Phytochrome Action in Oryza sativa L: IV. Red and Far Red Reversible Effect on the Production of Ethylene in Excised Coleoptiles

Excised apical segments of etiolated rice (Oryza sativa L.) coleoptiles produced ethylene. Increasing the number of cut sites per coleoptile increased the rate of ethylene formation. Ethylene produced by an etiolated-intact seedling in the dark was about a half of that by the excised coleoptile segment. Red light of low energy as well as of continuous irradiation inhibited the production of ethylene. The inhibition by a low energy dose of red light was partly relieved, if the red light was followed immediately by a small dose of far red light. The effect of red and far red light was repeatedly reversible, indicating that ethylene production was regulated by a phytochrome system. If the exposure to far red light was preceded by a period of darkness, this photoreversibility disappeared; 50% of the initial reversibility was lost within 5 hours. Applied ethylene (10 microliters per liter) significantly promoted the growth of intact coleoptiles of either totally etiolated or red light-treated seedlings, but had no effect on the excised apical segment of coleoptile.     

Promotion of radish cotyledon enlargement and reducing sugar content by zeatin and red light

Effects of zeatin on amino acid and sugar contents of detached radish (Raphanus sativus L.) cotyledons were investigated to determine if accumulation of these solutes contributes to cytokinin-enhanced growth. Protein and amino acid levels were not significantly affected, but in cotyledons incubated in light the hormone caused greater accumulations of reducing sugars than occurred in light controls. Continuous fluorescent light or a few minutes of red light increased both the growth rate and the reducing sugar levels compared to dark controls. A far red treatment following red light overcame the promoting effect of the latter. Amounts of reducing sugars were closely associated with growth under the above conditions. Activity of an unidentified amylase was elevated by continuous light or a red light treatment (nullifiable by far red), suggesting that reducing sugars were derived from starch. Zeatin-treated cotyledons exhibited less amylase activity than did light controls, perhaps implicating cytokinin-stimulated conversion of fats to sugars in light. In darkness zeatin promoted cotyledon growth but did not increase sugar levels nor amylase activity, suggesting that enhanced ion accumulation also contributes to the more rapid water uptake leading to growth.     

Action of red and far red light on ribosome formation in cabbage seedlings

The action of light on ribosome formation was examined in the cabbage seedlings, a system extensively used in the studies of anthocyanin synthesis. Ribosomes were extracted 18 h after the beginning of the irradiation and separated by sucrose gradient centrifugation. In the cotyledons of dark-grown cabbage seedlings, a brief red light induces an increase both in total ribosomes and in the fraction present as polysomes; the effect of red light is reversed by far red light, indicating the involvement of phytochrome in polysome formation in cabbage seedlings. Continuous red and continuous far red light are about equally effective in bringing about an increase of total ribosomes and of the polysome fraction. Streptomycin, which inhibits chlorophyll synthesis and chloroplast development, and enhances anthocyanin synthesis in cabbage seedlings, causes a decrease of total ribosomes and of the fraction present as polysomes. In hypocotyls, the red-far red reversibility is evident only for the polysome content and streptomycin does not decrease the polysome/monosomo ratio as it does in cotyledons.     

Phytochrome action on the timing of cell division in adiantum gametophytes

When filamentous protonemata of Adiantum capillus-veneris L. precultured under continuous red light were transferred to the dark, the apical cell divided about 24 to 36 hours thereafter. The time of the cell division was delayed for several hours by a brief exposure to far red light given before the dark incubation. The effect of far red light was reversed by a small dose of red light given immediately after the preceding far red light. The effects of red and far red light were repeatedly reversible, indicating that the timing of cell division was regulated by a phytochrome system. When a brief irradiation with blue light was given before the dark incubation, the cell division occurred after 17 to 26 hours in darkness. A similar red far red reversible effect was also observed in the timing of the blue light-induced cell division. Thus, the timing of cell division appeared to be controlled by phytochrome and a blue light-absorbing pigment.     

