Cucumber cotyledon expansion as a bioassay for cytokinins

Narain, Apoorva; Laloraya, Malini

doi:10.1016/s0044-328x(74)80038-3

Cited by 26 publications

(12 citation statements)

References 11 publications

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Section: Introductionmentioning

confidence: 99%

“…In light-sensitive lettuce seeds, cytokinins increase the growth rate of cotyledons (5), while red light primarily enhances elongation of radicle cells (20). Cotyledons from numerous other dicots also grow faster in the presence of exogenous cytokinins (2,4,9,10,16,19), and this phenomenon has been developed as a cytokinin bioassay by Esashi and Leopold (2), Letham (9,10), and Narain and Laloraya (16 ing wall plasticity, while red light-enhanced lettuce seed germination seems to arise from an osmotic effect due to more rapid degradation of some macromolecule (15). We are not aware of data indicating that either red light or cytokinins increase wall plasticity, and our studies were to determine whether increased cell expansion (10) of excised radish cotyledons by cytokinins could be due to water uptake resulting from osmotic effects of enhanced solute accumulation.…”

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Promotion of Radish Cotyledon Enlargement and Reducing Sugar Content by Zeatin and Red Light

Huff¹,

Ross²

1975

Plant Physiol.

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Effects of zeatin on amino acid and sugar contents of detached radish (Raphanus saivus L) cotyledons were investigated to determine if accumulation of these solutes contributes to cytokinin-enhanced growth. Protein (14,18,21), and certain portions of grass leaves expand faster after treatment with either of these stimuli, as evidenced by leaf unrolling (11,23). In light-sensitive lettuce seeds, cytokinins increase the growth rate of cotyledons (5), while red light primarily enhances elongation of radicle cells (20). Cotyledons from numerous other dicots also grow faster in the presence of exogenous cytokinins (2,4,9,10,16,19), and this phenomenon has been developed as a cytokinin bioassay by Esashi and Leopold (2), Letham (9,10), and Narain and Laloraya (16). ing wall plasticity, while red light-enhanced lettuce seed germination seems to arise from an osmotic effect due to more rapid degradation of some macromolecule (15). We are not aware of data indicating that either red light or cytokinins increase wall plasticity, and our studies were to determine whether increased cell expansion (10) of excised radish cotyledons by cytokinins could be due to water uptake resulting from osmotic effects of enhanced solute accumulation. We found that both cytokinins (in the presence of light) and red light increased the reducing sugar contents of the cotyledons, and these increases were highly correlated with cotyledon growth. MATRIAILS AND METHODSRadish seeds (Raphanus sativus L. var. Early Scarlet Globe) were surface sterilized with 10% (v/v) Clorox and, after thoroughly rinsing, were germinated in darkness for 48 hr on wet paper. The smaller cotyledon cut from each selected seedling was used in all studies. Usually five cotyledons (20-35 mg fresh weight) were randomly selected for each sample, blotted gently, weighed as a group, and placed adaxial side down on Whatman No. 1 filter paper covering the bottom of a 5.5-cm Petri dish. The filter paper was previously wetted with 1 ml of 2 mm potassium phosphate buffer (pH 6.4) containing designated additives. The Petri dishes were placed on wet paper towels in glass trays covered with clear plastic film, and cotyledons were incubated at 25 C. The trays were also covered with aluminum foil for incubation in darkness. After incubation, cotyledons were blotted and reweighed.Immediately after obtaining final weights, cotyledons in each sample to be analyzed for protein and amino acids were placed in 10 ml of hot 80% (v/v) ethanol and boiled until volumes were reduced to about 2 ml. An additional 10 ml of 80% ethanol was then added, and samples were homogenized with a Brinkmann Polytron and centrifuged for 15 min at 17,300g at 4 C. Supernatant volumes were adjusted to 20 ml, and a-amino nitrogen was determined on 1-ml aliquots, as described by Yemm and Cocking (24), using glutamine as a standard. Residues from centrifugation were prepared for protein analysis by twice dissolving in 0.1 N KOH and precipitating with 10% (w/v) trichloroacetic acid. The final precipitates were...

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Promotion of Radish Cotyledon Enlargement and Reducing Sugar Content by Zeatin and Red Light

Huff¹,

Ross²

1975

Plant Physiol.

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“…Nonwounded, cut, abraded, and zeatin-treated cotyledons were grown 3 d in 3.2 ml of 20 mM KCl in darkness at 27°C. Each group of 10 these results is unclear. Perhaps the experimental conditions were more favorable for growth than Chl formation, or perhaps an additional wound factor suppresses Chl formation (i.e.…”

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confidence: 96%

“…The bioassays studied, all of which seem quite specific to cytokinins, were growth (3,8,10), Chl formation (4), and cell division (6,8). All results are consistent with the hypothesis, but interpretations still suffer from those of most bioassays.…”

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Effects of Wounding on Cytokinin Activity in Cucumber Cotyledons

Crane¹,

Ross²

1986

Plant Physiol.

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Three known physiological responses to exogenous cytokinins were measured in wounded and nonwounded cotyledons from cucumber (Cucumis sativus L. cv Marketer) seedlings grown in darkness. Enhanced cell division, chlorophyll formation, and cotyledon expansion were detected in wounded cotyledons. The data suggest that wounding enhances endogenous cytokinin activity.MATERIALS AND METHODS Plant Material. Cucumber (Cucumis sativus L. cv Marketer) seeds were surface sterilized by quickly rinsing in 1% (w:v) NaOCl, followed by several rinses in distilled H20. Seeds were germinated and grown 5 d over wet paper towels in darkness at 27°C (1 1). All studies were done with cotyledons excised from 5-d-old seedlings under a dim green safelight. Ten cotyledons were cultured adaxial side down at 27°C on a layer of Whatman No.

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Cytological and Biochemical Aspects of Cytokinin‐enhanced Growth of Radish (Raphanus Sativus) Cotyledons

Thomas

Kugrens

Ross

1980

American J of Botany

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Light and electron microscopy revealed no stimulation of oleosome disappearance or chloroplast development associated with zeatin‐enhanced growth of excised radish cotyledons. Accelerated protein body breakdown was the only detectable effect of zeatin treatment. Isocitrate lyase activity, disappearance of total lipids, and appearance of galactolipids, phospholipids, and chlorophyll were unaffected by zeatin. Results indicate that cytokinins do not accelerate conversion of radish cotyledons from storage to photosynthetic organs.

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Cucumber cotyledon expansion as a bioassay for cytokinins

Cited by 26 publications

References 11 publications

Promotion of Radish Cotyledon Enlargement and Reducing Sugar Content by Zeatin and Red Light

Promotion of Radish Cotyledon Enlargement and Reducing Sugar Content by Zeatin and Red Light

Effects of Wounding on Cytokinin Activity in Cucumber Cotyledons

Cytological and Biochemical Aspects of Cytokinin‐enhanced Growth of Radish (Raphanus Sativus) Cotyledons

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