Nutation rhythm of growing pine hypocotyl (Pinus silvestris L.) interferred with a phototropic stimulus

The interaction of nutation oscillation and phototropic curvature mechanisms of growing pine hypocotyl(Pinus silvestris L.) was investigated. Nutation parameters of growing hypocotyl are not affected by continuous lateral illumination. Frequency and nutation amplitudes undergo changes which are dependent on plant development and are nearly the same when plants are illuminated from one side or from above. Lateral illumination, however, induces a phase shift. This deviation from a normal nutation rhythm usually disappears after a period of time equal to three nutation revolutions,i.e. after 12 h. The positive phototropio response of nutating hypocotyl is dependent on the phase in which the hypocotyl is exposed to the lateral illumination:(a) nutation perihelium,(b) ahelium and(c) nutation interphase. These response-variants are compared with the expected gradients of plant hormones at the opposite sites of the hypocotyle. Analysis of location of the individual movement reactions(i.e. oscillations as a component of the geocontrol system and phototropic curvature) together with the determination of the zone of maximum elongation indicates the existence of different receptory centres of these two movement systems. In the case of the phototropic response reaction it is possible to consider the presence of different photo- and biochemical mechanisms at least for a part of this system.     

Kinetics of the light-induced georeactivity of maize roots

Apical root segments of Zea mays L. cv. Orla 264 undergo some geotropic curvature in complete darkness but the curvature increases considerably if prior to geostimulation the segments are given a light pretreatment. If the light treatment is follwed by a dark treatment before the root is geostimulated the light-induced response is not changed by dark periods up to 2 h but declines with longer ones, and disappears completely after 5 h of darkness.     

Physiology of Movements in the Stems of Seedling Pisum sativum L. cv Alaska : III. Phototropism in Relation to Gravitropism, Nutation, and Growth

Phototropic response in etiolated pea (Pisum sativum L. cv Alaska) seedlings is poor. However, the curvature induced by unilateral blue light can be hastened and increased in magnitude by a previously administered red light pulse followed by several hours of darkness. Phytochrome is involved in the red light effect. Phototropic response was almost completely inhibited by removal of the apical bud and hook, but it was restored if exogenous indole-3-acetic acid was applied apically to the cut stump. Therefore, the stem contains both the phototropic photoreceptor and response mechanism. Perception of gravity and gravitropic response were also localized in the stem, but gravitropism was scarcely inhibited by decapitation. It was also observed that the kinetics and curvature pattern of gravitropism differed greatly from those of phototropism. Like phototropism, stem nutation required auxin and was promoted by red light. Unlike phototropism, photoenhanced nutational curvature required the apical hook and was propagated as a wave down the stem. Naphthylphthalamic acid inhibited, in order of decreasing effect, nutation, phototropism/gravitropism, and growth. Phototropism, gravitropism, and nutation appear to represent distinct forms of stem movement with fundamental differences in the mechanisms of curvature development.     

Physiology of Movements in Stems of Seedling Pisum sativum L. cv. Alaska : I. Experimental Separation of Nutation from Gravitropism

Gravitropism and nutation in the stems of dark-grown, seedling peas (Pisum sativum L. cv. Alaska) were recorded on time-lapse photographs made with photomorphogenetically inactive light. Although gravitropism and nutation have been connected by several different theories in the past, our experiments indicate that the two processes are in fact dissociable. The evidence is as follows: (a) Nutational patterns are asymmetric. There is much greater amplitude of oscillation in the plane parallel () to the plane of the apical hook than in the plane perpendicular (), yet the average gravitropic response is equal in these two planes. (b) Brief red light irradiation given 16 to 24 hours before observation greatly increases the amplitude of nutation in the -plane, but has no influence on the kinetics of gravitropic response. (c) An inhibitor of auxin transport, α-naphthylphthalamic acid, strongly inhibits nutation at 5 micromolar but affects gravitropism only at higher concentrations. (d) Nutation is also strongly inhibited by removal of the apical bud, but gravitropism is unaffected. (e) The period of nutation does not exhibit a constant relationship to the response time of gravitropism. The above evidence is inconsistent with theories that gravitropism is an asymmetrically modified nutation or, alternatively, that nutational oscillations result in a simple fashion from gravitropic overshoots. The evidence is consistent with, although not proof of, autonomous factors such as an endogenous rhythm of growth as the cause of nutation in pea stems. However, gravity and nutation do interact. Nutation in a population of seedlings can be synchronized and brought into phase by a single gravitropic induction. Furthermore, the response time and initial rate of gravitropic curvature depend to some extent on the phase of nutational curvature at which gravitropic induction is begun.     

