Modification of Respiration and Carbohydrate Status of Barley Roots by Selective Pruning

Farrar, J. F.; Jones, Cameron L.

doi:10.1111/j.1469-8137.1986.tb00827.x

Cited by 23 publications

(13 citation statements)

References 18 publications

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“…We argue that the most useful is the third, inducible capacity, since it can be used to compare with the current flux to determine whether the shoot is supplying roots at a rate substantially below their potential. There is no simple or agreed method of measuring inducible capacity, although the flux after 24 h on extra sucrose (Bingham and Farrar 1988;Gunn and Farrar 1999) or rate of sucrose uptake from solution (Farrar and Jones 1985;Ciereszko et al 1999) could be candidates.…”

Section: What Is Root'demand'?mentioning

confidence: 98%

The Control of Carbon Acquisition by and Growth of Roots

Farrar¹,

Jones²

2003

Root Ecology

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What controls the rate of growth of roots? Behind this deceptively simple question lie a very complex set of processes within the plant and a wide range of environmental variables that affect root growth. To begin to answer it, we will simplify by making the assumption that the question is nearly the same as this: what controls the rate of net acquisition of carbon by roots? A consideration of the gross fluxes of carbon (C) that together constitute the net flux into a root (Table 4.1) is thus central to our argument.We have recently provided a brief review of the main hypotheses for the control of C acquisition by roots (Farrar and Jones 2000). We concluded that each of the fluxes that contributes to the net acquisition of C exerts some degree of control over the process; we called this the 'shared control hypothesis'. Whilst many of these fluxes occur in the root, others are in the leaf or stern. We rejected two hypotheses wh ich are much simpler. These were the 'push hypothesis' , which suggests that net C acquisition is controlled by the supply of C from the shoot; and the 'pull hypothesis', where C acquisition is controlled by demand from within the root itself. Here we will concentrate on processes within roots, but these alone cannot give a complete understanding of control of fluxes within roots.Roots grow very quickly; young fibrous root systems can increase their dry weight by 25 % per day; root apices commonly elongate at 2 cm/day. To grow this quickly, the fluxes of assimilates and other compounds into, and metabolie rates in, the root must be correspondingly high. A root can gain C by import of carbohydrate and other compounds from the shoot, and by uptake of a variety of organic moleeules from the soil (Table 4.1). It can lose carbon by export to the shoot, by respiration, and by rhizodeposition involving loss of dead cells or exudation. The challenge is to determine just what controls each of the individual fluxes, and to evaluate just how important each is in the control of net C flux to the root.

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Section: What Is Root'demand'?mentioning

confidence: 98%

The Control of Carbon Acquisition by and Growth of Roots

Farrar¹,

Jones²

2003

Root Ecology

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“…Changing the source‐to‐sink ratio also causes effects that are consistent with this model. Excising all roots but one on a barley plant increases branching density and the length of secondary roots, but has little effect on the length of primary roots (Farrar & Jones 1986). Conversely, defoliating a wheat plant causes a rapid (few hours) decrease in primary and secondary root elongation rate (Bingham, Panico & Stevenson 1996).…”

Section: Introductionmentioning

confidence: 99%

Root elongation and branching is related to local hexose concentration in Arabidopsis thaliana seedlings

Freixes

Thibaud

Tardieu

et al. 2002

Plant Cell & Environment

144

123

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Root architecture can be profoundly affected by the carbon availability in the plant. We hypothesized that this effect could be mediated by the carbon status of root cells involved in elongation and branching processes. Arabidopsis thaliana plants were grown at several photosynthetic photon flux densities (PPFD) and were supplied with various sucrose concentrations in the root medium. Hexose and sucrose concentration was estimated in individual roots in the apical growing region of the primary root and of secondary roots as well as in the zone of primordia development. Local sugar concentration was high in fast‐growing and in highly branched roots and robust relationships between root elongation rate or branching and hexose concentration (but not sucrose) were found that were common to all situations experienced. Moreover, these relationships accounted for the plant‐to‐plant variability within a treatment as well as for the variability among individual secondary roots within a plant. These results support the view that local hexose concentration integrates changes in carbon availability from several sources and acts as a signal to induce at least part of the response of the root architecture to the environment.

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“…The sucrose concentration used was chosen as that which causes no net change in the sucrose content of Ricinus cotyledons (Waldhauser &• Komor, 1978). The cotyledon solution was changed after 24 h. After 48 h the tap roots were excised and ''C efflux from each root followed by the method of Farrar & Jones (1986), using 3 cm'' volumes, at O-''' and 30 °C. •RESULTS…”

Section: Methodsmentioning

confidence: 99%

Sugar unloading in roots of Ricinus communis L.

Chapleo

Hall

1989

New Phytologist

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S U M M A R Y' lie accumulation of exogenous D-fructose, D-glucose atid sucrose into root tips of Ricinus communis was studied. Accumulation of sucrose is biphasic with respect to substrate concentration, both saturable and non-saturable phases being discerned. Accumulation is sensitive to pH, the exogenous solute potential, PCMBS, and other sugars. Sap representative of the apoplast was collected by centrifugation and contains approximately 40 mol Tl -hexose equivalents. Plants were labelled to the steady state with respect to cotyledonary sucrose derivatives; \'hole roots were then analysed by compartmental analysis and the r-esults indicated similar apoplastic hexose concentrations. The vacuoles of roots grown in low salt solution contain most of the root soluble sugars, at a 'concentration of about 70 mol m '' hexose equivalents. The sugar content of such roots decreases with availability "f KCl to an extent which indicates that this involves a replacement of vacuolar hexose by alternative osmotica, 'supporting the results frot-n compartmental analysis.

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Modification of Respiration and Carbohydrate Status of Barley Roots by Selective Pruning

Cited by 23 publications

References 18 publications

The Control of Carbon Acquisition by and Growth of Roots

The Control of Carbon Acquisition by and Growth of Roots

Root elongation and branching is related to local hexose concentration in Arabidopsis thaliana seedlings

Sugar unloading in roots of Ricinus communis L.

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