Measurements of Differential Growth Causing Phototropic Curvature of Coleoptiles and Hypocotyls

Franssen, J.M.; Cooke, Susie; Digby, J.; Firn, Richard D.

doi:10.1016/s0044-328x(81)80153-5

Cited by 49 publications

(21 citation statements)

References 8 publications

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“…When coleoptiles of oats and maize are exposed to continuous unilateral light, a curvature of 90° is established (Franssen et al 1981; own data not shown), indicating that phototropism finally overrides gravitropism. In air-grown rice coleoptiles, however, a curvature of 25° or less is achieved during continuous stimulation, representing the equilibrium between phototropism and gravitropism (Fig.…”

Section: Discussionmentioning

confidence: 95%

Phototropism of rice (Oryza sativa L.) coleoptiles: fluence-response relationships, kinetics and photogravitropic equilibrium

Neumann

Iino

1997

Planta

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Phototropism of rice (Oryza sativa L.) coleoptiles induced by unilateral blue light was characterized using red-light-grown seedlings. Phototropic fluence-response relationships, investigated mainly with submerged coleoptiles, revealed three response types previously identified in oat and maize coleoptiles: two pulse-induced positive phototropisms and a phototropism that depended on stimulation time. The effective ranges of fluences and fluence rates were comparable to those reported for maize. Compared with oats and maize, however, curvature responses in rice were much smaller and coleoptiles straightened faster after establishing the maximal curvature. When stimulated continuously, submerged coleoptiles developed curvature slowly over a period of 6 h, whereas air-grown coleoptiles, which showed smaller phototropic responsiveness, established a photogravitropic equilibrium from about 4 h of stimulation. The plot of the equilibrium angle against log fluence rates yielded a bell-shaped optimum curve that spanned over a relatively wide fluence-rate range; a maximal curvature of 25 degrees occurred at a fluence rate of 1 micromole m-2 s-1. This optimum curve apparently reflects the light sensitivity of the steady-state phototropic response.

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Section: Discussionmentioning

confidence: 95%

Phototropism of rice (Oryza sativa L.) coleoptiles: fluence-response relationships, kinetics and photogravitropic equilibrium

Neumann

Iino

1997

Planta

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“…In the explanation of tropic movements, major emphasis has recently been placed upon the growth inhibition which is quickly, perhaps even uniformly, imposed along the length ofthe concave side of the curving organ (4,10). However, we have already suggested that 'the' georesponse involves two distinct and arguably separate, types of growth reaction, viz.…”

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confidence: 99%

Is There a Role for the Apex in Shoot Geotropism?

Hart¹,

MacDonald²

1984

Plant Physiol.

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) seedlings supported centrally such that both apical and basal ends are free to react to geostimulus, revealed that the apical end commences curvature I to 2 hours earlier than the basal end. The later curvature in the basal region is a consequence of the absence of growth in the initial period rather than merely slower growth. A comparison of zonal growth rates in a vertical and a horizontal seedling confirmed that geostimulus induces a renewal of growth in a region where growth had ceased. Removing the apical half of the hypocotyl showed that the curvature resulting from this growth initiation in the basal region is dependent on attachment to the apical region. Evidence that this dependence is unlikely to be due to energy deficiency is adduced. The prior response of the apical end to geostimulus and the apically dependent later initiation of new growth in the basal region are compatible with the delay inherent in message transport from apex to base and are considered as evidence for apical involvement in the totality of the seedling's georesponse.cussing geotropism in the second edition (1978) oftheir textbook (15) said 'there is transmission ofa growth-regulating factor from the region of perception to the region of response,' in the third edition (1981) they wrote 'gravitropism in shoots does not involve the longitudinal signal transduction mechanism which for many years has been frequently assumed to occur' (16).While in many respects the emphases of Digby and Firn constitute a helpful corrective to the too ready acceptance of assumptions implicit in the Cholodny-Went theory, we feel there is now the danger of some valid elements in the older work being discarded. Specifically, the claim that the apex has no special role (as distinct from its normal growth-sustaining role) in georesponse, involves the repudiation of the concept of apical coordination of directional growth.Our previous work (13,14) has emphasized that curvature involves growth stimulation as well as inhibition. Moreover, the polarity which we have discerned in the responses of the hypocotyl to light (13) and to gravity (14), suggests a contribution of the apical region to directional growth. In this paper, we reexamine the question of apical involvement in hypocotyl geotropism.The concept of a hormonal flow from the apex as the basis of growth regulation derives from the classical experiments of Charles Darwin who postulated the transmission ofan 'influence' to explain his finding that the region of perception in grass coleoptiles was separable from the region of response to a directional stimulus (2). Further refinements of this concept of a transmissible influence led eventually to the Cholodny-Went hypothesis which explained growth curvature in terms of the formation of a lateral gradient of auxin (17).This hypothesis has now been seriously challenged on several grounds by Digby and Firn. First, they have argued (3, 9) that not only is there no convincing experimental evidence for lateral auxin transmission sufficient to account for diff...

