Inhibition of Downy Brome (Bromus tectorum) Root Growth by a Phytotoxin fromPseudomonas fluorescensStrain D7

Field applications of the rhizobacterium,Pseudomonas fluorescensstrain D7 (D7), have selectively suppressed downy brome in winter wheat test plots. A phytotoxin produced by D7 inhibits downy brome root growth. An assay system was developed for future investigations of the mechanism of action of this and other phytotoxins that inhibit root growth. A crude preparation of the phytotoxin, cell-free supernatant (CFS), had little activity on downy brome root elongation in a sand-petri plate system. CFS was very active in a hydroponic system, in which a 6% (v/v) concentration inhibited root elongation within 1.5 h. Inhibition of root elongation was reversible in this system. Root elongation of downy brome seedlings resumed within 3 h after removal from a 9-h incubation in 8% CFS. CFS from genetic variants of D7 did not substantially inhibit root growth and a semi-crystallized precipitation product from D7 CFS inhibited root growth similarly to D7 CFS, indicating that the phytotoxin present in the CFS was responsible for growth inhibition.

Download Full-text

Effect of aluminium on root elongation in two Australian perennial grasses

Functional Plant Biology ◽

10.1071/pp97134 ◽

1998 ◽

Vol 25 (2) ◽

pp. 165 ◽

Cited By ~ 7

Author(s):

Simon A. Crawford ◽

Sabine Wilkens

Keyword(s):

Root Growth ◽

Root Elongation ◽

Root Apex ◽

Perennial Grasses ◽

Root Tips ◽

Al Stress ◽

Control Growth ◽

Hematoxylin Staining ◽

Inhibition Of Root Elongation ◽

Nutrient Solutions

Inhibition of net root elongation and patterns of hematoxylin staining were used to assess relative tolerance to phytotoxic Al in Danthonia linkii Kunth and Microlaena stipoides (Labill.) R.Br. According to net root elongation, M. stipoides is significantly more tolerant of phytotoxic Al than D. linkii. In nutrient solutions with Al concentrations of 370 µM and higher, root elongation is stopped in D. linkii after 24 h while in M. stipoides root elongation is maintained at 60–70% of control rates over 72 h. After removal of Al-stress, root growth in M. stipoides from all Al-treatments recovered to be at or above control growth after 72 h. In D. linkii, root elongation in plants exposed to Al levels that caused a reduction in growth (<370 µM), but not complete cessation, recovered after removal of Al stress. Greater intensities of hematoxylin staining were seen in Al-stressed root tips of D. linkii compared to M. stipoides, suggesting that inhibition of root elongation is associated with increased accumulation of Al in root tips. Roots of M. stipoides seedlings exposed to all Al-treatments showed a short band of intensely stained tissue, correlating with the position of the root apex at the exact point of initial Al- exposure. New root growth after this band did not stain with hematoxylin, indicating activation of a mechanism of Al-exclusion in roots of M. stipoides.

Download Full-text

Weed Control in Wheatgrass Seedbeds with Siduron and Picloram

Weed Science ◽

10.1017/s0043174500034159 ◽

1970 ◽

Vol 18 (5) ◽

pp. 546-549

Author(s):

James A. Young ◽

Raymond A. Evans

Keyword(s):

Soil Moisture ◽

Root Elongation ◽

Bromus Tectorum ◽

Moisture Stress ◽

Downy Brome ◽

Negative Relation ◽

Intermediate Wheatgrass ◽

Plant Moisture ◽

Broadleaf Species ◽

Semi Arid

Preemergence applications of 3 lb/A of 1-(2-methylcyclohexyl)-3-phenylurea (siduron) plus 0.3 lb/A of 4-amino-3,5,6-trichloropicolinic acid (picloram) sufficiently suppressed competition from downy brome (Bromus tectorumL.) or medusahead (Taeniatherum asperum(Sim.) Nevski) and associated broadleaf species to allow the marginal establishment of intermediate wheatgrass (Agropyron intermedium(Host.) Beauv., var. Amur) seedlings. The technique was only successful on semi-arid range sites with above-average soil moisture and moderately dense stands of weed grasses. The range in tolerance of the three species to siduron is very similar, but downy brome is slightly more susceptible than medusahead or intermediate wheatgrass. There is a significant negative relation between plant moisture stress and root length of intermediate wheatgrass plants when root elongation is suppressed by low rates of siduron.

