the shoot tissues, and their levels in these tissues increased with increasing PAE concentrations, supporting their more-serious toxic effects on roots than those on shoots. Further, the physicochemical properties of DBP rendered it more harmful than DEHP.

A cyst nematode effector binds to diverse plant proteins, increases nematode susceptibility and affects root morphology.

Cyst nematodes are plant-parasitic roundworms that are of significance in many cropping systems around the world. Cyst nematode infection is facilitated by effector proteins secreted from the nematode into the plant host. The cDNAs of the 25A01-like effector family are novel sequences that were isolated from the oesophageal gland cells of the soybean cyst nematode (Heterodera glycines). To aid functional characterization, we identified an orthologous member of this protein family (Hs25A01) from the closely related sugar beet cyst nematode H.schachtii, which infects Arabidopsis. Constitutive expression of the Hs25A01 CDS in Arabidopsis plants caused a small increase in root length, accompanied by up to a 22% increase in susceptibility to H.schachtii. A plant-expressed RNA interference (RNAi) construct targeting Hs25A01 transcripts in invading nematodes significantly reduced host susceptibility to H.schachtii. These data document that Hs25A01 has physiological functions inplanta and a role in cyst nematode parasitism. Invivo and invitro binding assays confirmed the specific interactions of Hs25A01 with an Arabidopsis F-box-containing protein, a chalcone synthase and the translation initiation factor eIF-2 β subunit (eIF-2bs), making these proteins probable candidates for involvement in the observed changes in plant growth and parasitism. A role of eIF-2bs in the mediation of Hs25A01 virulence function is further supported by the observation that two independent eIF-2bs Arabidopsis knock-out lines were significantly more susceptible to H.schachtii.

Root Morphology, Plant Growth, Nitrate Accumulation and Nitrogen Metabolism of Temperate Lettuce Grown in the Tropics with Elevated Root-Zone CO<sub>2</sub> at Different Root-Zone Temperatures

This paper investigated the effects of root-zone (RZ) CO2 concentration ([CO2]) on root morphology and growth, nitrate (NO3-) uptake and assimilation of lettuce plants at different root-zone temperatures (RZT). Elevated RZ [CO2] stimulated root development, root and shoot growth compared to ambient RZ [CO2]. The greatest increase in root growth was observed in plants grown under elevated RZ [CO2] of 50,000 ppm. However, RZ [CO2] of 10,000 ppm was sufficient to achieve the maximal leaf area and shoot productivity. Lettuce plants exhibited faster shoot and root growth at 20°C-RZT than at ambient (A)-RZT. However, under elevated RZ [CO2], the magnitude of increased growth was greater at A-RZT than at 20°C-RZT. Compared to RZ [CO2] of 360 ppm, elevated RZ [CO2] of 10,000 ppm increased NO3- accumulation and nitrate reductase activity (NRA) in both leaves and roots. NO3- concentrations of leaf and root were higher at 20°C-RZT than at A-RZT in all plants. NRA was higher in root than in leaf especially under A-RZT. The total reduced nitrogen (TRN) concentration was significantly higher in plants grown under elevated RZ [CO2] of 10,000 ppm than under ambient RZ [CO2] of 360 ppm with greater concentration in 20°C-RZT plants than in A-RZT plants. These results imply that elevated RZ [CO2] significantly affected root morphology, root and shoot growth and N metabolism of temperate lettuce with greater impacts at A-RZT than at 20°C-RZT. These findings have practical significance to vegetable production by growing the vegetable crops at cool-RZT with elevated RZ [CO2] to enhance its productivity.

Changes in soil nutrient availability explain biochar’s impact on wheat root development

Biochar is a carbon-rich product obtained from the pyrolysis of organic materials. Its use, combined with fertilizers, can modify soil properties and affect root morphology and functioning. The main objective of this study was to evaluate the impact of biochar and fertilizer addition on root development and morphology. Durum wheat was pot-grown for 2 months using two types of biochar (produced from wheat straw and olive-tree pruning) applied at four rates (0, 0.5, 1 and 2.5 % w/w) and combined with three fertilization levels (0, 40 %-low and 100 %-complete). Biochar addition at high rates increased the specific root length and decreased both root diameter and root tissue mass density, indicating a fine root proliferation, regardless of the fertilization level. This may have favoured the resource acquisition by increasing biochar-root interactions, soil exploration and the fertilizer efficacy. Biochar addition reduced N and Mn availability but increased P availability, which also influenced root growth. Changes in root morphology may therefore serve as an important indicator of soil changes induced by biochar and its study can contribute to a better understanding of the effects of the combined application of biochar and fertilizers on plant growth.

Impact of hydro-/biochars on root morphology of spring wheat

Despite suggested benefits of hydrochars and biochars, little is known about their effects on root development and root-char interactions. To compare effects of two types of biochar (Pyro and Pyreg) and one hydrochar (hydrothermal carbonization (HTC)) on root growth of spring wheat, two rhizobox experiments were set up where physical contact of roots with chars was prevented using nylon gauze. Rhizoboxes were filled with unamended soil as a control or with three different soil-char mixtures (Pyro, Pyreg and HTC). Shoots and roots were harvested before flowering and at tillering in the first and second experiment, respectively. Chemical soil properties (Nt, K, Ct, pH value) were affected differently by the different chars. Both shoot and root dry matter were influenced by chars. Pyro-char had positive effects on root dry matter in both experiments. At tillering, HTC-char affected root length, root surface and number of root tips negatively. Our findings suggest that nutrients released from chars may affect root morphology of spring wheat. The comparison of different types of chars showed different effects on root growth, shoot growth and soil changes depending on feedstock, production process and the varied amount of chars.

English

Frankia strains can induce N2-fixing root nodules on certain non-leguminous plants. It is known that exogenous application of 2,4-dichlorophenoxyacetate (2,4-D) affects root morphology. In this work, wheat roots were treated with 2,4-D and inoculated with the actinomycete Frankia. Wheat plants grew in a growth chamber with hydroponic medium. Binocular observation revealed that para-nodules were formed when wheat roots were inoculated with Frankia and the root length was enhanced. When the inoculation with Frankia was combined to 2,4-D treatment, the para-nodules formed were bigger and more numerous, while the root length was shortened. Keywords: Frankia , wheat, roots, para-nodules, 2,4-dichlorophenoxyacetate African Journal of Biotechnology Vol. 12(35), pp. 5427-5430

Root photomorphogenesis in laboratory-maintained Arabidopsis seedlings

In nature, root systems of most terrestrial plants are underground in darkness. Nevertheless, several photoreceptors have been found in roots and light-responsive mechanisms allowing roots to escape from strong light conditions have been discovered. In transparent Petri dishes, regular light exposure affects root morphology and behavior. We advocate the use of darkened Petri dishes to allow roots to be kept in darkness, thus mimicking more closely the conditions in nature.

Effect of copper excess in environment on soybean root viability and morphology

The effects of increase copper concentrations in medium (10–150 μM CuSO4) on growth and viability of the roots of two-week-old soybean seedlings (Glycine max L., cv. Dorintsa) were studied. Copper excess suppressed biomass accumulation and linear plant growth; copper affected root growth much stronger than shoot growth. The presence of 10 μM CuSO4 in medium suppressed accumulation of plant biomass by 40% and the root length by 70%; in the presence of 25 μM CuSO4, these indices were equal to 80 and 90%, respectively. In the presence of 50 μM CuSO4, roots ceased to grow but biomass and shoot length still increased slightly. 150 μM CuSO4 was lethal for plants. The earliest sign of excessive copper toxicity was the accumulation of MDA, indicating activation of membrane lipid peroxidation. A significant increase in MDA content was observed at plant incubation in medium with 10 μM CuSO4 for 1 h; in this case, the content of copper in the roots increased from 36 ±1.8 (in control) to 48 ± 2.4 μg/g dry wt. The number of dead cells (permeable for the dye Evans Blue) was doubled in the presence of 200 μg/g dry wt within the root; this occurred in 72 h of growth in medium with 10 μM CuSO4, in 6 h at 25 μM CuSO4, in 3 h at 50 μM CuSO4, and 1 h at 150 μM CuSO4. Toxicity of copper excess was manifested stronger in dividing and elongation cells of the root apex (root meristem and the zone of elongation) than in more basal root regions. Copper excess resulted in the formation of breaks in the surface cell layers of the root tips and affect root morphology. When plant grew in medium with 10 μM CuSO4, a distance of lateral root formation zone from the root tip decreased markedly, and spherical swellings were formed on the tips of lateral roots. The higher copper concentrations (50 and 150 μM) suppressed completely the development of lateral roots.