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“…It has been suggested that blue light inhibits longitudinal stem growth and induces phototropism through the same photoinhibition events at the cellular level (2), or that these responses share components in their signal transduction pathways (7,9). However, other studies indicate that cell elongation is controlled by discrete signal transduction systems in these two responses (5,15,18).…”

Section: Plant Materialsmentioning

confidence: 99%

“…Allelism was tested by crossing the blu mutants (d) to JK218 (9), and patterns of inheritance were determined from the F2 generation. Double mutants homozygous for a given blu mutation and JK218 were selected in blue light as F2 seedlings that grew tall and straight under the conditions described above.…”

Section: Genetic Analysismentioning

confidence: 99%

Genetic separation of phototropism and blue light inhibition of stem elongation.

Liscum¹,

Young²,

Poff³

et al. 1992

Plant Physiol.

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Blue light-induced regulation of cell elongation is a component of the signal response pathway for both phototropic curvature and inhibition of stem elongation in higher plants. To determine if blue light regulates cell elongation in these responses through shared or discrete pathways, phototropism and hypocotyl elongation were investigated in several blue light response mutants in Arabidopsis thaliana. Specifically, the blu mutants that lack blue light-dependent inhibition of hypocotyl elongation were found to exhibit a normal phototropic response. In contrast, a phototropic null mutant (IK218) and a mutant that has a 20-to 30-fold shift in the fluence dependence for first positive phototropism (IK224) showed normal inhibition of hypocotyl elongation in blue light. F1 progeny of crosses between the blu mutants and JK218 showed normal phototropism and inhibition of hypocotyl elongation, and approximately 1 in 16 F2 progeny were double mutants lacking both responses. Thus, blue light-dependent inhibition of hypocotyl elongation and phototropism operate through at least some genetically distinct components.light-induced phototropic and longitudinal growth responses of these hypocotyl elongation mutants as well as two phototropism mutants. The results show that blue light induces phototropism and inhibition of hypocotyl elongation through genetically distinct pathways. MATERIALS AND METHODS Plant MaterialHypocotyl elongation mutants (blul, blu2, and blu3) of Arabidopsis thaliana ecotype Columbia were described previously by Liscum and Hangarter (14). Phototropism mutants (JK218 and JK224) of A. thaliana ecotype Estland were described previously by Khurana and Poff (11). Specifically, the blu mutants lack blue light-dependent inhibition of hypocotyl elongation, JK218 seedlings lack phototropic curvature, and JK224 seedlings require 20-to 30-fold more actinic light to induce first positive phototropism than do wild-type seedlings.Regulation of cell elongation is an intrinsic step in blue light-dependent inhibition of stem elongation and induction of phototropic curvature in higher plants (6,8). It has been suggested that blue light inhibits longitudinal stem growth and induces phototropism through the same photoinhibition events at the cellular level (2), or that these responses share components in their signal transduction pathways (7, 9). However, other studies indicate that cell elongation is controlled by discrete signal transduction systems in these two responses (5,15,18 Genetic AnalysisFor genetic analysis, seeds were handled as described by Liscum and Hangarter (14). Surface-sterilized seeds were planted on agar medium and incubated at 40C in the dark for 2 to 3 d. The seeds were then given 30 min of red light at 230C, followed by 23.5 h in the dark, and then transferred to blue light (56 ± 2,umol m-2 s-1) given from directly above.After 4 d of growth in continuous blue light, the angle of the actinic light was changed to 550 from vertical for an additional 24 h to induce phototropic curvature. After...

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Measurements of Differential Growth Causing Phototropic Curvature of Coleoptiles and Hypocotyls

Cited by 49 publications

References 8 publications

Phototropism of rice (Oryza sativa L.) coleoptiles: fluence-response relationships, kinetics and photogravitropic equilibrium

Phototropism of rice (Oryza sativa L.) coleoptiles: fluence-response relationships, kinetics and photogravitropic equilibrium

Is There a Role for the Apex in Shoot Geotropism?

Genetic separation of phototropism and blue light inhibition of stem elongation.

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