Effects of Light Intensity on Root Development in a D-Root Growth System

Plant development is highly affected by light quality, direction, and intensity. Under natural growth conditions, shoots are directly exposed to light whereas roots develop underground shielded from direct illumination. The photomorphogenic development strongly represses shoot elongation whereas promotes root growth. Over the years, several studies helped the elucidation of signaling elements that coordinate light perception and underlying developmental outputs. Light exposure of the shoots has diverse effects on main root growth and lateral root (LR) formation. In this study, we evaluated the phenotypic root responses of wild-type Arabidopsis plants, as well as several mutants, grown in a D-Root system. We observed that sucrose and light act synergistically to promote root growth and that sucrose alone cannot overcome the light requirement for root growth. We also have shown that roots respond to the light intensity applied to the shoot by changes in primary and LR development. Loss-of-function mutants for several root light-response genes display varying phenotypes according to the light intensity to which shoots are exposed. Low light intensity strongly impaired LR development for most genotypes. Only vid-27 and pils4 mutants showed higher LR density at 40 μmol m–2 s–1 than at 80 μmol m–2 s–1 whereas yuc3 and shy2-2 presented no LR development in any light condition, reinforcing the importance of auxin signaling in light-dependent root development. Our results support the use of D-Root systems to avoid the effects of direct root illumination that might lead to artifacts and unnatural phenotypic outputs.

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Quantitative Studies on Root Development. III. Further Observations on Growth in the Seedling Phase

Functional Plant Biology ◽

10.1071/pp9750425 ◽

1975 ◽

Vol 2 (3) ◽

pp. 425 ◽

Cited By ~ 3

Author(s):

L Rahman ◽

D Aspinall ◽

LG Paleg

Keyword(s):

Light Intensity ◽

Root Growth ◽

Root System ◽

Root Development ◽

Elongation Rate ◽

Quantitative Studies ◽

Rooting Medium ◽

Early Phases

The influences of light intensity, rooting medium, and the excision of various organs on the early phases of root growth in barley seedlings (cv. Piroline) were explored. The emergence of root axes was affected by light intensity and excision of roots, endosperm or shoot, but was not altered by the rooring medium. Elongation of the emerged axes was similarly responsive. The elongation rate of both the set of axes and individual axes fell wi4h time. The elongation rate of laterals was less than that of the axes and was sensitive to the excision of seedling organs. The data are discussed in relation to the hypothesis that the growth of the root system is determined by the availability of substrate.

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Selective deficits in the circadian light response in mice lacking PACAP

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00268.2004 ◽

2004 ◽

Vol 287 (5) ◽

pp. R1194-R1201 ◽

Cited By ~ 89

Author(s):

C. S. Colwell ◽

S. Michel ◽

J. Itri ◽

W. Rodriguez ◽

J. Tam ◽

...

Keyword(s):

Wheel Running ◽

Light Exposure ◽

Light Response ◽

Phase Shifts ◽

Circadian System ◽

Loss Of Function ◽

Running Activity ◽

Wheel Running Activity ◽

Deficient Mice

Previous studies indicate that light information reaches the suprachiasmatic nucleus through a subpopulation of retinal ganglion cells that contain both glutamate and pituitary adenylyl cyclase-activating peptide (PACAP). Although the role of glutamate in this pathway has been well studied, the involvement of PACAP and its receptors is only beginning to be understood. To investigate the functions of PACAP in vivo, we developed a mouse model in which the gene coding for PACAP was disrupted by targeted homologous recombination. RIA was used to confirm a lack of detectable PACAP protein in these mice. PACAP-deficient mice exhibited significant impairment in the magnitude of the response to brief light exposures with both light-induced phase delays and advances of the circadian system impacted. This mutation equally impacted phase shifts induced by bright and dim light exposure. Despite these effects on phase shifting, the loss of PACAP had only limited effects on the generation of circadian oscillations, as measured by rhythms in wheel-running activity. Unlike melanopsin-deficient mice, the mice lacking PACAP exhibited no loss of function in the direct light-induced inhibition of locomotor activity, i.e., masking. Finally, the PACAP-deficient mice exhibited normal phase shifts in response to exposure to discrete dark treatments. The results reported here show that the loss of PACAP produced selective deficits in the light response of the circadian system.