Interactive effects of potassium and sodium on root growth and expression of K/Na transporter genes in rice

Sufficient supply of potassium (K) can alleviate the adverse effects of excess sodium (Na) on plant growth. However, it remains unclear if such a beneficial function is related to regulation of root growth and/or expression of K/Na transporters. Herein we report the responses of a rice cultivar, which was pretreated with normal nutrient solution for 1 month, to three levels of Na (0, 25, and 100 mM) without or with supply of K for 9 days. High Na (100 mM) significantly decreased plant growth, root activity, and total K uptake, and increased biomass ratio of roots to shoots. Short-term removal of K supply (9 days) did not affect root morphology and biomass ratio of roots to shoots, but decreased root activity of seedlings grown in high Na solution. K deficiency increased uptake of Na and transport of K from roots to shoots. Moreover, expression of OsHAK1, a putative K transporter gene, was upregulated by low Na (25 mM) and downregulated by high Na (100 mM) in roots. In leaves, its expression was suppressed by the Na treatments when K supply was maintained. Expression of OsHKT2;1, which encodes a protein that acts mainly as a Na transporter, was downregulated by high Na, but was enhanced by K deficiency both in roots and leaves. Expression of five other putative K/Na transporter or Na+/H+ genes, OsHKT1;1, OsHKT1;2, OsHKT2;3, OsNHX1, and OsSOS1, was not affected by the treatments. The results suggest that OsHAK1 and OsHKT2;1 were involved in the interactive effects of K and Na on their uptake and distribution in rice.

Responses of transformed Catharanthus roseus roots to femtomolar concentrations of salicylic acid

Catharanthus roseus transformed roots were cultured in the presence of salicylic acid (SA) at concentrations between 0.1 fM and 100 pM and the effect on root growth was evaluated. Significant morphological changes in the lateral roots were recorded on day two in the SA treatment. Presence of SA increased root cap size and caused the appearance of lateral roots closer to the root tip. The bioassay was sensitive enough to allow testing of low concentrations of other growth regulators that may affect root morphology and physiology.

Identification of cadmium-regulated genes by cDNA-AFLP in the heavy metal accumulator Brassica juncea L.

In this study, cDNA-amplified fragment length polymorphism (cDNA-AFLP) analysis was employed to identify genes that exhibited a modulated expression following cadmium (Cd) treatment in Brassica juncea grown in hydroponic culture. Plants were treated for 6 h, 24 h, and 6 weeks with 10 microM Cd(NO3)2 and untreated 6-week-old plants were used as controls. Cd content was measured at these four time points. Long exposure to Cd affected root morphology: roots appeared thinner and sent out side roots. Seventy-three transcript-derived fragments were identified as Cd responsive. Fifty-two of them showed significant homology to genes with known or putative function, 10 transcript-derived fragments were homologous to uncharacterized genes, while 11 transcript-derived fragments did not show significant matches. The expression pattern of several of these genes was confirmed by northern blot analysis. Fifty-two genes of known or putative function were transcriptional factors, expression regulators, and stress responding and transport facilitation genes, as well as genes involved in cellular metabolism and organization and the photosynthetic process, suggesting that a multitude of processes are implicated in Cd stress response. The transcription of drought- and abscisic acid-responsive genes observed in this study also suggested that Cd imposes water stress and that abscisic acid may be involved in the Cd plant response.

Effect of Two Glomus Species Inoculations on Survival, Photosynthetic Capacity, Growth, Morphology ana Root Ginsenoside Content of Panax quinquefolius L.

Vesicular-arbuscular mycorrhizae (VAM) fungi naturally colonise American ginseng roots and this relationship is highly beneficial to enhance plant productivity. Our goal was to determine the effect of adding two Glomus species (Glomus etuticatum, G. intraradices) on survival, photosynthetic capacity, growth, morphology and root ginsenoside content of one-year-old American ginseng plants grown in a broadleaf forest. While our study revealed that VAM inoculations significantly affected root morphology and Re ginsenoside content, the survival, photosynthetic capacity and root growth of American ginseng plants were not significantly influenced by VAM inoculations. Surface area and volume of rootlets were 16-25% higher for ginseng grown in VAM-inoculated soil compared to those grown in the control plots. Also, Re ginsenoside content was 18 ％ higher in YAM-inoculated roots compared to controls.

