Abstract

Large color variations can be observed across the face of a flower even when individual petals are the same color. We investigated whether these color variations could be explained by a model that incorporates multiple reflections of light between petals and transmissions of light through petals before the light returns to the observer. The three flowers that we selected for the study exhibited large color variations across the face of the intact flower but had no significant observable difference in color saturation across a single petal or between petals when petals were removed from the flower. We used a spectroradiometer to measure the spectrum across the faces of intact flowers and across individual petals. The measured spectra for all of the flowers were consistent with the proposed model.

© 2000 Optical Society of America

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References

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  1. G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982).
  2. R. Wehner, G. D. Bernard, “Photoreceptor twist: a solution to the false-color problem,” Proc. Natl. Acad. Sci. USA 90, 4132–4135 (1993).
    [CrossRef] [PubMed]
  3. C. L. Lawson, R. J. Hanson, Solving Least Squares Problems (Prentice-Hall, Englewood Cliffs, N.J., 1974), Chap. 23.
  4. D. M. Gates, H. J. Keegan, J. C. Schleter, V. R. Weidner, “Spectral properties of plants,” Appl. Opt. 4, 11–20 (1965).
    [CrossRef]
  5. L. Chittka, R. Menzel, “The evolutionary adaptation of flower colors and the insect pollinator’s color vision systems,” J. Comp. Physiol. A 171, 171–181 (1992).
    [CrossRef]
  6. R. Menzel, A. Shmida, “The ecology of flower colours and the natural colour vision of insect pollinators: the Israeli flora as a study case,” Biol. Rev. 68, 81–120 (1993).
    [CrossRef]
  7. N. Waser, L. Chittka, “Evolutionary ecology—bedazzled by flowers,” Nature 394, 835–836 (1998).
    [CrossRef]

1998

N. Waser, L. Chittka, “Evolutionary ecology—bedazzled by flowers,” Nature 394, 835–836 (1998).
[CrossRef]

1993

R. Wehner, G. D. Bernard, “Photoreceptor twist: a solution to the false-color problem,” Proc. Natl. Acad. Sci. USA 90, 4132–4135 (1993).
[CrossRef] [PubMed]

R. Menzel, A. Shmida, “The ecology of flower colours and the natural colour vision of insect pollinators: the Israeli flora as a study case,” Biol. Rev. 68, 81–120 (1993).
[CrossRef]

1992

L. Chittka, R. Menzel, “The evolutionary adaptation of flower colors and the insect pollinator’s color vision systems,” J. Comp. Physiol. A 171, 171–181 (1992).
[CrossRef]

1965

Bernard, G. D.

R. Wehner, G. D. Bernard, “Photoreceptor twist: a solution to the false-color problem,” Proc. Natl. Acad. Sci. USA 90, 4132–4135 (1993).
[CrossRef] [PubMed]

Chittka, L.

N. Waser, L. Chittka, “Evolutionary ecology—bedazzled by flowers,” Nature 394, 835–836 (1998).
[CrossRef]

L. Chittka, R. Menzel, “The evolutionary adaptation of flower colors and the insect pollinator’s color vision systems,” J. Comp. Physiol. A 171, 171–181 (1992).
[CrossRef]

Gates, D. M.

Hanson, R. J.

C. L. Lawson, R. J. Hanson, Solving Least Squares Problems (Prentice-Hall, Englewood Cliffs, N.J., 1974), Chap. 23.

Keegan, H. J.

Lawson, C. L.

C. L. Lawson, R. J. Hanson, Solving Least Squares Problems (Prentice-Hall, Englewood Cliffs, N.J., 1974), Chap. 23.

Menzel, R.

R. Menzel, A. Shmida, “The ecology of flower colours and the natural colour vision of insect pollinators: the Israeli flora as a study case,” Biol. Rev. 68, 81–120 (1993).
[CrossRef]

L. Chittka, R. Menzel, “The evolutionary adaptation of flower colors and the insect pollinator’s color vision systems,” J. Comp. Physiol. A 171, 171–181 (1992).
[CrossRef]

Schleter, J. C.

Shmida, A.

R. Menzel, A. Shmida, “The ecology of flower colours and the natural colour vision of insect pollinators: the Israeli flora as a study case,” Biol. Rev. 68, 81–120 (1993).
[CrossRef]

Stiles, W. S.

G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982).

Waser, N.

N. Waser, L. Chittka, “Evolutionary ecology—bedazzled by flowers,” Nature 394, 835–836 (1998).
[CrossRef]

Wehner, R.

