Nyctinastic Plants Research Articles

Enable Multi-Stimuli-Responsive Biomimetic Actuation with Asymmetric Design of Graphene-Conjugated Conductive Polymer Gradient Film.

In this paper, multiresponsive actuators based on asymmetric design of graphene-conjugated poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) gradient films have been developed by a simple drop casting method. The biomimetic actuation is attributed to the hygroscopic expansion property of PEDOT:PSS and the gradient distribution of graphene sheets within the film, which resembles the hierarchical swelling tissues of some plants in nature. Graphene-conjugated PEDOT:PSS (GCP) actuators exhibit reversible bending behavior under multistimuli such as moisture, organic vapor, electrothermal, and photothermal heating. Noticeably, the bending curvature reaches 2.15 cm-1 under applied voltage as low as 1.5 V owing to the high electrical conductivity of GCP actuator. To mimic the motions of nyctinastic plants, a GCP artificial flower that spreads its petals under sunlight illumination has been fabricated. GCP actuators have been also demonstrated as intelligent light-controlled switches for light-emitting diodes and smart curtains for thermal management. Not only do the GCP gradient films exhibit potential applications in flexible electronics and energy harvesting/storage devices but also the facile fabrication of multiresponsive GCP actuators may shed light on the development of soft robotics, artificial muscles, wearable electronics, and smart sensors.

The functions of foliar nyctinasty: a review and hypothesis.

ABSTRACTFoliar nyctinasty is a plant behaviour characterised by a pronounced daily oscillation in leaf orientation. During the day, the blades of nyctinastic plant leaves (or leaflets) assume a more or less horizontal position that optimises their ability to capture sunlight for photosynthesis. At night, the positions that the leaf blades assume, regardless of whether they arise by rising, falling or twisting, are essentially vertical. Among the ideas put forth to explain the raison d'être of foliar nyctinasty are that it: (i) improves the temperature relations of plants; (ii) helps remove surface water from foliage; (iii) prevents the disruption of photoperiodism by moonlight; and (iv) directly discourages insect herbivory. After discussing these previous hypotheses, a novel tritrophic hypothesis is introduced that proposes that foliar nyctinasty constitutes an indirect plant defence against nocturnal herbivores. It is suggested that the reduction in physical clutter that follows from nocturnal leaf closure may increase the foraging success of many types of animals that prey upon or parasitise herbivores. Predators and parasitoids generally use some combination of visual, auditory or olfactory cues to detect prey. In terrestrial environments, it is hypothesised that the vertical orientation of the blades of nyctinastic plants at night would be especially beneficial to flying nocturnal predators (e.g. bats and owls) and parasitoids whose modus operandi is death from above. The movements of prey beneath a plant with vertically oriented foliage would be visually more obvious to gleaning or swooping predators under nocturnal or crepuscular conditions. Such predators could also detect sounds made by prey better without baffling layers of foliage overhead to damp and disperse the signal. Moreover, any volatiles released by the prey would diffuse more directly to the awaiting olfactory apparatus of the predators or parasitoids. In addition to facilitating the demise of herbivores by carnivores and parasitoids, foliar nyctinasty, much like the enhanced illumination of the full moon, may mitigate feeding by nocturnal herbivores by altering their foraging behaviour. Foliar nyctinasty could also provide a competitive advantage by encouraging herbivores, seeking more cover, to forage on or around non‐nyctinastic species. As an added advantage, foliar nyctinasty, by decreasing the temperature between plants through its effects on re‐radiation, may slow certain types of ectothermic herbivores making them more vulnerable to predation. Foliar nyctinasty also may not solely be a behavioural adaptation against folivores; by discouraging foraging by granivores, the inclusive fitness of nyctinastic plants may be increased.

