Effect of Rapid Changes in Sink-Source Ratio on Export and Distribution of Products of Photosynthesis in Leaves of <i>Beta vulgaris</i> L. and <i>Phaseolus vulgaris</i> L.

Fondy, Bernadette R.; Geiger, Donald R.

doi:10.1104/pp.66.5.945

Cited by 64 publications

(39 citation statements)

References 12 publications

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“…Studies in sugar beet show that source leaf sucrose is relatively constant throughout the day except during the initial part of the light period, when it accumulates (3,4). This pattern is in contrast to that for barley where sucrose accumulates in photosynthesizing source leaves throughout the light period (10,11).…”

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confidence: 65%

Sources of Sucrose Translocated from Illuminated Sugar Beet Source Leaves

Geiger¹,

Ploeger²,

Fox³

et al. 1983

Plant Physiol.

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A search for source leaf sucrose pools that differed in their relation to export was carried out in photosynthesizing leaves of Beta vulgaris L. The time course of depletion of I14Cisucrose in a leaf in unlabeled CO2 following steady state labeling provided evidence for two distinct sucrose pools. After the start of the Ught period, leaf blade sucrose remained constant although it exchanged between the two pools. Newly synthesized sucrose destined for export passed through one pool more rapidly than through the other. All of the leaf blade sucrose appeared to exchange with export sucrose.Modeling and regression analysis of I14Clsucrose data provided a means for estimating the size of the two pools. From 20 to 40% of the sucrose was calculated to be present in the pool that provided the less direct path to export; this was likely vacuolar sucrose. The remainder of the sucrose in the blade was probably in the cytoplasm and veins. Added amounts of leaf blade sucrose, produced in response to elevated C02, appeared to be stored mainly in the vacuolar compartment.

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confidence: 65%

Sources of Sucrose Translocated from Illuminated Sugar Beet Source Leaves

Geiger¹,

Ploeger²,

Fox³

et al. 1983

Plant Physiol.

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“…When the light period is prolonged, both pathways continue to function and contribute to the higher rate of sucrose synthesis. Because export from sugar beet leaves is regulated by the availability of sucrose (6,8) and because its leaves are capable of exporting sucrose at rates much faster than those found during the usual day period (26), the additional sucrose is exported.…”

Section: Discussionmentioning

confidence: 99%

“…These data demonstrate that this circadian regulation is an ordinary occurrence in plants, which prepares metabolism for the accustomed day-night transition. Circadian regulation of starch accumulation is likely related to the strict regulation of transitory starch accumulation in relation to photosynthetic duration and the length of the night period (3,6,19).…”

Section: Discussionmentioning

confidence: 99%

“…In photosynthesizing sugar beet (Beta vulgaris L.) leaves, sucrose is exported essentially as fast as it is synthesized and therefore does not accumulate to a significant extent, even when plants are growing at irradiance levels that are half of full sunlight (9). Increasing photosynthesis by increasing CO2 or decreasing 02 concentrations can increase sucrose synthesis and export rate (10,26), whereas it is difficult to increase the proportion of currently assimilated carbon that is exported (6). Darkening or excising a number of sugar beet source leaves markedly lessens the supply of assimilate to sinks; yet, neither export nor sucrose synthesis increases in the remaining leaves, nor is the portion of newly fixed carbon allocated to starch altered (6).…”

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“…Increasing photosynthesis by increasing CO2 or decreasing 02 concentrations can increase sucrose synthesis and export rate (10,26), whereas it is difficult to increase the proportion of currently assimilated carbon that is exported (6). Darkening or excising a number of sugar beet source leaves markedly lessens the supply of assimilate to sinks; yet, neither export nor sucrose synthesis increases in the remaining leaves, nor is the portion of newly fixed carbon allocated to starch altered (6). Clearly, the pro- ' Supported by National Science Foundation grants DCB 89-15789 and summer fellowships from the University of Dayton Research Council.…”

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Evidence for Circadian Regulation of Starch and Sucrose Synthesis in Sugar Beet Leaves

Geiger²,

Shieh³

1992

Plant Physiol.