Download Full-text

Physiological Responses of Downy Brome (Bromus tectorum) Roots toPseudomonas fluorescensStrain D7 Phytotoxin

Weed Science ◽

10.1017/s004317450005222x ◽

1993 ◽

Vol 41 (3) ◽

pp. 483-489 ◽

Cited By ~ 11

Author(s):

Patrick J. Tranel ◽

David R. Gealy ◽

Gerald P. Irzyk

Keyword(s):

Root Elongation ◽

Membrane Integrity ◽

Lipid Synthesis ◽

Significant Inhibition ◽

Downy Brome ◽

Similar Treatment ◽

Physiological Processes ◽

Treatment Conditions ◽

Dose Dependent ◽

Inhibition Of Root Elongation

Effects of a crude preparation of a phytotoxin fromPseudomonas fluorescensstrain D7 (D7) on various physiological processes were evaluated in roots of downy brome seedlings. Cell division, respiration, and synthesis of protein, RNA, and DNA were not inhibited or only slightly inhibited under treatment conditions that caused substantial inhibition of root elongation. Significant inhibition of each of these processes was detected by known inhibitors included in each study to verify sensitivity of the procedures used. Disruption of lipid synthesis and membrane integrity by the crude phytotoxin preparation was significant and might account for inhibition of root elongation. Additional studies on these two possible target sites were conducted with partially purified phytotoxin. In intact roots, incorporation of [14C]acetate and [14C]malonic acid into lipophilic fractions was reduced by 50% or greater during a 1-h treatment with concentrations between 10 and 100 μg ml−1of the partially purified phytotoxin preparation. In a membrane integrity study, a similar treatment increased radioactivity efflux 250% from seedlings preloaded withscyllo-[R-3H]inositol. Additionally, disruption of lipid synthesis and membrane integrity by the partially purified phytotoxin was dose dependent. Collectively, these findings indicate that the D7 phytotoxin may inhibit downy brome root elongation through its effects on lipid synthesis and membrane integrity.

Download Full-text

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

Cells ◽

10.3390/cells10113110 ◽

2021 ◽

Vol 10 (11) ◽

pp. 3110

Author(s):

Lidiya Vysotskaya ◽

Leylya Timergalina ◽

Guzel Akhiyarova ◽

Alla Korobova ◽

Vadim Fedyaev ◽

...

Keyword(s):

Abscisic Acid ◽

Root Growth ◽

Plant Hormones ◽

Root Elongation ◽

Mineral Nutrients ◽

Growth Responses ◽

Root Tips ◽

Immunohistochemical Technique ◽

Dependent Transport ◽

Inhibition Of Root Elongation

Changes in root elongation are important for the acquisition of mineral nutrients by plants. Plant hormones, cytokinins, and abscisic acid (ABA) and their interaction are important for the control of root elongation under changes in the availability of ions. However, their role in growth responses to supra-optimal concentrations of nitrates and phosphates has not been sufficiently studied and was addressed in the present research. Effects of supra-optimal concentrations of these ions on root elongation and distribution of cytokinins between roots and shoots were studied in ABA-deficient barley mutant Az34 and its parental variety, Steptoe. Cytokinin concentration in the cells of the growing root tips was analyzed with the help of an immunohistochemical technique. Increased concentrations of nitrates and phosphates led to the accumulation of ABA and cytokinins in the root tips, accompanied by a decline in shoot cytokinin content and inhibition of root elongation in Steptoe. Neither of the effects were detected in Az34, suggesting the importance of the ability of plants to accumulate ABA for the control of these responses. Since cytokinins are known to inhibit root elongation, the effect of supra-optimal concentration of nitrates and phosphates on root growth is likely to be due to the accumulation of cytokinins brought about by ABA-induced inhibition of cytokinin transport from roots to shoots.

Download Full-text

Enhanced Autophagic Activity Improved the Root Growth and Nitrogen Utilization Ability of Apple Plants under Nitrogen Starvation

International Journal of Molecular Sciences ◽

10.3390/ijms22158085 ◽

2021 ◽

Vol 22 (15) ◽

pp. 8085

Author(s):

Liuqing Huo ◽

Zijian Guo ◽

Qi Wang ◽

Li Cheng ◽

Xin Jia ◽

...

Keyword(s):

Transgenic Plants ◽

Root Growth ◽

Nitrogen Starvation ◽

Degradation Pathway ◽

Physiological Status ◽

Hydroponic System ◽

Nitrogen Levels ◽

Nitrogen Concentrations ◽

Nitrogen Nutrients ◽

Autophagic Activity

Autophagy is a conserved degradation pathway for recycling damaged organelles and aberrant proteins, and its important roles in plant adaptation to nutrient starvation have been generally reported. Previous studies found that overexpression of autophagy-related (ATG) gene MdATG10 enhanced the autophagic activity in apple roots and promoted their salt tolerance. The MdATG10 expression was induced by nitrogen depletion condition in both leaves and roots of apple plants. This study aimed to investigate the differences in the growth and physiological status between wild type and MdATG10-overexpressing apple plants in response to nitrogen starvation. A hydroponic system containing different nitrogen levels was used. The study found that the reduction in growth and nitrogen concentrations in different tissues caused by nitrogen starvation was relieved by MdATG10 overexpression. Further studies demonstrated the increased root growth and the higher nitrogen absorption and assimilation ability of transgenic plants. These characteristics contributed to the increased uptake of limited nitrogen nutrients by transgenic plants, which also reduced the starvation damage to the chloroplasts. Therefore, the MdATG10-overexpressing apple plants could maintain higher photosynthetic ability and possess better growth under nitrogen starvation stress.

