Macroscopic and microscopic mechanical behaviors of climbing tendrils

Tendril-bearing climbing plants must recur to the tendril helices with chiral perversion or dual chirality for climbing and to obtain sun exposure. Despite researchers' prolonged fascination with climbing tendrils since Darwin's time and even earlier, why the soft and slender tendrils can bear heavy loads such as the self-weight of a plant or additional load caused by rain remains elusive. In this paper, we take towel gourd tendrils as an example and investigate the macroscopic and microscopic mechanical behaviors of tendrils through experiments and simulations. Our study indicates that the tendril filament exhibits rubber-like hyperelastic behaviors and can particularly endure large elongation, which is mainly attributed to the superelasticity of the cellulose fibril helix contained in the cell wall. Combination of the tendril helical structure with dual chirality or chiral perversion at a macroscale and a cellulose filament helix at a subcellular level creates superior elasticity for biological species relying on support and climbing. This study provides deep insight into the structure-property relationship of climbing tendrils, and the relationship is useful for the bioinspired design of composite systems with superior elasticity.

The intrinsic developmental age signal defines an age-dependent climbing behavior in cucumber

The tendril is a climbing organ in cucurbits and functions in physical support and to avoid shading by neighboring vegetation.However,how cucurbits produce tendrils to obtain climbing ability is largely unknown.In this study,tendril phenotypes were investigated during different developmental stages.Our results revealed that tendril growth exhibited an age-dependent pattern in cucurbits.Tendril growth was inhibited,and the tendril was formed as a short tendril[nonfunctional tendril(nonF-tendril),approximately 0.1 cm]during the seedling stage.In contrast,enhanced cell proliferation and cell expansion led to rapid elongation of the tendril during the climbing stage,and the tendril formed as a functional tendril(F-tendril,approximately 30 cm)to obtain climbing ability.RT-qPCR detection showed that age-dependent tendril growth correlated negatively with the abundance of the conserved age regulator CsmiR156.Defoliation induced CsmiR156 to inhibit CsSPLs,and F-tendril formation and climbing ability were delayed in defoliated cucumbers,which confirmed the role of CsmiR156 in regulating tendril growth in vivo.Additionally,exogenous gibberellin(GA)treatment showed that GA positively regulated tendril growth,and RT-qPCR detection showed that the GA bio-synthetic genes and metabolic genes were affected by age pathway,suggesting that the age pathway depended on GA bio-synthetic and metabolic pathway to regulate cell expansion to determine tendril growth.In summary,our work reveals that change in tendril type is an important marker of phase transition in cucumber,and tendril growth is regulated by an intrinsic developmental age signal,ensuring that the cucumber obtains climbing ability at a suitable age.

Self-shaping of bioinspired chiral composites

Self-shaping materials such as shape memory polymers have recently drawn considerable attention owing to their high shape-changing ability in response to changes in ambient conditions, and thereby have promising applications in the biomedical, biosensing, soft robotics and aerospace fields. Their design is a crucial issue of both theoretical and technological interest. Motivated by the shape-changing ability of Towel Gourd tendril helices during swelling/deswelling, we present a strategy for realizing self-shaping function through the deformation of micro/nanohelices. To guide the design and fabrication of selfshaping materials, the shape equations of bent configurations, twisted belts, and helices of slender chiral composite are developed using the variation method. Furthermore, it is numerically shown that the shape changes of a chiral composite can be tuned by the deformation of micro/nanohelices and the fabricated fiber directions. This work paves a new way to create self-shaping composites.

Transcriptomic analysis on cucumber tendril reveals GLRs play important roles in thigmotropism and thigmomorphogenesis

Thigmotropism and thigmomorphogenesis are two related and pervasive processes that play crucial roles in plant adaptation to the environment.However,there have been few investigations into the molecular regulatory mechanisms of these phenomena.Cucumber(Cucumis sativus L.)tendrils are ideal material for studying thigmotropism and thigmomorphogenesis because they display a combination of the two processes.Here,we generated the transcriptome profiles of cucumber tendrils at the young,stretch,and coiling stages.Genes related to receptor proteins,transmembrane transport,and ion transport were significantly enriched among those differentially expressed between stages.Pharmacological assays illustrated that three GLUTAMATE RECEPTOR(GLR)genes might play a vital function in perceiving or transducing touch stimulation signals.Comparing the transcriptomes of tendrils and roots after touch stimulation,we found that genes related to extracellular stimulus and xyloglucan metabolism might have conserved functions in the regulation of thigmomorphogenesis.The transcriptome atlas of thigmotropism and thigmomorphogenesis of cucumber tendrils constructed in this study will help further elucidate the molecular mechanisms behind these processes.