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Starch accumulation and sucrose synthesis and export were measured in leaves of sugar beet (Beta vulgaris L.) during a period of prolonged irradiance in which illumination was extended beyond the usual 14-hour day period. During much of the 14-hour day period, approximately 50% of the newly fixed carbon was distributed to sucrose, about 40% to starch, and less than 10% to hexose. Beginning about 2 hours before the end of the usual light period, the portion of newly fixed carbon allocated to sucrose gradually increased, and correspondingly less carbon went to starch. By the time the transition ended, about 4 hours into the extension of the light period, nearly 90% of newly fixed carbon was incorporated into sucrose and little or none into starch. Most of the additional sucrose was exported. Gradual cessation of starch accumulation was not the result of a futile cycle of simultaneous starch synthesis and degradation. Neither was it the result of a decrease in the extractable activity of adenosine diphosphoglucose pyrophosphorylase or phosphoglucose isomerase, enzymes important in starch synthesis. Nor was there a notable change in control metabolites considered to be important in regulating starch synthesis. Starch accumulation appeared to decrease markedly because of an endogenous circadian shift in carbon allocation, which occurred in preparation for the usual night period and which diverted carbon from the chloroplast to the cytosol and sucrose synthesis.Carbon that is exported from leaves of sugar beet at night or during times of slow photosynthesis comes mainly from diumal starch reserves rather than from accumulated sucrose (8,9,11). In photosynthesizing sugar beet (Beta vulgaris L.) leaves, sucrose is exported essentially as fast as it is synthesized and therefore does not accumulate to a significant extent, even when plants are growing at irradiance levels that are half of full sunlight (9). Increasing photosynthesis by increasing CO2 or decreasing 02 concentrations can increase sucrose synthesis and export rate (10,26), whereas it is difficult to increase the proportion of currently assimilated carbon that is exported (6).

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Expression of a yeast-derived invertase in the cell wall of tobacco and Arabidopsis plants leads to accumulation of carbohydrate and inhibition of photosynthesis and strongly influences growth and phenotype of transgenic tobacco plants.

et al. 1990

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Chimeric genes consisting of the coding sequence of the yeast invertase gene suc 2 and different N‐terminal portions of the potato‐derived vacuolar protein proteinase inhibitor II fused to the 35S CaMV promoter and the poly‐A site of the octopine synthase gene were transferred into tobacco and Arabidopsis thaliana plants using Agrobacterium based systems. Regenerated transgenic plants display a 50‐ to 500‐fold higher invertase activity compared to non‐transformed control plants. This invertase is N‐glycosylated and efficiently secreted from the plant cell leading to its apoplastic location. Whereas expression of the invertase does not lead to drastic changes in transgenic Arabidopsis thaliana plants, transgenic tobacco plants show dramatic changes with respect to development and phenotype. Expression of the invertase leads to stunted growth due to reduction of internodal distances, to development of bleached and/or necrotic regions in older leaves and to suppressed root formation. In mature leaves, high levels of soluble sugars and starch accumulate. These carbohydrates do not show a diurnal turnover. The accumulation of carbohydrate is accompanied by an inhibition of photosynthesis, and in tobacco, by an increase in the rate of respiration. Measurements in bleached versus green areas of the same leaf show that the bleached section contains high levels of carbohydrates and has lower photosynthesis and higher respiration than green sections. It is concluded that expression of invertase in the cell wall interrupts export and leads to an accumulation of carbohydrates and inhibition of photosynthesis.

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Effect of Rapid Changes in Sink-Source Ratio on Export and Distribution of Products of Photosynthesis in Leaves of Beta vulgaris L. and Phaseolus vulgaris L.

Cited by 64 publications

References 12 publications

Sources of Sucrose Translocated from Illuminated Sugar Beet Source Leaves

Sources of Sucrose Translocated from Illuminated Sugar Beet Source Leaves

Evidence for Circadian Regulation of Starch and Sucrose Synthesis in Sugar Beet Leaves

Expression of a yeast-derived invertase in the cell wall of tobacco and Arabidopsis plants leads to accumulation of carbohydrate and inhibition of photosynthesis and strongly influences growth and phenotype of transgenic tobacco plants.

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