ChemInform Abstract: Chemistry and Biology of Plant Leaf Movements

The leaves of Mimosa pudica L. are well known for their rapid movement when touched. Recently, we were able to isolate an excitatory substance in small quantities from this plant, which consists of three different components (potassium L-malate, magnesium trans-aconitate, and dimethylammonium salt). Many plants close their leaves in the evening, as if to sleep, and open them early in the morning (nyctinastic leaf movement). This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-opening substances (LOSs) and leaf-closing substances (LCSs). Based on our experiments on these bioactive substances, we found that the circadian rhythmic leaf movement of these plants is initiated by the regulated balance of LOSs and LCSs. The balance of concentration between the two leaf-movement factors (LMFs) is inversed during the day. The glycoside-type LMF is hydrolyzed with β-glucosidase, the activity of which is regulated by the biological clock. The circadian rhythm observed in the leaf movement is introduced by activation of β-glucosidase regulated by the biological clock.

Chemical Basis of Plant Leaf Movement

Nyctinastic plants open and close leaves with a circadian rhythm. Here we discuss chemical aspects of the mechanism of nyctinastic leaf movement. Nyctinastic plants from five different genera are known to contain species-specific leaf-opening and leaf-closing factors. The relative concentrations of leaf-closing and leaf-opening factors of the nyctinastic plant Phyllanthus urinaria change circadianly, suggesting that nyctinastic movement is regulated by two classes of circadianly regulated factors with opposing functions. A closing and an opening factor of Albizzia, when linked to a fluorescent dye, both specifically labeled motor cells of pluvini. A membrane fraction of pluvini contains proteins of 210 and 180 kDa that bind to a leaf-opening factor of Cassia mimosoides. The molecular identification of these proteins is underway.

Bioorganic studies on plant movement, from natural products to its receptor

The chemical aspects of the circadian leaf movement known as "nyctinasty" are discussed in this paper. Each of the nyctinastic plants of five different genera so far examined contained a pair of factors, one of which induced leaf closure and another induced leaf opening. The relative contents of the closing and opening factors changed correlating with the nyctinastic leaf movement. The use of fluorescence-labeled and photoaffinity-labeled factors revealed that the factors bind to specific cells, the motor cells, present in the pulvini, and that the membrane fraction of the motor cells contained two proteins of 210 and 180 kDa, which can bind to the factors.

Chemical studies on plant leaf movement controlled by a biological clock

Abstract Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning according to the circadian rhythm controlled by a biological clock. Extensive studies on nyctinastic plants led to the isolation of a variety of leaf-closing and -opening substances. And we found that the biological clock regulates the balance of concentration between leaf-opening and -closing substances in the plant body during the day.

Bioorganic Studies on Nyctinasty of the Plant Controlled by a Biological Clock

Abstract Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning. This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-closing and leaf-opening substances. And we found that the circadian rhythmic leaf-movement of these plants is controlled by a biological clock that regulates the balance of concentration between leaf-opening and -closing substances.

Leaf-closing substance in Leucaena leucocephala.

Potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate (1) was identified as a leaf-closing substance in the nyctinastic plant, Leucaena leucocephala. Compound 1 showed strong leaf-closing activity toward L. leucocephala and was not effective against other nyctinastic plants. The potassium ion was indispensable for the bioactivity of 1. Compound 1 gradually lost its bioactivity because of the exchange of the counter cation during isolation. A leaf-opening substance was also observed in the same plant.

Fluorescence study on the nyctinasty of Cassia mimosoides L. using novel fluorescence-labeled probe compounds

We synthesized fluorescence-labeled probe compounds bearing 6-((7-amino-4-methylcoumarin-3-acetyl)amino)-hexanoyl (AMCA, 1), 6- N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)-aminohexanoyl (NBD, 2), and 6-(4-((5-dimethylaminonaphthalene-1-sulfonyl)-amino))-hexanoyl (dansyl, 3) groups as the fluorescent functionality. In these probe compounds, NBD-type probe, 2, showed leaf-opening activity at 5×10 −6 M. The bioactivity of 2 is one-fifth as strong as that of the natural product, potassium isolespedezate ( 6). We carried out the binding experiment using 1 in a plant body. Then, it was suggested that fluorescence-labeled probe compound directly bound to a motor cell in pulvina of Cassia mimosoides. And this binding was specific to C. mimosoides. Probe compounds cannot bind plant sections of other nyctinastic plants.

Molecular Approach to the Nyctinastic Movement of the Plant Controlled by a Biological Clock

Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning. This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-closing and leaf-opening substances. And, we found that the circadian rhythmic leaf-movement of these plants is controlled by a biological clock that regulates the balance of concentration between leaf-opening and -closing substances.

