Growth Promotion of Vegetative Gametophytes of <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> by Blue Light

Through an acclimation period of 10 days, compared to white light, the maximal net photosynthetic rates were significantly higher for gametophytes of Undaria pinnatifida cultivated under blue light (400–500 nm), and were lower under red light (600–700 nm). Chlorophyll c and the carotenoid content of gametophytes were similar under blue light and red light but were much lower under white light. The growth rate of female gametophytes under blue light was higher than that under other lights, and the growth rate of male gametophytes showed little variation with respect to blue and white light. Male and female gametophytes were mixed together to form sporophytes under white, blue and red light. After approximately 5 days, 50% gametophytes became fertile under blue and white light, but remained vegetative under red light after 10 days.     

The effects of light on sex determination in gametophytes of the fern <Emphasis Type="Italic">Ceratopteris richardii</Emphasis>

The sexuality of homosporous fern gametophytes is usually determined by antheridiogen, a pheromone that promotes maleness. In this work the effect of photomorphogenically active light on antheridiogen-induced male development was examined for gametophytes of Ceratopteris richardii. Although blue light did not affect sensitivity to Ceratopteris antheridiogen (A_Ce) in wild-type gametophytes, it was found that the gametophytes of the her1 mutant, which are insensitive to A_Ce, developed into males when grown under blue light in the presence of A_Ce. Thus, we conclude that another A_Ce-signal transduction pathway activated by blue light exists latently in the gametophytes of C. richardii. Red light, on the other hand, suppressed male development. Because simultaneous red and blue light-irradiation did not promote male development in the her1 gametophytes, the action of red light seems to dominate that of blue light. The results of experiments with a photomorphogenic mutant also suggested that phytochrome may be involved in the action of red light.     

RNA and protein metabolism in the particulate fractions of the gametophytes of bracken fern during growth in red and blue light

Summary The metabolism of RNA and protein in the gametophytes of bracken fern (Pteridium aquilinum) is affected by the quality of light in which they are grown. When sporelings were grown as two-dimensional gametophytes in blue light, particulate fractions separated from the sporelings exhibited greater incorporation of uridine-³H and leucine-³H into RNA and protein, respectively, than those from sporelings grown as one-dimensional protonema in red light. After various periods of exposure of gametophytes to red or blue light in the presence of uridine-³H, the nuclei-rich fraction showed the highest specific activity in RNA, and irrespective of incubation time, blue light was more effective than red light. The possibility that enhanced synthesis of RNA in the nucleus in response to blue light is significantly related to the morphological growth pattern of the gametophytes, is discussed.     

Physiological and morphogenetic studies of fern gametophytes and sporophytes in aseptic culture

Summary Prolonged irradiation with red light and addition of sucrose to the basal medium induced two-dimensional growth in gametophytes of Pteris vittata. The results suggest that two-dimensional growth is controlled by the following three factors: 1. a photoreactive system which depends on blue light; 2. a photoreactive system which can utilize red light; and 3. the photosynthetic system which the level of carbohydrate. Media containing 2.4-dichlorophenoxyacetic acid and sucrose, and complex media containing peptone caused formation of tumor-like calli.     

PHOTOMORPHOGENESIS OF THE GAMETOPHYTES OF LYGODIUM JAPONICUM

Protonemata of Lygodium japonicum turn biplanar in both red and blue light regimes and remain filamentous in far-red light. Biplanar gametophytes formed in red light are longer than broad with long, rectangular cells, whereas in blue light they appear broader than long with short, isodiametric cells. Transfer of protonemata of all ages from far-red regime to red or blue light induces a morphological type of growth characteristic of the new light regime. However, only relatively young biplanar forms transferred from red or blue light are able to resume filamentous type of growth in a subsequent regime of far-red light.     

