The Analysis of Growth and Cell Production in Root Apices

Gandar, P. W.

doi:10.1086/337133

Cited by 65 publications

(39 citation statements)

References 18 publications

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“…Cell division rate (d,) was calculated in each segment (i) by combining the records of SER and of local cell length in the continuity equation (Gandar, 1980;Silk, 1992):…”

Section: Calculations Of Cell Division Rate Cell Flux and Duration mentioning

confidence: 99%

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Temperature Affects Expansion Rate of Maize Leaves without Change in Spatial Distribution of Cell Length (Analysis of the Coordination between Cell Division and Cell Expansion)

Ben-Haj-Salah¹,

Tardieu²

1995

Plant Physiol.

181

138

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We have analyzed the way in which temperature affects leaf elongation rate of maize (Zea mays L.) leaves, while spatial distributions (observed at a given time) of cell length and of proportion of cells in DNA replication are unaffected. We have evaluated, in six growth chamber experiments with constant temperatures (from 13 to 34°C) and two field experiments with fluctuating temperatures, (a) the spatial distributions of cell length and of leaf elongation rate, and (b) the distribution of cell division, either by using the continuity equation or by flow cytometry. Leaf elongation rate was closely related to meristem temperature, with a common relationship in the field and in the growth chamber. Cell division and cell elongation occurred in the first 20 and 60 mm after the ligule, respectively, at all temperatures. Similar quantitative responses to temperature were observed for local cell division and local tissue expansion rates (common x intercept and normalized slope), and both responses were spatially uniform over the whole expanding zone (common time courses in thermal time). As a consequence, faster cell elongation matched faster cell division rate and faster elongation was compensated for by faster cell displacement, resulting in temperature-invariant profiles of cell length and of proportion of dividing cells. Cell-to-cell communication, therefore, was not necessary to account for coordination.

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“…Cell division rate (d,) was calculated in each segment (i) by combining the records of SER and of local cell length in the continuity equation (Gandar, 1980;Silk, 1992):…”

Section: Calculations Of Cell Division Rate Cell Flux and Duration mentioning

confidence: 99%

“…Spatial analysis of elongation and use of the continuity equation (Gandar, 1980;Silk, 1992) provided an adequate framework for analyzing both processes. In monocot leaves, cell division is accompanied by cell expansion, with both processes partly overlapping in time and space.…”

mentioning

confidence: 99%

Temperature Affects Expansion Rate of Maize Leaves without Change in Spatial Distribution of Cell Length (Analysis of the Coordination between Cell Division and Cell Expansion)

Ben-Haj-Salah¹,

Tardieu²

1995

Plant Physiol.

181

138

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“…the velocity of displacement from the tip of particles located at z (Erickson and Sax, 1956), In the limit as At + O, which is the instantaneous "growth demand" for biomass apical to a. Equation 2 may also be derived by integrating the local deposition rates for biomass (Silk and Erickson, 1979;Gandar, 1980) over distance (see "Appendix 2").…”

Section: Determination Of the Crowth-sustaining Suc Fluxmentioning

confidence: 99%

“…In the co-moving reference frame, the growth demand for the root apical to the point u may also be expressed as the integral of a11 rates of deposition of biomass apical to a, according to the continuity equation (Silk and Erickson, 1979;Gandar, 1980 also holdlj, and the growth demand for biomass apical to a will be…”

Section: Ymentioning

confidence: 99%

Nonvascular, Symplasmic Diffusion of Sucrose Cannot Satisfy the Carbon Demands of Growth in the Primary Root Tip of Zea mays L

1994

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Nonvascular, symplasmic transport of sucrose (Suc) was investigated theoretically in the primary root tip of maize (Zea mays 1.cv WF9 x Mo 17) seedlings. Symplasmic diffusion has been assumed to be the mechanism of transport of Suc to cells in the root apical meristem (R.T. Ciaquinta, W. Lin, N.L. Sadler, V.R. Franceschi [1983] Plant Physiol 72: 362-367), which grow apical to the end of the phloem and must build all biomass with carbon supplied from the shoot or kernel. We derived an expression for the growthsustaining Suc flux, which is the minimum longitudinal flux that would be required to meet the carbon demands of growth in the root apical meristem. We calculated this flux from data on root growth velocity, area, and biomass density, taking into account construction and maintenance respiration and the production of mucilage by the root cap. We then calculated the conductivity of the symplasmic pathway for diffusion, from anatomical data on cellular dimensions and the frequency and dimensions of plasmodesmata, and from two estimates of the diffusive conductance of a plasmodesma, derived from independent data. Then, the concentration gradients required to drive a growth-sustaining Suc flux by diffusion alone were calculated but were found not to be physiologically reasonable. We also calculated the hydraulic conductivity of the plasmodesmatal pathway and found that mass flow of Suc solution through plasmodesmata would also be insufficient, by itself, to satisfy the carbon demands of growth. However, much of the demand for water to cause cell expansion could be met by the water unloaded from the phloem while unloading Suc to satisfy the carbon demands of growth, and the hydraulic conductivity of plasmodesmata is high enough that much of that water could move symplasmically. Either our current understanding of plasmodesmatal ultrastructure and function is flawed, or alternative transport mechanisms must exist for Suc transport to the meristem.Understanding the control of plant growth and development must include an understanding of the transport of photoassimilates from sources into developing sinks. Transport of solutes through the differentiated phloem is explained well by quantitative treatments of Miinch's (1930) pressure flow hypothesis (Christy and Femer, 1973;Tyree et al., 1974a;Ross and Tyree, 1980), and experimental data are in reasonably good agreement with their predictions (cf. Zimmermann and Brown, 1971; Pickard et al.,

