Root Growth Inhibitors from Root Cap and Root Meristem ofZea maysL.

The observation was made previously that the reduction in radiosensitivity in Vicia faba (as measured by postirradiation root growth) by prolonging the exposure time from about 10 minutes to 24 hours is much less marked at 3°C. than at 19°C. If chromosome damage is mainly responsible for the reduced root growth, this observation might be explained by a smaller drop in the "two-hit" aberration component, resulting from an increased time for which breaks are available for rejoining at 3°C. This hypothesis was tested by comparing chromatid aberration frequencies in root meristem cells produced by 105 rads of 60Co γ rays, given at dose rates of 19.4 and 0.073 rads per minute. Beans were maintained in aerated water at 2°C. prior to and during irradiation, and at this temperature the rate of development of cells was such that the two different exposure times both occupied a period during which the cell sensitivity was approximately constant. Immediately subsequent to irradiation, the roots were returned to 19°C. and examined cytologically. All chromatid aberrations were less frequent after low dose rate treatment, but only the chromatid interchange reduction was significant. The average time for which breaks are available for reunion, calculated from Lea's G function, was found to be 12 hours (95 per cent C.L. 6 to 24 hours).

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A role for Ca2+ in the cellular differentiation of root cap cells: A re-examination of root growth control mechanisms

Environmental and Experimental Botany ◽

10.1016/0098-8472(90)90032-y ◽

1990 ◽

Vol 30 (4) ◽

pp. 515-523 ◽

Cited By ~ 16

Author(s):

R.J. Bennet ◽

C.M. Breen ◽

V.H. Bandu

Keyword(s):

Root Growth ◽

Cellular Differentiation ◽

Growth Control ◽

Root Cap ◽

Control Mechanisms

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Rhizogénèse adventive dans l'épicotyle du Pois : initiation et structuration de la racine

Canadian Journal of Botany ◽

10.1139/b82-035 ◽

1982 ◽

Vol 60 (3) ◽

pp. 261-280 ◽

Cited By ~ 8

Author(s):

A. Nougarède ◽

P. Rondet

Keyword(s):

Adventitious Roots ◽

Root Meristem ◽

Cell Layer ◽

Cell Number ◽

Root Cap ◽

Root Initiation ◽

Elongation Zone ◽

No Formation ◽

Depth Position ◽

Growing Conditions

The ability of the first internode of Pisum sativum epicotylary axis to produce adventitious roots was examined with respect to dark and light growing conditions and depth position of the soaked seeds in vermiculite. Root initiation began on the 7th day and moved acropetally until the 16th day, with no formation of new roots between older ones. DNA synthesis in the diploid interfascicular cells followed the first mitoses of root initiation. The cell layer that would normally have differentiated into an endodermis reacted more slowly and built a primordial root cap, protecting the root as it grew through the cortex. When the new root emerged a new root cap – protoderm complex was rebuilt from the subapical cells of the root meristem. The increase in cell number was highest during the first 24 h following root initiation, and the cell cycle was extremely short with a very reduced G1 phase. Only the elongation zone of the mature adventitious root showed polyploidy.

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Nitrogen Deficiency-Induced Decrease in Cytokinins Content Promotes Rice Seminal Root Growth by Promoting Root Meristem Cell Proliferation and Cell Elongation

Cells ◽

10.3390/cells9040916 ◽

2020 ◽

Vol 9 (4) ◽

pp. 916

Author(s):

Qi Wang ◽

Yanchun Zhu ◽

Xiao Zou ◽

Fengfeng Li ◽

Jialiang Zhang ◽

...

Keyword(s):

Cell Proliferation ◽

Root Growth ◽

Cell Elongation ◽

Developmental Plasticity ◽

Root Meristem ◽

Seminal Root ◽

Down Regulation ◽

Meristem Cell ◽

Root Meristem Cell ◽

N Deficiency

Rice (Oryza sativa L.) seedlings grown under nitrogen (N) deficiency conditions show a foraging response characterized by increased root length. However, the mechanism underlying this developmental plasticity is still poorly understood. In this study, the mechanism by which N deficiency influences rice seminal root growth was investigated. The results demonstrated that compared with the control (1 mM N) treatment, N deficiency treatments strongly promoted seminal root growth. However, the N deficiency-induced growth was negated by the application of zeatin, which is a type of cytokinin (CK). Moreover, the promotion of rice seminal root growth was correlated with a decrease in CK content, which was due to the N deficiency-mediated inhibition of CK biosynthesis through the down-regulation of CK biosynthesis genes and an enhancement of CK degradation through the up-regulation of CK degradation genes. In addition, the N deficiency-induced decrease in CK content not only enhanced the root meristem cell proliferation rate by increasing the meristem cell number via the down-regulation of OsIAA3 and up-regulation of root-expressed OsPLTs, but also promoted root cell elongation by up-regulating cell elongation-related genes, including root-specific OsXTHs and OsEXPs. Taken together, our data suggest that an N deficiency-induced decrease in CK content promotes the seminal root growth of rice seedlings by promoting root meristem cell proliferation and cell elongation.