Elongation and circumnutation oscillations of hypocotyl of pine seedlings (Pinus silvestris L.)

The elongation of pine seedlings (Pinus silvestris L.) is associated with nutation movements. Trajectories of these growth oscillations were recorded by film technique in horizontal and vertical projection during a three day period of growth. On the basis of these data the parameters of elongation and nutation oscillations,i.e. rate, amplitudes and frequency of oscillations, were calculated and their changes during plant development compared. Oscillation trajectories are circular or elliptic spirals the amplitudes of which are increasing with the age of hypocotyl from 1.5 mm to 7.5 mm. The frequencies of nutations are decreasing during the growth from 0.5 to 0.2 rev. h^?1. On the other hand, the growth rate of hypocotyl increased from values near to 10^?3 mm h^?1 at the beginning of the experiment to 4×10^?1 mm h^?1 recorded at the end of the third day. The zone of nutation curvature was slightly transferred from the middle of the hypocotyl toward the apex and its location has not been identical with that of elongation. This indicates that the system controlling nutation oscillations need not be identical with that controlling direction of elongation. At a certain stage of development behaviour of the decapitated pine hypocotyl is analogical to that of the root without the centre of georeception. A possibility of analogy of the system controlling direction of hypocotyl growth and of the system proposed for geotropical control of root growth is discussed.     

The effect of lateral illumination on growth oscillations of pine seedling hypocotyls (Pinus silvestris L.)

Phototropic sensitivity of forest wood seedlings to lateral illumination was proposed as an early assay for distinquishing various ecotypes of woody plants of the same species. Statistical analysis showed that results were significantly influenced by heterogenity of experimental material caused by an interference of phototropic movements and natural oscillations of hypocotyl. Both movements of pine seedlings (Pinus silvestris L.) were registered by phase photography and their mechanism was analyzed. The apical part of growing hypocotyl illuminated from above oscillates in a space spiral with frequency 3.3 h at mean growth rate 0.66 mm h^?1. The mean size of spiral amplitudes is 2.9 mm. The oscillation rhythm is disturbed after the lateral illumination and a phase shift was observed as a result. A new oscillation rhythm with frequency 3.9 h and mean growth rate 0.69 mm h^?1 was stabilized after a period of time equal to one nutation turn. Oscillation amplitudes were increased to 4.3 mm. In addition to the radiation intensity the appearance of the phototropic response to light pulse is first of all effected by the actual position of the apical part of hypocotyl in the course of endogenous circumnutations. A uniform plant material for the early assay may be obtained by selection of seedlings which are at the beginning of lateral illumination in the same phase of nutation rhythm. Under such conditions the deviations of longitudinal axis of oscillating spirals characterize the actual phototropic curvature.     

Growth and nutation parameters of primary root of pedunculated oak (Quercus robur L.)

The elongation of primary roots of pedunculated oak (Quercus robur L.), which is associated with nutation oscillations, was registered by a time lapse cinematography. The following characteristics were expressed graphically: relative growth rate [mm h-¹], frequency [rev. h-¹] and amplitudes [mm] of nutation oscillations, their direction and location of nutation curvatures. The growth-oscillation mechanism is interpreted as a part of the geocontrol system of the root and was evaluated on the basis of its physiological efficiency. Comparison of nutation periods showed that the control system of pedunculated oak is three times more and two times less efficient than that of pea and maize, respectively. Comparison of the oscillation amplitudes of growing roots gives similar results.     

Circumnutation oscillations of the hypocotyl and hypocotyl hook formation: A comparison of Norway spruce (Picea abies (L.)Karst.) and Scots pine (Pinus silvestris L.) seedlings

Circumnutation oscillations of hypocotyls were studied in Norway spruce and Scots pine using time-lapse cinematography. It was found that the circumnutations were specific in species. The analysis of hypocotyl ontogeny (100 h) revealed a different duration of the phases I, II and III of nutation oscillations in the first and second taxon. From the quantitative point of view it can be stated that during the phase I of nutation oscillations the Norway spruce hypocotyls exhibited higher frequency activity (corrections in direction of the hypocotyl by an elongation-controlling system corrected by a feedback mechanism), while in the phase III of nutation oscillations higher growth rate and larger amplitudes were observed in the Scots pine hypocotyl when compared with those of Norway spruce. The hypocotyl hook appeared only in Norway spruce.     