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“…1), and the velocity of cell displacement from the leaf base at successive positions along the leaf. A relationship derived from the continuity equation (d = bP/bt + V bP/5x + P 6V/6x; 10,23,24) was used to determine the velocity of cell displacement at successive positions along the elongating leaf blade. In this application, cell supply (division rate) at any position (d) is equal to change in cell density (P) with change in time (t), plus displacement velocity (V) multiplied by change in cell density with change in distance from the leaf base (x), plus cell density multiplied by the change in displacement velocity with change in distance (WK Silk, personal communication).…”

Section: Plant Culturementioning

confidence: 99%

Effects of Nitrogen on Mesophyll Cell Division and Epidermal Cell Elongation in Tall Fescue Leaf Blades

MacAdam¹,

Volenec²,

Nelson³

1989

Plant Physiol.

181

114

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Leaf elongation rate (LER) in grasses is dependent on epidermal cell supply (number) and on rate and duration of epidermal cell elongation. Nitrogen (N) fertilization increases LER. Longitudinal sections from two genotypes of tall fescue (Festuca arundinacea Schreb.), which differ by 50% in LER, were used to quantify the effects of N on the components of epidermal cell elongation and on mesophyll cell division. Rate and duration of epidermal cell elongation were determined by using a relationship between cell length and displacement velocity derived from the continuity equation. Rate of epidermal cell elongation was exponential. Relative rates of epidermal cell elongation increased by 9% with high N, even though high N increased LER by 89%. Duration of cell elongation was approximately 20 h longer in the high-than in the low-LER genotype regardless of N treatment. The percentage of mesophyll cells in division was greater in the high-than in the low-LER genotype. This increased with high N in both genotypes, indicating that LER increased with cell supply. Division of mesophyll cells adjacent to abaxial epidermal cells continued after epidermal cell division stopped, until epidermal cells had elongated to a mean length of 40 micrometers in the high-LER and a mean length of 50 micrometers in the low-LER genotype. The cell cycle length for mesophyll cells was calculated to be 12 to 13 hours. Nitrogen increased mesophyll cell number more than epidermal cell number: in both genotypes, the final number of mesophyll cells adjacent to each abaxial epidermal cell was 10 with low N and 14 with high N. A spatial model is used to describe three cell development processes relevant to leaf growth. It illustrates the overlap of mesophyll cell division and epidermal cell elongation, and the transition from epidermal cell elongation to secondary cell wall deposition.Leaf growth in grasses is predominantly unidirectional, parallel with the longitudinal axis of the leaf. A 3 Abbreviations: SLW, specific leaf weight; LER, leaf elongation rate; PPFD, photosynthetic photon flux density. 549Volenec and Nelson (29) used high and low rates of N fertilization to further alter LER of two genotypes of tall fescue selected for contrasting leaf growth rates. Mean LER of these genotypes was 89% higher with high N, but length of fully elongated epidermal cells was unaffected by N treatment. The number of epidermal cells produced per file per day increased 90% with high N, suggesting that much of the increase in LER following N fertilization was due to increased cell division.Our long-term goal is to understand carbohydrate metabolism during the growth of grass leaves. Our objectives in the present study were to evaluate the effect of N on mesophyll cell division and rate and duration of epidermal cell elongation in leaf blades of two genotypes of tall fescue. Data for epidermal cell lengths utilized here have been reported previously (28, 29).Mesophyll cell division data reported here, and data for leaf elongation rate and structural ...

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The Analysis of Growth and Cell Production in Root Apices

Cited by 65 publications

References 18 publications

Temperature Affects Expansion Rate of Maize Leaves without Change in Spatial Distribution of Cell Length (Analysis of the Coordination between Cell Division and Cell Expansion)

Temperature Affects Expansion Rate of Maize Leaves without Change in Spatial Distribution of Cell Length (Analysis of the Coordination between Cell Division and Cell Expansion)

Nonvascular, Symplasmic Diffusion of Sucrose Cannot Satisfy the Carbon Demands of Growth in the Primary Root Tip of Zea mays L

Effects of Nitrogen on Mesophyll Cell Division and Epidermal Cell Elongation in Tall Fescue Leaf Blades

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