Petal Movement Research Articles

Petal movement in cape wildflowers protects pollen from exposure to moisture

We investigated diurnal patterns of petal movement (upright and reflexed) and sensitivity of pollen to moisture in a winter-flowering flora from the desert coast of Namaqualand, South Africa. Specifically, we tested the hypothesis that nocturnal flower closure associated with upright petal movement affords protection to pollen from winter precipitation. The proportion of open flowers in eight species from seven genera and three families, increased rapidly above air temperatures of about 20 °C. Flower temperature explained most of the variance in petal status. About 90% of the variance in flower temperature was explained by air temperature while radiation, wind speed and relative humidity had no significant independent effect. Petal opening was more closely correlated with temperature than the closing response, which may be under the additional control of endogenous factors. Pollen exposed to moisture overnight had a significantly higher frequency of damaged grains than control pollen in the majority of study species within the Aizoaceae and Neuradeceae. We found no evidence that pollen of asteraceous species exhibiting flower closure is sensitive to moisture. We conclude that pollen damage and the reduction in male fitness that may result from exposure to rain, dew and fog has provided an important selective impetus for the widespread evolution of upright petal movement and associated flower closure found among more than 3500 species in the predominantly winter and spring flowering Cape fynbos and succulent karoo floras.

Control of circadian rhythm-regulated nyctinastic movement in water lily (Nymphea stellataWilld.) flowers

SummaryFlowers of Nymphea stellataWilld., like other water lilies, are subject to circadian clock-controlled petal closure in the afternoon. To investigate the effects of plant growth regulators, and various other chemicals, in arresting nyctinastic movement (petal closure), cut flowers of N. stellata were exposed to different concentrations of gibberellic acid (GA), benzyl amino purine (BAP), naphthalene acetic acid (NAA), abscisic acid (ABA), ethanol, AgNO3, NaCl or RinsoTM (laundry detergent powder). The most effective treatment to control the biological clock of petal movement was keeping flowers continuously in 25 mg l–1 GA.This treatment kept flowers open, to an acceptable cut flower standard, for over 28 h. Continuous exposure to 5 mg l–1 BAP also kept flowers open to the same acceptable standard for over 15 h. Considering low-cost applications, immersing flowers in 25 g l–1 NaCl for 1 h kept them open for almost 17 h, to an acceptable cut flower standard. Immersing in 2 g l–1 RinsoTM (Unilever, Sri Lanka) for 1 h also kept flowers open for 14 h in an acceptable condition. By inhibiting nyctinastic closure using any of the above chemicals, N. stellata could now be considered and exploited as a cut flower.

Methyl-jasmonate Affects the Circadian Petal Movement of Kalanchoe Flowers

Application of methyl jasmonate for several hours dampens or stops the circadian petal movement rhythm of Kalanchoe blossfeldiana flowers depending on the duration and concentration. Period length is shortened by more than an hour if methyl jasmonate is offered continuously. This indicates an effect of this substance on the underlying oscillator. A red light of three hours can reinduce rhythmicity in flowers which became motionless by a methyl jasmonate pulse.

Modelling the circadian system of the weta,Hemideina thoracica(Orthoptera: Stenopelmatidae)

The development of the current model of the circadian system of the nocturnal insect Hemideina thoracica is traced from a single feedback oscillator, to more complex interactions of two populations of oscillators. Each unit oscillator is based on a negative feedback system incorporating time‐delay and sensitivity to light and temperature. Individual oscillators are linked to one or more similar oscillators to form populations or networks of units. The components of each unit reflect functions which are physiologically relevant with respect to the biochemical evidence for circadian clocks. The single oscillator model accounts for many of the basic properties of the Hemideina locomotor rhythms, including temperature compensation, light and temperature entrainment and the effects of constant dim and bright light. The population concept enhances the model by explaining much of the spontaneous and induced lability of the free‐running rhythm. The single population model has been extended, and we now propose that there is more than one clock control centre in this insect. The overall pattern of temporal behaviour may result from the interaction of two major clock centres, one regulating, among other functions, the locomotor activity subsystem, and the other the control of cuticle deposition. The concept of feedback control of the clock system of this insect is based on the original circadian feedback model of Johnsson and Karlsson which they proposed for the rhythmic petal movements of the plant Kalanchoe blossfeldiana.

Chapter 26 Cellular oscillators and biological timing: the role of proteins and Ca2+

Publisher Summary In the control of growth and reproduction, biological timing mechanisms as well as peptidergic neurons and endocrine cells play important roles, and the timing of sleep and waking in mammals depends on a circadian oscillator in each of the bilateral suprachiasmatic nuclei (SCN) of the hypothalamus. This chapter describes what is presently known about three oscillators, two of which are ultradian (Ca 2+ oscillations and the cell division cycle). Circadian cycles of activity are commonplace in multicellular animals and unicellular eukaryotes as are circadian cycles of photosynthesis, petal movements, and streaming in plant cells, for example, time of day measurement is in bird navigation. In poikilotherms, biological clocks would be useless as timing devices, if they respond passively, as biochemical machines, to environmental temperature changes. Cyclin appears to be the master oscillator. Investigations into the biochemical basis of the circadian oscillation are in their infancy. However, much more needs to be learned about the genes and proteins that are expressed during a circadian cycle before common patterns among different phyla will reveal what has been conserved in the course of evolution.