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Strong morphological defects in conditional Arabidopsis abp1 knock-down mutants generated in absence of functional ABP1 protein

F1000Research ◽

10.12688/f1000research.7654.1 ◽

2016 ◽

Vol 5 ◽

pp. 86 ◽

Cited By ~ 12

Author(s):

Jaroslav Michalko ◽

Matouš Glanc ◽

Catherine Perrot-Rechenmann ◽

Jiří Friml

Keyword(s):

Biological Function ◽

Normal Growth ◽

Growth Conditions ◽

Auxin Signaling ◽

Loss Of Function ◽

Knock Out ◽

Knock Down ◽

Morphological Defects ◽

Auxin Binding Protein ◽

Target Effects

The Auxin Binding Protein 1 (ABP1) is one of the most studied proteins in plants. Since decades ago, it has been the prime receptor candidate for the plant hormone auxin with a plethora of described functions in auxin signaling and development. The developmental importance of ABP1 has recently been questioned by identification of Arabidopsis thaliana abp1 knock-out alleles that show no obvious phenotypes under normal growth conditions. In this study, we examined the contradiction between the normal growth and development of the abp1 knock-outs and the strong morphological defects observed in three different ethanol-inducible abp1 knock-down mutants (abp1-AS, SS12K, SS12S). By analyzing segregating populations of abp1 knock-out vs. abp1 knock-down crosses we show that the strong morphological defects that were believed to be the result of conditional down-regulation of ABP1 can be reproduced also in the absence of the functional ABP1 protein. This data suggests that the phenotypes in abp1 knock-down lines are due to the off-target effects and asks for further reflections on the biological function of ABP1 or alternative explanations for the missing phenotypic defects in the abp1 loss-of-function alleles.

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Living in Biological Darkness: Objective Sleepiness and the Pupillary Light Responses Are Affected by Different Metameric Lighting Conditions during Daytime

Journal of Biological Rhythms ◽

10.1177/0748730419847845 ◽

2019 ◽

Vol 34 (4) ◽

pp. 410-431 ◽

Cited By ~ 4

Author(s):

Jan de Zeeuw ◽

Alexandra Papakonstantinou ◽

Claudia Nowozin ◽

Sophia Stotz ◽

Mandy Zaleska ◽

...

Keyword(s):

Light Exposure ◽

Light Condition ◽

Light Response ◽

Light Spectrum ◽

Light Responses ◽

Lighting Condition ◽

Lighting Conditions ◽

Pupillary Light ◽

Light Effects ◽

Dim Light

Nighttime melatonin suppression is the most commonly used method to indirectly quantify acute nonvisual light effects. Since light is the principal zeitgeber in humans, there is a need to assess its strength during daytime as well. This is especially important since humans evolved under natural daylight but now often spend their time indoors under artificial light, resulting in a different quality and quantity of light. We tested whether the pupillary light response (PLR) could be used as a marker for nonvisual light effects during daytime. We also recorded the wake electroencephalogram to objectively determine changes in daytime sleepiness between different illuminance levels and/or spectral compositions of light. In total, 72 participants visited the laboratory 4 times for 3-h light exposures. All participants underwent a dim-light condition and either 3 metameric daytime light exposures with different spectral compositions of polychromatic white light (100 photopic lux, peak wavelengths at 435 nm or 480 nm, enriched with longer wavelengths of light) or 3 different illuminances (200, 600, and 1200 photopic lux) with 1 metameric lighting condition (peak wavelength at 435 nm or 480 nm; 24 participants each). The results show that the PLR was sensitive to both spectral differences between metameric lighting conditions and different illuminances in a dose-responsive manner, depending on melanopic irradiance. Objective sleepiness was significantly reduced, depending on melanopic irradiance, at low illuminance (100 lux) and showed fewer differences at higher illuminance. Since many people are exposed to such low illuminance for most of their day—living in biological darkness—our results imply that optimizing the light spectrum could be important to improve daytime alertness. Our results suggest the PLR as a noninvasive physiological marker for ambient light exposure effects during daytime. These findings may be applied to assess light-dependent zeitgeber strength and evaluate lighting improvements at workplaces, schools, hospitals, and homes.

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Cell kinetics of auxin transport and activity in Arabidopsis root growth and skewing

Nature Communications ◽

10.1038/s41467-021-21802-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yangjie Hu ◽

Moutasem Omary ◽

Yun Hu ◽

Ohad Doron ◽

Lukas Hoermayer ◽

...

Keyword(s):

Root Growth ◽

Single Cell ◽

Root Development ◽

Normal Growth ◽

Growth Conditions ◽

Auxin Biosynthesis ◽

Auxin Synthesis ◽

Spatio Temporal ◽

Auxin Transporter ◽

Kinetics Of

AbstractAuxin is a key regulator of plant growth and development. Local auxin biosynthesis and intercellular transport generates regional gradients in the root that are instructive for processes such as specification of developmental zones that maintain root growth and tropic responses. Here we present a toolbox to study auxin-mediated root development that features: (i) the ability to control auxin synthesis with high spatio-temporal resolution and (ii) single-cell nucleus tracking and morphokinetic analysis infrastructure. Integration of these two features enables cutting-edge analysis of root development at single-cell resolution based on morphokinetic parameters under normal growth conditions and during cell-type-specific induction of auxin biosynthesis. We show directional auxin flow in the root and refine the contributions of key players in this process. In addition, we determine the quantitative kinetics of Arabidopsis root meristem skewing, which depends on local auxin gradients but does not require PIN2 and AUX1 auxin transporter activities. Beyond the mechanistic insights into root development, the tools developed here will enable biologists to study kinetics and morphology of various critical processes at the single cell-level in whole organisms.