Correlations between proton-efflux patterns and growth patterns during geotropism and phototropism in maize and sunflower

By placing seedlings of sunflower (Helianthus annuus L.) or maize (Zea mays L.) on agar plates containing a pH indicator dye it is possible to observe surface pH patterns along the growing seedling by observing color changes of the indicator dye. Using this method we find that in geotropically stimulated sunflower hypocotyls or maize coleoptiles there is enhanced proton efflux on the lower surface of the organ prior to the initiation of curvature. As curvature develops the pattern of differential acid efflux becomes more intense. A similar phenomenon is observed when these organs are exposed to unilateral illumination, i.e. enhanced acid efflux occurs on the dark side of the organ prior to the initiation of phototropic curvature and the pattern of differential acid efflux intensifies as phototropic curvature develops. These observations indicate that differential acid efflux occurs in response to tropistic stimuli and that the acid efflux pattern may mediate the development of tropistic curvatures.     

Interspecific and Ontogenetic Variation in Proximal Pedal Phalangeal Curvature of Great Apes (Gorilla gorilla, Pan troglodytes, and Pongo pygmaeus)

Considerable attention has been devoted to understanding phalangeal curvature in primates, particularly with regard to locomotion. Previous work has found that increased phalangeal curvature may be indicative of increased grasping during suspensory and climbing behaviors, but the details of this relationship, particularly as regards feet, is still unclear. Using behavioral studies to predict an interspecific gradient of variation in pedal phalangeal curvature, I collected digital data from the third and fifth digit proximal pedal phalanges in adult Gorilla gorilla, Pan troglodytes, and Pongo pygmaeus and calculated included angles of phalangeal curvature to assess the appropriateness of pooling digits within taxa and evaluate the association between variation in pedal phalangeal curvature and frequency of climbing behavior. I also used an ontogenetic sample of Pan troglodytes to evaluate the postnatal relationship between variation in phalangeal curvature and grasping behaviors. I found intraspecific variation in phalangeal curvature suggesting among-digit variation in grasping behaviors. Curvature of Pongo was significantly greater than of both Pan and Gorilla. In contrast, Pan was significantly more curved than Gorilla only in comparison of third digits. Ontogenetic decreases in pedal phalangeal curvature among Pan troglodytes accorded well with postnatal decreases in documented climbing frequency. These findings largely support earlier work regarding the association between arboreal grasping and phalangeal curvature, and provide a unique intraspecific analysis that illuminates a number of areas where our knowledge of the behavioral and biomechanical determinants of phalangeal curvature should be explored further, particularly with respect to the role of among-digit variation in phalangeal curvature.     

Plant regeneration from in vitro leaf tissues of <Emphasis Type="Italic">Viburnum dentatum</Emphasis> L

Shoots were regenerated from in vitro leaf tissues of two genotypes of Viburnum dentatum, a popular shrub species for landscape use. Adventitious shoots were induced when leaf tissues were cultured on woody plant medium (WPM) supplemented with either benzyladenine (BA) or thidiazuron (TDZ). Effects of cytokinin concentration, indole-3-butyric acid (IBA), and dark treatment on shoot regeneration were investigated. Dark treatment for the first 4 weeks of leaf explants cultured in the regeneration medium significantly increased the frequency of regeneration. The highest frequency of shoot regeneration (70%) for ‘Synnesvedt’ was obtained when leaf tissues were cultured in the medium with 40 μM BA or 8 μM TDZ with 4 weeks dark treatment. The highest frequency of shoot regeneration (90%) for ‘MN34’ was found in the 4 μM TDZ medium with 4 weeks dark treatment. Addition of IBA significantly enhanced shoot regeneration. Ethyl methanesulfonate (EMS) treatment inhibited callus proliferation, particularly in the early stage of callus recovery; however, no significant difference in shoot regeneration among different treatments was observed, indicating that the inhibitory effect of EMS was minimal after calluses re-acquired their capacity to grow and regenerate in the regular medium. Regenerated shoots (>1.5 cm) were rooted in the half-strength MS medium containing 5-10 μM IBA or naphthalene acetic acid (NAA). Rooted plants were transferred to the potting medium and grown in the greenhouse.     

Physiology of Movements in Stems of Seedling Pisum sativum L. cv Alaska : II. The Role of the Apical Hook and of Auxin in Nutation

The relationship between the apical hook and stem nutation in etiolated Alaska pea (Pisum sativum L. cv Alaska) seedlings was explored. The hook and maximum nutational displacement have the same plane of symmetry, and both are affected by light acting through phytochrome. However, the two processes do not appear to be obligatorily coupled. Light effects on nutation involve at least two components, an increase in amplitude as well as an increase in frequency. These components can be separated from one another on the basis of developmental time course or red light fluence. Excision of the plumule, leaving the hook attached to the stem, inhibits photostimulated nutation. This inhibition can be overcome by application of indole-3-acetic acid to the remaining stem. If the hook is also excised, then nutation in the stem cannot be restored by indole-3-acetic acid. It is possible, although not yet proven, that the oscillatory process regulating nutation in the stem is itself localized in the hook and that rhythms in the transport of indole-3-acetic acid are involved.     

