Biological Sciences
Gravitropism
Gravitropism is a biological phenomenon in which plants respond to gravity by growing in a specific direction. The roots exhibit positive gravitropism, growing downward, while the shoots display negative gravitropism, growing upward. This response allows plants to orient themselves for optimal growth and nutrient uptake.
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7 Key excerpts on "Gravitropism"
- Ben Greenebaum, Frank Barnes, Ben Greenebaum, Frank Barnes(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
The growth response that is required to maintain the spatial orientation is called Gravitropism and consists of three phases: reception of a gravitational signal, its transduction to a biochemical signal that is transported to the responsive cells and finally the growth response, or bending of root or shoot. Primary roots exhibit positive Gravitropism, i.e., they grow in the direction of a gravitational vector. Shoots respond negatively gravitropic and grow upright opposite to the gravitational vector. However, lateral roots and shoots branches are characterized by intermediate set-point angles and grow at a particular angle that can change over time (Firn and Digby, 1997). Gravitropism typically is generated by dense particles that respond to gravity. Experimental stimulation by high-gradient MF provides a new approach to selectively manipulate the gravisensing system.High-gradient MF has been used to induce intracellular magnetophoresis of amyloplasts and the obtained data indicate that a magnetic force can be used to study the gravisensing and response system of roots (Kuznetsov and Hasenstein, 1996). The data reported strongly support the amyloplast-based gravity-sensing system in higher plants and the usefulness of high MF to substitute gravity in shoots (Kuznetsov and Hasenstein, 1997; Kuznetsov et al., 1999). For example, in shoots of the lazy-2 mutant of tomato that exhibit negative Gravitropism in the dark, but respond positively gravitropically in (red) light, induced magnetophoretic curvature showed that lazy-2 mutants perceive the displacement of amyloplasts in a similar manner than wild type and that the high MF does not affect the graviresponse mechanism (Hasenstein and Kuznetsov, 1999). Arabidopsis stems positioned in a high MF on a rotating clinostat demonstrate that the lack of apical curvature after basal amyloplast displacement indicates that gravity perception in the base is not transmitted to the apex (Weise et al., 2000). The movement of corn, wheat, and potato (Solanum tuberosum ) starch grains in suspension was examined with videomicroscopy during parabolic flights that generated 20–25 s of weightlessness. During weightlessness, a magnetic gradient was generated by inserting a wedge into a uniform, external MF that caused repulsion of starch grains. Magnetic gradients were able to move diamagnetic compounds under weightless or microgravity conditions and serve as directional stimulus during seed germination in low-gravity environments (Hasenstein et al., 2013). The response of transgenic seedlings of Arabidopsis, containing either the CycB1-GUS proliferation marker or the DR5-GUS auxin-mediated growth marker, to diamagnetic levitation in the bore of a superconducting solenoid magnet was evaluated. Diamagnetic levitation led to changes that are very similar to those caused by real [i.e., on board the International Space Station (ISS)] or mechanically simulated microgravity [i.e., using a random positioning machine (RPM)]. These changes decoupled meristematic cell proliferation from ribosome biogenesis, and altered auxin polar transport (Manzano et al., 2013). Arabidopsis in vitro
eBook - PDF- Helgi Öpik, Stephen A. Rolfe(Authors)
- 2005(Publication Date)
- Cambridge University Press(Publisher)
Rotation at higher speed, in a centrifuge, allows the gravitational force experienced by the plant to be readily increased. A true reduction in the force of gravity is somewhat more challenging and requires flights on rockets on parabolic trajectories or into space. Such studies have shown that Gravitropism exhibits reciprocity , i.e. the response observed is the product of the time of stimulation  the intensity of stimulation: a long period of weak stimulation causes the same response as a shorter period of more intense stimulation. For the oat coleoptile this relationship holds true for forces between 58.4 and 0.0014  g , requiring exposure of 5 s or 68 h respectively. The threshold for the oat coleoptile is therefore approximately 300  g s at room temperature. Once this threshold has been exceeded the magnitude of the response generally increases with the intensity of the stimulus until a maximum is reached. Axis of centrifuge Growth 5 4 3 2 1 a b c Fig : 12 : 9 Centrifugal stimulation of the root tip and base in opposite directions.The arrows a to c show the direction of the forces acting on the tip which projects beyond the centrifuge axis; the arrows 1 to 5 represent forces acting on the basal part; the lengths of the arrows are proportional to the force. If 1.5–2 mm of the tip is allowed to project beyond the axis, the root behaves as if the tip alone were stimulated, even though the forces acting on the base in the opposite direction are much stronger. From Larsen (1962). 332 GROWTH MOVEMENTS The role of statoliths The primary perception of gravity must involve the movement of some entity in the sensitive cells – this is the only way in which the physical force can interact with the cell. In 1900, Haberlandt and Neme ˇc independently put forward the statolith theory of gravitrop-ism. This supposes that in the perceptive cells (the statocytes ), mobile starch grains (the statoliths ) move under gravity to lie in the lower parts of the cell.
