CHARACTERIZATION OF A CALCIUM-REQUIRING PHASE DURING PHYTOCHROME-MEDIATED FERN-SPORE GERMINATION OF Dryopteris paleacea Sw.*

Abstract— For phytochrome-mediated fern-spore germination in Dryopteris paleacea Sw., initiated by a saturating red light (R) irradiation 20 h after imbibition, an almost absolute requirement for extracellular Ca²+ is found. To investigate the kinetics of this Ca²+ requirement spores were sown on a Ca²+-free medium (Ca²+ < 10^?8M) and Ca²+ was raised to 1 mM at defined periods after R. Alternatively, spores were sown on a Ca²+-containing medium (1 mM) and transferred to a Ca²+-free medium. A clearly defined period for the Ca²+ requirement is found between 30 and 50 h after R, while Ca²+ had to be present in the medium for at least 9 h to obtain half-maximal germination. However, since the kinetics of deprivation and delayed addition of Ca²+ do not provide significantly different results, only a relative short presentation time for extracellular Ca²+ has to be expected at the level of a single cell. Ca²+ sensitivity is determined by the timing of the R irradiation, i.e. the timing of Pfr formation, which has been concluded from the observation that the variation of the imbibition time does not affect the kinetics of Ca²+ requirement and that the temporal application of polyethylene glycol (PEG), which is assumed to interrupt Pfr action, shifts the Ca²+ requirement to delayed intervals. These observations, as well as the fact that the requirement of Ca²+ has been observed for a limited period are interpreted as indirect evidence that Ca²+ action plays the role of a specific link in the phytochrome-mediated signal-transduction chain. The “Ca²+ kinetics” are compared with the kinetics of escape from reversibility by far-red (FR) light and with kinetics of basic cell physiological processes occurring during germination. “Escape kinetics”, indicating “coupling” of Pfr to subsequent dark reactions, are observed at significant earlier intervals, and a gap of about 15 h is found for both the action of Pfr and of Ca²+. Thus, the direct interaction of Pfr with external Ca²+ as a first transduction step can be excluded experimentally. The kinetics of chlorophyll formation are found to be only slightly delayed, whereas the kinetics of mitosis are shifted by approximately 30 h. Almost the same slope is obtained for all kinetics investigated so far and one reaction spans a period of approximately 35 h. Obviously, variability found in the spore population is due to the coupling of Pfr whereas subsequent reactions proceed with almost identical velocity.     

AN ANALYSIS OF PHYTOCHROME-MEDIATED THRESHOLD CONTROL OF HYPOCOTYL GROWTH IN MUSTARD (Sinapis alba L.) SEEDLINGS†

Hypocotyl elongation in mustard (Sinapis alba L.) seedlings is known to be controlled by phytochrome (P_fr) through a threshold response. This phytochrome-mediated threshold response was studied in detail with the following results: (i) The P_fr threshold value required to suppress hypocotyl growth is much lower (0.03% P_rr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%) than those threshold valued observed previously in threshold control by hook phytochrome of appearance of 'potential capacity for photophosphorylation' and lipoxygenase appearance in the mustard cotyledons (1.25% P_tr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%). This probably explains why hypocotyl elongation is so extremely sensitive to light, (ii) The P_fr threshold value controlling hypocotyl growth is a system constant, independent of total phytochrome content, developmental age and actual growth rate, (iii) Threshold control of hypocotyl elongation is unaffected by the removal of the cotyledons and half of the hook. However, removal of the whole hook totally eliminates any light control over the residual hypocotyl growth, (iv) After termination of the threshold control, the hypocotyl growth rate immediately returns to precisely that found in untreated dark control even though the partial growth rates of the different parts of the hypocotyl are quite different, relative to their dark controls. Obviously, the organ grows as an integrated unit.
It is concluded that the all-or-none threshold control over hypocotyl growth is exerted from the plumular hook. It appears that the hook can send off phytochrome all-or-none signals in both directions, to the cotyledons and to the hypocotyl.     