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.     

Cellular basis for the automorphic curvature of rice coleoptiles on a three-dimensional clinostat: possible involvement of reorientation of cortical microtubules

Coleoptiles of rice (Oryza sativa L.) show a spontaneous (automorphic) curvature toward the caryopsis under microgravity conditions. The possible involvement of the reorientation of cortical microtubules in automorphic curvature was studied in rice coleoptiles grown on a three-dimensional clinostat. When rice seedlings that had been grown in the normal gravitational field were transferred to the clinostat in the dark, cortical microtubules of epidermal cells in the dorsal side of the coleoptiles oriented more transversely than the ventral side within 0.5 h. The rotation on the clinostat also increased the cell wall extensibility in the dorsal side and decreased the extensibility in the ventral side, and induced automorphic curvature. The reorientation of cortical microtubules preceded the changes in the cell wall extensibility and the curvature. The irradiation of rice seedlings with white light from above inhibited microtubule reorientation and changes in the cell wall extensibility, as well as curvature of coleoptiles. Also, colchicine, applied to the bending region of coleoptiles, partially inhibited the automorphic curvature. These results suggest that reorientation of cortical microtubules is involved in causing automorphic curvature in rice coleoptiles on the clinostat.     

Callus induction and plant regeneration in <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis>

To establish a successful in vitro plant regeneration system in Alternanthera philoxeroides (Mart.) Griseb, an orthogonal design was used to investigate the effects of three factors (plant growth regulators, explant types and dark treatment in initial-stage), each having three levels. The effects of these factors and levels on callus induction and shoot regeneration were quantitatively evaluated by analysis of variance. The experimental results showed that the callus induction was significantly affected by 2, 4-dichlorophenoxyacetic acid (2, 4-D), and shoot differentiation from subcultured pieces of callus was enhanced mostly by dark treatment in initial-stage. The optimal conditions for callus induction are obtained from the stem explants cultured on semi-solid Murashige and Skoog (MS) medium plus 2.2 μM BA and 2.2 μM 2, 4-D, with 20 days dark treatment in initial-stage. The highest frequency of shoot regeneration is obtained from the calli cultured on semi-solid MS medium plus 8.8 μM BA, without dark treatment in initial-stage.     

Reproductive strategies of two forms of flightless males in a non‐pollinating fig wasp under partial local mate competition

1. The underlying basis of alternative male reproductive strategies is either genetic or environmental. Several non‐pollinating fig wasp lineages have dimorphic males, typically with winged males that disperse from natal figs to mate and flightless males that seek mating opportunities in natal figs. 2. Walkerella sp. from Ficus benjamina has dark and pale wingless males. Observations and experiments in Xishuangbanna, Southern China found that (i) the sex ratio of Walkerella sp. did not vary with foundress number or brood size. (ii) The frequency of dark males increased with brood size and foundress number and they were absent from figs with a single foundress. This produced a higher proportion of dark males at higher densities. (iii) Males of both morphs fought, but injuries to dark males were more frequent. (iv) Dark males were more likely to disperse away from their natal figs and (v) they were more resistant to dehydration. 3. Responses to selection are constrained by the genetic options available. Consequently, selection pressures acting on different lineages can produce similar outcomes that are achieved in different ways. Walkerella species lack winged males, but dark males display some of their features, dispersing from natal figs and displaying appropriate physiological and behavioural adaptations. However, dark males also displayed increased levels of damage from fighting – a feature unlikely to be shared with the winged males of other species.     