Construction of a Pea Tendril cDNA Library and Sequence Analysis of a Pea Actin cDNA, PEAcl

Actins are ubiquitous to all of the known eukaryotic organisms. Since the firstdiscovery of actins in higher plants by Yen et al. in 1960s, the actin research ofhigher plants has been extensively carried out. It has been shown that the actin is animportant part of cytoskeleton, being involved in many important biological processes,

Rare SNP Identified a TCP Transcription Factor Essential for Tendril Development in Cucumber

Rare genetic variants are abundant in genomes but less tractable in genome-wide association study. Here we exploit a strategy of rare variation mapping to discover a gene essential for tendril development in cucumber （Cucumis sativus L.）. In a collection of 〉3000 lines, we discovered a unique tendril-less line that forms branches instead of tendrils and, therefore, loses its climbing ability. We hypothesized that this unusual phenotype was caused by a rare variation and subsequently identified the causative single nucleotide poly- morphism. The affected gene TEN encodes a TCP transcription factor conserved within the cucurbits and is expressed specifically in tendrils, representing a new organ identity gene. The variation occurs within a pro- tein motif unique to the cucurbits and impairs its function as a transcriptional activator. Analyses of transcrip- tomes from near-isogenic lines identified downstream genes required for the tendril＇s capability to sense and climb a support. This study provides an example to explore rare functional variants in plant genomes.

Neuro-muscular" mechanism in rapid coiling of Luffa tendril

Darwin, in his retiring years, conducted long-term studies at home on various modes of the movement of ordinary plant organs and sensitive floral parts, in climbing and twining plants, and in insectivorous plants. His conclusions derived therefrom laid emphasis on the fundamental similarty in irritability between plant and animal species, thereby, Supporting his theory of the biological evolution. Since then, Darwin’s

Electrochemical wave transmission and rapid coiling movement in tendril of luffa

The tendril of luffa (Luffa officinale),in response to various non-injurious and injuriousstimulations,will first give rise to electrochemical transmission including the action wave,variation wave,andwave complex.It is then followed by rapid coiling movement which appears within 25—30 s after stimulation.The coiling process continues for 10 min or more.When it is over,the tendril begins to uncoil itself.Tendrils pretreated with the narcotic drug,ethyl ether fail to response to stimulation entirely.Specific inhibitorsof microfilament,cytochalasins B and D,and of myosin,N-ethylmaleimide and iodoacetic acid,are both able toprevent the coiling of tendril,without any effect on the electrical wave transmission.Colchicine,known toinhibit microtubule action,is ineffective in preventing coiling.Acetylcholine is able to provoke the tendril coilingdirectly.The effects of drug pretreatments support the proposal that the electrochemical wave transmission elicitedby stimulation is the forerunner for arousing the rapid movement of the sensitive tendril that the actin and myosinare taking part in.Turgor changes in tendril cells are intimately connected with the transmitted and the motoraction of the compact tissues lining along the more sensitive ventral side of the tendril.As the ventral cellsundergo the abrupt contraction and slightly shrink,the dorsal cells become expanded in coiling.Eventually,turgotresumes normal on both sides when uncoiling occurs.

Tendril-Based Climbing Plants to Model, Simulate and Create Bio-Inspired Robotic Systems

Bioinspiration can be considered one of the keys for future smart and versatile robotic systems. Plants could be an im- portant source of ideas despite the fact that they have not yet been deeply observed and considered. In this paper, climbing tendril-bearer plants that, by means of irritable filiform organs called tendrils, search for a support, grasp it and climb to gain height, have been used to study and develop an effective climbing robot. The study aimed first to evaluate the main movements and behaviors of the tendril from a biomimetic point of view. The tendril complexity was then simplified, a robotic model was developed and a kinematic simulator was designed and implemented to visualize and evaluate the chosen system. Finally, based on the biological, technical and numerical evaluations, the main tendril behaviors were replicated by proof of concept devices made of smart materials to move towards a practical realization and to replicate the simulated results. The designed proof of concept prototypes showed food repeatability and feasibility.