Circumnutation as a visible plant action and reaction

Abstract

Circumnutation is a helical organ movement widespread among plants. It is variable due to a different magnitude of trajectory (amplitude) outlined by the organ tip, duration of one cycle (period), circular, elliptical, pendulum-like or irregular shape and clock-and counterclockwise direction of rotation. Some of those movement parameters are regulated by circadian clock and show daily and infradian rhythms. Circumnutation is influenced by light, temperature, chemicals and can depend on organ morphology. The diversity of this phenomenon is easier to see now that the digital time-lapse video method is developing fast. Whether circumnutation is an endogenous action, a reaction to exogenous stimuli or has a combined character has been discussed for a long time. Similarly, the relationship between growth and circumnutation is still unclear. In the mechanism of circumnutation, epidermal and endodermal cells as well as plasmodesmata, plasma membrane, ions (Ca 2+ , K + and Cl -), ion channels and the proton pump (H + ATPase) are engaged. Based on these data, the hypothetical electrophysiological model of the circumnutation mechanism has been proposed here. In the recent circumnutation studies, gravitropic, auxin, clock and phytochrome mutants are used and new functions of circumnutation in plants' life have been investigated and described.

Experimental observations of root growth in a controlled photoelastic granular material

“…However, it is difficult to analyse if this speed variation is due to biological or mechanical parameters. We also observed root tip circumnutation [23] in 2D (not shown here), how it is affected by the surrounding granular medium, how it changes the granular local organization and how it creates the root tortuosity.…”

Circumnutation on the water surface: female flowers of Vallisneria

“…At present, circumnutation is presumed to depend upon the internal oscillatory movement and gravity sensing458. However, other stimuli, such as light, temperature, and mechanical stress, also affect circumnutation9. Further, reversible cellular volume changes10, orientation of microtubules11 and the circadian clock1213 were reported to be involved.…”

Plant Responses to Brief Touching: A Mechanism for Early Neighbour Detection?

“…Hyponastic leaf movement can also cause modest mechanical stimuli through touching of leaf tips with neighbouring plants and is perceived as the earliest signal to detect future competitors [19]. Other widespread organ movements, such as circumnutation [20] and phototropism [21] can also cause touching. Evidence that these frequently occurring phenomena are involved in plant-plant interactions in nature is still lacking.…”