摘要:

The circadian caecotrophy rhythm of 15 rabbits of a group 1 and 12 rabbits of a group 2 was continuously monitored in LD 12:12, 14:10, 16:8, 18:6, 20:4, and 22:2. The photoperiod was extended in opposite directions either by advancing the onset (group 1) or by delaying the end (group 2) of the photoperiod. The response of the animals to photoperiod extension differed significantly both between the groups and within either group during the different steps of photoperiod extension. Generally the caecotrophy rhythm was advanced in group one and delayed in group two. The shift rate at the respective new LD schedule was determined by the phasically changing sensitivity of the rabbit to light stimulation. The results showed that the rabbit is entrained predominantly non‐parametrically, while the LD timeratio is of importance mainly for the precision of phase control.

ISSN:0022-1945    

DOI:10.1080/09291018309359794

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The possible role of different kind of photoreceptors in synchronization of circadianlocomotoractivity in cockroaches is presently still contradictory. We try to clarify the part played by the compound eyes and the ocelli with lesion and black‐varnishing experiments. The locomotor activity of isolated animals is automatically recorded in ring‐shaped cages equiped with infra‐red beams. Circadian rhythms are detected by using the Whittaker and Robinson periodogram.

ISSN:0022-1945    

DOI:10.1080/09291018309359795

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Oscillatory plant transpiration has been observed in numerous plants, and it is now believed to be a common rather than an exceptional phenomenon. It is related directly to cyclic variations of the stomatal aperture and indirectly to the water content of guard, subsidiary and mesophyll cells. At least for small plants the upward transport of water from the roots to the leaves and the surrounding atmosphere can be explained entirely in terms of the biologically passive forces of capillarity and transpiration‐cohesion. Biologically active forces involving energy consuming pumping also exist, but in small plants they play a minor rôle in the dynamics of the oscillatory water transport. On the macroscopic level of the whole plant the water transport can thus be formulated in terms of an analogue hydraulic‐elastic model, by modifying somewhat that formulated in 1972 by Cowan. Differential equations corresponding to this modified model are established and conditions for the existence of periodic solutions are derived. It turns out that these conditions are not very severe mathematically. A considerable freedom is left in particular in the choice of the non‐linear dependence between the stomatal aperture and the water content of guard, subsidiary and mesophyll cells. In a given plant there is of course no such freedom, because this dependence is entirely fixed by the mechanical structure of the stomatal complex. Several types of operation of the stomatal complex are possible, because mathematically there is more than one possibility to match the oscillatory waveforms to the experimentally observed ones.

ISSN:0022-1945    

DOI:10.1080/09291018309359796

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The choice of an appropriate phase of reference (the reference phase) is important in determining (i)τcharacteristics, (ii) α: p ratios and (iii) ? ϕ (phase shifts). Earlier authors have variously favoured the peaks (or troughs), onset, mid‐point or end of activity, center of gravity of the activity period or median values, as reference phases. We report on our work on the activity rhythms of microchiropteran bats in the tropics under field, seminatural and laboratory conditions. Facts and figures have been specially marshalled to show that the greaterprecisionexhibited by bats at emergence and thelabilitycharacterizing their end of activity in the field, are also mirrored in the actograms obtained in the laboratory. We, therefore, favour the “onset” of activity as reference value. The onset of activity (i) is often very stable and may thus reflect the state of the basic oscillator better, (ii)unlike mid point it does not depend on the end of activity, (iii) and may be more directly under the clock control than the end which may be decidedde novoday to day depending on hunger, satiation, availability of prey, predator pressure and meteorological conditions.

ISSN:0022-1945    

DOI:10.1080/09291018309359797

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The changes of chromatin organization and condensation between G1and G2of the cell cycle were studied in a monocot and a dicot plant species and digitized with different systems. It is shown that there are objective criteria by which an automated identification of cell cycle stages is possible in structural terms.

ISSN:0022-1945    

DOI:10.1080/09291018309359798

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Photoperiodic insects are able to distinguish between long days and short days. In various models the long day response is classifically considered the “actively” induced state. The short day response is thought to be “passive”, caused by failure of light to coincide with a photosensitive part of the night or failure of coincidence of constituent oscillators. The photoperiodic response curve ofPieris brassicaeshowed that diapause is induced by short days (4–14 h), and non‐diapause state by several conditions (natural and non‐natural): long days (16 h or more), LL, DD and ultrashort days (0.1 h). By reciprocal transfers of larvae between non‐diapausing determining and diapause determining conditions, it was proved possible to estimate the differential capacity of four non‐diapausing conditions vs. the diapausing action of LD 8: 16 in decreasing sequence: LD 16:8 > LL > DD = LD 0.1: 23.9. DD may be considered a “neutral” condition. In darkness the development seems to be determined by an endogenous program without external influence. LL, although beingan aperiodic signal as DD, has a weak antidiapausingeffect.Thebiological clock ofPierisdifferentiates between two constant conditions. The four non‐diapausing conditions have the same effect on the development when applied during the entire larval life, but have different effects when only applied during a few days. Both ecological conditions LD 16:8 and LD 8:16 have an action on the development but in an opposite way. There was not a “passive” state caused by failure of another inductive photoperiod. Ultra‐short days, DD and LL are without ecological meaning. Nevertheless, in these experiments, they provided informations in attempts to determine the mechanism of the time measurement. The external coincidence model of Pittendrigh and Minis (1964) was the more adequate to explain theearlier results on the biological clock ofPieris.However, this model has to be modified to account for the differential significance of several non‐diapausing conditions.

ISSN:0022-1945    

DOI:10.1080/09291018309359799

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Daily injections of corticosterone and prolactin have been shown previously to either stimulate or inhibit reproductive and migratory indices in sparrows as a function of the time interval between injection times (Meier and Ferrell, 1978). The present studies were performed to test whether the hormonal effects can be duplicated by timed injections of drugs which influence brain neurotransmitter activities in a manner similar to that of the hormones. DOPA (catecholamine precursor) injections at 12 h after daily injections of 5‐HTP (serotonin precursor) was stimulatory for gonadal growth and body fat stores in white‐throated sparrows(Zonotrichia albicollis)whereas other time relations (3, 8, or 18 h intervals between daily injections of 5‐HTP and DOPA) were not. The 8‐h relation was inhibitory for fat stores and reproductive indices. In house sparrows(Passer domesticus), DOPA injections 16 h after daily injections of 5‐HTP reduced the sizes of photoperiodically‐stimulated oviducts whereas an 8‐h relation had no effect. These effects are similar to those produced by hormone injections; they indicate that 5‐HTP can be substituted for corticosterone injections and DOPA can be substituted for prolactin. Both the hormones and the drugs are thought to reorganize two circadian neural oscillations which interact temporally to control seasonal conditions.

ISSN:0022-1945    

DOI:10.1080/09291018309359800

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291018309359793

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor