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Root systems of prairie plants (from ) 

Root systems of prairie plants (from ) 

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... called root hairs extend into the soil to absorb water and minerals. Root hairs are a competitive tool to increase the surface area of the roots, increasing the capacity to absorb nutrients and water. Therefore plants demonstrate to successfully reach their needs even without a conventional locomotion system. Although plants cannot physically move, active root growth allows exploration of soil niches for nutrition. This implies that root apices are not only sites of nutrient uptake but also sites of forward movement. The root system of plants has an additional role that proves again their ability to contrive simple but effective mechanisms to overcome the varied situations occurring in their life: they are used to stock molecules important for their metabolism and energy. Reserve stored in the root system are safe and protected from many external adversities, and help plants to satisfy higher requests occurring during their annual cycle (e.g. energy for reproduction), or to survive over period of plant dormancy, or to regenerate organs or the whole aerial part after natural or deliberate destruction. Plants are also characterized by inter-individual interactions. Plants communicate with members of the same or different species, as well as members from a different genre, including animals and insects, by means of various signals, mostly chemical (pheromones and other compounds), through which they can send and receive information over a long distance (Dicke et al., 2003; Bruine and Dicke, 2001; Chamberlain et al., 2001). As a consequence, plants have historically played a successful role in the conquest of the land. Once they had taken their first step (420 million years ago), nothing could stop them from spreading across the empty continents, giving their ability to “move” towards any region with regular rainfall and nutrient rich soil, adapting themselves each time to new landscapes and climates. The structure of the seeds plays a key role, especially concerning their size that allows them to be dispersed ensuring a good opportunity to explore and conquer the land, and their ability to survive even for long period before reaching the optimal environment to germinate protected by special teguments and supported by the food stored inside themselves; the same food is also responsible for the sustenance of the new plant originated from the seed until it becomes completely heterotrophic. Plant root systems perform many essential adaptive functions including water and nutrient uptake, anchorage to the soil and the establishment of biotic interactions at the rhizosphere. Evidently, roots monitor a wide spectrum of physical and chemical parameters, and then integrate the signals obtained in order to perform appropriate and often complex growth responses to cope with the immediate environmental circumstances. The more acute sensitivity of roots to various types of signals already mentioned, when compared to shoots, is related to the root apex . Changes in the architecture of the root system, therefore, can profoundly affect the capacity of plants to take up nutrients and water. Three major processes affect the overall architecture of the root system. First, cell division at the primary root meristem (i.e. of initial cells) enables indeterminate growth by adding new cells to the root. Second, lateral root formation increases the exploratory capacity of the root system; and third, root-hair formation increases the total surface of primary and lateral roots. Alterations to any of these three processes can have profound effects on root-system architecture and on the capacity of plants to grow in soils in which water and nutrient resources are limiting. As a preliminary example of plants’ ability to form an extensive, wide and deep root system, in the desert the roots of mesquite (genus Prosopis ) may extend down more than 50 m to reach groundwater. Annual crop plants developed a root system that can usually grow until 2.0 m in depth and extend laterally to distances up to 1.0 m. As a general behaviour, the annual production of roots may easily surpass that of shoots, so the aboveground portions of a plant can be correctly defined as the tip of an iceberg. The growth of a root system can continue through the year, but this capacity mainly depends on the availability of water and minerals in the immediate microenvironment surrounding the root ( rhizosphere ). If the rhizosphere lacks in nutrients or water, root growth becomes slow. As rhizosphere conditions improve, root growth increases. Changes in root architecture can mediate the adaptation of plants to soils in which nutrient availability is limited by increasing the total absorptive surface of the root system. The development of root systems is usually highly asymmetric and reflects the ability of roots to adjust their growth and development to environmental factors (Lopez-Bucìo et al., 2006). The form of the root system is different regarding plant species (Fig. 4). Germinating seeds in monocots initiate root development from the emergence of three to six primary root axes. Monocot plants form new adventitious roots, called nodal roots or brace roots , with further growth, then both the primary and nodal root axes continue their growth and branch extensively to form a complex fibrous root system. On the contrary, plants belonging to dicots develop a root system from a single root axis, called taproot . From this main root axis, lateral roots develop