Nocturnal petal movements in the Asteraceae

Nocturnal petal movements were recorded from 48 genera and 106 species growing in cultivation at the Royal Botanic Gardens, Kew and in the wild in Canada, Great Britain, France, Italy, Greece, Canary Islands and South Africa. Seven different night positions of petals, as distinct from day positions, are recognized and discussed.

The Action of Abscisic Acid on the Circadian Petal Movement of Kalanchoe blossfeldiana

Summary Permanently offered abscisic acid (10 -8 to 10 -4 M) has no influence on the period length of the circadian rhythm of petal movement in Kalanchoe . It does, however, dampen the amplitude of the rhythm, especially at the higher concentrations. With abscisic acid offered as a 4 hr pulse (10 -5 M), the rhythm is phase delayed by about 1 hr around the time the flowers are wide open up to about 5 hr at the time the flowers are closed. This effect is not due to the circadian rhythm in water uptake. On a cellular level, abscisic acid almost abolishes the rhythmic change of osmotic pressure in the upper epidermis cells of the petals. It is hypothezised, that the effect of abscisic acid on the circadian rhythm in Kalanchoe is not a direct one on the circadian oscililator itself, but rather an indirect one on a driven oscillator which influences the driving oscillator.

Attenuation of the Petal Movement Rhythm in Kalanchoë with Light Pulses

AbstractThe circadian petal movement rhythm of Kalanchoë flowers has been studied. The amplitude of the rhythm can be drastically reduced by an appropriate stimulus of a light pulse. It has also been shown that it is possible to stop the rhythm permanently by administering a single light pulse to the flowers. This is interpreted to indicate that the light pulse has sent the circadian rhythm into a stable state of singularity.The conditions which attenuate the rhythm have been investigated both theoretically (on the basis of a previously published model for circadian rhythms) and experimentally. 120 min red light of 230 μW · cm−2, starting briefly before the second petal closure about 30 h after transfer to constant safe light conditions is optimal in inducing rhythm‐damping. Damping requires the same duration when the light is given at the corresponding phase during the third or fourth cycle of the rhythm. However, in the first cycle 240 min red light of 230 μW · cm−2 is required to get optimal damping of the rhythm.Conditions to achieve damping for other irradiances are investigated. Individual recordings are presented which show the behaviour of the rhythm when perturbed by light stimuli close to its singularity.

DIURNAL PERIODICITY IN SOME COMMON FLOWERS

SUMMARYThe time of flower opening and closure has been observed in twenty species belonging to nine different families. Increasing light initiates opening in some flowers and different species have different thresholds of response. Other species appear to be unaffected by light intensity.Experiments on the effect of photoperiod on petal movement in Talinum triangulare and Mirabilis jalapa indicate that the photo‐fraction affects the period of the rhythm by altering phase‐timing. A close correlation is suggested between phase‐timing and the automatic self‐pollination mechanism in Talinum possibly also in Mirabilis.Temperature also modifies the period of the rhythm in Tradescantia and Talinum; in the latter, a temperature of 24°C promoted closing.

Effect of D2O on the circadian rhythm of petal movement of Kalanchoe.

Abstract D2O lengthens the free running period of the circadian petal movement of isolated Kalanchoe flowers by 1.6% per 10% heavy water. This corresponds to findings reported in the literature for other organisms. 100% D2O administered in the form of 4 hour pulses at various phases of the circadian cycle lead to phase responses zero to maximally 1.5 hour delays. No advancing phase shifts occur. Possible ways in which lengthening of the period occurs are discussed.

