Rhythms and Their Relations to Hormones

Koukkari, Willard L.; Warde, S. B.

doi:10.1007/978-3-642-67734-2_3

Cited by 5 publications

(2 citation statements)

References 167 publications

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“…3). The endogenous level of phytohormones changes over time and is altered by application of exogenous phytohormones (21). In November and December, group A was more stimulated by 5.9 mT, whereas group B responded best to 3.2 mT.…”

mentioning

confidence: 98%

Electromagnetic Stimulation of Buds of Castanea Sativa Mill. In Tissue Culture

RuiiC¹,

Jerman

JegliC

et al. 1992

Electro- and Magnetobiology

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Buds of chestnut (Castanea sativa, Mill.) were grown on modified Heller's solid material medium with the addition of 0.1 mg/mL 6-benzylaminopurine (BAP). They were divided monthly and used for experiments with homogeneous sinusoidal magnetic fields of 5.9, 3.2, and 1.2 mT for 1 h/day, 6 days a week, for 28 weeks.The results are season-dependent; bud growth was significantly enhanced over controls in early summer (50% at 5.0 mT, 64% at 3.2 mT, and 62% at 1.2 mT). In late summer and fall, growth was inhibited slightly. In early winter, it was stimulated again. We also measured significant effects 1 month after cessation of stimulation.

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mentioning

confidence: 98%

Electromagnetic Stimulation of Buds of Castanea Sativa Mill. In Tissue Culture

RuiiC¹,

Jerman

JegliC

et al. 1992

Electro- and Magnetobiology

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“…For example, higher frequency oscillations of a fundamental nature may become evident during certain phases (7,10). The response of a plant to environmental agents and the regulation of growth and development are also temporally organized relative to phase (9,14). In the present study, the paradox regarding the night position of Xanthium leaves has been resolved.…”

Section: Results and Discussion Two Ecotypesmentioning

confidence: 66%

Phase Shift in Leaf Movements of Xanthium Attributed to Age and Rhythm Patterns

Koukkari

Hobbs²

1992

Plant Physiol.

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Leaves of cockelbur (Xanthium strumarium L.) have been reported to be in either an upright or downward position during the dark span (night) of a 24-hour cycle. Results from our studies clearly indicate that such differences in leaf position are not related to differences in ecotypes but can be attributed to age of the leaf, pattem of the waveform of the rhythm at various stages of the light-dark synchronizer regimen, and the statistical model used for the analysis of the waveform. Younger leaves reached a maximum upright position closer to the middle of the dark span, whereas older leaves reached this position closer to the end of the dark span. A phase shift of up to 6 to 10 hours may occur as the leaf ages. Results from the examination of the pattem of the waveform at four different times showed that the pattem of a younger leaf was different from that of an older leaf during the middle of the dark span, during the light-to-dark transition, and during the middle of the light span, but not during the dark-tolight transition. Linear regression, statistical analyses, and the fitting of harmonics clearly indicate that it is the trough, more than the peak, that differs with the age of the leaf.Going back at least to the Darwins in 1881 (5), the study of leaf movements has been a classic area of plant physiology (4,16,23,24). Although much of the work has centered on the circadian rhythms of legumes (Phaseolus and Glycine species), the leaves of many other plants, including cocklebur (Xanthium strumarium), also display rhythms (1, 20). Andersen and Koukkari (1) reported that leaves ofXanthium moved upward to a night position and downward to a day position. This night position of Xanthium leaves was different from that ofbean plants (6), and, as we discovered later, the position was exactly opposite to that illustrated for Xanthium in the plant physiology textbook by Salisbury and Ross (21 Preliminary experiments showed that it was primarily the young Xanthium leaves that were in a more upward position during darkness. If movements of older leaves differ from those of younger leaves, then the leaves ofXanthium undergo a large phase shift that follows the developmental and morphological changes associated with leaves during the process of maturation. It is rare for a phase shift of 1800 or even 900 to occur in a synchronized circadian rhythm without a prior change in the phase of a synchronizer (e.g. an LD cycle). In this paper we report how an apparent paradox in the rhythm ofXanthium leaf movements is related to the development of the plant and the pattern of the rhythm and how the rhythm characteristics are mathematically analyzed. MATERIALS AND METHODS Plant MaterialCommon cocklebur (Xanthium strumarium L.) plants were raised from seeds of burs obtained from either Minnesota (1) or Michigan (Chicago strain ofXanthium supplied by Professor Jan A.D. Zeevaart, Michigan State University). Chicago strain seeds were used in most of the experiments. For each experiment, the burs were placed in distilled water an...

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The Discovery of Biological Clocks

Salisbury

1998

Discoveries in Plant Biology

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Rhythms and Their Relations to Hormones

Cited by 5 publications

References 167 publications

Electromagnetic Stimulation of Buds of Castanea Sativa Mill. In Tissue Culture

Electromagnetic Stimulation of Buds of Castanea Sativa Mill. In Tissue Culture

Phase Shift in Leaf Movements of Xanthium Attributed to Age and Rhythm Patterns

The Discovery of Biological Clocks

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