to form an extensively branched root system. The ability of dicots to activate a secondary growth from the cambium (secondary cambial activity, not present in the monocots) can thick these roots. The development of the root system in both monocots and dicots depends on the activity of the root apical meristem and the production of lateral root meristems. As reported before, the apical region of a plant root is called root apex and morphologically includes three regions: meristem, transition zone (see par. 4.2), and elongation region (Fig. 5). The meristem is mainly delegated to cell division, which happens in both the direction of the root base in order to form new-born cells with the aim to differentiate into the tissues of the functional root and to form the root cap in the direction of the root apex. Cell division at the real root apex proper is relatively slow; for this reason this region is known as the quiescent center . After a few cycles of slow cell divisions, root cells displaced from the apex by about 0.1 mm begin to divide more rapidly. Cell division again tapers off at about 0.4 mm from the apex, and the cells expand equally in all directions. After the transition zone, the root apex shows the elongation region , which begins 0.7 to 1.5 mm from the apex. In this zone, the elongation of the cells goes on a very rapid manner; more, they undergo a final round of divisions in order to produce a central ring of cells called the endodermis , whose walls become thickened due to a marked suberification to forms the Casparian strip , a hydrophobic structure that prevents the apoplastic movement of water or solutes across the root. Root hairs, with their large surface area for absorption of water and solutes, first appear outside the proper root apex, in another region called the maturation zone . Here that the ascendant conducting pathway of the plants (xylem) develops the capacity to translocate substantial quantities of water and solutes to the shoot (Gilroy and Jones, 2000). The formation of root hairs increases the volume of soil in contact with, and therefore exploitable by, the root. It has been speculated for many decades that the primary reason for root hair existence is to increase the efficiency of nutrient ion uptake from the soil, based on the observation that the number and density of root hairs greatly increase under nutrient stress. The driving force for most nutrient uptake in plants is the electrochemical gradient across the plasma membrane, a major proportion of which is generated by the H + -ATPase. In support of the theory that root hairs are centers of nutrient uptake, high levels of expression of H + -ATPase genes in root hairs has been demonstrated in Nicotiana (Moriau et al., 1999), with the strongest expression occurring in developing root hairs and reduced expression in mature root hairs. Although the spatial localization of H + -ATPase proteins within the root hairs themselves is unknown, evidence obtained with vibrating pH-sensitive microelectrodes indicates a strong H + efflux from the base of the root hair and an apparent tip-localized H + influx. This suggests that the proximity of H + -ATPases to the zone of new growth is closely regulated (Jones et al., 1995). A new vision of the root system comes out from the morphological observation that root apices are composed of three distinct zones, the interplay of which allows their effective exploration of soil (Baluška et al., 2004) in searching both nutrients and water. In standard conditions, root cell elongation is much more rapid than the shoot cells one: as a consequence, any cell division in the region of rapid elongation is not allowed. On the contrary, cell cycling and cell elongation occur concomitantly in shoot apices. The clear separation of division and elongation regions in root apices permits to identify a very unique zone, the so-called transition zone, included between the two other (and well-known) regions (Baluška et al., 1994, 2001), which is a peculiar region for environmental sensing. In fact, this region is able to detect more than 10 chemical and physical parameters Why this region has a particular physiological behaviour? The main reason derives from a morphological observation (Fig. 5): in fact, the cells of the transition zone present a unique cytoarchitecture, with centralised nuclei surrounded by perinuclear microtubules radiating towards the cell periphery (Baluška et al., 2001). This configuration ...

Citations

... Plants use osmosis phenomenon to explore their environment resourcefully, to uptake water and nutrients, [27] or even to hunt in case of some carnivorous plants. [27][28][29][30][31][32][33][34] Recently, bioinspired low-power-consumption actuators have been described which were capable of generating appropriate forces during a few minutes actuation tim. [34] This actuator is one of the fastest osmotic actuator developed so far [25][26][34][35][36] and has an actuation time comparable to a typical plant cell but is too slow in comparison with actuators that are used in applications such valves. ...
... The hydraulic permeability of the membrane was initially assumed to be A = 3 x 10 −13 m 3 /m 2 pa.s and salt rejection coefficient (σ) was considered to be 1 in order to compare the results with published experimental data. [33] This membrane was one of the first generation of FO membranes developed by Hydration Technology Innovations (HTI) and since then membranes with higher water permeability have been developed. [40][41][42][43][44][45][46][47][48] Membranes listed in Table 1 are available FO membranes, sorted based on their water permeability. ...
