scholarly journals 991 REGULATION OF PLANT GROWTH RESPONSES TO LOW SOIL WATER POTENTIALS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 571b-571
Author(s):  
Robert E. Shar
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Growth Inhibition ◽  
Shoot Growth ◽  
Crop Improvement ◽  
Plant Water ◽  
Growth Responses ◽  
Water Deficits ◽  
Definitive Evidence ◽  
Water Potentials

Plant water deficits usually result in severe inhibition of shoot growth, while root growth is less inhibited or even promoted. Recent advances in understanding the physiology of the differential responses of root and shoot growth to low water potentials will be reviewed. While it might be readily accepted that hormones arc important in transducing environmental conditions into growth responses, there is surprisingly little definitive evidence for the role of any hormone in regulating plant growth in soils of low water potential. Using maize seedlings as a model system, the increase in ABA that accompanies plant water deficits has been shown to be required for root growth maintenance, and also to play a role in shoot growth inhibition. The action of ABA in root growth maintenance appears to involve regulation of ethylene synthesis and/or sensitivity, while the mechanism of shoot growth inhibition is not known. Evidence that ABA acts as a root `signal controlling shoot growth in drying soil will also be considered. The importance of osmotic adjustment as a mechanism of growth maintenance at low water potentials has been questioned by suggestions that solute accumulation may be merely a consequence of stress-induced growth inhibition. Recent studies will be discussed which do not support this idea, and suggest that the response may be useful for crop improvement.

scholarly journals Root Microbiome Modulates Plant Growth Promotion Induced by Low Doses of Glyphosate

mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Dario X. Ramirez-Villacis ◽  
Omri M. Finkel ◽  
Isai Salas-González ◽  
Connor R. Fitzpatrick ◽  
Jeffery L. Dangl ◽  
...  
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Growth Inhibition ◽  
Growth Promotion ◽  
Action Spectrum ◽  
Dry Weight ◽  
Agricultural Fields ◽  
Low Doses ◽  
Shoot Dry Weight ◽  
Root Microbiome

ABSTRACT Glyphosate is a commonly used herbicide with a broad action spectrum. However, at sublethal doses, glyphosate can induce plant growth, a phenomenon known as hormesis. Most glyphosate hormesis studies have been performed under microbe-free or reduced-microbial-diversity conditions; only a few were performed in open systems or agricultural fields, which include a higher diversity of soil microorganisms. Here, we investigated how microbes affect the hormesis induced by low doses of glyphosate. To this end, we used Arabidopsis thaliana and a well-characterized synthetic bacterial community of 185 strains (SynCom) that mimics the root-associated microbiome of Arabidopsis. We found that a dose of 3.6 × 10−6 g acid equivalent/liter (low dose of glyphosate, or LDG) produced an ∼14% increase in the shoot dry weight (i.e., hormesis) of uninoculated plants. Unexpectedly, in plants inoculated with the SynCom, LDG reduced shoot dry weight by ∼17%. We found that LDG enriched two Firmicutes and two Burkholderia strains in the roots. These specific strains are known to act as root growth inhibitors (RGI) in monoassociation assays. We tested the link between RGI and shoot dry weight reduction in LDG by assembling a new synthetic community lacking RGI strains. Dropping RGI strains out of the community restored growth induction by LDG. Finally, we showed that individual RGI strains from a few specific phyla were sufficient to switch the response to LDG from growth promotion to growth inhibition. Our results indicate that glyphosate hormesis was completely dependent on the root microbiome composition, specifically on the presence of root growth inhibitor strains. IMPORTANCE Since the introduction of glyphosate-resistant crops, glyphosate has become the most common and widely used herbicide around the world. Due to its intensive use and ability to bind to soil particles, it can be found at low concentrations in the environment. The effect of these remnants of glyphosate in plants has not been broadly studied; however, glyphosate 1,000 to 100,000 times less concentrated than the recommended field dose promoted growth in several species in laboratory and greenhouse experiments. However, this effect is rarely observed in agricultural fields, where complex communities of microbes have a central role in the way plants respond to external cues. Our study reveals how root-associated bacteria modulate the responses of Arabidopsis to low doses of glyphosate, shifting between growth promotion and growth inhibition.

