Growth Responses of <i>Plantago major</i> L. ssp. <i>pleiosperma</i> (Pilger) to Changes in Mineral Supply

Kuiper, Daan

doi:10.1104/pp.87.3.555

Cited by 55 publications

(32 citation statements)

References 5 publications

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“…5). Such a restricted role of cytokinins in Pi-starvation signaling is in conflict with reports associating the increase of the root-to-shoot growth ratio of plants during Pi starvation with the observed reduction of cytokinin signaling under these conditions (Kuiper, 1988;Kuiper et al, 1988). In addition, it is plausible that senescence, a Pi-mobilizing condition that can be stimulated by Pi starvation, involves reduced cytokinin signaling.…”

Section: Cytokinin Interactions With Sugar and Pi-starvation Signalingcontrasting

confidence: 50%

Interaction between Phosphate-Starvation, Sugar, and Cytokinin Signaling in Arabidopsis and the Roles of Cytokinin Receptors CRE1/AHK4 and AHK3

et al. 2005

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Cytokinins control key processes during plant growth and development, and cytokinin receptors CYTOKININ RESPONSE 1/WOODEN LEG/ARABIDOPSIS HISTIDINE KINASE 4 (CRE1/WOL/AHK4), AHK2, and AHK3 have been shown to play a crucial role in this control. The involvement of cytokinins in signaling the status of several nutrients, such as sugar, nitrogen, sulfur, and phosphate (Pi), has also been highlighted, although the full physiological relevance of this role remains unclear. To gain further insights into this aspect of cytokinin action, we characterized a mutant with reduced sensitivity to cytokinin repression of a Pi starvation-responsive reporter gene and show it corresponds to AHK3. As expected, ahk3 displayed reduced responsiveness to cytokinin in callus proliferation and plant growth assays. In addition, ahk3 showed reduced cytokinin repression of several Pi starvation-responsive genes and increased sucrose sensitivity. These effects of the ahk3 mutation were especially evident in combination with the cre1 mutation, indicating partial functional redundancy between these receptors. We examined the effect of these mutations on Pi-starvation responses and found that the double mutant is not significantly affected in long-distance systemic repression of these responses. Remarkably, we found that expression of many Pi-responsive genes is stimulated by sucrose in shoots and to a lesser extent in roots, and the sugar effect in shoots of Pi-starved plants was particularly enhanced in the cre1 ahk3 double mutant. Altogether, these results indicate the existence of multidirectional cross regulation between cytokinin, sugar, and Pi-starvation signaling, thus underlining the role of cytokinin signaling in nutrient sensing and the relative importance of Pi-starvation signaling in the control of plant metabolism and development.

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Section: Cytokinin Interactions With Sugar and Pi-starvation Signalingcontrasting

confidence: 50%

Interaction between Phosphate-Starvation, Sugar, and Cytokinin Signaling in Arabidopsis and the Roles of Cytokinin Receptors CRE1/AHK4 and AHK3

et al. 2005

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“…This increase is generally caused by an increased relative growth rate of the roots and a decreased relative growth rate of the shoot shortly after nitrogen deprivation (Kuiper, 1988;Wickens and Cheeseman, 1991;Figure t). If nitrogen is supplied at an exponential rate below the one to sustain maximum growth and all other environmental variables being constant, finally the relative growth rate of shoot and root become equal with time and RWR does not change any more (McDonald et al, 1986;Van der Weft et al, 1993b,c; Figure 1).…”

Section: Short-and Long-term Effects Of Reduced Nitrogen Supply On Romentioning

confidence: 96%

Carbon allocation to shoots and roots in relation to nitrogen supply is mediated by cytokinins and sucrose: Opinion