PHYTOCHROME-MEDIATED THRESHOLD CONTROL OF HYPOCOTYL GROWTH IN PARTLY DE-ETIOLATED MUSTARD (Sinapis alba L.) SEEDLINGS

Abstract— Hypocotyl elongation in etiolated mustard ( Sinapis alba L.) seedlings is known to be controlled by phytochrome (Pfr) through a threshold mechanism. The Pfr threshold value required to suppress hypocotyl growth was low (3 times 10⁻²% Pfr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%). In the present study the question was addressed whether the threshold control by Pfr of hypocotyl elongation also operates in light-pretreated, partly de-etiolated seedlings after transfer to darkness. The experimental results show that this is the case. Calculation of the threshold level in far-red light pretreated seedlings led to a very low value (3 times 10⁻⁷%) compared to etiolated seedlings (3 times 10⁻²%). In red light pretreated seedlings the threshold level was calculated to be 9 times 10⁻⁷%. Since the light pretreatment affected the rate of degradation of phytochrome strongly (half-life of Ptot in continuous red light was found to be 35 min in far-red pretreated instead of 47 min in etiolated material), the difference in threshold level between far-red and red pretreated material cannot be interpreted unambiguously. However, the conclusion can be drawn that light nretreatment strongly increases the degradation rate of Pfr and decreases the threshold level.     

THE ROLE OF CYTOKININS IN THE PHYTOCHROME-MEDIATED GERMINATION OF DORMANT IMBIBED CELERY (APIUM GRAVEOLENS) SEEDS

The dormancy of celery seeds was broken by red light treatment given during imbibition and this effect was reversed by far-red light. The exact quantitative relationship between the timing and duration of red light treatment and dormancy-break has not been elucidated. However, the accumulated effect of daily 5 min exposures was greater than a single 5 min exposure on the second day of imbibition. The effects of red light treatment were simulated by treatment with a mixture of the gibberellins A₄ and A₇ and N⁶-^-benzyladenine. A correlation between the requirement for red light and the requirement for exogenous cytokinins in the presence of GA_4/7 was demonstrated by using six cultivars with different dormancy characteristics. In order to investigate the role of natural cytokinins in dormancy-break, quantitative and qualitative changes in cytokinins were measured in celery seeds immediately after red-light treatments. Rapid increases in n-butanol-soluble cytokinins following irradiation were associated with concomitant decreases in water-soluble cytokinins, suggesting a red light induced cytokinin conversion. Three of the cytokinins present in the n-butanol fraction of celery seed extracts were chromatographically similar to zeatin, zeatin riboside and N⁶-^-A²-^-isopentenyladenosine (i⁶Ado). The elution profiles from a PVP column of two others were similar to BA and its riboside. The possibility that these two cytokinins act as specific dormancy-breaking cytokinins in celery seeds is discussed. There was little evidence of reversal of the cytokinin conversion mechanism by far-red light exposure.     

NITRATE EFFECT ON Pfr-MEDIATED AND GA3-INDUCED GERMINATION IN SPORES OF Anemia phyllitidis (L.) Sw*

Spore germination in Anemia phyllitidis can be induced by red light (R) via the phytochrome system and by gibberellic acid (GA₃) in the dark. An enhancing effect of NO₃-ions on the Pfr-mediated germination could be demonstrated. This NO₃-effect was found to be pronounced during the preinduction phase and could be described by biphasic kinetics depending on the formation of Pfr by the R-irradiation. Besides NO₃, other electron accepting substances also increased germination significantly. In contrast to Pfr-mediated germination, no enhancing effect by NO₃ could be obtained for the GA₃-induced germination response. The application of an inhibitor of gibberellic acid synthesis, AMO1618, as well as the analysis of combined R and GA₃ treatment, support the hypothesis that for germination of Anemia phyllitidis spores no synergism between the factors exists. Thus, it is proposed that the gibberellic acid receptor starts a signal-transduction pathway resulting in germination which is in part independent of the Pfr-mediated signal-transduction chain. The NO₃-effect is specific for the Pfr-mediated signal-transduction chain.     

PHYTOCHROME-MEDIATED PHOTOTROPISM AND DIFFERENT DICHROIC ORIENTATION OF Pr AND Pfr IN PROTONEMATA OF THE FERN ADIANTUM CAPILLUS-VENERIS L.

Abstract— Single-celled protonemata of Adiantum capillus-veneris were cultured under continuous red light for 6 days and then in the dark for 15 h. Brief local exposure of a flank (5 times 20 /mi) of the subapical region of a protonema to a microbeam of red light effectively induced a phototropic response toward the irradiated side. The degree of the response was dependent upon the fluence of the red light. Red/far-red reversibility was typically observed in this photoreaction, showing that phytochrome was the photo-receptive pigment. When the flank was irradiated with a microbeam of linearly polarized red and far-red light, red light with an electrical vector parallel to the cell surface was most effective. However, the far-red light effect was most prominent when its electrical vector was normal to the cell surface. These polarized light effects indicate the different dichroic orientation of P_r (red-light-absorbing form of phytochrome) and P_r (far-red-light-absorbing form of phytochrome) at the cell flank.     