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Root development under fluctuating soil physical stress – plastic and elastic responses

10.5194/egusphere-egu2020-19056 ◽

2020 ◽

Author(s):

Tino Colombi ◽

Hanna Sjulgård ◽

Daniel Iseskog ◽

Thomas Keller

Keyword(s):

Growth Rate ◽

Root Growth ◽

Root Development ◽

Optimal Growth ◽

Penetration Resistance ◽

Growth Conditions ◽

Physical Stress ◽

Soil Air ◽

Physical Conditions ◽

Root Growth Rate

<p>Physical properties of soil such as penetration resistance and oxygen concentration of soil air strongly influence root system development in plants. Soils typically exhibit considerable spatial and temporal fluctuations in penetration resistance and oxygen concentration of soil air due to wetting-drying cycles, small-scale differences in soil compactness or hotspots of biological activity. Hence, roots of a single plant are exposed to different physical environments and thus physical stresses during their growth through the soil profile. Plants are known to adjust their root development to these spatiotemporal fluctuations in soil physical conditions. Such phenotypic adjustments include changes of root growth rate as well as alterations of root morphology and anatomy. However, these adjustments reduce accessibility of water and nutrients and may increase the carbon demand for soil exploration, which limits aboveground plant development. Until now, it is unclear whether such adjustments in root development are plastic (i.e. the phenotype is irreversibly changed even when roots re-enter zones with optimal growth conditions) or elastic (i.e. the phenotype is only temporarily changed and recovers again when roots re-enter zones with optimal growth conditions).</p><p>To investigate the plasticity and elasticity of root development, we designed customized microrhizotrons in which soil penetration resistance and the concentration of oxygen in soil air can be varied. Near-infrared (&#955;=830 nm) time-lapse imaging was applied to quantify root growth rates, and combined with measurements of root morphology and anatomy. A series of experiments was conducted using different crop species with contrasting root system properties (fibrous vs. taproot system, thin vs. thick roots). After an establishment period of three days under optimal growth conditions, roots were exposed for 24 hours to increased penetration resistance, hypoxia and the combination of both stresses. Following this, the stress was released, and plants continued to grow for 24 hours at optimal conditions, before a second stress was applied for another 24 hours. Generally, root development responded to changes in soil physical conditions across all species. However, depending on the species, the adjustments in root development were found to be constant or temporary, i.e. plastic or elastic. This difference between species was particularly pronounced for root growth rate. Root growth rate in pea recovered after soil physical stress was released, while root growth rate in wheat remained low after stress release. The obtained findings will be discussed with respect to the tolerance of different plants to soil physical stress as well as the effects of root growth on soil structure dynamics.</p>

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Sound Waves Promote Arabidopsis thaliana Root Growth by Regulating Root Phytohormone Content

International Journal of Molecular Sciences ◽

10.3390/ijms22115739 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5739

Author(s):

Joo Yeol Kim ◽

Hyo-Jun Lee ◽

Jin A Kim ◽

Mi-Jeong Jeong

Keyword(s):

Arabidopsis Thaliana ◽

Cell Division ◽

Root Growth ◽

Apical Meristem ◽

Cell Number ◽

Root Apical Meristem ◽

Control Group ◽

Auxin Signaling ◽

Ethylene Signaling ◽

Sound Waves

Sound waves affect plants at the biochemical, physical, and genetic levels. However, the mechanisms by which plants respond to sound waves are largely unknown. Therefore, the aim of this study was to examine the effect of sound waves on Arabidopsis thaliana growth. The results of the study showed that Arabidopsis seeds exposed to sound waves (100 and 100 + 9k Hz) for 15 h per day for 3 day had significantly longer root growth than that in the control group. The root length and cell number in the root apical meristem were significantly affected by sound waves. Furthermore, genes involved in cell division were upregulated in seedlings exposed to sound waves. Root development was affected by the concentration and activity of some phytohormones, including cytokinin and auxin. Analysis of the expression levels of genes regulating cytokinin and auxin biosynthesis and signaling showed that cytokinin and ethylene signaling genes were downregulated, while auxin signaling and biosynthesis genes were upregulated in Arabidopsis exposed to sound waves. Additionally, the cytokinin and auxin concentrations of the roots of Arabidopsis plants increased and decreased, respectively, after exposure to sound waves. Our findings suggest that sound waves are potential agricultural tools for improving crop growth performance.