Short term phytochrome control of oat coleoptile and pea epicotyl growth

Continuous recordings of the effect of light on oat (Avena sativa L. cv. Victory) coleoptile and pea (Pisum sativum L. cv. Alaska) epicotyl growth were made. Using a single excised coleoptile 10 minutes of red light was found to promote growth after a latent period of 46 minutes. The stimulation was transient and was not far red-reversible. Blue and far red light also promoted growth with similar kinetics. The action of continuous red or far red light was similar to that of 10-minute light. The growth of the intact pea third internode (as well as excised segments) was strongly inhibited by red light, with a latent period of 80 minutes. This effect was far red-reversible, and far red and blue light caused only a slight inhibition of growth.     

Kinetics and time dependence of the effect of far red light on the photoperiodic induction of flowering in wintex barley

Flowering in the long day plant Hordeum vulgare L. var. Wintex barley was enhanced by the addition of far red light to the main light portion of the photoperiod. Far red energy was provided to produce quantum flux ratios (660/730 nm) and phytochrome photoequilibria (Pfr/total phytochrome) equivalent to those reported both beneath a leaf canopy and outside a canopy at twilight. The photoperiodic requirement for long days can be completely eliminated by the addition of far red light. However, both the effect of extending the photoperiod without far red and the addition of far red to 12-hour photoperiods were suboptimal. Maximal stimulation was achieved only when far red was added to continuous light. The duration of the period of maximal apex elongation rate, as well as the reduction of the time required for floral initiation, were saturated by three inductive cycles. When far red energy was provided intermittently during 3 days of continuous light, the ability to respond varied in a circadian manner. This enhancement of flowering by far red appears to be mediated by the “high irradiance response” of phytochrome.     

Far red light control of elongation in light-grown bean hypocotyl: Effect on different age zones and interaction with indole-3-acetic acid

The effect of far red light on the light-grown bean hypocotyland its interaction with indole-3-acetic acid (IAA) were studied.Elongation of younger zones of the hypocotyl was inhibited butthat of older zones was promoted by far red light. This wascontrolled by phytochrome. Both the hook and shank portionscould receive far red light and its effect could be transmittedto either portions of the hypocotyl. When IAA was applied to the upper cut surface of the hypocotylunit, elongation of the shank portion was promoted even withoutfar red irradiation. IAA did not change the aspect of the growthcurves but amplified the elongation of each zone. When IAA wasapplied to each zone of the shank portion, elongation of zonesolder than the treated one was promoted but that of youngerzones was inhibited. This effect was emphasized by far red light.When IAA was applied to the older shank portion, elongationof the treated zone was synergistically promoted by IAA andfar red light, but when applied to the elbow or younger shankportion, far red light completely nullified the promoting effectof IAA. (Received October 1, 1979; )     

Effect of red light on the phototropic sensitivity of corn coleoptiles

The effect of red light in alteration of the phototropic sensitivity of corn coleoptiles (Zea mays L., cultivar Burpee Barbecue Hybrid) is investigated. Phototropic dosage-response curves for etiolated coleoptiles are compared with those for coleoptiles receiving 1 hour of continuous red light immediately prior to phototropic induction. In the former case, only curvature comparable to the first positive curvature of oat coleoptiles is obtained. There is no evidence for first negative curvature and only minimal second positive curvature. The reciprocity law proved valid for all curvatures obtained. With red light, the sensitivity of the first positive curvature was decreased over ten-fold and there was clear appearance of second positive curvature for which the reciprocity law was not valid. Once again there was no evidence for negative curvature. Time course studies indicated that within 1 hour of the beginning of red light treatment at 25°, reactions leading to the decrease in phototropic sensitivity of the first positive component had gone to completion whether the red light was continuous or consisted of a single 1 second exposure followed by a 1 hour dark period. An action spectrum for the red-induced change in phototropic sensitivity showed a marked peak near 660 mμ with a small broad shoulder between 610 and 630 mμ, characteristic of phytochrome-mediated responses. The effect of red light could be fully reversed by low dosages of far-red light, but longer doses of far red were less effective. Large dosages of far-red light alone induced the same alteration in phototropic sensitivity as did red light.     