INDUCTION OF SEED GERMINATION IN Lactuca sativa L. BY NANOSECOND DYE LASER FLASHES*,†

Abstract— A 15 ns, tunable dye laser was used to induce germination of the photoblastic seeds of Lactuca sativa. One red laser flash in the range from 620 to 690 nm was sufficient to increase germination significantly above the dark level. Repeated flashes, however, were necessary to saturate the physiological response. The wavelength dependence for induction of germination differed for single and repetitive flashes. After saturating far-red irradiation, the effect of single-flash induction was a function primarily of the absorption spectrum of P_r. In addition, the establishment within the lifetime of a flash of a photochromic system between the red absorbing form of phytochrome (P_r) and the sum of photoreversible intermediate forms (ΣI₇₀₀) contributes to this wavelength dependence at high fluence rates. This photochromic system is assumed to be shifted significantly toward P_r by wavelengths 660 nm. Similarly, a strong double-flash effect, which is seen as an increase in effectiveness when a given total fluence is provided by two consecutive flashes rather than by one flash only, is restricted to those wavelengths that considerably shift the photochromic system P_r?ΣI₇₀₀ toward P_r. Finally, the saturation level produced by a series of laser flashes depends, additionally, on absorption by P_fr.     

EFFECT OF LIGHT ON OSCILLATIONS OF ENZYME ACTIVITY DURING PHOTOMORPHOGENESIS IN CHENOPODIUM RUBRUM L.

An approach to determine the photomorphogenic effect of light (white or continuous far-red) on the development of rhythmic enzyme activity in Chenopodium rubrum L. is described. Previous results, obtained from mature seedlings grown in white light, demonstrated stable oscillations with periods ranging between 12 and 15 h for all of the enzymes tested. The present results, obtained during deetiolation, were complicated by the presence of a higher frequency component with a period of about 6 h. When the various oscillating components were defined, the analysis showed: (1) the enzymes of the Krebs cycle (malate and isocitrate dehydrogenase), the closely associated glutamate dehydrogen-ase, and the glycolytic pathway ((NAD) glyceraldehyde-3-phosphate dehydrogenase) had a dominant period in the range of 12–15 h, (2) those of the oxidative pentose phosphate pathway were either weakly circadian (glucose-6-phosphate dehydrogenase) or apparently arhythmic (6-phosphogluconate dehydrogenase), (3) the (NADP) glyceraldehyde-3-phosphate dehydrogenase from the Calvin cycle was circadian when kept in continuous darkness but becomes 15 h when placed in light, and (4) only the Calvin cycle enzyme is affected by light in the level of its activity and in its oscillatory behavior.     

LIGHT CONTROL OF ELONGATION OF FILAMENT IN SUNFLOWER (Helianthus annuus L.)

Abstract— In sunflower ( Helianthus annuus L.) it has been found that continuous white-light during the flowering stage causes loss of protandry so that filaments do not elongate. Experiments have been carried out to test the nature of the pigment involved in the photoinhibition of elongation. The results suggest that the elongation of the filament is controlled by the phytochrome system and that a low photoequilibrium is required to obtain the response. Our results do not show light control of style elongation.     

VARIATION IN THE RATES OF SYNTHESIS AND DEGRADATION OF PHYTOCHROME IN COTYLEDONS OF CUCURBITA PEPO L. DURING SEEDLING DEVELOPMENT

Abstract— The time courses for P_r appearance, P_r disappearance and P_fr destruction have been analysed in cotyledons of Cucurbita pepo L. after different preirradiation programs. In etiolated seedlings the rate of P_r appearance is low in young seedlings reaching a maximum in 3.5–5 day old seedlings then decreasing rapidly with increasing age. The rate of P_fr destruction is very low in young seedlings, increases rapidly up to the 4th day and then remains almost constant. The disappearance of P_r becomes significant for seedlings older than 45 days. These reactions seem not to be influenced by short preirradiations. However, after prolonged preirradiation, a degree of control of P, appearance and/or disappearance by the "internal clock appears to be operative.     