The Geotropic Curvature in Roots of Norway Spruce (Picea abies) Containing Anthocyanins

Seedlings of Norway spruce (Picea abies L.) have been found to synthesize anthocyanins in the root tips as well as in the hypocotyls upon irradiation with white light when kept at 4°C for 6–8 days. In addition, it has also been found that the elongation and the geotropic curvature of spruce roots are dependent on the light conditions. The course of the geotropic curvature in spruce roots containing anthocyanins has been followed during a period of 5 h, in which the seedlings were geotropically stimulated continuously in the horizontal position. When the stimulation was performed in white light and in darkness at 21°C, significantly larger curvatures were observed in the roots pretreated at 4°C in darkness than in the roots containing anthocyanins. The specific curvature (curvature in degrees per mm elongation), however, was approximately the same in both types of roots stimulated in white light. This was due to a retarded elongation of the roots pretreated with light at 4°C and containing anthocyanins. A smaller difference in elongation rate between roots with and without anthocyanins was observed in the dark than in the light, but even in the dark the anthocyanin-containing roots grew more slowly than roots without anthocyanins. In order to find out if it is the anthocyanin content or the illumination which affects the elongation and geotropic curvature in the roots, a series of similar experiments was performed using cress seedlings grown at 4°C in light or darkness. Roots of cress seedlings cultivated under conditions which would induce anthocyanin formation in spruce roots exhibited the highest geotropic responses both in light and darkness as compared to cress seedlings grown at 4°C in darkness. As in the case of spruce roots an increase in elongation was observed in cress roots illuminated during the geotropic stimulation. These similarities in the behaviour made it relevant to compare the development of the geotropic curvature in cress and spruce roots.     

Scale-up of tubular photobioreactors

The effect of the light/dark cycle frequency on theproductivity of algal culture at differentday-averaged irradiance conditions was evaluated forPhaeodactylum tricornutum grown in outdoortubular photobioreactors. The photobioreactor scale-upproblem was analyzed by establishing the frequency oflight–dark cycling of cells and ensuring that thecycle frequency remained unchanged on scale-up. Thehydrodynamics and geometry related factors wereidentified for assuring an unchanged light/dark cycle.The light/dark cycle time in two different tubularphotobioreactors was shown to be identical when thelinear culture velocity in the large scale device(U _LL) and that in the small scale unit (>U _LS)were related as follows:U_LL = \frac f ^9/7 \alpha^8/7 U_LS.Here f is the scale factor (i.e., the ratio oflarge-to-small tube diameters), is afunction of the illuminated volumes in the tworeactors, and `dark' refers to any zone of the reactorwhere the light intensity is less than the saturationvalue. The above equation was tested in continuouscultures of P. tricornutum in reactors with 0.03 mand 0.06 m diameter tubes, and over the workableculture velocity range of 0.23 to 0.50 m s^-1. Thepredicted maximum realistic photobioreactor tubediameter was about 0.10 m for assuring a cultureperformance identical to that in reactors with smaller tubes.     

Gravitropic response of primary maize rootlets as influenced by light and temperature

Abstract. The gravitropic curvature of primary maize rootlets was measured as a function of temperature, both in the presence and absence of light. In two different cultivars, light strongly increased the downward curvature of roots developing from horizontally-oriented embryos. At 15–20°C, the bending angle was in the range of 70–80° in the light, and 25–50° in the dark, depending on the cultivar. When the temperature was increased above the 15–20°C range, marked differences were found between the two cultivars in their response to light. In one variety tested, JX180, the effect of light was relatively small at 30–35°C. Gravitropic curvature in another variety, Halamish, depended strongly on light throughout the temperature range tested. In both cultivars, gravitropic curvature was only slightly temperature dependent when germination and growth were in total darkness. In the dark, the extent of gravitropic curvature also depended on whether the kernels were oriented with their embryos facing upwards or downwards. Under continuous light, the gravitropic bending of roots of cultivar Halamish did not show a marked temperature dependence. When the seedlings were subjected to only a 15 min illumination, their gravitropic response was partial, and the dependence on temperature somewhat increased. In cultivar JX180, a combination of temperature and light modulates gravitropism. The gravitropic response of different maize cultivars thus differs considerably in its combined dependence on light and temperature.     

A morph-ratio cline for keel petal colour in Lotus corniculatus L. along the north coastof Scotland

Summary

A survey of the relative frequencies of the dark and light keel variants of Lotus corniculatus L. was conducted in early July 1981, over 18 different sites located along the north coast of Scotland. Half of the sites surveyed were resampled in late July/early August 1984,to check for constancy of morph frequencies. The frequency of the dark keel morph recorded in 1981 showed a gradual increase from a value of 23% at Sheigra in the west to 87% at Duncansby Head in the east. Morph frequencies at sites sampled in 1981 and 1984 were highly correlated, and it was established that the change in dark keel frequency over eight of the sites surveyed in 1981 was significantly associated with parallel changes in mean annual rainfall and temperature. It is suggested that an experimental analysis of the morph-ratio cline for keel colour along the north coast of Scotland would aid our understanding of the factors which determine the distribution of the two keel colour morphs in Britain.