Chemistry and Biology of Plant Leaf Movements.

The leaves of Mimosa pudica L. are well known for their rapid movement when touched. Recently, we were able to isolate an excitatory substance in small quantities from this plant, which consists of three different components (potassium L-malate, magnesium trans-aconitate, and dimethylammonium salt). Many plants close their leaves in the evening, as if to sleep, and open them early in the morning (nyctinastic leaf movement). This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-opening substances (LOSs) and leaf-closing substances (LCSs). Based on our experiments on these bioactive substances, we found that the circadian rhythmic leaf movement of these plants is initiated by the regulated balance of LOSs and LCSs. The balance of concentration between the two leaf-movement factors (LMFs) is inversed during the day. The glycoside-type LMF is hydrolyzed with beta-glucosidase, the activity of which is regulated by the biological clock. The circadian rhythm observed in the leaf movement is introduced by activation of beta-glucosidase regulated by the biological clock.

The diversity of chemical substances controlling the nyctinastic leaf-movement in plants

Leaf-movement in nyctinastic plants has long been believed to be controlled by plant hormones that are common among all nyctinastic plants. We have identified several bioactive substances for nyctinasty, whose bioactivities were highly specific to the original plant, based on the bioassay using the original plant leaf, and have shown that nyctinastic leaf-movement is not regulated by plant hormones. Our present results are in accordance with Umrath et al. physiologically significant opinion.

Leaf-movement factors of nyctinastic plant, Phyllanthus urinaria L.; the universal mechanism for the regulation of nyctinastic leaf-movement

Phyllanthurinolactone ( 1) and phyllurine ( 2) were isolated from Phyllanthus urinaria L. as bioactive substances for nyctinasty. Compound 1 was quite effective for leaf-closing of the plant at 1 × 10 −7 M in the daytime and 2 was quite effective for the leaf-opening at 2.5 × 10 −5 M, whereas both 1 and 2 were not effective for other nyctinastic plants even at 1 × 10 −4 M. The concentration of 1 increased before leaf-closure in the plant body, whereas that of 2 was constant through a day. Thus, the leaf-movement of P. urinaria L. is proposed to be controlled by the change in the balance of concentration between 1 and 2, which is regulated by a β-glucosidase, similar to the case of Lespedeza cuneata G. Don.

植物の運動を引き起こす化学物質 生物時計による就眠運動のコントロール

Many plants close their leaves in the evening like sleeping and open early in the morning. Such a circadian rhythm has been known to be controlled by their internal clock. Moreover, rapid seismonastic movement was also observed in Mimosa pudica L.Since Ricca's ingenious experiments suggested that some chemicals play an important role in leaf-movement of Mimosa pudica, many biologists and chemists have attempted to search for leaf-closing substances, and a number of compounds have been obtained, particularly, by Schildknecht et al. But, we have now demonstrated that the genuine leaf-movement factor of Mimosa is the mixture of three chemical substances, two of the three were identified as potassium L-malate and magnesium transaconitate. The mixture of these substances was effective at 10-8-10-9 M.On the other hand, we have isolated chemical substances that control the nyctinastic leaf-movement from several nyctinastic plants. Each substance was effective at 10-6-10-7 M only for the original plant, but not for other nyctinastic species. Thus, different leaf-movement factors exist in every nyctinastic plants. This is contrary to the old theory established by Schildknecht. This movement is controlled by the change in the balance of two inversely effective factors, leaf-closing and opening factor. Me0H-extracts of a nyctinastic plant, Lespedeza cuneata G. Don. collected in the daytime and at night showed inverse bioactivity. Thus, the balance of concentration between two leaf-movement factors in this plant which is controlled by biological clock was really inversed through a day. This mechanism for the control of nyctinastic movement is common among all nyctinastic plants.