Biphasic effect of red light on the growth of coleoptiles in etiolated barley seedlings

InHordeum vulgare cultivar “Kirin-choku No. 1”, the final length of intact coleoptiles of totally etiolated seedlings was approximately twice as long as that of those grown under continuous red light. The fluence response curve of the latter was biphasic; the low-energy effect was saturated by red light of ca. 50 J m⁻² which gave rise to about 40% of the maximum inhibition by continuous irradiation with red light of 1.2 W m⁻², whereas the high-energy effect was induced by irradiation for 1 hr or longer. Coleoptiles of 3-day-old seedlings were most sensitive to light causing the low-energy effect, which was repeatedly red/far-red reversible. The growth inhibition was correlated to the photometrically measured percentage of Pfr so that the maximum effect was induced by red light of 50 J m⁻² which transformed 70% of phytochrome to Pfr in the coleoptile tip. Wavelength dependence of the high-energy effect showed that monochromatic light of 400, 600 and 650 nm greatly inhibited the coleoptile growth, whereas light of 700 and 750 nm promoted it instead. The effect was also induced by intermittent irradiation with red light, and the more frequently the intermittent treatment was given, the more the growth was inhibited.     

The effect of red and far red light on the desaturation of Fatty acids in barley leaves

Barley (Hordeum vulgare) leaf tissue was either (a) exposed to continuous red light or (b) exposed to red, far red, or red followed by far red light. The fatty acid composition and incorporation of acetate-2-¹⁴C into linolenate were determined. Changes occurred in the fatty acid composition of dark-grown barley leaves regardless of whether the plants were subsequently exposed to red light or whether the tissue remained in the dark. Measurements were also made of the fatty acids of the coleoptile. Red light treatment did not reduce the lag period for the synthesis of linolenate when chlorophyll synthesis was inhibited. It appears that the desaturation process per se in the synthesis of linolenate is not phytochrome-mediated but may appear to be phytochrome mediated if, possibly, galactolipid and chlorophyll syntheses occur concomitantly.     

Effect of red and infrared radiation on the growth of Escherichia coli cells and production of recombinant barstar protein

Incoherent red and infrared low-intensity light enhanced the growth of the auxotrophic strain Escherichia coli AD494(DE3)pLysS and the production of the recombinant polypeptide barstar. Illumination also stimulated the growth of nonrecombinant E. coli cells.     

Effect of red light on coleoptile growth

The effects of red light in reducing the growth of the oat (Avena sativa L.) coleoptile and the synthesis of auxin in the coleoptile tip are detectable 2 hours after treatment and become more pronounced with time. When the coleoptile tip is supplied with additional tryptophan the synthesis of auxin is doubled both in darkness and when exposed to red light. Treatment of the tip with gibberellic acid or pyridoxal phosphate overcomes the reduction of auxin synthesis caused by red light. The uptake of exogenous indoleacetic acid, at pH 6.5, by coleoptile tissue is doubled by exposure to red light. The effect of red light on coleoptile growth appears to be mediated by phytochrome in the cell membrane which delocalizes the tryptophan utilized for auxin synthesis.     

Red and far red effects on phenylalanine ammonia-lyase in raphanus and sinapis seedlings do not correlate with phytochrome spectrophotometry

In seedlings of Raphanus sativus (radish) and Sinapis alba (mustard), irradiation for 6 hours with far red light significantly increases the extractable activity of phenylalanine ammonia-lyase by the end of the light period. A schedule of 10 minutes red light-110 minutes darkness-10 minutes red-110 minutes darkness-10 minutes red-110 minutes darkness has no effect as compared to dark controls. However, the red light program maintains a level of far red-absorbing phytochrome always measurable by in vivo spectrophotometry during the 6-hour experimental period. We conclude that the far red effect on this enzyme and for this specific material cannot be explained solely by formation and maintenance of far red-absorbing phytochrome.     

