Kinematic Evidence of Root-to-Shoot Signaling for the Coding of Support Thickness in Pea Plants

Abstract

Plants such as climbers characterized by stems or tendrils need to find a potential support (e.g., pole, stick, other plants or trees) to reach greater light exposure. Since the time when Darwin carried out research on climbing plants, several studies on plants’ searching and attachment behaviors have demonstrated their unique ability to process some features of a support to modulate their movements accordingly. Nevertheless, the strategies underlying this ability have yet to be uncovered. The present research tries to fill this gap by investigating how the interaction between above- (i.e., stems, tendrils, …) and below-ground (i.e., the root system) plant organs influences the kinematics of their approach-to-grasp movements. Using three-dimensional (3D) kinematic analysis, we characterized the movements of pea plants (Pisum sativum L.) as they leaned towards supports whose below- and above-ground parts were characterized by different thicknesses (i.e., thin below- thick above-ground, or the opposite). As a control condition, the plants were placed next to supports with the same thickness below and above ground (i.e., either entirely thin or thick). The results suggest that the information regarding below- and above-ground parts of a support appears to be integrated and modulates the reach-to-grasp behavior of the plant. Information about the support conveyed by the root system seems to be particularly important to achieve the end-goal of movement.

Unveiling Circumnutation in Pea Plants via Supervised Machine Learning

“…In this connection, previous evidence provides a degree of support that some climbing plants can modify their circumnutation patterns to a greater or lesser extent depending on the presence/absence of a potential support in the environment [24,25]. Experimental evidence demonstrating that this is the case has been forthcoming from recent studies that used kinematic analysis to characterize the movements of the tendrils of pea plants [6,[26][27][28]. Guerra and colleagues [29], for example, demonstrated that pea plants (Pisum sativum L.) are able to perceive a stimulus and modulate the kinematics of the tendrils according to the features of a potential support.…”

Classifying Circumnutation in Pea Plants via Supervised Machine Learning

“…Accordingly, previous evidence provides a degree of support that some climbing plants can modify their circumnutation patterns to a greater or lesser extent depending on the presence/absence of a potential support in the environment [ 24 , 25 ]. Experimental evidence demonstrating that this is the case has been forthcoming from recent studies that used kinematic analysis to characterize the movements of the tendrils of pea plants [ 6 , 26 , 27 , 28 ]. Guerra and colleagues [ 29 ], for example, demonstrated that pea plants ( Pisum sativum L.) are able to perceive a stimulus and modulate the kinematics of the tendrils according to the features of a potential support.…”

“…Numerous studies on climbing plant behavior have elucidated mechanistic details of support searching and attachment [e.g., 3]. This body of research relies chiefly on field observations reporting on morphological or physiological responses [ 4 ], as well as on laboratory studies focused on the characterization of kinematical patterning through the use of time-lapse photography [ 5 , 6 ]. Although this body of research provides some quantitative data, the process is admittedly subjective and rather preliminary.…”

Decision-Making Underlying Support-Searching in Pea Plants

“…A point worth noting is that most studies on how climbers select a support based on diameter information focus on the final coiling response, with no or little reference to the choreography assumed by the tendrils during the approach phase [7,8,22]. To fill this gap, we have measured the kinematics of tendrils' circumnutation from the start of their growth until they grasped the support.…”

“…circumnutation patterns to a greater or lesser extent depending on features of potential supports with respect to what would be expected by chance movement. Experimental evidence demonstrating that this might indeed be the case has been forthcoming from recent studies that used kinematic analysis to characterize the movements of the tendrils of pea plants (Pisum sativum L.) [5][6][7][8][9]. Guerra and colleagues demonstrated that pea plants are able to perceive a support and modulate the kinematics of the tendrils' aperture depending on its thickness [7].…”