Plant hormones in the control of abscission
TL;DR: In this article, the authors present an approach to solve the problem of how to find the minimum number of nodes for a node in order to obtain the maximum number of vertices.
Abstract: s, XZth Znt. Bot. Congr. Seattle, U.S.A. Lancaster 41, 826-30. Physiol., Lancaster 26, 189-91.
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TL;DR: The results considered in the chapter suggest that plant hormones, and especially auxin, play an essential role both in the relation among plant organs and in the relations among neighboring cells.
Abstract: Publisher Summary This chapter discusses the interactions and internal programmes that result in the patterned differentiation of vascular tissues. The term “pattern” is used to refer to the high degree of order, or predictability, of the system at all levels— the orientation and contacts of the strands forming a coherent system supplying all the organs of the plant, the organization of the transporting cells in files that are functional vessels and sieve tubes, and the relations among the different vascular tissues (phloem, cambium and xylem) and their component cells. The stress is, thus, on relations between cells of the same and of different types and not on the processes of differentiation and controlled gene expression. It is shown that all aspects of the development and maintenance of the vascular tissues might depend on one control system, which is at least partially hormonal. The way this control could operate is in the working hypothesis that together with the problems and possibilities it poses is the central conclusion of this work. A major characteristic of the hypothesis considered is that a gradual, feedback relation between differentiation and signal distribution creates a reliable pattern. Controls of this type may not result in very precise patterns, but they would be simple and dependable in avoiding mistakes of functional significance. They could, thus, account for the vascular patterns found in plants, where no two halves of the same leaf are exactly the same. These controls also have the virtue of depending on known signals and cellular responses. It is, thus, possible that the principles on which these controls are based have a wide relevance, both in plants and in other cases of biological development. The results considered in the chapter suggest that plant hormones, and especially auxin, play an essential role both in the relation among plant organs and in the relations among neighboring cells.
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08 Feb 2011
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TL;DR: This monograph discusses the development of experimental methods to study ABSCmission, and the role ofIGNIN, CALLOSE, and TYLOSes in theorganization of ABSCISSION.
Abstract: INTRODUCTION ... ........ ...... 133 DEVELOPMENT OF EXPERIMENTAL METHODS TO STUDY ABSCISSION . 135 THE TIME COURSE OF ABSCISSION ....... 136 INFLUENCE OF HORMONES ON THE TIME COURSE 137 The Lag Phase 137 The Separation Phase 139 ANATOMY OF ABSCISSION ...... , , 140 Structural Features of Abscission Zones 140 Changes During the Lag Phase 143 Changes During the Separation Phase 145 BIOCHEMISTRY OF WALL BREAKDOWN 148 OTHER ENZYMIC CHANGES DURING CELL SEPARATION ,.... 152 ROLE OF LIGNIN, CALLOSE. AND TYLOSES , ,.... 153 MECHANICS OF SEPARATION . ........ ........ .. ..... ......... 153 ORGANIZATION OF ABSCISSION .... 155 SUMMARY AND CONCLUSIONS .... ........ 157
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TL;DR: An electrostatic spray apparatus and method for spraying electrically conductive coating materials on a continuous basis from an electrically grounded bulk coating supply.
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TL;DR: Data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules, and the similarity in the kinetics of inhibition between abscisin and 8-azaguanine or 6-methylpurine on the other suggests that abscillin may exert its action by inhibiting the synthesisOf these enzyme- specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit.
Abstract: Gibberellic acid (GA) enhances the synthesis of alpha-amylase and ribonuclease in isolated aleurone layers and this process is inhibited by abscisin. Removal of gibberellic acid in mid-course of alpha-amylase production results in a slowing down of alpha-amylase synthesis, suggesting a continued requirement of GA for enzyme synthesis. This is paralleled by a continuous requirement for RNA synthesis. Addition of 6-methylpurine or 8-azaguanine in mid-course results in an inhibition of alpha-amylase synthesis within 3 to 4 hours. However, actinomycin D added in mid-course is almost without effect. This is not due to its failure to enter the cells, because it does inhibit (14)C-uridine incorporation at this stage. Addition of abscisin to aleurone layers which are synthesizing alpha-amylase results in an inhibition of this synthesis within 2 to 3 hours. Cycloheximide on the other hand inhibits enzyme synthesis immediately upon its addition. These data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules. The similarity in the kinetics of inhibition between abscisin on the one hand and 8-azaguanine or 6-methylpurine on the other suggests that abscisin may exert its action by inhibiting the synthesis of these enzyme-specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit.
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