INFLUENCE, RÉVERSIBLE PAR LA LUMIÈRE ROUGE‐CLAIR, DE COURTS ÉCLAIREMENTS ROUGE‐FONCÉ A LA FIN DE LA PHOTOPÉRIODE, SUR LA CROISSANCE ET LA TENEUR EN CHLOROPHYLLES DE MARCHANTIA POLYMORPHA L

Abstract

Abstract— 1. Thalli of Marchantia polymorpha L. grow plagiotropically with 4, 8 or 16 hr of white fluorescent light per day (24‐hr cycles), and have round lobes; male thalli are not as uniformly flat as the female thalli and their lobes are not so broad. 2. The growth of both kinds of thalli is strongly modified by 5 min far‐red (or even 1 min) at the end of short days. Already after the first cycle of 8 hr fluor. light + 5 min fr+16 hr darkness, the margins of the young parts are bent upwards; further growth is orthotropic and the newly formed lobes are much narrower and elongated and their green colour is different. After 2 weeks of treatment, the appearance is completely different. 3. The strong action of the terminal far‐red irradiation is fully reversible by red light or by white fluorescent light. The efficiency of the rather short exposure times and the repeatable nature of the reversibility, the last irradiation determining the type of growth, strongly suggest that the orientation and the growth of the thalli is controlled by the same red, far‐red photo‐reaction as in the case of the growth of higher plants and on the basis of our physiological experiments we think that the same photoreversible pigment, the phytochrome, is present in the thalli of Marchantia. 4. Our hypothesis is that the far‐red absorbing form, P730, is responsible for the horizontal growth and for the broad and round shape of the lobes. Even under short days, the percentage of P730 left during part of the long night must be sufficient for flat growth, since a 5 min far‐red irradiation at the middle of the 16‐hr night still causes orthotropism, and this is reversible by red light. Complete absence of P730 for 16 hr per day should then allow a stronger orthotropism and etiolation than the absence of P730 for only 8 hr per day; we in fact found that the effect of a far‐red irradiation is much stronger at the end of an 8‐hr photoperiod than at the end of a 16‐hr photoperiod. 5. These and other similarities between our results on light‐grown, green Marchantia thalli and the results of Downs et uZ.(1) on light‐grown pinto beans, with white fluorescent light during the photoperiods in both cases, is stressed. 6. We have obtained similar but weaker effects in two other species of liverworts. 7. Under an 8‐hr photoperiod of red fluorescent light, Marchantia grows horizontally; a terminal 1‐min far‐red exposure causes orthotropism and etiolation, reversible by another short red exposure. However, the controls under 8 hr of red fluorescent light have narrower lobes which are not round, as compared to the controls under 8 hr of white fluorescent light. On the basis of other results, we suppose that this last mentioned difference is not due to differences in light intensities, but rather that, besides the participation of the P730 form as indicated by the experiments with terminal exposures after white light photoperiods, also the blue light included in the white fluorescent light plays a role in the formation of broad round lobes. The same blue lig...

Control of Senescence in Marchantia by Phytochrome

“…by a subsequent exposure to red light (10). These same effects were present with plants on longer daily photoperiods but the bleaching was less pronounced.…”

“…The point of departure for the present work was an observation from experiments on the effects of red and far red light on the growth of liverwort, Marchantia polymorpha L. (8)(9)(10)(11), that a brief irradiation with far red light given at the end of very short (1 hr) daily photoperiods induced a marked bleaching in the basal parts of the thalli after 4 days and that the bleaching effects induced by far red light could be nullified 'Present address: Rijksuniversitair Centrum Antwerpen, Laboratory of General Botany, Groenenborgerlaan, 171, Antwerpen, Belgium.…”

Light Mediated Changes in the Chloroplasts of the Liverwort, Sphaerocarpos donnellii Aust.

“…Such responses have been described in ferns (8), mosses (5), and liverworts (3), including Sphaerocarpos (20). In a previous paper (16) we discussed the effects of light on the growth o'f Sphaerocarpos.…”

Photomorphogenesis in Sinningia speciosa, cv. Queen Victoria I. Characterization of Phytochrome Control

“…Although stem elongation induced by far red radiation has been correlated with promotion of flowering in a number of plants (7,22) We interpret the data of tables I and II as follows: leaf blade expansion and inhibition of stem elongation both require a high PFR level (6,8,22). Chlorophvll content is also regulated by phytochrome (12,13). It is quite likely that a low PFR level during the night impedes chloroplast de-velopment in Sinningia, since this condition has been shown to inhibit structural development of the bean plastid (16,20).…”

“…This contrasted sharply with the short, thick stems and large, horizontal leaf blades of controls receiving dark nights. Some of these phenomena have been noted in other species and been attributed to the effect of the light source upon the phytochrome3 svstem (6,8,12,13,22). Our preliminarv experiments implicated phvtochrome as a regulatory mechanism in Sinininia, too, since morphological changes potentiated by far red could be reversed by red.…”