Leaf-opening substance of Mimosa pudica L.; chemical studies on the other leaf movement of mimosa

We have isolated mimopudine ( 1) as a leaf-opening substance of mimosa that keeps the leaves open even at night. 1 was quite effective for leaf-opening of Mimosa pudica L. at 2 ×10 −5 M at night, but not effective for other nyctinastic plants even at 1 ×10 −2 M. Interestingly, the leaves kept open at night with 1 were sensitive to stimulus by touch. This result suggests that 1 is effective only for the obstruction of slow nyctinastic leaf-closing movement, but not effective for the rapid thigmonastic movement. Therefore, the slow nyctinastic movement of mimosa is controlled by a different mechanism from that of the rapid thigmonastic movement.

Phyllurine, leaf-opening substance of a nyctinastic plant, Phyllanthus urinaria L.

We have isolated phyllurine ( 1) as the leaf-opening substance of Phyllanthus urinaria L. that keeps the Phyllanthus leaves open. 1 was quite effective for the leaf-opening of Phyllanthus urinaria L. at 2.5 ×10 −5 M, but not effective for other nyctinastic plants even at 1 × 10 −4 M. The leaf-closing substance of this plant has already been identified as phyllanthurinolactone ( 2). Thus, the leaf-movement of Phyllanthus urinaria L. is proposed to be controlled by the interaction between 1 and 2, similar to the case of Lespedza cuneata G. Don.

Molecular mechanism of the control of nyctinastic leaf-movement in Lespedeza cuneata G. Don

The nyctinastic leaf-movement of plants is controlled by an endogenous biological clock. In a nyctinastic plant, Lespedeza cuneata G. Don, this movement is controlled by the balance of the concentration between the leaf-closing and -opening substances. Quantitative HPLC analysis revealed that the change in the concentration of this leaf-opening substance is inversed through a day, and the deactivation of this substance is performed by a glucosidase whose activity is controlled by a biological clock. The leaf-movement of nyctinastic plants is caused by the balance of two leaf-movement factors, which is controlled by the enzymatic transformation.

Chemical Studies on Plant Movement

<p> Many plants close their leaves in the evening, as if to sleep, and open them early in the morning. Such a circadian rhythm has been known to be controlled by their internal clock. Since Ricca's ingenious experiments suggested that some chemicals play an important role in the leaf-movement of Mimosa pudica, many biologists and chemists have attempted to locate the leaf - closing substances, and a number of compounds have been obtai­ ned, particularly, by Schildknecht et al. Recently, we were also able to isolate a small amount of a stimulant (activity: ca. 10<sup>8</sup> - 10<sup>·9</sup> M) from the same plant, which consists of three different components (potassium L-malate; magnesium trans-acconitate; dimethylammonium salt). Further extensive study on other nyctinastic plants led to the isolation of a variety of leaf-closing substances. </p> <p> On the other hand, indole-3-acetic acid (IAA) has been reported to be effective for Mimosa pudica as a leaf-opening factor. Three leaf-opening substance named potassium lespedezate, cis-p-coumaroylagmatine, and calcium 4-O-β-D-glucopyranoyl-cis-p-coumarate have been isolated from Lespedeia cuneate G. Don , Albizzia julibrissin D. and Cassia mimosoides, respectively. Based on our experiments using the leaf-opening and -closing substances, the circadian rhythm of these plants must be controlled by their internal clock which regulates a balance of concentration between the leaf-opening and closing substances.</p>

Leaf-opening Substance in the Nyctinastic Plant,Albizzia julibrissinDurazz

cis-p-Coumaroylagmatine (1) was isolated from Albizzia julibrissin Durazz, a nyctinastic plant, as a leaf-opening substance. The compound was quite effective for opening the plant leaves at 5×10(-6) M at night, but was not effective for other nyctinastic plants. The bioactive fraction with leaf-closing activity was also separated from the plant extract. Although the leaf-opening activity of the plant extract changed between the day and night, the content of 1 was almost constant through a 24-h day. These results suggest that the change in content of an unknown leaf-closing factor induced balance between the two leaf-movement factors through a 24-h day.

Phyllanthurinolactone, a leaf-closing factor of nyctinastic plant, Phyllanthus urinaria L

Phyllanthurinolactone ( 1) was isolated from Phyllanthus urinaria L. as bioactive substance for nyctinasty. The compound was quite effective for leaf-closing of the plant at 1 × 10 −7 M in the daytime and caused leaf-closing movement only for Phyllanthus urinaria L., but not for other nyctinastic plants.