Regulation of Protein Synthesis during Photomorphogenesis of Gametophytes of the Fern Onoclea sensibilis

Gametophytes of the fern Onoclea sensibilis grow as filaments in the dark and in red light and become planar in blue light. Pulse-labeling 4-day-old gametophytes with [³⁵S]methionine at different times after transfer to dark, red, and blue light environments revealed higher rates of amino acid uptake and protein synthesis in blue light than in red light or in the dark. Characterization of the extant and newly synthesized soluble proteins by one- and two-dimensional gel electrophoresis showed that the patterns of protein accumulation and synthesis in gametophytes exposed to short periods of red or blue light were qualitatively indistinguishable from those of gametophytes maintained in the dark. However, some striking increases and decreases in the levels of certain polypeptides were noted and these changes were accentuated during continued growth of gametophytes in the different environments. The results show that photomorphogenesis of gametophytes of O. sensibilis is associated with quantitative rather than qualitative changes in the population of mRNAs available for translation.     

Electrical Changes in the Apical Cell of the Fern Gametophyte during Irradiation with Photomorphogenetically Active Light

Electrophysiological procedures were used to evaluate cellular responses of fern (Onoclea sensibilis L.) gametophytes to photomorphogenetically active light. Red, far red, and blue light caused rapid changes in the membrane potential of the apical cell of the gametophyte filament; other cells in the filament were not similarly responsive. Measurements made with one electrode in the apical cell revealed that the membrane potential depolarized in red light and repolarized in far red light. Irradiation with blue light caused a hyperpolarization, the rapidity of which was dependent on a red light pretreatment. More refined measurements with one electrode in the tip of the apical cell and another in the base of the cell showed that both red and blue light treatments cause the apical cell to behave as a dipole. Because of the profound, long-term morphological changes that follow light irradiation in this organism, it was hoped to use it to elucidate the role that electrical parameters play in determining subsequent developmental events.     

Light-stimulated respiration in the green algaDunaliella tertiolecta: Involvement of the ultraviolet/blue-light photoreceptor(s) and phytochrome?

Starch breakdown and respiratory O₂ uptake in the green algaDunaliella tertiolecta (Butcher) are stimulated not only by blue, but also by red light. In the present study, attempts are described to identify the photoreceptor(s) involved. Fluence rate-response curves with different slopes in the ultraviolet (UV)/blue and in the red spectral region as well as differences in the kinetics and in the unfluence of dark pre-incubation on the stimulation of respiratory O₂ uptake by blue and red light strongly indicate the action of two photoreceptors. Since the effect of red light shows some far-red reversibility, and since simultaneous irradiation with red and far-red light decreases the effectiveness of red light, the involvement of phytochrome — in addition to the UV/blue photoreceptor(s) — is suggested in the light-stimulated respiration inDunaliella.Abbreviation UV ultraviolet     

Light germination ofAnthoceros miyabeanus spores

The effects of light on the spore germination of a hornwort species,Anthoceros miyabeanus Steph., were investigated. Spores of this species were photoblastic, but their sensitivities to light quality were different. Under either continuous white, red or diffused daylight, more than 80% of the spores germinated, but under blue light none or a few of them germinated. Under continuous far-red light or in total darkness, the spores did not germinate at all.Anthoceros spores required red light irradiation for a very long duration, i.e., over 12–24 hr of red light for saturated germination. However, the spore germination showed clear photo-reversibility by repeated irradiation of red and far-red light. The germination pattern clearly varied with the light quality. There were two fundamental patterns; (1) cell mass type in white or blue light: spores divide before germination, and the sporelings divide frequently and form 1–2 rhizoids soon after germination, and (2) germ tube type in red light: spores germinate without cell division, and the single-cell sporelings elongate without cell division and rhizoid formation.     

Ribonucleic Acid and Protein Changes in the Subcellular Components of the Gametophytes of Pteridium aquilinum during Growth in Red and Blue Light

The distribution of RNA and protein in the gametophytes of bracken fern, Pteridium aquilinum is affected by the quality of light in which they are grown. Two-dimensional gametophytes growing in blue light have a greater amount of RNA and protein than one-dimensional protonema growing in red light. Fractions rich in nuclei, chloroplasts, mitochondria, ribosomes and soluble supernatants obtained from blue-light grown gametophytes by differential centrifugation contain greater amounts of RNA and protein than corresponding fractions of red-light grown plants. Differences in RNA and protein content are detected in some of the fractions within 24 hours after start of the treatment.     

