The physiological significance of phenylacetic Acid in abscising cotton cotyledons.
The physiological role of phenylacetic acid (PAA) as an endogenous regulator of cotyledon abscission was examined using cotton (Gossypium hirsutum L. cv LG 102) seedlings. Application of 100 micromolar or more PAA to leafless cotyledon abscission-zone explants resulted in the retardation of petiole abscission and a decrease in the rise of ethylene evolution that normally accompanies aging of these explants in vitro. The partial inhibition of ethylene evolution in these explants by PAA was indirect since application of this compound stimulated short-term (<24 hours) ethylene production. PAA treatment partially suppressed the stimulation of petiole abscission elicited by either ethylene or abscisic acid. Both free and an acid-labile, bound form of PAA were identified in extracts prepared from cotyledons. No discernible pattern of changes in free or bound PAA was found during the course of ethylene-induced cotyledon abscission. Unlike indole-3-acetic acid, transport of PAA in isolated petiole segments was limited and exhibited little polarity. On the whole, these results are not consistent with the direct participation of PAA in the endogenous regulation of cotyledon abscission.
Regulation of auxin transport in pea (Pisum sativum L.) by phenylacetic acid: inhibition of polar auxin transport in intact plants and stem segments
The transport of [14C]phenylacetic acid (PAA) in intact plants and stem segments of light-grown pea (Pisum sativum L. cv. Alderman) plants was investigated and compared with the transport of [14C]indiol-3yl-acetic acid (IAA). Although PAA was readily taken up by apical tissues, unlike IAA it did not undergo long-distance transport in the stem. The absence of PAA export from the apex was shown not to be the consequence of its failure to be taken up or of its metabolism. Only a weak diffusive movement of PAA was observed in isolated stem segments which readily transported IAA. When [1-14C]PAA was applied to a mature foliage leaf in light, only 5.4% of the 14C recovered in ethanol extracts (89.6% of applied 14C) had been exported from the leaf after 6.0 h. When applied to the corresponding leaf, [14C]sucrose was readily exported (46.4% of the total recovered ethanol-soluble 14C after 6.0 h). [1-14C]phenylacetic acid applied to the root system was readily taken up but, after 5.0 h, 99.3% of the recovered 14C was still in the root system.When applied to the stem of intact plants (either in lanolin at 10 mg·g-1, or as a 10-4 M solution), unlabelled PAA blocked the transport through the stem of [1-14C]IAA applied to the apical bud, and caused IAA to accumulate in the PAA-treated region of the stem. Applications of PAA to the stem also inhibited the basipetal polar transport of [1-14C]IAA in isolated stem segments. These results are consistent with recent observations (C.F. Johnson and D.A. Morris, 1987, Planta 172, 400–407) that no carriers for PAA occur in the plasma membrane of the light-grown pea stem, but that PAA can inhibit the carrier-mediated efflux of IAA from cells. The possible functions of endogenous PAA are discussed and its is suggested that an important role of the compound may be to modulate the polar transport and-or accumulation by cells of IAA.
Managerial Economics and Organizational Architecture
PART 1: Basic Concepts Chapter 1: Introduction Chapter 2: Economists' View of Behavior Chapter 3: Markets, Organizations, and the Role of Knowledge PART 2: Managerial Economics Chapter 4: Demand Chapter 5: Production and Cost Chapter 6: Market Structure Chapter 7: Pricing with Market Power Chapter 8: Economics of Strategy: Creating and Capturing Value Chapter 9: Economics of Strategy: Game Theory Chapter 10: Incentive Conflicts and Contracts PART 3: Designing Organizational Architecture Chapter 11: Organizational Architecture Chapter 12: Decision Rights: The Level of Empowerment Chapter 13: Decision Rights: Bundling Tasks into Jobs and Subunits Chapter 14: Attracting and Retaining Qualified Employees Chapter 15: Incentive Compensation Chapter 16: Individual Performance Evaluation Chapter 17: Divisional Performance Evaluation Capstone Case Study on Organizational Architecture: Arthur Andersen LLP PART 4: Applications of Organizational Architecture Chapter 18: Corporate Governance Chapter 19: Vertical Integration and Outsourcing Chapter 20: Leadership: Motivating Change within Organizations Chapter 21: Understanding the Business Environment: The Economics of Regulation Chapter 22: Ethics and Organizational Architecture Chapter 23: Organizational Architecture and the Process of Management Innovation Glossary Index