Effects of red light on the growth of intact wheat and barley coleoptiles

The final lengths of intact dark-grown coleoptiles vary with species and cultivar. The growth distribution pattern in the apical 25-mm growing zone and the absolute amount of growth in each zone depend on the age and species of the coleoptile. A comparative study of several cultivars of wheat, Triticum vulgare, and barley, Hordeum vulgare, indicates that the growth distribution pattern in 30- to 38-mm coleoptiles varies with the species and cultivar. In barley, there are two patterns of growth distribution among the several cultivars, whereas in wheat, all cultivars exhibit a common zonal growth pattern. The total growth of coleoptiles, initially 30 to 38 mm in length, during a 24-hour dark incubation period is the same in dark-grown coleoptiles as in those irradiated with 3 minutes of red (660 nm) light prior to the incubation period. The growth distribution pattern in the growing zone of this 30- to 38-mm coleoptile is, however, altered by red light. Growth of the apical 5-mm zone is stimulated by red light and the zonal growth 5 to 10 mm below the apex is only slightly affected, whereas growth in the zones 10 to 15 to 20, and 20 to 25 mm below the apex is inhibited. This growth distribution pattern in irradiated coleoptiles changes as the coleoptile increases in length. The response of a zone following exposure to red light is dependent upon the age of the seedlings irradiated. The over-all effect of red light on growth of the intact coleoptile varies with the length of the coleoptile. In young seedling 20 to 29 mm in length, the cells of the coleoptile can compensate for the effects of red light, with the over-all growth of the dark-grown and irradiated coleoptile about the same. As the seedling grows older, the cells of the coleoptile can no longer make up for the effects of red light, and the over-all effect changes from compensation to pronounced inhibition.     

Rapid suppression of extension growth in dark-grown wheat seedlings by red light

Continuous recordings were made using a linear displacement transducer to investigate short-term growth responses of intact dark-grown wheat (Triticum aestivum L. cv Maris Huntsman) seedlings to red light. To eliminate any effect of light prior to the experimental treatments, the seedlings were grown and mounted on the transducer apparatus in total darkness. The growth kinetics after irradiation were complex and appeared to consist of three successive phases of growth deceleration. When the tip of the intact coleoptile was irradiated with red light from two opposite fiber bundles (fluence rate: 2 × 64 micromoles per square meter per second) for varying periods of time (10 seconds, 1 minute, 5 minutes, continuous), a decrease in extension rate was detectable after a latent period of 8 to 10 minutes. Up to 30 minutes after the start of the irradiation treatment, there was no difference in the kinetics of inhibition (about 20 to 25% inhibition) between the different lengths of irradiation. Extension rate reached a minimum (65% inhibition) at about 85 minutes, after which growth acceleration toward the dark control rate was observed. Far-red reversibility of the rapid effect of red light on growth was not observed, even when far-red light was given only 4 seconds after the end of 10 seconds red light. Short (15 seconds) far-red light did not induce a response.     

Physiological dissection of blue and red light regulation of apical dominance and branching in M9 apple rootstock growing in vitro

This paper presents the results of the interaction of red light (R) with blue light (B), applied to shoots of M9 apple (Malus pumila paradisiaca Schmid) rootstock, on the regulation of stem growth, apical dominance and branching. These results are compared with the active form of phytochromes (PHYs) under monochromatic and dichromatic light treatments. The inhibition of internode elongation was determined by PHY photoequilibrium, with the additional effect of B, by means of a separate photoreceptor. The development of phytomers appeared to be primarily due to the active form of PHY, with a marginal effect from B. Shoot growth, which combines internode elongation and development of the phytomer, was highest under R and lowest under B and far red light (FR), showing the largely positive role of PHY photoequilibrium. Under FR, reduced stem elongation was due to the very small number of phytomers formed. Apical dominance was inhibited, while branching was increased under R, corresponding to the highest values of PHY photoequilibrium determined. Apical dominance was increased and branching was reduced by B, indicating a complex interaction between PHY and B receptor. In the shoot cluster system, photomorphogenic behavior was dependent on the time of exposure to the different light qualities. The information gained from the study will be helpful in improving the set up of in vitro growth light conditions, and in providing useful insights into research of the development of the woody plant canopy, an important factor in ecological plant communities.     