The Role of Light in the Interrelated Processes of Morphogenesis and Photosynthesis in the Fern Gametophyte

The interrelationship of photosynthesis and photomorphogenesis in the gametophyte of the fern Pteridium aquilinum was examined in detail. High energy red light produces filamentous gametophytes composed of greatly elongated cells. Blue light of equal energy produces normal cordate gametophytes composed of isodiametric cells. The assimilative rates of the two forms are identical during the initial stages of development. However, the filamentous gametophytes eventually exhibit a decline in assimilation not matched by their normal counterparts. Although this decrease in assimilation of gametophytes exposed to red light may be traced to a decrease in the photo-synthetic rate due to a decrease in chlorophyll synthesis, these events occur subsequent to the establishment of the filamentous mode of growth and are therefore a result, not a cause, of filamentous development. Gametophyte assimilation is also impeded under low energy blue light, due to a reduction in the photosynthetic rate at this low energy; and the initial filamentous stage, in which the cells remain normally isodiametric, is not exceeded. The addition of extra exogenous sucrose restores the capacity for growth and normal cordate prothalli result. It may therefore be concluded that the ultimate form of the gametophyte is under the control of a photoreceptor that is sensitive to blue light, and activated at a relatively low energy level. Red light at any level is ineffective in promoting normal cordate development, but is effective in supporting growth through vigorous photosynthesis, yielding a filament composed of greatly elongated cells. The eventual photosynthetic decline of the filamentous form is due directly to this particular growth mode. Low energy blue light is sufficient to effect form (the cells remain isodiametric), but insufficient to provide the necessary energy for growth through vigorous photosynthesis. Therefore, in order for the gametophyte to reach maturity it must be supplied with light energy that not only satisfies the requirement for form but the requirement for growth as well. The implications of these requirements are discussed in the text.     

Speed of signal transfer in the chloroplast accumulation response

Chloroplast photorelocation movement is important for plants to perform efficient photosynthesis. Phototropins were identified as blue-light receptors for chloroplast movement in Arabidopsis thaliana and in the fern Adiantum capillus-veneris, whereas neochrome functions as a dual red/blue light receptor in the latter. However, the signal transduction pathways involved in chloroplast movement remain to be clarified. To investigate the kinetic properties of signalling from these photoreceptors to the chloroplasts, we deduced the speed of signal transfer using Adiantum capillus-veneris gametophytes. When a region of dark-adapted gametophyte cells was subjected to microbeam irradiation, chloroplasts moved towards the irradiated area even in subsequent darkness. We therefore recorded the movement and calculated the speeds of signal transfer by time-lapse imaging. Movement speeds under red or blue light were similar, e.g., about 1.0 μm min⁻¹ in prothallial cells. However, speeds varied according to cell polarity in protonemal cells. The speed of signal transfer from the protonemal apex to the base was approximately 0.7 μm min⁻¹, but roughly 2.3 μm min⁻¹ in the opposite direction. The speed of signal transfer in Arabidopsis thaliana mesophyll cells was approximately 0.8 μm min⁻¹ by comparison. Surprisingly, chloroplasts located farthest away from the microbeam were found to move faster than those in close proximity to the site of irradiation both in Adiantum capillus-veneris and A. thaliana.     

