Hydrotropism: The current state of our knowledge

Takahashi, Hideyuki

doi:10.1007/bf02509304

Cited by 89 publications

(62 citation statements)

References 39 publications

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“…For example, roots show hydrotropism in response to moisture gradients, which represents an example of cross talk between the gravity signal and another environmental cue. Hydrotropism plays a very important role in plant growth and development to tolerate drought stress (Jaffe et al, 1985;Takahashi, 1997;Mizuno et al, 2002;Takahashi et al, 2003). Perception and subsequent response to interaction between gravitropism and hydrotropism may enable plants to direct root growth in the direction that maximizes the acquisition of water, thereby providing a fitness advantage during root development under drought conditions.…”

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confidence: 99%

Salt Modulates Gravity Signaling Pathway to Regulate Growth Direction of Primary Roots in Arabidopsis

et al. 2007

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Plant root architecture is highly plastic during development and can adapt to many environmental stresses. The proper distribution of roots within the soil under various conditions such as salinity, water deficit, and nutrient deficiency greatly affects plant survival. Salinity profoundly affects the root system architecture of Arabidopsis (Arabidopsis thaliana). However, despite the inhibitory effects of salinity on root length and the number of roots, very little is known concerning influence of salinity on root growth direction and the underlying mechanisms. Here we show that salt modulates root growth direction by reducing the gravity response. Exposure to salt stress causes rapid degradation of amyloplasts in root columella cells of Arabidopsis. The altered root growth direction in response to salt was found to be correlated with PIN-FORMED2 (PIN2) messenger RNA abundance and expression and localization of the protein. Furthermore, responsiveness to gravity of salt overly sensitive (sos) mutants is substantially reduced, indicating that salt-induced altered gravitropism of root growth is mediated by ion disequilibrium. Mutation of SOS genes also leads to reduced amyloplast degradation in root tip columella cells and the defects in PIN2 gene expression in response to salt stress. These results indicate that the SOS pathway may mediate the decrease of PIN2 messenger RNA in salinity-induced modification of gravitropic response in Arabidopsis roots. Our findings provide new insights into the development of a root system necessary for plant adaptation to high salinity and implicate an important role of the SOS signaling pathway in this process.

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Salt Modulates Gravity Signaling Pathway to Regulate Growth Direction of Primary Roots in Arabidopsis

et al. 2007

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“…For example, roots of starchless mutants or roots in which columella cells were ablated with a laser showed severely reduced gravitropism (Kiss et al, 1989;Blancaflor et al, 1998). Roots also show hydrotropism, phototropism, and thigmotropism in response to moisture gradients, unilateral light, and touch stimuli, respectively (Jaffe et al, 1985;Okada and Shimura, 1990;Takahashi, 1997;Sakai et al, 2000;Ruppel et al, 2001). That is, roots grow toward the higher water potential and toward or away from light or touch, depending on the water status, the wavelength, or the cells of stimulus perception.…”

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confidence: 99%

“…The latter response is much weaker than the former (Ruppel et al, 2001). Although the perception mechanisms for those tropisms in roots are still obscure, the sensory cells are likely to reside in the root cap (Jaffe et al, 1985;Kiss et al, 1989;Takahashi and Suge, 1991;Takahashi and Scott, 1993;Takahashi, 1997;Sakai et al, 2000). These tropisms, including gravitropism, interact with one another in orienting the roots.…”

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confidence: 99%

“…These tropisms, including gravitropism, interact with one another in orienting the roots. Amyloplasts in the gravisensing cells are required for the full gravitropic response but are inhibitory to other tropisms because of the counteracting effect of the gravitropic response (Jaffe et al, 1985;Takahashi, 1997;Vitha et al, 2000;Ruppel et al, 2001). Among the tropisms, gravitropism and hydrotropism in particular have an important role in plant growth in areas where there is little precipitation.…”

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confidence: 99%

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Hydrotropism Interacts with Gravitropism by Degrading Amyloplasts in Seedling Roots of Arabidopsis and Radish

Takahashi

2003

PLANT PHYSIOLOGY

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In response to a moisture gradient, roots exhibit hydrotropism to control the orientation of their growth. To exhibit hydrotropism, however, they must overcome the gravitropism that is dominant on Earth. We found that moisture gradient or water stress caused immediate degradation of the starch anchors, amyloplasts, in root columella cells of Arabidopsis and radish (Raphanus sativus). Namely, development of hydrotropic response was accompanied by a simultaneous reduction in starch content in columella cells. Rapid degradation of amyloplasts in columella cells also occurred in the water-stressed roots with sorbitol or mannitol. Both hydrotropically stimulated and water-stressed roots showed a reduced responsiveness to gravity. Roots of a starchless mutant, pgm1-1, showed an enhanced hydrotropism compared with that of the wild type. These results suggest that the reduced responsiveness to gravity is, at least in part, attributable to the degradation of amyloplasts in columella cells. Thus, the reduction in gravitropism allows the roots to exhibit hydrotropism.

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“…Most studies of hydrotropism have been done using either pea mutants (Takahashi et al, 1991(Takahashi et al, , 1993Steinmetz et al, 1996), ABA, auxin, or agravitropic mutants of Arabidopsis (Takahashi et al, 2002), or maize roots (Takahashi and Scott, 1993) From early work, it is known that calcium is important for a hydrotropic response, as is auxin and potentially other plant hormones (for a review on early work in hydrotropic studies, see Takahashi, 1997). Recently, however, research has focused on using screens for Arabidopsis mutants that do not show a hydrotropic response making use of a water potential gradient system.…”

Section: Water Water Everywhere …mentioning

confidence: 99%

Plant tropisms: providing the power of movement to a sessile organism

Esmon¹,

Pedmale²,

Liscum³

2005

Int. J. Dev. Biol.

113

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In an attempt to compensate for their sessile nature, plants have developed growth responses to deal with the copious and rapid changes in their environment. These responses are known as tropisms and they are marked by a directional growth response that is the result of differential cellular growth and development in response to an external stimulation such as light, gravity or touch. While the mechanics of tropic growth and subsequent development have been the topic of debate for more than a hundred years, only recently have researchers been able to make strides in understanding how plants perceive and respond to tropic stimulations, thanks in large part to mutant analysis and recent advances in genomics. This paper focuses on the recent advances in four of the best-understood tropic responses and how each affects plant growth and development: phototropism, gravitropism, thigmotropism and hydrotropism. While progress has been made in deciphering the events between tropic stimulation signal perception and each characteristic growth response, there are many areas that remain unclear, some of which will be discussed herein. As has become evident, each tropic response pathway exhibits distinguishing characteristics. However, these pathways of tropic perception and response also have overlapping components -a fact that is certainly related to the necessity for pathway integration given the everchanging environment that surrounds every plant.

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Hydrotropism: The current state of our knowledge

Cited by 89 publications

References 39 publications

Salt Modulates Gravity Signaling Pathway to Regulate Growth Direction of Primary Roots in Arabidopsis

Salt Modulates Gravity Signaling Pathway to Regulate Growth Direction of Primary Roots in Arabidopsis

Hydrotropism Interacts with Gravitropism by Degrading Amyloplasts in Seedling Roots of Arabidopsis and Radish

Plant tropisms: providing the power of movement to a sessile organism

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