eBook - PDF- Simon Gilroy, Patrick Masson, Simon Gilroy, Patrick Masson(Authors)
- 2008(Publication Date)
- Wiley-Blackwell(Publisher)
totropism and Gravitropism is to use the microgravity conditions during spaceflight (Correll et al. 2005; Kiss et al. 2007; see also Chapter 8 of this book). In these experi-ments on the international space station, we plan to study the role of phytochromes in phototropism and to determine whether red light affects phototropism directly or indi-rectly by the attenuation of Gravitropism. However, through the increased use of the new tools of molecular and systems biology in the next decade, we should gain an even bet-ter understanding of the basic mechanisms of phototropism, its relationship to gravitro-pism, and its importance to plants. 4.7 Literature Cited Ahmad, M., J.A. Jarillo, O. Smirnova, and A.R. Cashmore. 1998. Cryptochrome blue-light pho-toreceptors of Arabidopsis implicated in phototropism. Nature 392: 720–723. Ballare, C.L., A.L. Scopel, S.R. Radosevich, and R.E. Kendrick. 1992. Phytochrome-mediated phototropism in de-etiolated seedlings: occurrence and ecological significance. Plant Physiol. 100: 170–177. Ballare, C.L., A.L. Scopel, M.L. Roush, and S.R. Radosevich. 1995. How plants find light in patchy canopies. A comparison between wild-type and phytochrome-B-deficient mutant plants of cucumber. Funct. Ecol. 9: 859–868. Blakeslee, J.J., W.A. Peer, and A.S. Murphy. 2005. Auxin transport. Curr. Opin. Plant Biol. 8: 494–500. Briggs, W.R., and J.M. Christie. 2002. Phototropins 1 and 2: versatile plant blue-light receptors. Trends Plant Sci. 7: 204–210. Britz, S.J., and A.W. Galston. 1982. Light-enhanced perception of gravity in stems of intact pea seedlings. Planta 154: 189–192. Cashmore, A.R. 2003. Cryptochromes: enabling plants and animals to determine circadian time. Cell 114: 537–543. Cho, H.-Y., T.-S. Tseng, E. Kaiserli, S. Sullivan, J.M. Christie, and W.R. Briggs. 2007. Physiological roles of the Light, Oxygen, or Voltage domains of phototropin 1 and phototropin 2 in Arabidopsis . Plant Physiol. 143: 517–529. Christie, J.M., M. Salomon, K.