Biological studies of soils in paired old and new land sites growing sugarcane

1997 ◽  
Vol 37 (4) ◽  
pp. 451 ◽  
Author(s):  
B. L. Blair ◽  
R. C. Magarey ◽  
J. I. Bull ◽  
E. J. Johnson
Keyword(s):  
Root Growth ◽  
Shoot Growth ◽  
Major Contributor ◽  
Growth Responses ◽  
Biological Community ◽  
Root Pathogens ◽  
Biological Studies ◽  
Growth Constraints ◽  
Growth Differences

Summary. The growth of sugarcane in soils from land monocultured with sugarcane, and from land which had either never been cropped with sugarcane, or just recently cropped, was compared under glasshouse conditions. In general, cane growth in new land soils was greater than in monocultured soil (shoot growth 7.4%, root growth 21.4%). Responses to soil pasteurisation were investigated in some soils and were greater in monocultured soils suggesting that root growth constraints were larger in the monocultured soil (210% response in monocultured soils v. 64% in new land soils). Assays for sugarcane root pathogens suggested that Pachymetra chaunorhiza was a major contributor to the old/new land growth responses, but it is unlikely that Pythium spp. were factors in the growth differences. Monitoring of other groups of organisms in soil from one site suggested that sugarcane monoculture may affect populations in the broader biological community.

scholarly journals EFFECTS OF IRRIGATION FREQUENCY ON PLANT GROWTH AND NUTRIENT LEVELS OF PINE BARK MEDIA

HortScience ◽  
1990 ◽  
Vol 25 (8) ◽  
pp. 849c-849
Author(s):  
T.E. Bilderback
Keyword(s):  
Plant Growth ◽  
Shoot Growth ◽  
Chemical Properties ◽  
Dry Weight ◽  
Pine Bark ◽  
Growth Responses ◽  
Irrigation Frequency ◽  
Foliar Tissue ◽  
Physical And Chemical ◽  
And Chemical Properties

Ilex × `Nellie R. Stevens' holly, Rhododendron sp. `Hinodegeri' azalea and Pyracantha coccinea, scarlet firethorn rooted cuttings were potted in • 3.81 containers. Irrigation was applied by Dram rings daily, or every 2,4,or 6 days. Approximately 1000 ml of water were applied at each irrigation. Three container media, including pine bark, and pine bark amended with either Terra-Sorb AG synthetic moisture extender incorporated at 1.2 kg/m3 or Aqua-Gro G wetting agent incorporated at 0.9 kg/m3 plus monthly drenches of 700 ml of 2500 ppm Aqua-Gro L were compared for physical and chemical properties and plant growth responses. Decreasing irrigation decreased pH, increased nutrient leachate levels, and increased foliar tissue levels of N,P,K,Ca,and Fe in holly and azalea. Pyracantha top and root dry weight was reduced at 4 and 6 day irrigation intervals, holly top growth was reduced by 6 day and azalea had greatest shoot growth at 2 day irrigation and was reduced by other irrigation frequencies. Top growth of all 3 species and root growth of pyracantha was reduced in the pine bark treatment.

scholarly journals Dwarf Bermudagrass Responses to Flurprimidol and Paclobutrazol

HortScience ◽  
2005 ◽  
Vol 40 (5) ◽  
pp. 1549-1551 ◽  
Author(s):  
Patrick E. McCullough ◽  
Haibo Liu ◽  
Lambert B. McCarty
Keyword(s):  
United States ◽  
Plant Growth ◽  
Growth Inhibition ◽  
Growth Regulators ◽  
Shoot Growth ◽  
Shoot Density ◽  
Root Mass ◽  
Clemson University ◽  
Putting Green ◽  
Dwarf Type

Plant growth regulators are applied to inhibit uneven shoot growth of putting green turf but research is limited on responses of dwarf-type bermudagrass cultivars to growth inhibition. Experiments were conducted at the Clemson University Greenhouse Complex with `Champion' and `TifEagle' bermudagrass grown in polyvinylchloride containers with 40 cm depths and 177 cm2 areas built to United States Golf Association specification. Flurprimidol was applied at 0.14, 0.28, and 0.48 kg·ha–1 a.i. and paclobutrazol at 0.14 kg·ha–1 a.i. on separate containers. Flurprimidol at 0.28 and 0.42 kg·ha-1 caused 17% and 31% reduction in turf color 5 weeks after treatment (WAT), respectively. `Champion' exhibited unacceptable turf injury (>30%) 2 WAT from paclobutrazol and all flurprimidol rates. `TifEagle' had unacceptable turf injury from flurprimidol at 0.42 kg·ha–1 2 WAT, 0.28 kg·ha–1 3 WAT, and 0.14 kg·ha–1 4 WAT that did not recover. Moderate injury (16% to 30%) was observed from paclobutrazol on `TifEagle' but ratings were acceptable. After 6 weeks, flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1 reduced bermudagrass green shoot density (GSD) per square centimeter by 20%, 40%, and 40%, respectively, while paclobutrazol reduced GSD 12%. `TifEagle' total clipping yield was reduced 60%, 76%, and 86% from flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1, respectively, and 37% from paclobutrazol. `Champion' total clipping yield was reduced 82%, 90%, and 90% from flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1, respectively, and 58% from paclobutrazol. After 6 weeks, flurprimidol reduced `Champion' total root mass by 44% over all three rates. `Champion' treated with paclobutrazol had similar total root mass to the untreated. `TifEagle' treated with all PGRs had similar rooting to the untreated. Overall, flurprimidol will likely not be suitable for dwarf bermudagrass maintenance at these rates; however paclobutrazol may have potential at ≤0.14 kg·ha–1. Chemical names used: Flurprimidol {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl] 5-pyrimidine-methanol}; Paclobutrazol, (+/-)–(R*,R*)-β-[(4-chlorophenyl) methyl]-α-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol.

scholarly journals Thermal treatment and leaching biochar alleviates plant growth inhibition from mobile organic compounds

2016 ◽  
Author(s):  
Nigel V Gale ◽  
Tara E Sackett ◽  
Sean C Thomas
Keyword(s):  
Plant Growth ◽  
Growth Inhibition ◽  
Organic Compounds ◽  
Solid Phase ◽  
Direct Injection ◽  
Gas Chromatography Mass Spectrometry ◽  
Plant Responses ◽  
Growth Responses ◽  
Water Leaching ◽  
Glasshouse Experiment

Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40 %. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, 50 t/ha) to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME) – gas chromatography – mass spectrometry (GC-MS) to qualitatively describe organic compounds in both biochar (through headspace extraction), and in the water leachates (through direct injection). Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, bisphenol and benzonoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species-specific patterns plant responses to biochar amendments in short-term experiments.

Ten-year growth and survival of Douglas-fir seedlings treated with plant growth regulating substances at transplant

2000 ◽  
Vol 30 (11) ◽  
pp. 1778-1787 ◽  
Author(s):  
C F Scagel ◽  
R G Linderman ◽  
R K Scagel
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Douglas Fir ◽  
Growth Responses ◽  
Indole Butyric Acid ◽  
Growth And Survival ◽  
Growing Seasons ◽  
Tree Survival ◽  
Stock Types ◽  
The Cost

Commercially available plant growth regulators (PGRs) or moisture retention gels, applied to the roots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) before planting, can modify indole-3-acetic acid (IAA) levels in roots, root growth responses, and tree survival. We treated two different 1+0 stock types (PSB313B and PSB323) of Douglas-fir with indole-butyric acid (IBA), ethephon (Ethrel®), alginate, or a combination of IBA and alginate. New root growth and IAA levels in roots were measured 2 weeks after planting, and aboveground growth and tree survival were monitored over 10 growing seasons after planting. Treatment with IBA or the combination of IBA and alginate increased IAA conjugate and free IAA levels in roots, root growth, and tree survival. Alginate treatment alone increased new root growth and tree survival, but did not increase free IAA levels in roots. Ethrel® treatment increased free IAA levels and root growth, but had no effect on IAA conjugates or tree survival. A cost analysis suggests that use of certain PGRs or alginate decreases the cost required to attain target stocking and increased tree size. Our results suggest that application of PGRs or other root-promoting materials to the roots of Douglas-fir before planting has the potential to be a cost-beneficial method for increasing root growth and tree survival.

scholarly journals Effects of green seaweed extract on Arabidopsis early development suggest roles for hormone signalling in plant responses to algal fertilisers

2018 ◽  
Author(s):  
Fatemeh Ghaderiardakani ◽  
Ellen Collas ◽  
Deborah Kohn Damiano ◽  
Katherine Tagg ◽  
Neil S. Graham ◽  
...  
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Growth Inhibition ◽  
Early Development ◽  
Land Plant ◽  
Root Growth Inhibition ◽  
Plant Responses ◽  
Germination Inhibition ◽  
Green Seaweed ◽  
Algal Extracts

AbstractThe growing population requires sustainable, environmentally-friendly crops. The plant growth-enhancing properties of algal extracts have suggested their use as biofertilisers. The mechanism(s) by which algal extracts affect plant growth are unknown.We examined the effects of extracts from the common green seaweed Ulva intestinalis on germination and root development in the model land plant Arabidopsis thaliana. Ulva extract concentrations above 0.1% inhibited Arabidopsis germination and root growth. Ulva extract <0.1% stimulated root growth. All concentrations of Ulva extract inhibited lateral root formation. An abscisic-acid-insensitive mutant, abi1, showed altered sensitivity to germination- and root growth-inhibition inhibition. Ethylene- and cytokinin-insensitive mutants were partly insensitive to germination-inhibition. This suggests that different mechanisms mediate each effect of Ulva extract on early Arabidopsis development and that multiple hormones contribute to germination-inhibition.Elemental analysis showed that Ulva contains high levels of Aluminium ions (Al3+). Ethylene and cytokinin have been suggested to function in Al3+-mediated root growth inhibition: our data suggest that if Ulva Al3+ levels inhibit root growth, this is via a novel mechanism. We suggest algal extracts should be used cautiously as fertilisers, as the inhibitory effects on early development may outweigh any benefits if the concentration of extract is too high.

scholarly journals Differential Growth Responses of Apple Species to Chilling and Root Pruning

1990 ◽  
Vol 115 (2) ◽  
pp. 196-202 ◽  
Author(s):  
Michael A. Arnold ◽  
Eric Young
Keyword(s):  
Root Growth ◽  
Shoot Growth ◽  
Root Pruning ◽  
Growth Responses ◽  
Differential Growth ◽  
Chilling Requirements ◽  
Root And Shoot Growth ◽  
Bare Root ◽  
Chilling Hours ◽  
Root Types

Malus dometica Borkh., M. anis, M. prunifolia Borkh., M. × robusta Rehd., M. antonovka, M. borwinkw, and M. ranetka bare-root seedlings were chilled at 5C for 0, 400, 800, 1200, or 1600 hours. After chilling treatments, one-half of the seedlings were root-pruned and all seedlings were placed in a greenhouse for 15 days. Quantitative differences between species in the timing and magnitude of new root and shoot growth responses to chilling were observed. Root pruning decreased and delayed the production of roots <0.6 mm in diameter in response to chilling, while the production of larger roots was less affected. Regeneration of both root types differed among species. For new large (≥ 0.6 mm in diameter) root growth criteria, interactions between chilling hours and species were apparent. Chilling requirements and growing degree hour requirements for vegetative budbreak of each species were estimated.

The effect of waterlogging on the growth and isoflavone concentration of Trifolium subterraneum L.

1969 ◽  
Vol 20 (5) ◽  
pp. 819 ◽  
Author(s):  
CM Francis ◽  
AC Devitt
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Shoot Growth ◽  
Trifolium Subterraneum ◽  
Relative Increase ◽  
General Increase ◽  
Isoflavone Content ◽  
Relative Tolerance ◽  
Isoflavone Concentration

Seventy-five cultivars were used to determine the effect of waterlogging on the yield and isoflavone content of three subspecies of Trifolium subterraneum L. The 21-day flooding treatment affected root growth more than shoot growth. The relative tolerance of the subspecies to waterlogging was yanninicum > subterraneum > brachycalycinurn. These results were in keeping with ecological evidence. The flooding treatment resulted in a general increase in leaf isoflavone concentrations. As with plant growth there was a significant subspecies x waterlogging interaction, the relative increase in isoflavone concentration being least for subsp. yanninicum.

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