INVOLVEMENT OF PHYTOCHROME IN LIGHT CONTROL OF STEM ELONGATION IN CUCUMBER (Cucumis sativus L.) SEEDLINGS

A series of polycondensed aromatic N-heterocycles (acridine, benzo-f-quinoline 1,2,7,8-dibenzacridine and 3,4,5,6-dibenzacridine) were adsorbed from the gas phase and from liquid solution on highly dispersed silica gels with very different specific surface areas and pore sizes. The translational mobility of the adsorbed species was quantified by the triplet decay and the delayed fluorescence following bimolecular triplet-triplet annihilation after pulsed laser irradiation. The decay kinetics were analyzed with conventional second order rate equations and with the fractal approach. The first method is reliable without limitations on adsorbents with large pore diameters. It yields second order annihilation constants of 4 times 10¹²-6 times 10¹¹ dm² mol^?1 s^?1 depending on the masses and sterical requirements of the adsorbates. For the second method a spectral dimension d_s= 4/3 was used. This method is quantitatively applicable to all heterocycles adsorbed on silica gel 60 that have very small pore sizes. An activation energy of 4.9 ± 0.5 kcal mol^?1 was obtained for the translational diffusion of acridine on hydroxylated silica gel.     

A New Glycoside and a Novel‐Type Diterpene from Hemerocallis fulva (L.) L.

The CHCl₃ extract of dried roots of Hemerocallis fulva (L.) L. afforded a novel diterpene named hemerocallal A ( 1 ), which is the second reported naturally occurring diterpene with a trans‐bicyclo[5.1.0]octane system. The BuOH extract afforded a new glycoside named hemerocalloside ( 2 ). Their structures were established on the basis of spectroscopic and chemical studies.     

THE ROLE OF SOLAR UV-B IN GROWTH REGULATION OF CRESS (Lepidium sativum L.) SEEDLINGS

Abstract— Action spectra for growth reduction within the 260 nm to 305 nm waveband were measured for hypocotyls and roots of young etiolated cress ( Lepidium sativum ) seedlings. The action spectra show increasing photon effectiveness with decreasing wavelength and resemble those due to DNA damage. Using short term irradiations, photoreceptors absorbing in the visible range were found to be without influence. As no photoreactivation could be found and the seedlings showed no outward signs of damage, this growth effect may be due to a UV photoreceptor. A modeling calculation was carried out to estimate the effectiveness of solar UV-B on this response both under present conditions and under reduced ozone levels. Even under present conditions, solar UV-B could be involved in regulating growth during the period immediately after germination.     

RAPID TRANSMISSION OF A PHYTOCHROME SIGNAL FROM HYPOCOTYL HOOK TO COTYLEDONS IN MUSTARD (Sinapis alba L.)

Abstract— In mustard ( Sinapis alba L.) cotyledons appearance of 'potential capacity' to phosphorylate is controlled by phytochrome (P_fr) through a threshold, all-or-none reaction. Phytochrome operates only if the hypocotyl hook is connected to the cotyledons for at least 2.5 min after the end of a 1 min inductive light pulse. Partial irradiations of hook and cotyledons show that in the case of induction of 'potential capacity' rapid transmission of the P_fr signal occurs from the hypocotyl hook to the cotyledons. Phytochrome within the cotyledons is totally ineffective in this regard. A 3 min red light pulse suffices for full transmission of the signal. It seems that an explanation of the facts we have observed requires a revision of the present views about communication between the organs of a plant.     

EFFECT OF DILUENTS ON CRYSTALLIZATION OF POLY(VINYLIDENE FLUORIDE) AND PHASE SEPARATED STRUCTURE IN A TERNARY SYSTEM via THERMALLY INDUCED PHASE SEPARATION

The phase diagram of a ternary system of PVDF,dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture.The experimental results showed that as the DBP content increased in diluent mixture,the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation,and both the cloudy point for L-L phase separation and crystallization temperature shif...     

Essential oil composition of Rydingia michauxii (Briq.) Scheen & V.A. Albert endemic of Iran

The chemical composition of the essential oil (EO) obtained from the aerial parts of Rydingia michauxii (Briq.) Scheen & V.A. Albert was analysed by gas chromatography and gas chromatography/mass spectrometry (GC/MS). Eighty components were identified in the oil with caryophyllene oxide (20.1%), trans-verbenol (10.2%), linalool (5.3%) and humulene epoxide II (4.6%) as main constituents. We reported here the chemical compositions of R. michauxii EOs from southern Zagros of Iran with a distinct chemical profile for the first time.