The Inhibition of Brussels Sprout Leaf Senescence by Kinins

Dennis, David T.; Stubbs, M.; Coultate, Tom

doi:10.1139/b67-106

Cited by 45 publications

(16 citation statements)

References 18 publications

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“…Within only a few exceptions, the loss of protein from the discs was no greater than the loss from the attached leaves. (2,3,5,14), although bean leaf discs lose little protein and only 20% chlorophyll (7,15).…”

Section: Methodsmentioning

confidence: 99%

“…Some workers have reported differences in the senescence pattern of attached leaves compared to leaf discs (10,11,13,16,18,19). Dennis et al (5) found different changes in the chloroplast ultrastructure during senescence of attached old leaves and detached aged leaves. Lewington et al (11) con-cluded that senescence of detached leaves was not the same process as senescence of attached leaves.…”

mentioning

confidence: 98%

mentioning

confidence: 99%

“…Discs from young leaves senesce more slowly than discs from old leaves (4,5,7,19). The ability of plant growth regulators to retard senescence is less on discs from young leaves than from old leaves (2,5,18). Some workers have reported differences in the senescence pattern of attached leaves compared to leaf discs (10,11,13,16,18,19).…”

mentioning

confidence: 99%

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Apple Leaf Senescence: Leaf Disc Compared to Attached Leaf

Spencer¹,

Trrus²

1973

Plant Physiol.

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Section: Methodsmentioning

confidence: 99%

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confidence: 98%

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confidence: 99%

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confidence: 99%

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Apple Leaf Senescence: Leaf Disc Compared to Attached Leaf

Spencer¹,

Trrus²

1973

Plant Physiol.

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“…Radioactive spots were eluted with 2 ml of 20(% ethanol, and 0.1 ml was estimated. Spots 6 Table IV. Effect of Kilietint onl "CO2 Ilicorporationt info PIhosphate-Esters Fifty leaf discs (9-mm diameter) pretreated for 24 hr with kinetin (5 ,g/ml) were exposed to "CO2 for 1.5 hr.…”

Section: Effects Of Plant Growth Hormones On Starch Content Of Leaf Dmentioning

confidence: 99%

Kinetin and Carbohydrate Metabolism in Chinese Cabbage

Berridge¹,

Ralph²

1971

Plant Physiol.

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The effects of kinetin on starch and sugar levels and on 4CO2 and aP-orthophosphate labeling patterns of floated Chinese cabbage (Brassica pekinensis) leaf discs were investigated. Kinetin caused gross starch degradation. Neutral sugars were depressed by 30 to 40% in leaf tissue treated with kinetin for 24 hours. 14CO2 labeling of leaf discs pretreated with kinetin for 24 hours showed increased radioactivity in chloroform-soluble material and most sugar phosphates, and a 35 to 40% decrease in radioactivity in the neutral sugars, glucose, sucrose, and fructose. Incorporation into ATP was increased by 40 % by kinetin. "P-Orthophosphate uptake was inhibited 30 % by kinetin. When corrected for uptake, kinetin stimulated incorporation into chloroform-soluble material but had little effect on other cell fractions. These results indicate that kinetin mobilizes starch reserves and increases the flow of sugars required for the synthesis of lipids and structural materials in floated discs.We have previously shown (2) that cytokinins stimulate expansion of floated Chinese cabbage leaf discs while maintaining the levels of ribosomes and RNA in the discs. We report here effects of kinetin and sucrose on Chinese cabbage leaf disc expansion; on starch, sugar, and sugar phosphate levels; and on fixation and metabolism of "CO2 in floated leaf discs. MATERIALS AND METHODS PLANT GROVVTH AND SAMPLINGChinese cabbage (Brassica pekinensis, var. Wong Bok) plants were grown in a glasshouse at 25 C under natural light. Young rapidly expanding leaves 7 to 11 cm long from 4-to 6-weekold plants were routinely used. Discs (9-mm diameter) were removed from interveinal areas with a cork borer and floated on solutions made up in Vickery's solution (2). Equal numbers of discs from each half-leaf were randomly distributed between Petri dishes, and the dishes were incubated in a light room (600 lumens/sq ft) at 25 C under a 16-hr photoperiod. Following incubation the discs were washed with water, blotted dry, weighed and extracted.The mechanism of action of the plant hormones, cytokinins, is at present unknown. Cytokinins have been shown to modify the incorporation of radioactive precursors into nucleic acids and proteins in excised leaf tissue (11). However, recent more critical studies (8,14) (10,15). STARCH AND SUGAR DETERMINATIONStarch. Leaf discs were ground with 4 ml of TM buffer (0.01 M MgCl2, 0.01 M tris-HCl, pH 7.6). The homogenate was strained through fine cheesecloth. The mortar and cheesecloth were rinsed with 4 ml of TM buffer, and the total extract was centrifuged at 12,000g for 10 min. The pellet was extracted twice with TM buffer containing 2% Triton X-100 (to remove chlorophyll). After centrifugation the resulting pellet was suspended in 2 ml of TM buffer and incubated with pancreatic deoxyribonuclease I (10 ,tg) at 27 C for 25 min. The remaining insoluble material was washed twice with 95% ethanol. Starch in the residue was hydrolyzed with perchloric acid, and the resulting sugars were determined with anthrone (9).Sugars....

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Ultrastructural Changes of Chloroplasts in Attached and Detached, Aging Primary Wheat Leaves

Hurkman

1979

American J of Botany

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Degradation of chloroplasts is shown in mesophyll cells of primary leaves of wheat. The sequence of ultrastructural changes in chloroplasts of naturally senescing leaves is compared with that of detached, aging leaves. In chloroplasts of naturally senescing leaves, the first indications of aging are the appearance of osmiophilic globuli and reorientation of the thylakoidal system. The membranes of the grana and intergrana lamellae then become distended and later dissociate into distinct vesicles. Concurrent with these membrane changes, osmiophilic globuli increase in size and number, and the stroma breaks down. Finally, the chloroplast envelope ruptures and plastid contents disperse throughout the cell's interior. In chloroplasts of mesophyll cells in detached, aging leaves, initial changes also include appearance of osmiophilic globuli, but later stages of chloroplast degradation are different. The chloroplast envelope ruptures before the lamellae break down. Swelling of grana and intergrana lamellae is not pronounced and, additionally, the thylakoidal system degenerates without forming vesicles or numerous osmiophilic globuli. These differences in the sequence of chloroplast degradation indicate that naturally senescing leaves rather than detached, aging leaves should be used in studies of chloroplast senescence.

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The Inhibition of Brussels Sprout Leaf Senescence by Kinins

Cited by 45 publications

References 18 publications

Apple Leaf Senescence: Leaf Disc Compared to Attached Leaf

Apple Leaf Senescence: Leaf Disc Compared to Attached Leaf

Kinetin and Carbohydrate Metabolism in Chinese Cabbage

Ultrastructural Changes of Chloroplasts in Attached and Detached, Aging Primary Wheat Leaves

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