Download Full-text

Carbon dots inhibit root growth by disrupting auxin biosynthesis and transport in Arabidopsis

Ecotoxicology and Environmental Safety ◽

10.1016/j.ecoenv.2021.112168 ◽

2021 ◽

Vol 216 ◽

pp. 112168

Author(s):

Xiaoyan Yan ◽

Qiang Xu ◽

Dongxia Li ◽

Jianhua Wang ◽

Rong Han

Keyword(s):

Root Growth ◽

Carbon Dots ◽

Auxin Biosynthesis ◽

Inhibit Root Growth

Download Full-text

Foliar vs. Root Sensitivity of Hairy Bittercress (Cardamine hirsuta) to Isoxaben

Weed Technology ◽

10.1614/wt-05-054r1.1 ◽

2006 ◽

Vol 20 (2) ◽

pp. 326-333 ◽

Cited By ~ 6

Author(s):

Glenn Wehtje ◽

Charles H. Gilliam ◽

Michael E. Miller ◽

James E. Altland

Keyword(s):

Root Growth ◽

Environmental Conditions ◽

Day Length ◽

Root Growth Inhibition ◽

Root Absorption ◽

Nursery Production ◽

Plant Maturity ◽

Higher Temperature ◽

Inhibit Root Growth ◽

Hydroponically Grown

It has been previously reported that POST-applied isoxaben can effectively control established hairy bittercress. Experiments were conducted to determine the relative importance of root vs. foliar entry of POST-applied isoxaben. At a common isoxaben rate of 0.56 kg/ha, foliar-only and foliar plus soil applications provided 10.5 and 23.3% control, respectively, as determined by fresh weight reduction. In contrast, soil-only application provided 47.0% control. Hairy bittercress foliar absorption of14C–isoxaben did not exceed 15% of the amount applied after 72 h. Therefore, the comparatively less effectiveness of foliar-only applications may be attributed primarily to limited absorption. Minimal isoxaben concentration required to inhibit root growth of hydroponically grown hairy bittercress was 0.0025 mg/L. Higher concentrations were required to produce a response in the foliage. Sorption of isoxaben by pine bark rooting substrate, typical of what is used in container nursery production, exceeded 99% of amount applied after 36 h. Even with 99% sorption, the probable concentration within the aqueous phase remains sufficient to inhibit hairy bittercress root growth. Additional studies with14C–isoxaben established that approximately 35% of the root-absorbed isoxaben was translocated into the foliage. Translocation from the roots into the foliage was reduced to 16% when the experiment was repeated during environmental conditions less favorable for vegetative growth (i.e., longer day length and higher temperature). Results indicate that the control of hairy bittercress with POST-applied isoxaben is likely the result of root absorption and root-growth inhibition. Expression of phytotoxicity within the foliage is also a component, but is dependent upon the root-absorbed isoxaben being translocated into the foliage. Extent of this translocation is dependent upon plant maturity and prevalent environmental conditions.

Download Full-text

Genome-wide identification and transcriptional analyses of MATE transporter genes in root tips of wild Cicer spp. under aluminium stress

10.1101/2020.04.27.063065 ◽

2020 ◽

Cited By ~ 1

Author(s):

Xia Zhang ◽

Brayden Weir ◽

Hongru Wei ◽

Zhiwei Deng ◽

Xiaoqi Zhang ◽

...

Keyword(s):

