Studies on the relative physiological value of spectral lights. II. The sensibility of Volvox to wave‐lengths of equal energy content

Abstract

Estudios sobre el valor fisiol6gico relativo de las luces espectrales.11. La sensibilidad del Volvox a longitudes de onda de igual contenido de energia.La sensibilidad del Volvox a la radiacidn de diferentes longitudes de onda e igual energia (sensibilidad a la radiaci6n de la misma energia) ha sido investigada por 10s autores siguiendo dos mktodos: a) la duraci6n relativa del tiempo de presentacibn, y b) la velocidad relativa de la locomoci6n (y precisi6n de la orientaci6n). Una longitud de onda de 494p tiene el mayor valor estimulante, como demuestran ambos mktodos. La eficacia de las otras longitudes de onda presenta una disminuci6n gradual cuando se emplean longitudes de onda mas o menos largas. Los autores insisten sobre la necesidad de usar un espectro de igual energia en tales investigaciones. Tambikn llaman la atenci6n acerca de la presente incapacidad para hacer comparaciones con la visibn humana (normal o dalthica), es decir, con las curvas de luminosidad fot6pica y scot6pica (0 acromAtica) por las siguientes razones: a) a causa de nuestra ignorancia sobre las reacciones fotoquimicas y la naturaleza de las substancias fotosensitivas, y b) porque las investigaciones efectuadas recientemente sobre la visibilidad de la radiaci6n por el ojo normal y dalt6nico demuestran que el efecto maxim0 no depende de Ias longitudes de onda mencionadas en investigaciones mas antiguas.

The influence of intrinsically-photosensitive retinal ganglion cells on the spectral sensitivity and response dynamics of the human pupillary light reflex

“…In an effort to refute earlier claims that the human PLR was driven exclusively by cones (Brown & Page, 1939), Wagman and Gullberg (1942) examined the spectral sensitivity of the human steady-state PLR for a 0.5 mm criterion response and generated a spectral sensitivity well matched by the scotopic luminosity function and therefore rod dominated. This result is not unreasonable given the small light evoked change in pupil diameter chosen as a criterion response, and it is consistent with the findings of previous and subsequent studies using the same criterion (Alpern & Campbell, 1962, Laurens, 1923). It is interesting to note that, although a 0.5 mm criterion response was chosen by the authors, data throughout the complete range of pupillary diameters was collected and published.…”

“…It has been shown that the pupils of rod achromats continues to respond to light increments well over levels commonly accepted to saturate rod photoreceptors (Alpern, Falls & Lee, 1960), thus implying that an additional photopigment is involved in the pupillary responses of these individuals. Additionally, spectral sensitivity measurements of pupillary constriction to steady state illumination have shown short wavelength sensitivity that is not well matched by either rod or S-cone contributions (Bouma, 1962, Laurens, 1923). Historical investigations of the response dynamics of the PLR are also suggestive of a role for ipRGCs in the behavior of the pupil in response to light increments.…”

The spectral sensitivity of the consensual light reflex

“…Since the spectral sensitivities of the photopic and scotopic eye are well established the identification of the photoreceptors activating the pupil should be readily achieved by measuring the spectral characteristics of the response of the pupil to retinal stimulation. Laurens (1923) was able to demonstrate that the curve relating pupil size to wave-length (equal energy spectrum) depended upon the adaptation state of the eye. The curve for the light-adapted eye had a minimum at 554-2 m,u, the dark-adapted curve had one at 514-3 m,u.…”

Phototropism and Phototaxis

“…I t has been considered either as consisting of a series of phobic reactions (11,17,39,46,57) and therefore termed "pseudo-topotaxis" (39,46), in which the orientation is postulated to be dependent on a periodic shading of the photoreceptor (11,17,39,46), or as a mechanism totally dif ferent from phobotaxis (4,11,35,45). Later the maximum in the blue-green light has been repeatedly verified for unicellular and colonial forms of flagellates (44,45,48). Conclusions as to the nature of the pigments active in phototaxis are based almost exclusively on investigations of the spectral sensitivity of the algae.…”