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Effect of noisy galvanic vestibular stimulation on dynamic posture sway under visual deprivation in patients with bilateral vestibular hypofunction

Scientific Reports ◽

10.1038/s41598-021-83206-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Po-Yin Chen ◽

Ying-Chun Jheng ◽

Chien-Chih Wang ◽

Shih-En Huang ◽

Ting-Hua Yang ◽

...

Keyword(s):

Clinical Trial ◽

Light Exposure ◽

Light Condition ◽

Vestibular Stimulation ◽

Galvanic Vestibular Stimulation ◽

Lateral Deviation ◽

Clinical Trial Registration ◽

Vestibular Hypofunction ◽

Dark Conditions ◽

Bilateral Vestibular Hypofunction

AbstractA single-blind study to investigate the effects of noisy galvanic vestibular stimulation (nGVS) in straight walking and 2 Hz head yaw walking for healthy and bilateral vestibular hypofunction (BVH) participants in light and dark conditions. The optimal stimulation intensity for each participant was determined by calculating standing stability on a force plate while randomly applying six graded nGVS intensities (0–1000 µA). The chest–pelvic (C/P) ratio and lateral deviation of the center of mass (COM) were measured by motion capture during straight and 2 Hz head yaw walking in light and dark conditions. Participants were blinded to nGVS served randomly and imperceivably. Ten BVH patients and 16 healthy participants completed all trials. In the light condition, the COM lateral deviation significantly decreased only in straight walking (p = 0.037) with nGVS for the BVH. In the dark condition, both healthy (p = 0.026) and BVH (p = 0.017) exhibited decreased lateral deviation during nGVS. The C/P ratio decreased significantly in BVH for 2 Hz head yaw walking with nGVS (p = 0.005) in light conditions. This study demonstrated that nGVS effectively reduced walking deviations, especially in visual deprived condition for the BVH. Applying nGVS with different head rotation frequencies and light exposure levels may accelerate the rehabilitation process for patients with BVH.Clinical Trial Registration This clinical trial was prospectively registered at www.clinicaltrials.gov with the Unique identifier: NCT03554941. Date of registration: (13/06/2018).

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Opposite Root Growth Phenotypes of hy5 versus hy5 hyh Mutants Correlate with Increased Constitutive Auxin Signaling

PLoS Genetics ◽

10.1371/journal.pgen.0020202 ◽

2006 ◽

Vol 2 (11) ◽

pp. e202 ◽

Cited By ~ 94

Author(s):

Richard Sibout ◽

Poornima Sukumar ◽

Chamari Hettiarachchi ◽

Magnus Holm ◽

Gloria K. Muday ◽

...

Keyword(s):

Root Growth ◽

Auxin Signaling

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A low-cost aeroponic phenotyping system for storage root development: unravelling the below-ground secrets of cassava (Manihot esculenta)

Plant Methods ◽

10.1186/s13007-019-0517-6 ◽

2019 ◽

Vol 15 (1) ◽

Cited By ~ 4

Author(s):

Michael Gomez Selvaraj ◽

Maria Elker Montoya-P ◽

John Atanbori ◽

Andrew P. French ◽

Tony Pridmore

Keyword(s):

Root Growth ◽

Root Development ◽

Low Cost ◽

Root Traits ◽

Suitable Model ◽

Root Initiation ◽

Storage Root ◽

Economic Traits ◽

Storage Roots ◽

Storage Root Development

Abstract Background Root and tuber crops are becoming more important for their high source of carbohydrates, next to cereals. Despite their commercial impact, there are significant knowledge gaps about the environmental and inherent regulation of storage root (SR) differentiation, due in part to the innate problems of studying storage roots and the lack of a suitable model system for monitoring storage root growth. The research presented here aimed to develop a reliable, low-cost effective system that enables the study of the factors influencing cassava storage root initiation and development. Results We explored simple, low-cost systems for the study of storage root biology. An aeroponics system described here is ideal for real-time monitoring of storage root development (SRD), and this was further validated using hormone studies. Our aeroponics-based auxin studies revealed that storage root initiation and development are adaptive responses, which are significantly enhanced by the exogenous auxin supply. Field and histological experiments were also conducted to confirm the auxin effect found in the aeroponics system. We also developed a simple digital imaging platform to quantify storage root growth and development traits. Correlation analysis confirmed that image-based estimation can be a surrogate for manual root phenotyping for several key traits. Conclusions The aeroponic system developed from this study is an effective tool for examining the root architecture of cassava during early SRD. The aeroponic system also provided novel insights into storage root formation by activating the auxin-dependent proliferation of secondary xylem parenchyma cells to induce the initial root thickening and bulking. The developed system can be of direct benefit to molecular biologists, breeders, and physiologists, allowing them to screen germplasm for root traits that correlate with improved economic traits.

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