eBook - ePubThe Life of Plants
A Metaphysics of Mixture
- Emanuele Coccia(Author)
- 2018(Publication Date)
- Polity(Publisher)
Society and Space, 27 (2009): 73–86. But, in this case as in the orthodox use of the concept in biology, one assumes a successive habitation of two or more environments.14 . Julius Sachs, “Über Orthotrope und Plagiotrope Pflanzenteile,” Arbeiten des Botanischen Instituts in Würzburg, 2 (1882): 226–84.15 . On Gravitropism, apart from the monographs by Chamovitz and Karban [cited in ch. 1, nn. 1 and 10 respectively] and Koller’s Restless Plant, see the classic by Theophil Ciesielski, Untersuchungen über die Abwärtskrümmung der Wurzel: Beiträte zur Biologie der Pflanzen, 1 (1872): 1–30; also Peter W. Barlow, “Gravity Perception in Plants: A Multiplicity of Systems Derived by Evolution?” Plant, Cell, and Environment, 18 (1995): 951–62; R. Chen, E. Rosen, and P. H. Masson, “Gravitropism in Higher Plants,” Plant Physiology, 120 (1999): 343–50; C. Wolverton, H. Ishikawa, and M. L. Evans, “The Kinetics of Root Gravitropism: Dual Motors and Sensors,” Journal of Plant Growth Regulation, 21 (2002): 102–12; R. M. Perrin, L.-S. Young, N. Murthy, B. R. Harrison, Y. Wang, J. L. Will, and P. H. Masson, “Gravity Signal Transduction in Primary Roots,” Annals of Botany, 96 (2005): 737–43; and Miyo Terao Morita, “Directional Gravity Sensing in Gravitropism,” Annual Review of Plant Biology, 61 (2010): 705–20.16 . Augustin Pyramus de Candolle, Vegetable Organography, or, an Analytical Description of the Organs of Plants, trans. by Boughton Kingdon (London: Houlston & Stonesman, 1839), p. 209. The motif is Aristotelian. See Aristotle, De anima 2.4, 416a : “Empedocles is wrong in adding that growth in plants is to be explained, the downward rooting by the natural tendency of earth to travel downwards, and the upward branching by the similar natural tendency of fire to travel upwards” [translation from Jonathan Barnes (ed.), The Complete Works of Aristotle, vol. 1, Princeton: Princeton University Press, 1984), pp. 661–2].17 . Thomas Andrew Knight, “On the Direction of the Radicle and Germen during the Vegetation of Seeds,” Philosophical Transactions of the Royal Society
eBook - PDF- Jules Janick(Author)
- 2010(Publication Date)
- Wiley(Publisher)
6. Gravitropism: CHANGING IDEAS 245 cellulose destroy the cells' ability to respond to gravity although stream- ing continues, whereas enzymes that digest pectins have no effect. Some proteases also stopped the response to gravity although others did not. The authors conclude that the gravity receptors may be proteins located in the junctionbetween the protoplast and the wall. Could this also be the case in higher plants? III. PERCEPTION: ELECTRICAL FIELDS, CURRENTS, AND POTENTIALS As we noted, the theory of starch statoliths was eclipsed for many years during the early part ofthis centuryby discussion of a gravielectric effect. Then, in the 1960s, it was concluded that the observed electrical changes are caused by migrating auxin molecules rather than being the cause of their migration (see Wilkins 1979 review). Interest in the role ofelectrical effects in Gravitropism has resurfaced. It has long been clear, for example, that directional growth of various plant organs will respond to an electrical field. Roots of Lepidium seedlings, for example, will grow in a 1-3 V cm- 1 DC-electric field in a low-salt medium at pH 6 toward the cathode but toward the anode if the solution is at pH 5 (Stenz and WiesenseeI1991). Is it possible that gravistimulation causes immediate changes in electrical fields, currents, and/or potentials? If so, do these changes lead to other changes (e.g., in growth-regulator concentrations or movements) that ultimately leadto the bending response? Several authors have detected changes in the pattern of electric current around root tips as a result of gravistimulation. Behrens et al. (1982), for example, used a vibrating electrode to find a symmetrical current flow around vertically oriented Lepidium roots with current leaving the root along most of the elongation zone and in the root-hair zone and entering the root at the root cap and the meristem, close to the beginning ofthe elongation zone.