Root Growth ◽

Root Elongation ◽

Transcriptional Profiling ◽

Functional Characterization ◽

Relative Reduction ◽

Root Tips ◽

Al Tolerance ◽

Genome Wide ◽

Encoding Genes ◽

Al Treatment

AbstractChickpea is an economically important legume crop with high nutritional value in human diets. Aluminium-toxicity poses a significant challenge for the yield improvement of this increasingly popular crop in acidic soils. The wild progenitors of chickpea may provide a more diverse gene pool for Al-tolerance in chickpea breeding. However, the genetic basis of Al-tolerance in chickpea and its wild relatives remains largely unknown. Here, we assessed the Al-tolerance of six selected wild Cicer accessions by measuring the root elongation in solution culture under control (0 µM Al3+) and Al-treatment (30 µM Al3+) conditions. Al-treatment significantly reduced the root elongation in all target lines compared to the control condition after 2-day’s growth. However, the relative reduction of root elongation in different lines varied greatly: 3 lines still retained significant root growth under Al-treatment, whilst another 2 lines displayed no root growth at all. We performed genome-wide identification of multidrug and toxic compound extrusion (MATE) encoding genes in the Cicer genome. A total of 56 annotated MATE genes were identified, which divided into 4 major phylogeny groups (G1-4). Four homologues to lupin LaMATE (> 50% aa identity; named CaMATE1-4) were clustered with previously characterised MATEs related to Al-tolerance in various other plants. qRT-PCR showed that CaMATE2 transcription in root tips was significantly up-regulated upon Al-treatment in all target lines, whilst CaMATE1 was up-regulated in all lines except Bari2_074 and Deste_064, which coincided with the lines displaying no root growth under Al-treatment. Transcriptional profiling in five Cicer tissues revealed that CaMATE1 is specifically transcribed in the root tissue, further supporting its role in Al-detoxification in roots. This first identification of MATE-encoding genes associated with Al-tolerance in Cicer paves the ways for future functional characterization of MATE genes in Cicer spp., and to facilitate future design of gene-specific markers for Al-tolerant line selection in chickpea breeding programs.

Download Full-text

Root Growth of Avocado is More Sensitive to Salinity than Shoot Growth

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.129.2.0188 ◽

2004 ◽

Vol 129 (2) ◽

pp. 188-192 ◽

Cited By ~ 32

Author(s):

N. Bernstein ◽

A. Meiri ◽

M. Zilberstaine

Keyword(s):

Salt Stress ◽

Root Growth ◽

Biomass Production ◽

Root Elongation ◽

Shoot Growth ◽

Elongation Rate ◽

Persea Americana ◽

Root Growth Inhibition ◽

Leaf Biomass ◽

Volumetric Growth

In most crop species, growth of the shoot is more sensitive to salt stress than root growth. Avocado [Persea americana Mill.] is very sensitive to NaCl stress. Even low concentrations of salt (15 mm) inhibit tree growth and decrease productivity. Observations in experimental orchards have suggested that root growth in avocado might be more restricted by salinity than shoot growth. In the present study, we evaluated quantitatively the inhibitory effects of salt stress on growth of the avocado root in comparison to the shoot. Seedling plants of the West-Indian rootstock `Degania 117' were grown in complete nutrient solution containing 1, 5, 15, or 25 mm NaCl. The threshold NaCl concentration causing root and shoot growth reduction occurred between 5 and 15 mm. At all concentrations, root growth was much more sensitive to salinity than shoot growth. A concentration of 15 mm NaCl, which did not affect the rate of leaf emergence on the plant and decreased leaf biomass production only 10%, induced a 43% reduction in the rate of root elongation and decreased root volumetric growth rate by 33%. Under 25 mm NaCl, leaf biomass production, leaf initiation rate and leaf elongation rate were reduced 19.5%, 12%, and 5%, respectively, while root volumetric growth and root elongation rate were reduced 65% and 75%, respectively. This strong root growth inhibition is expected to influence the whole plant and therefore root growth under salinity should be considered as an important criterion for rootstocks' tolerance to NaCl.

Download Full-text

Effect of Herbicides on Germination and Growth of Four Grass Weeds

Weed Science ◽

10.1017/s0043174500059397 ◽

1984 ◽

Vol 32 (4) ◽

pp. 489-493 ◽

Cited By ~ 12

Author(s):

Frank L. Young ◽

David R. Gealy ◽

Larry A. Morrow

Keyword(s):

Bromus Tectorum ◽

Soil Surface ◽

Dry Weight ◽

Shoot Elongation ◽

Downy Brome ◽

Aegilops Cylindrica ◽

Shoot Height ◽

Shoot Dry Weight ◽

Jointed Goatgrass ◽

Germination And Growth

In the greenhouse, glyphosate [N-(phosphonomethyl)glycine] at 0.6 kg ae/ha applied directly to seeds alone or seeds on the soil surface reduced germination and shoot dry weight of common rye (Secale cerealeL. ♯3SECCE). Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) applied similarly at 0.6 kg ai/ha reduced germination and shoot dry weight of downy brome (Bromus tectorumL. ♯ BROTE) and wheat (Triticum aestivumL. ‘Daws' ♯ TRZAX). Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one] at 0.6 kg ai/ha applied to seeds, soil, or seeds and soil had very little effect on germination, but significantly reduced shoot dry weight of common rye, downy brome, wheat, and jointed goatgrass (Aegilops cylindricaHost. ♯ AEGCY). Pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] at 0.6 kg ai/ha, and propham (isopropyl carbanilate) at 3.4 kg ai/ha plus extender (p-chlorophenyl-N-methylcarbamate) at 0.4 kg ai/ha substantially reduced shoot height and dry weight of all species, regardless of application method, with pronamide completely inhibiting shoot elongation and dry-weight production in three of the four species.

Download Full-text