... The model to simulate actuator operation was validated by using a water permeability A = 3 x 10 −13 m 3 /m 2 pa.s, a salt rejection coefficient σ = 1, and diaphragm material properties the same as reported by Sinabaldi et al.. [33] Experiments involved a reservoir chamber (side A) which was filled with distilled water while the actuator chamber (side B) was filled with NaCl solution. The tests were performed at two salt concentrations, namely 1 and 2 mol/L. ...
Article
The aim was to determine the impact of membrane properties and operating conditions upon predicted performance of osmotically driven actuators. An actuator fitted with a forward osmosis membrane was studied, and significantly we examined the reversibility of the actuation process. It was discovered that the actuation-retraction cycle could be repeated for over 60 cycles before salt concentration became similar on both sides of the membrane. The cycle length and number of operative cycles were shown to be a dependent on membrane properties. It was demonstrated that issue of long actuation time can be addressed using membranes with high water permeability.
... In addition to this, the search for nutrient (water or chemical substances) is the other fundamental goal of the root. In Ref. [9] some of the plant features are reported: the decision center is detected in the so-called transition zone, just near the geometric root apex: for the purposes of the present analysis, geometric apex and decision center will be considered as coincident. ...
Conference Paper
Full-text available
Control algorithms for complex systems aim to improve the robustness of the desired behavior with respect to environmental changes, and this characteristic is even more appreciated while dealing with autonomous systems, where a supervisor cannot help during operations. The behavior of many species of living beings can provide interesting insight in order to design these algorithm. In fact, it can be assumed that many natural phenomena, even the most complex, are determined by the chaotic sum of very simple actions, whose sum leads to the successful completion of a typical natural process. This is the basic concept of the so-called behavioral strategies: global goals can be reached thanks to the implementation of rudimental control rules that govern the motion of a number of agents. Efficiency as well as simplicity of these rules make them interesting as control strategies. In the frame of this biologically-inspired control, the paper discusses and implement a root-like behavior, and shows two different applications of this approach in the field of space exploration. The first one copies the roots' working principle in order to direct a team of penetrators exploring the underground of a planetary surface. The second example calls for the guidance of a fleet of probes descending on the surface of an unknown celestial bodies, looking to manoeuvre in order to reach their landing points as the safest and most promising ones.
... Plants process information gathered from the environment and autonomously identifies optimal paths to 1) efficiently penetrate into the terrain, 2) search for and absorb nutrients, and 3) provide anchorage albeit on a longer timescale. By taking inspiration from nature, a plant-inspired space probe might be designed [Dario et al. 2008;Menon and Broschart, 2006c;Menon et al., 2006d]. Plant roots display several characteristics that would be useful if able to be translated to an engineering system including: -1) Low power consumption. ...
Chapter
Why Subsurface Exploration?Methods for Subsurface Access on Extraterrestrial BodiesGrinders and Rock Abrasion ToolsScoopsMolesUltrasonic and Percussive Actuated DrillsSurface DrillsShallow Drilling: One Meter Class DrillsTen-Meter Class DrillsDeep Drills (>10 m)Past and Present Subsurface Access MissionsFuture Sampling MissionsFuture European Prospects in Science and Exploration ProgramsBio-Inspired Drilling Systems for Future Space ApplicationsDrilling AutomationTesting of Subsurface SystemsSpace Analogs on Earth for Field Test Simulations of In Situ Planetary DrillingDrill Evaluation CriteriaConclusions References
... After having landed, the once mobile spacecraft might anchor and probe the substrate for scientific reasons. Inspired by this analogy, a team of biologists and engineers investigated both the actuation and the control mechanisms of plant roots in the focus of a biomimetic transfer for con- ceptually novel anchoring solutions for exploratory spacecraft [1]. ...
Conference Paper
Full-text available
Export Date: 15 March 2011, Source: Scopus
Article
Full-text available
Our vision of plants is changing dramatically: from insensitive and static objects to complex living beings able to sense the environment and to use the information collected to adapt their behaviour. At all times humans imitate ideas and concepts from nature to resolve technological problems. Solutions coming from plants have the potential to face challenges and difficulties of modern engineering design. Characteristic concepts of the plant world such as reiteration, modularity and swarm behaviour could be of great help resolving technological problems. On the other hand a biorobotic approach would facilitate the resolution of many biological problems. In this paper, the concept of a plant-inspired robot is proposed for the investigation of both biological and technological issues.