Chlorophyll Degradation by Light in Leaf Discs in the Presence of Sugar

Khudairi, A. K.

doi:10.1111/j.1399-3054.1970.tb06454.x

Cited by 16 publications

(5 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In bean leaf discs Goldthwaite and Laetsch (1967) observed that chlorophyll loss was retarded at low light intensities and enhanced at intensities above 3200 lux. A similar light response was described by Khudairi (1970) for Xanthium leaves. He also observed that chlorophyll loss was accelerated in the light in the presence of a 0.01 M sucrose bathing solution, while such a sugar application retarded chlorophyll loss slightly in darkness.…”

Section: Introductionsupporting

confidence: 81%

Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors

Vanhasselt

Strikwerda

1976

Physiologia Plantarum

View full text Add to dashboard Cite

Chlorophyll degradation in Cucumis leaf discs was measured at different temperatures between 1 and 25°C in the light and in darkness, and in the presence or absence of sucrose. Two different processes of chlorophyll degradation could be distinguished, a lightrequiring process operating at 1 and 5°C and another, light and sucrose enhanced degradation process which was evident at 25°C. Degradation of leaf pigments at low temperatures was of a photooxidative nature since there was no degradation in the dark. The chlorophyll a/b ratio was decreased, carotene was degraded at a faster rate than chlorophyll, and 3-(3,4-dichlorophenyl)-l,ldimethylurea (DCMU) and triphenyltetrazolium chloride (TTC) which prevent photo-oxidation, protected against chlorophyll degradation. The light and sucrose enhanced chlorophyll degradation at 25°C was of an enzymatic nature since it occurred in the dark as well as in the light. The chlorophyll a/b ratio was not affected, and carotene and chlorophyll degradation occurred at the same rate. Since DCMU completely inhibited the light enhancement at 25°C and experimentation in a low oxygen atmosphere also protected chlorophyll against the effect of light and sugar application, it is suggested that the enhancement of chlorophyll degradation by light and sucrose at 25°C may be due to increased sugar uptake of the chloroplasts and consequently excessive starch formation in the organelles.

show abstract

Section: Introductionsupporting

confidence: 81%

Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors

Vanhasselt

Strikwerda

1976

Physiologia Plantarum

View full text Add to dashboard Cite

show abstract

“…Acceleration of leaf yellowing by sugars in light‐incubated leaf discs was first described by Khudairi (1970). Other treatments that result in leaf sugar accumulation, such as phloem interruption to prevent sugar export out of the leaves (Fröhlich & Feller 1991; Parrott et al.…”

Section: Introductionmentioning

confidence: 99%

Metabolic regulation of leaf senescence: interactions of sugar signalling with biotic and abiotic stress responses

Wingler¹,

Roitsch²

2008

Plant Biology

253

152

View full text Add to dashboard Cite

Sugars are important signals in the regulation of plant metabolism and development. During stress and in senescing leaves, sugars often accumulate. In addition, both sugar accumulation and stress can induce leaf senescence. Infection by bacterial and fungal pathogens and attack by herbivores and gall-forming insects may influence leaf senescence via modulation of the sugar status, either by directly affecting primary carbon metabolism or by regulating steady state levels of plant hormones. Many types of biotic interactions involve the induction of extracellular invertase as the key enzyme of an apoplasmic phloem unloading pathway, resulting in a source-sink transition and an increased hexose/sucrose ratio. Induction of the levels of the phytohormones ethylene and jasmonate in biotic interactions results in accelerated senescence, whereas an increase in plant- or pathogen-derived cytokinins delays senescence and results in the formation of green islands within senescing leaves. Interactions between sugar and hormone signalling also play a role in response to abiotic stress. For example, interactions between sugar and abscisic acid (ABA) signalling may be responsible for the induction of senescence during drought stress. Cold treatment, on the other hand, can result in delayed senescence, despite sugar and ABA accumulation. Moreover, natural variation can be found in senescence regulation by sugars and in response to stress: in response to drought stress, both drought escape and dehydration avoidance strategies have been described in different Arabidopsis accessions. The regulation of senescence by sugars may be key to these different strategies in response to stress.

show abstract

“…There was some question as to whether senescen lebur leaf discs could be accelerated by abscisic acib (4). Discs were cut from second node, 5-week-olh leaves and sterilized with 2% calcium hypochlorite washed with sterile distilled water, and placed dicated sterile solution.…”

Section: Methodsmentioning

confidence: 99%

Lipid Transformations in Greening and Senescing Leaf Tissue

Newman¹,

Rowell²,

Byrd³

1973

Plant Physiol.

View full text Add to dashboard Cite

An effort has been made to study the lipid transformations, especially acyl groups, during two important changes in leaves. These two changes were greening and senescence. Since no one single tissue, in general, lends itself to such a study, two kinds of leaf tissue were selected-barley (Hordeum vulgare L.) and Cocklebur (Xanthium strumarium L.). These two changes are of interest since one is a phase in which photosynthesis is initiated and the other is a phase during which photosynthesis shuts down. To follow changes in the fatty acid composition during greening, barley leaf tissue was used. An effort was made to alter the lag phase in the chlorophyll and fatty acid changes by treating the tissue with red, far red, or red followed by far red light prior to a continuous white light treatment. As opposed to following the greening process, several experiments were conducted to follow lipid changes in the senescent phase of photosynthetic tissues. For example, the changes in pigments and fatty acids of green barley leaf tissue placed in the dark were followed. Placing the barley leaf tissue in the dark causes a simulated senescence effect. To continue the study of senescence, cocklebur leaf discs were floated on an aqueous medium. Cocklebur is an excellent choice since the excised leaf discs senesce rapidly without a concomitant necrosis. We also followed the rate of acetate-`C incorporation into senescing cocklebur leaf lipids such as MGDG2, DGDG, and the phospholipids.Unser and Mohr (11) ated an increase in MGDG and DGDG in mustard seedlings. We wondered if a red light treatment might reduce the lag effect in chlorophyll synthesis as well as in the fatty acid changes which are associated with greening. We have found that if greening is prevented red light did not reduce the lag period for the synthesis of linolenate (8). However, no attempt was made to allow chlorophyll synthesis to occur while determining the effect of a prior red light treatment on the subsequent fatty acid synthesis. Akoyunoglou (1) found that there was a pronounced effect of red and far red light treatment on chlorophyll synthesis in old leaves; no effect was observed in young leaves. We therefore allowed the plants to green while studying the effect of a prior red light treatment on the fatty acid changes. Concerning the senescent phase, Draper (2) found that the final stages of this phase in cucumber cotyledons are marked by a loss of all classes of lipids. We have attempted to make a rough estimate of acetate incorporation and carbon retention in the lipids in senescing cocklebur leaf discs treated with either sucrose or abscisic acid. Khudairi (4) found that leaf discs floated on sucrose showed a more rapid loss of chlorophyll than those floated on water. We tried the same experiment using RNase-free sucrose. We wondered if the sucrose would also hasten changes in the lipids which were characteristic of the senescence phase. The abscisic acid was used to accelerate the senescence process. MATERIALS AND METHODSGrowth of Plants and Light T...

show abstract

Chlorophyll Degradation by Light in Leaf Discs in the Presence of Sugar

Cited by 16 publications

References 11 publications

Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors

Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors

Metabolic regulation of leaf senescence: interactions of sugar signalling with biotic and abiotic stress responses

Lipid Transformations in Greening and Senescing Leaf Tissue

Contact Info

Product

Resources

About