Auxin Transport in Roots

Auxin Transport in Roots

Transport and Accumulation of IAA-14C in Tumour-formingNicotianaHybrids

The polar transport of indol-3yl-acetic acid (IAA-2-14C) in stem expiants and decapitated shoots of tumour-prone Nicotiana hybrids (2n, 3n, and 4n) was compared with that in the normal, non-tumorous parent species N. glauca and N. langsdorffii. The total uptake of the auxin from donor blocks was greatest in the hybrids and N. glauca. The velocity of the basi petal movement of IAA-14C was the same in all species tested, i.e. 8 mm/h. The transport capacity for the hormone, however, was decreased in the three tumour-prone hybrids. Gas chromatography showed that between 70 and 90 per cent of the transported auxin was present in the form of IAA, between 10 and 30 per cent in the form of indol-3yl-aldehyde (IAld). The basipetal transport exceeded the acropetal transport in young (third) internodes of all plants studied, whereas in older stem segments (tenth internodes) the reverse was found. The polarity of auxin transport was less well expressed in the tumorous hybrids. Blocking the active transport by pre-treatment of stem cuttings with 2,4-dinitrophenol (2,4-DNP) caused a drastic reduction in the polar IAA-14C movement ; in all plants tested the auxin transport was reduced to the same low level. The accumulation of auxin at the base of cuttings was higher in N. glauca and the 2n hybrid than in N. langsdorffii, i.e. about seven times higher after 1-h and three times higher after 12-h transport experiments. The release of 14C from the cutting into an agar receiver block, however, was markedly reduced in the 2n hybrid, whereas in N. glauca the labelled substances moved more freely into the receiver blocks. Differences in the capacity for the accumulation and the release of IAA-14C in hybrid and N. glauca stem tissues were studied using decapitated greenhouse plants wounded by incision above the fourth internode. Accumulation of the auxin occurred only above the wound cut in hybrid plants. This observation is consistent with the view that tumour formation on hybrid stems occurs at sites of wounding. Our data suggest an elevated auxin level to be present during tumour initiation at these sites. These results on polar transport and accumulation of IAA-14C in tumorous Nicotiana plants together with our previous data on various endogenous auxins suggest that the induction of neoplastic growth in tobacco plants is correlated with increased auxin levels and an accumulation of the hormone at sites of wounding.

Versuche zur Phasenverschiebung endogener Rhythmen: Blütenblattbewegung von Kalanchoe blossfeldiana

Studies on phase shifts of endogenous rhythms: The petal movement of Kalanchoe blossfeldiana. It takes up to 5 cycles until the phase shifts of the diurnal petal movement of Kalanchoe by short light periods are constant. Effects of a second light break are explainable neither by the suggestion of BUNNING and ZIMMER that the behaviour of the oscillator is immediately reflected in the course of the curves of the movement nor by that of PITTENDRIGH that an A-oscillator is immediately phase shifted by light, with several cycles being required for phase control of the B-oscillator. We propose to explain the results, especially those shown in curve 5 of fig. 2, in terms of a coaction of on- and off-rhythms.

An endogenous rhythm in the rate of carbon dioxide output of Bryophyllum. IV. Effect of intensity of illumination on entrainment of the rhythm by cycles of light & darkness

Excised leaves of the succulent plant Bryophyllum fedtschenkoi show an endogenous circadian rhythm in their rate of carbon dioxide emission (17,18). The rhythm occurs when leaves kept at a constant temperature and in an air stream initially free from carbon dioxide are transferred from light to prolonged darkness. The of the basic oscillating system in Bryophyllum leaf cells by various cycles of light and darkness and the extent to which depends upon the light intensity in the cycles are described in this paper. Exposure of an organism to cycles other than 24 hours in length can modify the period of its endogenous circadian rhythm. When this occurs the period usually becomes either equal to, or a multiple of, that of the stimulating cycles. The former phenomenon is termed entrainment and the latter is a special type of known as frequency demultiplication. Both plant and animal rhythms can be entrained by cycles of light and darkness having a period other than 24 hours. In most organisms such occurs only when the amount by which the period differs from 24 hours lies within certain limits, and these appear to be different in different organisms. When the period of the light-dark cycles is less than 24 hours, clearly defined limits of have been observed in all organisms investigated. For example, the rhythm of leaf movement in Canavalia ensiformis entrains to 8: 8 but not to 6: 6 hour cycles of light and darkness (8), whereas that of petal movement in Kalanchoe blossfeldiana entrains to 6: 6 but not to 4: 4 hour cycles (5). On the other hand, when the period of the stimulating cycles exceeds 24 hours limits of have been observed in a few organisms (2, 4, 12) but not in others (8,9, 10, 14, 15). Entrainment data for plant and animal rhythms have recently been tabulated and discussed by Bruce (1). Although the limits of have been determined for a number of biological oscillating systems and given considerable emphasis in the literature (1, 3), the extent to which they are a function of the light intensity in the stimulating cycles has not previously been critically investigated. Furthermore, little attention has been given to the possibility that the observed is the result only of a direct effect of light on the biochemical or physiological process being used to monitor the behavior of the unidentified basic oscillating systems.

Initiation of rhythmical petal movements InKalanchoe blossfeldiana by transfer from continuous darkness to continuous light or vice versa

The approximately diurnal movements of the flowers ofKalanchoe blossfeldiana come to a standstill after several days if they are kept in continuous light (LL) or darkness (DD). In LL (“White”) the flowers are closed and in DD they are opened. The rhythmical movement can be reinitiated by transfering the flowers from one continuous condition to the other. In the present investigation we have studied the effects of various wavelengths of light upon this phenomenon. The results were as follows: