Hormonal Aspects of Senescence in Detached Tobacco Leaves

Even‐Chen, Zeev; Atsmon, Dan; Itai, Chanan

doi:10.1111/j.1399-3054.1978.tb01641.x

Cited by 24 publications

(11 citation statements)

References 26 publications

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“…As leaves begin to senesce, the cytokinin level in xylem sap (Sitton, Itai & Kende, 1967;Hewett & Wareing, 1973 ;Nooden, Singh & Letham, 1990) and leaves (Singh, Letham & Palni, 19926) declines markedly. Even-Chen, Atsmon & Itai (1978) detected a decrease in the endogenous cytokinin level of detached leaves before any major changes in the measured parameters of senescence were detected. This suggested that the drop in the cytokinin level could be related to the induction of senescence in detached leaves.…”

Section: Plant Grozcth Regulators (A) Cytokininsmentioning

confidence: 99%

Gene expression during leaf senescence

1994

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SUMMARY Leaf senescence is a hiphly‐controlled sequence of events comprising the final stage of development. Cells remain viable during the process and new gene expression is required. There is some similarity between senescence in plants and programmed cell death in animals. In this review, different classes of senescence‐related genes are defined and progress towards isolating such genes is reported. A range of internal and external factors which appear to cause leaf senescence is considered and various models for the mechanism of senescence‐ initiation are described. The current understanding of senescence at the wrganelle and molecular levels is presented. Finally, same ideas are mooted as to why senescence occurs and why it should be studied further.

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Section: Plant Grozcth Regulators (A) Cytokininsmentioning

confidence: 99%

Gene expression during leaf senescence

1994

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“…In some plant tissues, auxins stimulate ethylene synthesis (Even-Chen et al, 1978;Van Der Straeten et al, 1990) and ethylene synthesis can be induced by auxins in a tissue-specific manner (Van Der Straeten et al, 1990;Yip et al, 1992). Both Ethrel and IAA can induce stomatal opening in epidermis detached from leaves of Vicia faba (Levitt et al, 1987), and there is evidence that auxin-induced stomata1 opening (Levitt et al, 1987;Marten et al, 2991) is mediated through auxin-induced ethylene synthesis (Levitt et al, 1987 ethylene synthesis is required both for growth of callus and for embryo maturation (Kepczynski et al, 1992).…”

Section: Electrophoresis Of Total Sds-extractable Proteinsmentioning

confidence: 99%

Temperature and Abscisic Acid Can Be Used to Regulate Survival, Growth, and Differentiation of Cultured Guard Cell Protoplasts of Tree Tobacco

et al. 1995

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Cuard cell protoplasts isolated from leaves of Nicofiana g h c a (Craham) were cultured. Conditions were sought that would maximize survival and maintain cells i n their differentiated state. Temperature was an important determinant of survival, growth, and differentiation. As temperatures were increased from 24 to 32'C, survival for 1 week in culture increased from approximately 20% to approximately 80% of cells used to initiate cultures. At all of these temperatures, approximately 90% of surviving cells divided to form callus tissue. "Footprint" areas of cells cultured for 1 week at 32°C increased almost 30-fold. Cells cultured for 1 week at 34 t o 40°C also survived i n high percentages (approximately 80%), but they retained a morphology similar to that of guard cells and they did not divide. Footprint areas of cells cultured for 1 week at 38°C increased 6-fold. Cells cultured at 36 t o 4OoC in media containing 0.1 or 1.0 W M abscisic acid survived in high percentages and did not divide. At 38°C their footprint areas did not increase, but cells so cultured increased in diameter when treated with fusicoccin. Morphologies and electrophoretic profiles of total sodium dodecyl sulfate-extractable proteins suggest that cells cultured at 38°C in media containing abscisic acid remain differentiated. ~-a-(2-Aminoethoxyviny1)-glycine reduced survival t o <1 O/O at 26 or 32°C but had no effect at 38OC. At lower temperatures, cell growth and survival appear to be ethylene dependent.

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“…Additionally, an increase in free IAA level was found in the course of leaf senescence so far in tobacco (13), oat (23), and bean (24) leaves. In the last system, the increase in free IAA level was accompanied by a decrease in the level of IAA conjugates (24).…”

mentioning

confidence: 99%

Carbohydrates Stimulate Ethylene Production in Tobacco Leaf Discs

Meir¹,

Philosoph‐Hadas²,

Epstein³

et al. 1985

Plant Physiol.

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Various natrlly occurrg carbohydrates, applied at a concentration range of I to 100 m, lated ethyene producto for severl days in indoleacetic acid (IAA)-treated or untreated tobacco (Nicotiana tabacam L cv 'Xanthi') laf discs. The lag period for this sugr-stimulated ethylene prodution was 8 to 12 hours after excision in the untreated leaf discs, but less than 2 hours in the IAA-treated ones. Among the tested carbohydrates, 12 were foud to increase synergistically ethylene production, with D-galatose, sucrose, and lactose being the most active; annitol and L-ghose had o effec. The extent and duration of the increased ethylene production was dependent upon the type of sur applied, the tissu's age, and the existence of both exogeonos IAA and sar in the medium. Sucrose appeared to elicit a continuous IAA effect for 48 hours, as expressed by increased ethylene production, even when IAA was removed from the medium after a 4-hour pulse. Sucrose stimulted both the uptake and decarboxylation of [1-'4CIAA, as well as the hydrolysis of the esteric and amide IAA conjuptes formed in the tissue after appication of free IAA. This gradual hydrolysis was accompanied by a further accumulation of a third IAA metabolite. Moreover, synthetic indole-3-acetyl-L-alanine increased ethylene production mainly with sucrose, and this effect was accompanied by its increased decarboxylation and turnover pattern suggesting that release of free IAA was involved. An esteric IAA conjugate, tentatively identified by GC retention time was found to be the major component (84%) of the naturally occwuing IAA conjugates in tobacco leaves. Accordingly the sucrosestimuted ethylene production in tobacco leaves can be ascribed maily to the sucrose-stimulated hydrolysis of the esteric IAA conjugate.carbohydrates tested could elicit a stimulating effect in either of those systems, nor in pea epicotyls (8), and it was therefore suggested that the increased ethylene production in these tissues might be related to the toxicity of galactose (I 1) or stress effect of mannitol (21).Our recent study (3) established that sucrose could stimulate IAA-induced ethylene production in a synergistic action. This occurred only in tissues which were responsive to IAA with respect to ethylene production.A possible involvement of IAA in the sugar-stimulated ethylene production could be related to ACC2 formation from SAM, which is the rate-limiting step in ethylene biosynthesis and was found to be stimulated both by IAA (26) Intact leaves as well as leafdiscs of tobacco, incubated in plain water or buffer, produced very small amounts of ethylene (2). When 2% sucrose was added to tobacco leaf discs as a medium constituent, a remarkable increase in ethylene production, which lasted for several days, was observed. This occurred both in IAAtreated and untreated leaf discs, with the increase being much more pronounced in the former (3). A carbohydrate-stimulated ethylene production has been described so far in mung bean hypocotyls treated with D-galactose (I 1) and recent...

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Hormonal Aspects of Senescence in Detached Tobacco Leaves

Cited by 24 publications

References 26 publications

Gene expression during leaf senescence

Gene expression during leaf senescence

Temperature and Abscisic Acid Can Be Used to Regulate Survival, Growth, and Differentiation of Cultured Guard Cell Protoplasts of Tree Tobacco

Carbohydrates Stimulate Ethylene Production in Tobacco Leaf Discs

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