Chloroplastenausbildung und Morphogenese der Gametophyten von Dryopteris filix-mas (L.) Schott nach Applikation von Chloramphenicol und Actidion (Cycloheximid)

Summary Morphogenesis and differentiation of the young gametophytes (=sporelings) of Dryopteris filix-mas are controlled by light. Blue light leads to the formation of normal two-dimensional prothallia; under red light, however, the gametophytes grow as cellular filaments. Morphogenesis in blue light is connected with an increase in protein synthesis; in red light the protein content of the sporelings is markedly lower. The size of the chloroplasts is correlated with the protein content of the sporelings.In the present paper the diverse effect of chloramphenicol (CAP) and actidione (cycloheximide, ACT) was studied in connection with the formation of chloroplasts. ACT blocks the growth of the gametophytes, while the chloroplasts remain functional. On the other hand, CAP does not influence morphogenesis of the gametophytes. In particular the activity of the dividing apical cells remains untouched. Even when the light quality is changed during the development the corresponding specific effect of the light quality on morphogenesis is normal. The chloroplasts, however, become smaller, probably by inhibition of synthesis of structural proteins. But their synthetic activity is not completely suppressed. The specific blue or red light dependent morphogenesis is not changed, when protein synthesis in the chloroplasts is inhibited.     

Negative phototropism in young gametophytes of the fern Schizaea pusilla

Schizaea pusilla is a rare fern that occurs in acidic bogs and is one of the few fern species that maintains a filamentous gametophyte throughout its development. To expand our knowledge of the physiology of this fern, phototropic responses were examined in young gametophytes. In contrast to germ filaments of other fern species, apical protonemata of young gametophytes are negatively phototropic in continuous white, red and blue light at all fluence rates tested. The expression of phototropic curvature is not limited by time since apical protonemata are also negatively phototropic when they are given brief exposures of light and then placed in the dark. In other lower plant groups such as mosses and some algae, the direction of phototropic curvature can change depending on light quality and intensity, but in young gametophytes of Schizaea, negative phototropic curvature was observed in all conditions studied. Blue light is the most effective in promoting the negative phototropic response in Schizaea.     

<Emphasis Type="Italic">In vitro</Emphasis> culture of <Emphasis Type="Italic">Drynaria fortunei</Emphasis>, a fern species source of Chinese medicine “Gu-Sui-Bu”

This study reports spore germination, early gametophyte development and change in the reproductive phase of Drynaria fortunei, a medicinal fern, in response to changes in pH and light spectra. Germination of D. fortunei spores occurred on a wide range of pH from 3.7 to 9.7. The highest germination (63.3%) occurred on ½ strength Murashige and Skoog basal medium supplemented with 2% sucrose at pH 7.7 under white light condition. Among the different light spectra tested, red, far-red, blue, and white light resulted in 71.3, 42.3, 52.7, and 71.0% spore germination, respectively. There were no morphological differences among gametophytes grown under white and blue light. Elongated or filamentous but multiseriate gametophytes developed under red light, whereas under far-red light gametophytes grew as uniseriate filaments consisting of mostly elongated cells. Different light spectra influenced development of antheridia and archegonia in the gametophytes. Gametophytes gave rise to new gametophytes and developed antheridia and archegonia after they were transferred to culture flasks. After these gametophytes were transferred to plastic tray cells with potting mix of tree fern trunk fiber mix (TFTF mix) and peatmoss the highest number of sporophytes was found. Sporophytes grown in pots developed rhizomes.     

Effects of blue and red light on unrolling of rice leaves

Unrolling of the second leaf of 8-day-old rice (Oryza sativa L.) seedlings was promoted by weak blue light (B), but not by red light (R). The effect of B was counteracted by irradiation with R just before or after the B. The counteracting effect of R was reversed by subsequent irradiation with far-red light but not by B, even if B was applied for 10 h. The B was effective when the region 0.5–2 cm from the tip of the leaf was irradiated. These results indicate that in rice photoreceptors for blue light located in the region 0.5–2 cm from the tip of the leaf play a key role in leaf unrolling and that a B-absorbing pigment and phytochrome participate in leaf unrolling in a closely related manner.Abbreviations B blue light - R red light - FR far-red light - W white light - D dark This work was presented at the Annual Meeting of the Japanese Society of Plant Physiologists on April 4, 1978, in Hiroshima     

Egg release in gametophytes of Laminaria saccharina: Induction by darkness and inhibition by blue light and u.v.