Localized supply of phosphorus induces root morphological and architectural changes of rice in split and stratified soil cultures

A localized supply of phosphorus may affect root morphology and architecture, and thereby affect phosphorus uptake by rice plants. In the present study, we attempted to test this hypothesis using two rice cultivars representing upland and lowland ecotypes grown in specially designed split and stratified soil cultures with a low-phosphorus red soil. Our data indicate that a localized supply of phosphorus increased both total root length and root fineness, particularly in the high-phosphorus zone. In split culture, plants roots tended to preferentially grow on the high-phosphorus zone, with about 70–75% of the total root length allocated to the high-phosphorus compartment. The total root length on the high-phosphorus side in the split-phosphorus treatment was significantly longer than that in the homogenously high-phosphorus treatment, implying that a phosphorus-deficiency signal from the low-phosphorus side may stimulate the growth of the roots located in the high-phosphorus zone. In stratified soil culture, changes in root morphology and architecture were also observed as indicated by increased total root length, root fineness and relative root allocation in the high-phosphorus layers, again suggesting altered root morphology and preferential root proliferation in the high-phosphorus regions. The induced changes in root morphology and architecture by localized phosphorus supply may have both physiological significance and practical implications in that plants can meet the demand for phosphorus with parts of the roots reaching the high-phosphorus zone, hence localized fertilization methods such as side dressing or banded application of phosphorus fertilizers may both minimize phosphorus fixation by the soil and increase phosphorus uptake efficiency from the fertilizers.

Inheritance of Root Traits in Alfalfa

Root growth patterns influence nutrient uptake, productivity, and persistence in alfalfa (Medicago sativa L.). Inheritance of traits affecting root growth patterns in alfalfa are not well understood. Objectives of this research were to determine the affects of plant spacing and geographic location on root traits in alfalfa, to determine the inheritance of seven root morphological traits of alfalfa, and to evaluate the association between root traits, fall dormancy, and seedling year herbage yield. Progenies of diallels and design II matings were planted during May 1991 at two locations in 30‐cm rows with 2.5 cm between plants within the row. Plants were evaluated for seedling year herbage yield and fall dormancy. During October 1991, they were dug and evaluated for taproot diameter (TD), lateral root number (LRN), lateral root diameter (LRD), lateral root position (LRP), fibrous mass (FRM), percentage of determinate taproots (PDT), and determinate taproot position (DTP). Border effects were determined by evaluating single plants from the ends of the plots separately from plants in the middle of the plots. Extra space on plot borders affected root morphology, but few progeny × border interactions were found. Location affected root morphology, and a few location × cross interactions were observed for TD and LRP. Additive genetic effects were important in controlling inheritance for TD, LRN, LRD, LRP, and FRM. These traits had moderate (45) to high (87) heritabilities. genetic variances were detected for PDT or DTP. Taproot diameter was the root trait most highly correlated with fall dormancy (0.46–0.50) and seedling year herbage yield (0.61–0.75). Selection for LRN, LRD, and FRM at one location with uniform plant spacing should be successful. Multiple location selection programs may be more appropriate for TD and LRP.

Influence of hydroponic culture method on morphology and hydraulic conductivity of roots of honey locust.

The morphology and hydraulic conductivity of root systems of Gleditsia triacanthos L. var. inermis Willd. (honey locust) grown hydroponically in sand and solution cultures were compared. Total root system length was similar in the two cultures. However, root systems grown in solution had longer primary roots, fewer lateral roots and root hairs, and a greater distance between the tip of the primary root and the junction of the youngest secondary root and the primary root than root systems grown in sand. Hydraulic conductivities of root systems grown hydroponically for 21 or 35 days in sand or solution culture were similar. These findings show that different methods of hydroponic culture can affect root morphology without altering root resistance to water transport.

Influence of phenolic acids on morphological changes in roots of Pisum sativum

AbstractAt relatively high concentrations (1 mM), ferulic, vanillic, p‐coumaric, p‐hydroxybenzoic, syringic and caffeic acids inhibited the growth of roots of Pisum sativum L cultured in a Hoagland nutrient solution under axenic conditions. These phenolic acids also profoundly affected root morphology in terms of extension growth of the main root and the number and size of the lateral roots. The precise growth effects depended on the phenolic acid. At concentrations that inhibited an increase in the length of the main root, the phenolic acids also inhibited cell division. To produce the maximum growth effect, the phenolic acids must be present continuously. Lower concentrations (1 μM)of the phenolic acids also affected root growth and morphology when the nitrogen content of the nutrient solution was limiting.