eBook - PDFBiology in Space and Life on Earth
Effects of Spaceflight on Biological Systems
- Enno Brinckmann(Author)
- 2008(Publication Date)
- Wiley-VCH(Publisher)
The study indicates that pH changes correlate with early gravitropic processes that do not require an intact actin cytoskeleton. A contribution of InsP 3 in plant Gravitropism has recently been found by con- stitutively expressing an enzyme that specifically hydrolyzes InsP 3 in transgenic Arabidopsis plants [87]. The InsP 3 level was significantly reduced, which did not negatively affect growth and the overall habitus of the plants, but reduced gravi- tropic curvature by 30%. The InsP 3 level, which was reported to increase approx. three-fold following gravistimulation, was not altered in transgenic plants, indicat- ing that InsP 3 is involved in early gravitropic signalling. Although there is correla- tive data for the involvement of signalling molecules and second messengers in Gravitropism, the mode of action, especially in the early steps of gravity signalling, remains elusive. More work is needed to clarify the sequence of events that links statolith displacement to the relocalization of PIN proteins and differential auxin transport preceding gravitropic curvature (Fig. 2.2). 2.8 Modifying Gravitational Acceleration Forces – Versatile Tools for Studying Plant Gravity Sensing Mechanisms As mentioned above, several instruments have been developed to modify the per- sistent gravitational acceleration. Centrifugation is used to alter the amount and the direction of the mass acceleration that acts on the susceptible masses of gravi- sensing mechanisms. Centrifugation intensifies weak gravity responses; intracel- lular processes are more clearly recognizable, e.g. gravity-induced displacement of statoliths, and centrifugal forces have been used to directly interfere with suscep- tion and perception processes. The actomyosin forces and the gravisensitive membrane area in characean rhizoids, for instance, have been studied by using centrifugal accelerations in different angles to displace statoliths to different cyto- plasmic regions and membrane areas [60, 88].
eBook - PDFPlant Physiology 10
A Treatise: Growth and Development
- F.C. Steward(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Plant Physiol. 77, 722-730. 101. Jet Propulsion Laboratory. California Institute of Technology. (1988). Cargo Bay Environmental Data from STS-26 Oasis Low-Frequence Acceleration Data, 3 Vols. S. D. Data Report 003. JPL, Pasadena. 102. Johnsson, A . (1979). Growth movements not directed primarily by external stimuli. Circumnutation. Encycl. Plant Physiol. N.S. 7, 627—646. 103. Johnsson, Α . , and Heathcote, D. G. (1973). Experimental evidence and models on circumnutation. Z. Pflanzenphysiol. 70, 371-405. 104. Johnsson, Α . , and Pickard, B. G. (1979). The threshold stimulus for geotropism. Physiol. Plant. 45, 315-319. 105. Juniper, Β. E. (1976). Geotropism. Annu. Rev. Ρ font Physiol. 27, 385-406. 106. Juniper, Β. E. (1977). T h e perception of gravity by a plant. Proc. R. Soc. (London) Ser. Β 199, 537-550. 548 A . D . KRIKORIAN AND HOWARD G. LEVINE 107. Kaldeway, H . (1962). Plagio-und Diageotropismus der Sprosse und Blaetter, einschliesslich Epinastie, Hyponastie, Entfaltungsbewegungen. Handb. Pflanzenphysiol 17/2, 200-321. 108. Kaufman, P. B., Brock, T. G., Song, I., Young, B. R., and Ghosheh, N . S. (1987). H o w cereal grass shoots perceive and respond to gravity. Am. J. Bot. 74, 1446-1457. 109. Keefe, J. R., and Krikorian, A . D. (1983). Gravitational biology on the space platform. Paper presented at the 13th Intersociety Conference on Environmental Systems. 11-13 July, San Francisco. SAE (Society of Automotive Engineers) Technical Paper Se-ries 931133. 110. Kelly, C. F., and Smith, A . H . (1974). Experimental procedures in gravitational biolo-gy. In Aeromedical Review. Principles of Biodynamics, pp. 1-52. Review 8-74 U S A F School of Aerospace Medicine, Aerospace Medical Division (AFSC), Brooks Air Force Base, Texas 78235. 111. Kessler, J. Ο. (1978). Convective control of long-range coherence in plant growth regulation. In COSPAR, Life Sciences and Space Research W . R. Holmquist, ed.), Vol. 16, pp. 99-104. Pergamon, Oxford. 112. Kiss, J. Z., and Sack, F.
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