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Growth inhibitors in oat grains. II. Bioassays for characterization of a new substance in leachate of oat hulls (Avena sativa) regulating root growth

Physiologia Plantarum ◽

10.1111/j.1399-3054.1988.tb05854.x ◽

1988 ◽

Vol 72 (2) ◽

pp. 414-422 ◽

Cited By ~ 8

Author(s):

M.-L. Haggquist ◽

K.-O. Widell ◽

M. Fredriksson ◽

C. Liljenberg

Keyword(s):

Root Growth ◽

Avena Sativa ◽

Growth Inhibitors ◽

Oat Hulls

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Supraoptimal Cytokinin Content Inhibits Rice Seminal Root Growth by Reducing Root Meristem Size and Cell Length via Increased Ethylene Content

International Journal of Molecular Sciences ◽

10.3390/ijms19124051 ◽

2018 ◽

Vol 19 (12) ◽

pp. 4051 ◽

Cited By ~ 11

Author(s):

Xiao Zou ◽

Junwei Shao ◽

Qi Wang ◽

Peisai Chen ◽

Yanchun Zhu ◽

...

Keyword(s):

Root Growth ◽

Cell Elongation ◽

Root Meristem ◽

Ethylene Biosynthesis ◽

Cell Length ◽

Seminal Root ◽

Dependent Manner ◽

Meristem Size ◽

Dose Dependent ◽

Ethylene Level

Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In this study, treatments of lovastatin (an inhibitor of CK biosynthesis) and kinetin (KT; a synthetic CK) were found to inhibit rice seminal root growth in a dose-dependent manner, suggesting that endogenous CK content is optimal for rapid growth of the seminal root in rice. KT treatment strongly increased ethylene level by upregulating the transcription of ethylene biosynthesis genes. Ethylene produced in response to exogenous KT inhibited rice seminal root growth by reducing meristem size via upregulation of OsIAA3 transcription and reduced cell length by downregulating transcription of cell elongation-related genes. Moreover, the effects of KT treatment on rice seminal root growth, root meristem size and cell length were rescued by treatment with aminoethoxyvinylglycine (an inhibitor of ethylene biosynthesis), which restored ethylene level and transcription levels of OsIAA3 and cell elongation-related genes. Supraoptimal CK content increases ethylene level by promoting ethylene biosynthesis, which in turn inhibits rice seminal root growth by reducing root meristem size and cell length.

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Isolation and Purification of Potent Growth Inhibitors from Piper methysticum Root

Molecules ◽

10.3390/molecules23081907 ◽

2018 ◽

Vol 23 (8) ◽

pp. 1907 ◽

Cited By ~ 9

Author(s):

Truong Van ◽

Tran Xuan ◽

Truong Minh ◽

Nguyen Quan

Keyword(s):

Mass Spectrometry ◽

Plant Growth ◽

Root Growth ◽

Ethyl Acetate ◽

Pepper Plant ◽

Piper Methysticum ◽

Growth Inhibitors ◽

Etoac Extract ◽

Inhibitory Activities ◽

Potent Growth

Piper methysticum (kava) root is known to possess promising weed suppressing activity. The present study was conducted to search for potent plant growth inhibitors from the root of this medicinal pepper plant. The ethyl acetate (EtOAc) extract exhibited the strongest reduction on growth of Raphanus sativus (radish) (IC50 shoot and root growth = 172.00 and 51.31 µg/mL respectively) among solvent extracts. From this active extract, nine potent growth inhibitors involved in the inhibitory activities of P. methysticum root were isolated, purified and characterized by column chromatography (CC), gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR). The six fractions purified by CC included two flavanones: 5-hydroxy-4′,7-dimethoxyflavanone (C1) and 5,7-dihydroxy-4′-methoxy-6,8-dimethylflavanone (matteucinol, C2) and six kavalactones: 5,6-dehydro-kavain (C3), a mixture of kavain and yagonin (C4), yagonin (C5) and dihydro-5,6-dehydrokavain, 7,8-dihydrokavain, dihydromethysticin and methysticin (C6). The amounts of 5-hydroxy-4′,7-dimethoxyflavanone, matteucinol, 5,6-dehydrokavain and yangonin were 0.76, 2.50, 2.75 and 2.09 mg/g dry weight (DW), respectively. The two flavanones C1 and C2 exhibited the strongest inhibition on shoot elongation (IC50 = 120.22 and 248.03 µg/mL, respectively), whilst the two kavalactone mixtures C4 and C6 showed the highest suppression on root growth of R. sativus (IC50 = 7.70 and 15.67 µg/mL, respectively). This study was the first to report the purification and inhibitory activities of the two flavanones 5-hydroxy-4′,7-dimethoxyflavanone and matteucinol in P. methysticum root. The isolated constituents from P. methysticum root including the flavanones C1 and C2 and the mixtures C4 and C6 may possess distinct modes of action on plant growth. Findings of this study highlighted that the combinations of hexane-ethyl acetate by 9:1 and 8:2 ratios successfully purified flavanones and kavalactones in P. methysticum root.

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