Low sink demand limits photosynthesis under P(i) deficiency

The role of the demand for carbon assimilates (the 'sink') in regulating photosynthetic carbon assimilation (Pn: the 'source') in response to phosphate (P(i)) deficiency was examined in tobacco (Nicotiana tabacum L.). P(i) supply was maintained or withdrawn from plants, and in bo...

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Veröffentlicht in:Journal of experimental botany. - 1985. - 52(2001), 358 vom: 31. Mai, Seite 1083-91
1. Verfasser: Pieters, A J (VerfasserIn)
Weitere Verfasser: Paul, M J, Lawlor, D W
Format: Aufsatz
Sprache:English
Veröffentlicht: 2001
Zugriff auf das übergeordnete Werk:Journal of experimental botany
Schlagworte:Journal Article Research Support, Non-U.S. Gov't Phosphates Adenosine Triphosphate 8L70Q75FXE Phosphotransferases (Alcohol Group Acceptor) EC 2.7.1.- phosphoribulokinase EC 2.7.1.19 Ribulose-Bisphosphate Carboxylase EC 4.1.1.39
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245 1 0 |a Low sink demand limits photosynthesis under P(i) deficiency 
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520 |a The role of the demand for carbon assimilates (the 'sink') in regulating photosynthetic carbon assimilation (Pn: the 'source') in response to phosphate (P(i)) deficiency was examined in tobacco (Nicotiana tabacum L.). P(i) supply was maintained or withdrawn from plants, and in both treatments the source/sink ratio was decreased in some plants by darkening all but two source leaves (partially darkened plants). The remaining plants were kept fully illuminated. P(i)-sufficient plants showed little variation in rate of Pn, amounts of P(i) or phosphorylated intermediates. Withdrawal of P(i) decreased Pn by 75% under the growing conditions and at both low and high internal CO2 concentration. Concomitantly, P(i), phosphorylated intermediates and ATP contents decreased and starch increased. RuBP and activity of phosphoribulokinase closely matched the changes in Pn, but Rubisco activity remained high. Partial darkening P(i)-deficient plants delayed the loss of photosynthetic activity; Rubisco and phosphoribulokinase activities and amounts of sucrose and metabolites, particularly RuBP and G6P, were higher than in fully illuminated Pi-deficient plants. Rates of sucrose export from leaves were more than 2-fold greater than in fully illuminated P(i)-deficient plants. Greater sucrose synthesis, facilitated by increased G6P content, an activator of SPS, would recycle P(i) from the cytosol back to the chloroplast, maintaining ATP, RuBP and hence Pn. It is concluded that low sink strength imposes the primary limitation on photosynthesis in P(i)-deficient plants which restricts sucrose export and sucrose synthesis imposing an end-product synthesis limitation of photosynthesis 
650 4 |a Journal Article 
650 4 |a Research Support, Non-U.S. Gov't 
650 7 |a Phosphates  |2 NLM 
650 7 |a Adenosine Triphosphate  |2 NLM 
650 7 |a 8L70Q75FXE  |2 NLM 
650 7 |a Phosphotransferases (Alcohol Group Acceptor)  |2 NLM 
650 7 |a EC 2.7.1.-  |2 NLM 
650 7 |a phosphoribulokinase  |2 NLM 
650 7 |a EC 2.7.1.19  |2 NLM 
650 7 |a Ribulose-Bisphosphate Carboxylase  |2 NLM 
650 7 |a EC 4.1.1.39  |2 NLM 
700 1 |a Paul, M J  |e verfasserin  |4 aut 
700 1 |a Lawlor, D W  |e verfasserin  |4 aut 
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