Far red end-of-day treatment restores wild type-like plant length in hybrid aspen overexpressing phytochrome A

Shoot elongation in woody plants is modulated by a multitude of light signals, including irradiance, photoperiod and spectral composition, for which the phytochrome system is the probable photoreceptor. In hybrid aspen ( Populus tremula  ×  tremuloides ) overexpression of the oat phytochrome A ( PHYA ) prevents growth cessation in response to short photoperiod, and plants exhibit dwarf growth that is related to reduced cell numbers and reduced gibberellin contents. End-of-day far-red treatment significantly enhances internode elongation in PHYA overexpressors as well as in the wild type, and this was found here to be caused by stimulation of cell division and cell extension. In PHYA overexpressors the effects were substantially larger than in the wild type, and resulted in complete restoration of wild type-like plant length as well as cell numbers, and gibberellin content was greatly increased. No clear effect of far-red end-of-day treatment on gibberellin levels could be detected in the wild type. It thus appears that the far-red end-of-day treatment might modify the responsiveness of the tissue to GA rather than the GA levels. The observed effects were completely reversed by a subsequent irradiation with red light. The present data show that dwarfism due to PHYA overexpression can be completely overcome by far red end-of-day treatment, and the observations indicate that effects of far red end-of-day treatments appear to be mediated by phytochrome(s) other than phytochrome A.     

Persistence of red light induction in lettuce seeds of varying hydration

Incubation of lettuce seeds (Lactuca sativa L. cv. Grand Rapids) in 0.3 m mannitol allows sufficient water uptake to make seeds fully sensitive to red light. But germination is possible only after lowering the osmotic potential of the incubation medium. The red light induction of these incompletely hydrated seeds can be reversed by far red light. Their reversibility declines with time at a slower rate than seeds incubated in water. About half the seeds in 0.3 m mannitol respond to far red light when all seeds in water have escaped control by far red light. Close to 100% of the seeds remain sensitive to far red exposure if 0.6 m mannitol is used as osmoticum. The retention of the original red light stimulus is inversely related to the concentration of the incubation medium.The fresh weight of viable seeds incubated with water or with an osmoticum increases rapidly during the first 5 hours, then remains stationary for about 12 hours. After that only germinating seeds experience a second increase in fresh weight. Heat-killed seeds do not show such a discontinuity in water uptake.     

Luria effect in bacteriophages and the role of the products of recA+ and lexA+ genes in its induction

An analysis of UV-damages accumulation in the phages as revealed by delay of intracellular growth is represented using temperate lambda phage. The maximum of growth delay of phage lambda at given UV-dose was found with lambda red+, infecting Escherichia coli AB1886 uvrA strain. The growth delay was absent, when a strain RH-1 uvrA-recA- was infected with UV-irradiated phage lambda red3. A moderate growth delay was obtained with the phages lambda red+, infecting E. coli RH-1 uvrA-recA- or phage lambda red3, infecting E. coli AB1886 uvrA-. THe growth delay was also absent when wild type, recA- and uvrA mutants of E. coli were infected with phage lambda after 8-metnoxypsoralen + light (lambda > 310 nm) treatment. It is known that the crosslinks appear to be the DNA defects which give rise to the observed biological inactivation following psoralen + light treatment. However, a considerable growth delay of phage lambda, treated by 8-metnoxypsoralen + light, was only found under condition of crosslinks repair (W-reactivation and prophage-reactivation). The results obtained are best explained by the assumption that the growth delay reflects the time required for the postreplication repair (RecA, LexA, Red) of any lethal UV-lesion.     

Effect of growth regulators on overcoming the light inhibition on germination ofCucumis anguria L.

The effects of some growth regulators on the dark-germinating seeds ofCucumis anguria have been investigated. GA₃, 6-BA and ethrel strongly promoted the germination of seeds kept in white light. GA₃ had no effect in counteracting the far red effect, but did counteract partially the blue light. Ethrel partially counteracted both the far red and blue light effect. No interaction could be found between red light and GA₃ or 6-BA.