Phloem transport : a review of mechanisms and controls

It is generally believed that an osmotically generated pressure gradient drives the phloem mass flow. So far, this widely accepted Münch theory has required remarkably few adaptations, but the debate on alternative and additional hypotheses is still ongoing. Recently, a possible shortcoming of the M...

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Veröffentlicht in:Journal of experimental botany. - 1985. - 64(2013), 16 vom: 22. Nov., Seite 4839-50
1. Verfasser: De Schepper, Veerle (VerfasserIn)
Weitere Verfasser: De Swaef, Tom, Bauweraerts, Ingvar, Steppe, Kathy
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2013
Zugriff auf das übergeordnete Werk:Journal of experimental botany
Schlagworte:Journal Article Research Support, Non-U.S. Gov't Review Carbon transport Münch theory leakage-retrieval mechanism loading phloem plant defence relay hypothesis mehr... signalling sink sources sugar transport unloading.
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520 |a It is generally believed that an osmotically generated pressure gradient drives the phloem mass flow. So far, this widely accepted Münch theory has required remarkably few adaptations, but the debate on alternative and additional hypotheses is still ongoing. Recently, a possible shortcoming of the Münch theory has been pointed out, suggesting that the Münch pressure flow is more suitable for herbs than for trees. Estimation of the phloem resistance indicates that a point might be reached in long sieve tubes where the pressure required to drive the Münch flow cannot be generated. Therefore, the relay hypothesis regained belief as it implies that the sieve tubes are shorter then the plant's axial axis. In the source phloem, three different loading strategies exist which probably result from evolutionary advantages. Passive diffusion seems to be the most primitive one, whereas active loading strategies substantially increase the growth potential. Along the transport phloem, a leakage-retrieval mechanism is observed. Appreciable amounts of carbohydrates are lost from the sieve tubes to feed the lateral sinks, while a part of these lost carbohydrates is subsequently reloaded into the sieve tubes. This mechanism is probably involved to buffer short-term irregularities in phloem turgor and gradient. In the long term, the mechanism controls the replenishment and remobilization of lateral stem storage tissues. As phloem of higher plants has multiple functions in plant development, reproduction, signalling, and growth, the fundamental understanding of the mechanisms behind phloem transport should be elucidated to increase our ability to influence plant growth and development 
650 4 |a Journal Article 
650 4 |a Research Support, Non-U.S. Gov't 
650 4 |a Review 
650 4 |a Carbon transport 
650 4 |a Münch theory 
650 4 |a leakage-retrieval mechanism 
650 4 |a loading 
650 4 |a phloem 
650 4 |a plant defence 
650 4 |a relay hypothesis 
650 4 |a signalling 
650 4 |a sink 
650 4 |a sources 
650 4 |a sugar transport 
650 4 |a unloading. 
700 1 |a De Swaef, Tom  |e verfasserin  |4 aut 
700 1 |a Bauweraerts, Ingvar  |e verfasserin  |4 aut 
700 1 |a Steppe, Kathy  |e verfasserin  |4 aut 
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