1996

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In this paper we firstly show some general responses of biomass partitioning upon nitrogen deprivation. Secondly, these responses are explained in terms of allocation of carbon and nitrogen, photosynthesis and respiration, using a simulation model. Thirdly, we present a hypothesis for the regulation of biomass partitioning to shoots and roots.Shortly after nitrogen deprivation, the relative growth rate (RGR) of the roots generally increases and thereafter decreases, whereas that of the shoot decreases immediately. The increased RGR of the root and decreased RGR of the shoot shortly after a reduction in the nitrogen supply, cause the root weight ratio (root weight per unit plant weight) to increase rapidly.We showed previously that allocation of carbon and nitrogen to shoots and roots can satisfactorily be described as a function of the internal organic plant nitrogen concentration. Using these functions in a simulation model, we analyzed why the relative growth rate of the roots increases shortly after a reduction in nitrogen supply. The model predicts that upon nitrogen deprivation, the plant nitrogen concentration and the rate of photosynthesis per unit plant weight rapidly decrease, and the allocation of recently assimilated carbon and nitrogen to roots rapidly increases. Simulations show that the increased relative growth rate of the root upon nitrogen deprivation is explained by decreased use of carbon for root respiration, due to decreased carbon costs for nitrogen uptake. The stimulation of the relative growth rate of the root is further amplified by the increased allocation of carbon and nitrogen to roots. Using the simple relation between the plant nitrogen concentration and allocation, the model describes plant responses quite realistically.Based on information in the literature and on our own experiments we hypothesize that allocation of carbon is mediated by sucrose and cytokinins. We propose that nitrogen deprivation leads to a reduced cytokinin production, a decreased rate of cytokinin export from the roots to the shoot, and decreased cytokinin concentrations. A reduced cytokinin concentration in the shoot represses cell division in leaves, whereas a low cytokinin concentration in roots neutralizes the inhibitory effect of cytokinins on cell division. A reduced rate of cell division in the leaves leads to a reduced unloading of sucrose from the phloem into the expanding cells. Consequently, the sucrose concentration in the phloem nearby the expanding cells increases, leading to an increase in turgot pressure in the phloem nearby the leaf's division zone. In the roots, cell division continues and no accumulation of sugars occurs in dividing cells, leading to only marginal changes in osmotic potential and turgot pressure in the phloem nearby the root's cell division zone. These changes in turgor pressure in the phloem of roots and sink leaves affect the turgor pressure gradients between source leaf-sink leaf and source leaf -root in such a way that relatively more carbohydrates are exported to...

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“…Though the molecular mode of action is unknown, it is generally assumed that they play a decisive role in the control of sink activity and nutrient partitioning (Kuiper 1988;Kuiper et al 1989). …”

Section: Introductionmentioning

confidence: 99%

Loading and translocation of various cytokinins in phloem and xylem of the seedlings of Ricinus communis L.

Komor

Liegl

Schobert

1993

Planta

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Abstract. The phloem sap of Ricinus seedlings was analyzed for cytokinins and the concentration was compared with that in cotyledons and xylem sap. The dominant cytokinin in the phloem sap was isopentenyladenine (70 nM) when the endosperm was attached to the cotyledons; zeatin, dihydrozeatin and cytokinin-ribosides were present at relatively low concentrations (1-2 nM). Removal of the endosperm and incubation of the cotyledons in buffer led to a sharp decrease in the level of isopentenyladenine in the phloem sap, down to the value for zeatin, namely 1-2 nM. Similar low cytokinin concentrations were found in the xylem sap, too, whereas in the cotyledons the cytokinin content was at least 10-fold higher. Incubation of the cotyledons with various cytokinins (isopentenyladenine, zeatin and their ribosides) led to an increase of each of the applied cytokinins in the phloem sap, including also the metabolically closely related cytokinins. Zeatin was especially well loaded. It is concluded that the phloem translocates most free bases and ribosides of the various cytokinin species, if they are offered to the phloem. The data also show that the cytokinin levels in the phloem, which may be far higher than in the xylem, are subject to strong fluctuations depending on the physiological situation.

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Growth Responses of Plantago major L. ssp. pleiosperma (Pilger) to Changes in Mineral Supply

Abstract: MATERIALS AND METHODS

Cited by 55 publications

References 5 publications

Interaction between Phosphate-Starvation, Sugar, and Cytokinin Signaling in Arabidopsis and the Roles of Cytokinin Receptors CRE1/AHK4 and AHK3

Interaction between Phosphate-Starvation, Sugar, and Cytokinin Signaling in Arabidopsis and the Roles of Cytokinin Receptors CRE1/AHK4 and AHK3

Carbon allocation to shoots and roots in relation to nitrogen supply is mediated by cytokinins and sucrose: Opinion

Loading and translocation of various cytokinins in phloem and xylem of the seedlings of Ricinus communis L.

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