Gametophytes of Laminaria saccharina cultivated from zoospores in a light-dark regime (16:8), release eggs exclusively during the dark cycles, 8–10 days after seeding of the zoospores, and mainly during the first 30 min of darkness. The inhibiting effects of light during the light cycle of 16 h per day is also apparent in gametophytes which have experienced only two dark cycles prior to day 8, when egg release begins. Egg release can be shifted to any time during the light cycle by prolonging the irradiation with white fluorescent light and by subsequent darkening for 1 h. In gametophytes cultivated in continuous white fluorescent light eggs are also released from day 8–10, so in this case no inhibiting activity of light is apparent. Egg release is inhibited by blue light and u.v., with peak wavelengths for inhibition at 372, 413, 438 and 481 nm. No inhibition occurs at wavelengths above 513 nm. The light requirement for inhibition is very low. A photon fluence rate of 1·4 μE m^-2s^-1, given for 45 min at 449 nm, inhibits egg release in 50% of the mature gametophytes. There is some evidence that a circadian rhythm is involved, primarily since in gametophytes which are transferred at the beginning of day 8 from 16:8 to constant conditions (darkness, continuous red or green light) the diel rhythm of egg release persists until day 11.     

Blue- and red-light action in photoorientation of chloroplasts in Adiantum protonemata

An action spectrum for the low-fluencerate response of chloroplast movement in protonemata of the fern Adiantum capillus-veneris L. was determined using polarized light vibrating perpendicularly to the protonema axis. The spectrum had several peaks in the blue region around 450 nm and one in the red region at 680 nm, the blue peaks being higher than the red one. The red-light action was suppressed by nonpolarized far-red light given simultaneously or alternately, whereas the bluelight action was not. Chloroplast movement was also induced by a local irradiation with a narrow beam of monochromatic light. A beam of blue light at low energy fluence rates (7.3·10^-3-1.0 W m^-2) caused movement of the chloroplasts to the beam area (positive response), while one at high fluence rates (10 W m^-2 and higher) caused movement to outside of the beam area (negative response). A red beam caused a positive response at fluence rates up to 100 W m^-2, but a negative response at very high fluence rates (230 and 470 W m^-2). When a far-red beam was combined with total background irradiation with red light at fluence rates causing a low-fluence-rate response in whole cells, chloroplasts moved out of the beam area. When blue light was used as background irradiation, however, a narrow far-red beam had no effect on chloroplast distribution. These results indicate that the light-oriented movement of Adiantum chloroplasts is caused by red and blue light, mediated by phytochrome and another, unidentified photoreceptor(s), respectively. This movement depends on a local gradient of the far-red-absorbing form of phytochrome or of a photoexcited blue-light photoreceptor, and it includes positive and negative responses for both red and blue light.Abbreviations BL blue light - FR far-red light - Pfr far-red-absorbing form of phytochrome - Pr red-absorbing form of phytochrome - R red light - UV ultraviolet     

Growth control by phytochrome of de-etiolated bean hypocotyls mediated by chlorophyll fluorescence

The elongation of hypocotyls excised from de-etiolated seedlings of beans (Phaseolus vulgaris L. cv. British Wax) is inhibited by light, blue and red irradiations being equally effective. Conditions which decrease chlorophyll fluorescence, such as CO₂-free air, abolish the inhibitory effect of blue irradiation and enhance the inhibition by red light. Conversely, conditions which increase chlorophyll fluorescence, such as a N₂ atmosphere or irradiation through a chlorophyll filter, abolish the inhibitory effect of red light and enhance the inhibition by blue irradiation. The inhibitory effect of blue light is reversible by red irradiation under increased fluorescence as well as by far red. We propose that the chlorophyll fluorescence excited by blue and red irradiations in λ_F > 660 nm and λ_F > 720 nm, respectively, is responsible for the inhibitory effect of blue light and the reduction of the inhibitory effect of non fluorescing red light. Both red and blue wavelengths seem, therefore, to control hypocotyl elongation through phytochrome.