R. Wehner, G. D. Bernard, “Photoreceptor twist: a solution to the false-color problem,” Proc. Natl. Acad. Sci. USA 90, 4132–4135 (1993).
[CrossRef] [PubMed]

Weidner, V. R.

Wyszecki, G.

G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982).

Appl. Opt.

Biol. Rev.

R. Menzel, A. Shmida, “The ecology of flower colours and the natural colour vision of insect pollinators: the Israeli flora as a study case,” Biol. Rev. 68, 81–120 (1993).
[CrossRef]

J. Comp. Physiol. A

L. Chittka, R. Menzel, “The evolutionary adaptation of flower colors and the insect pollinator’s color vision systems,” J. Comp. Physiol. A 171, 171–181 (1992).
[CrossRef]

Nature

N. Waser, L. Chittka, “Evolutionary ecology—bedazzled by flowers,” Nature 394, 835–836 (1998).
[CrossRef]

Proc. Natl. Acad. Sci. USA

R. Wehner, G. D. Bernard, “Photoreceptor twist: a solution to the false-color problem,” Proc. Natl. Acad. Sci. USA 90, 4132–4135 (1993).
[CrossRef] [PubMed]

Other

C. L. Lawson, R. J. Hanson, Solving Least Squares Problems (Prentice-Hall, Englewood Cliffs, N.J., 1974), Chap. 23.

G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982).

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Figures (8)

Fig. 1
Fig. 1

Picture of a pink carnation, a purple daisy, and a yellow rose used in this study, along with isolated petals. The picture was taken outside under overcast conditions.

Fig. 2
Fig. 2

Diagram of experimental setup. The samples were placed on a flat, black stand (less than 1% reflectance at all wavelengths), within the diffuser. The telemicroscope assembly was inserted through a hole at the top of the diffuser. Multiple measurements were obtained for individual samples by horizontally translating the specimen stand within the diffuser.

Fig. 3
Fig. 3

Different modes of light reflecting from and transmitting through a petal. The probability of an increased number of reflections and transmissions increases significantly toward the base of the petal.

Fig. 4
Fig. 4

Reflectance spectra from a single pink carnation petal (top curve) and the simulated spectrum for 2, 3,…, 10 multiple reflections. The magnitude of each curve has been normalized to illustrate the change in the shape of the reflectance spectrum. The bottom curve, representing ten reflections, is highly saturated and contains, for the most part, energy only at wavelengths longer than 650 nm. As reflections increase, the band edge moves right, and the difference between the high and the low reflectance regions gets larger.

Fig. 5
Fig. 5

Reflectance spectra from a flower and a petal for a purple daisy. Dashed curve, reflectance spectrum of a petal; pluses, measured reflectance spectrum of a saturated region within a purple daisy, scaled to equal the petal reflectance spectrum at 750 nm; solid curve, best model fit [Eq. (1)] of the reflectance function to the saturated region in the flower. It required four reflections and transmissions to adequately fit the flower measurements.

Fig. 6
Fig. 6

Measurements of a petal and a flower for a yellow rose and the fit with use of Eq. (1). The top graph illustrates the fit of Eq. (1) with four reflections and transmissions, and the bottom graph illustrates the best fit with ten reflections and transmissions. Dashed curve, reflectance spectrum of a rose petal; pluses, measured reflectance spectrum of a saturated region within the flower; solid curve, best fit with use of Eq. (1). Clearly, the higher order is needed to adequately fit the transition region near 550 nm.

Fig. 7
Fig. 7

CIE xy chromaticity coordinates for a standard observer under D65 illuminant for each of the measurements. Circles, all 12 petal measurements; crosses, all 36 flower measurements for each flower. A point near the white point (plus) is desaturated, and a point near an edge represents complete saturation. Simulations of pure reflectance from a single pink carnation are plotted above the carnation data (shifted upward for display purposes). Diamond, single petal measurement; asterisks, multiple reflection simulations. Each simulated higher-order term is represented by a small shift toward the red point.

Fig. 8
Fig. 8

Reflectance (dashed curves), scaled reflectance (circles), transmittance (dotted curves), and absorptance (solid curves) for a single petal from a carnation and from a rose. The transmittance is closely modeled by a scaled version of the reflectance. The total absorptance of both petals is quite low at some wavelengths. As an example, very little light between 600 and 700 nm is absorbed by either petal. These measurements were obtained with the LICOR spectroradiometer with integrating sphere for maximum accuracy.

Equations (2)

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F(λ)=I(λ)[a1p(λ)+a2p2(λ)++anpn(λ)],
a1, a2,, an0,

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