Negative Phototropism in Vaucheria terrestris Regulated by Calcium III. The Role of Calcium Characterized by Use of a High-Power Argon-Ion Laser as the Source of Unilateral Blue Light

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概要

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• A tip-growing Xanthophycean algal coenocyie, Vaucheria terrestris sensu Gotz, is able to change the sign of its phototropic response from positive to negative as a result of its ability to sense the fluence rate (=intensity) of unilateral blue light (BL). The mechanism that determines the sign of phototropism was investigated using a high-power argon-ion laser (457.9 nm) as a source of very strong unilateral BL. The fluence-response relationship was determined by changing both the fluence rate and the duration of irradiation. Positive phototropic bending was induced when the fluence rate of BL from the laser was below 60 W m^<-2>. The positive bending obeyed the reciprocity law and was not affected by the concentrations of external Ca^<2+> ions between 0.4 mM and 4.4 mM. The positive curvature decreased when the alga was exposed to a unilateral pulse of BL with a duration of 10-300 s at fluence rates higher than 60 W m^<-2>. The alga finally showed a deep negative curvature when either the fluence rate or the duration of irradiation was further increased. The inversion of the phototropic response and development of the negative phototropic response was greatly enhanced in the presence of 4.4 mM Ca^<2+> ions. However, the mechanism that determine the sign of phototropism seemed to require a BL pulse of longer than several seconds, even when the fluence rate was sufficiently high. The role of cytoplasmic Ca^<2+> ions in positive and negative phototropic responses is discussed.

• 日本植物生理学会の論文

著者

• Kataoka Hironao

  Institule For Agricultural Research Tohoku University

• WATANABE Mmasakatsu

  National Institute for Basic Biology

関連論文

• Bimodal Polarotropism of Vaucheria to Polarized Blue Light:Parallel Polarotropism at High Fluence Rate Corresponds to Negative Phototropism
• Effects of chemical components and nitrogen sources on zygospore development in Phycomyces blakesleeanus
• Blue Light-Induced Branching in Vaucheria. Requirement of Nuclear Accumulation in the Irradiated Region
• Expansion of Vaucheria Cell Apex Caused by Blue or Red Light
• Negative Phototropism in Vaucheria terrestris Regulated by Calcium I. Dependence on Background Blue Light and External Calcium Concentration
• Negative Phototropism in Vaucheria terrestris Regulated by Calcium III. The Role of Calcium Characterized by Use of a High-Power Argon-Ion Laser as the Source of Unilateral Blue Light
• Negative Phototropism of Vaucheria terrestris Regulated by Calcium II. Inhibition by Ca^-Channel Blockers and Mimesis by A23187
• The Light-Growth Response of Vaucheria. A conditio sine qua non of the Phototropic Response?

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