Spontaneous action potentials and circumnutation in Helianthus annuus

Abstract

Action potentials (APs) in plants are involved in fast leaf or trap closure as well as elongation, respiration, photosynthesis, and fertilization regulation. Here, spontaneous APs (SAPs) in relation to endogenous stem movement named circumnutation (CN) have been investigated in Helianthus annuus in different light conditions in freely circumnutating and immobilized plants. Extracellular electrical measurements and time-lapse photography were carried out simultaneously. The parameters of CN (trajectory length, period, and direction) and the number and transmission direction of SAPs were analysed. In continuous light (25-40 lmol m -2 s -1), all plants circumnutating vigorously in a regular elliptical manner and no SAPs were observed. In light/dark conditions, the plants circumnutated in a daily pattern, most SAPs were observed in the dark and freely circumnutated sunflowers had two times more SAPs (10 SAPs/24 h/plant) than the immobilized plants (5 SAPs/24 h/plant). In continuous very low light (5 lmol m -2 s -1 ), the plants circumnutated weakly and irregularly and SAPs appeared without the circadian pattern. 3-5 SAPs/24/plant occurred in the freely circumnutating and immobilized plants. In light/dark and continuous very low light conditions, an ultradian rhythm of SAPs was observed and the mean spacing between SAPs was approx. 121-271 min in the freely circumnutating and immobilized plants. Under all light conditions, more SAPs were transmitted basipetally than acropetally. One-hour lasting series of 3-4 min spaced SAPs locally propagated were observed as well in very low light. Basipetal and acropetal SAPs passing along the stem motor region accompany irregularity, changes in the CN trajectory direction, and stem torsion. These results demonstrate that APs and CN changes play a role in plant adaptation to light conditions and that there is an ultradian rhythm of SAPs beside ultradian CN rhythm.

Circumnutation and Growth of Inflorescence Stems of Arabidopsis thaliana in Response to Microgravity under Different Photoperiod Conditions

“…This data supports the existence of a threshold on growth rates, below which circumnutation does not occur [12]. However, circumnutation can be blocked without the simultaneous inhibition of growth, suggesting that growth and circumnutation are governed by different mechanisms [13]. The mechanism for circumnutation remains unknown.…”

“…Two main models for circumnutation have been discussed. One is an 'internal oscillator' model created by Darwin [14], which is connected with the biological clock mechanism that is being investigated extensively [1,13,15,16].…”

Osmotic and Salt Stresses Modulate Spontaneous and Glutamate-Induced Action Potentials and Distinguish between Growth and Circumnutation in Helianthus annuus Seedlings

“…They spontaneously depolarize and generate an AP usually at a regular rate/rhythm. This SAP rate/rhythm can be adjusted by environmental condition as was shown recently in H. annuus (Stolarz and Dziubinska, 2017 ). The external stimuli or environmental conditions do not cause SAPs, but merely alter their rate/rhythm.…”

“…The complete lack of SAPs in distilled water and D-sorbitol (with an ability to generate Glu-induced APs) growing seedlings with strongly inhibited CN may be associated with CN inhibition. In our recent work, the relationship between SAPs and CN was shown, i.e., the number of SAPs decreased with the restricted CN (Stolarz and Dziubinska, 2017 ). On the other hand, the similarly circumnutating seedlings had a significantly lower number of SAPs in the strong salt stress [4 ± 1 SAPs 24 h −1 plant −1 ( n = 8)] than in the mild salt stress [10 ± 2 SAPs 24 h −1 plant −1 ( n = 12)].…”

Effects of light quality on circumnutation of Vigna unguiculata seedlings

“…Chinese Journal of Plant Ecology, 42, 1192-1199. DOI: 10.17521/cjpe.2018 环旋运动在植物界中普遍存在 (Darwin, 1865(Darwin, , 1876Darwin & Darwin, 1880), 它是植物的某些器 官如根、芽等在生长过程中所做出的一种生长运动 ( Brown, 1993), 大致可描述为钟摆状、椭圆形或圆 形等 (Melin, 1975;刘公社和张俊英, 1994)。影响植 物环旋运动的因素很多, 有研究发现其受重力的调 节 (Brown & Chapman, 1977;Yoshihara & Iino, 2006;Kim et al, 2016) 素 (Mccomb, 1962;Weiler et al, 1993;Atala & Gianoli, 2008;Iida et al, 2018) (Brown et al, 1990), 多从二维平面上对运动进行 描述 (Buda et al, 2003;Charzewska & Zawadzki, 2006;Solheim et al, 2006;Stolarz & Dziubińska, 2017)。 近年来研究者注重在三维空间上描述环旋运 动 (Gill et al, 2009)…”