The action of the plant growth hormone

Although the control of cell elongation in plant tissues by a special growth-promoting substance or substances has been well established for some time, the processes by which this substance is able to bring about growth have remained obscure. Since the general properties of the response to growth substance by plant tissues, in particular of the Arena coleoptiles which have been most extensively studied, have been recently summarized by Thimann and Bonner (1933), only the principal points of interest for the present discussion need be given. These are briefly as follows: (a) The growth-promoting substance of the Avena coleoptile is produced only in the coleoptile tip and passes from there downward (Went, 1928). After removal of the tip new growth substance is formed by the uppermost cells of the stump ("physiological regeneration," Dolk, 1926). (b) The growth of the Avena coleoptile is for some time proportional to the amount of growth substance supplied to it (Thimann and Bonner, 1933). (c) The growth substance which enters the plant and causes growth cannot be recovered; i.e., is used up (Went, 1928). (d) Growth substance is an unsaturated acid of empirical formula C18H32O5 (Kögl, Haagen-Smit and Erxleben, 1933) and readily loses its growth-promoting activity by oxidation. (e) The growth substance is a true hormone, i.e., it acts in minute amounts and bears no direct stoichiometrical relationship to the number of molecules of soluble substance transformed during growth into, for example, cell walls. Thus one molecule of growth substance causes an amount of growth of the Avena coleoptile at 27°C. which requires the changing of 3 X 10^5 molecules of hexose to cellulose in cell walls (Thimann and Bonner, 1933). The changes in the physical properties of coleoptiles under the influence of growth substance have been studied to some extent. Heyn (1931), and independently, Söding (1931, 1932) have shown that the plasticity, and also to a considerable extent the elasticity, of the coleoptile is increased after action of growth substance, and that this increase is independent of whether growth has occurred or not; i.e., this action of growth substance is preliminary to active elongation. Heyn also found an increase in extensibility in coleoptiles which had been plasmolyzed after growth substance action, so that it is the physical properties of the cell wall, and not of the protoplasm, which are changed. The action of growth substance has now been further studied, and a few of the results will be described in the present paper. This study has been made easier by discovery of the fact that short sections of coleoptiles grow at a rapid rate if immersed in a growth substance solution of suitable concentration. This method of using coleoptiles is convenient because, under proper conditions, a large amount of growth takes place in a relatively short time, and the "physiological regeneration" mentioned in (a) occurs slightly or not at all. It has the added advantage that the effect of known concentrations of growth substance upon the growth of younger and older portions of the same coleoptile may be examined independently

The growth and respiration of the Avena coleoptile

In a previous paper (1) a relation was shown to exist between the respiration of the plant cell and its elongation under the influence of the plant growth hormone. A more extensive investigation of this relation was therefore undertaken with the hope that elongation would exhibit a close correlation with some relatively accessible property of the respiration, for example with the magnitude or the respiratory quotient of the latter. It may be said at once, however, that this was not the case, and that the work reported in the present paper, while revealing several points of interest and defining more clearly the dependence of elongation upon respiration, has not resulted in any explanation of the way in which respiration is essential to growth

Promoting Justice in the Classroom: Looking Beyond the Label to See the Individual

Christian educators are faced with the task of promoting and encouraging justice from the viewpoint of Christ as they encounter the broad strokes of diversity within their classrooms and schools. Following Christ means that the Christian educator must look beyond the labels that have been applied by the religious and secular to see each student as made in the image of God. This article presents a paradigm that recognizes the worth of each individual within the context of the student’s background knowledge, language abilities, academic achievement, and behavior (BLAB) instead of the singularly focused labels that marginalize students

A reversible growth inhibition of isolated tomato roots

Introduction. - It is known that certain bacteria are inhibited in their growth by the presence of sulfanilamide or related compounds in the nutrient medium, and it has been suggested by Fildes(1) and by Woods(2) that this inhibition is due to specific interference with the utilization of essential metabolites, in particular p-amino benzoic acid. In the present paper data will be presented which show that the growth of isolated tomato roots(3) is inhibited in the presence of appropriate concentrations of sulfanilamide or its derivatives, but that this growth inhibition can be in whole or in part abolished by the further presence of p-amino benzoic acid, a substance not otherwise essential as a supplement for the growth of isolated tomato roots

Plant tissue cultures from a hormone point of view

A botanist, Haberlandt,(1) first pointed out the possibilities of the culture of isolated tissues. He suggested that not only could the potentialities of individual cells be determined, but that also some insight might be gained as to the reciprocal influences of tissues upon one another, that is, as to "correlation.

Building a Community of Christ in a Mathematics Classroom

The prevalence of mathematics anxiety and math phobia is an accepted phenomenon in our culture today (Boaler, 2013; Kimball & Smith, 2013). Multiple research studies have been conducted investigating the levels of mathematics anxiety present in both preservice and in-service elementary education teachers (Bekdemir, 2010; Mizala, Martínez, & Martínez, 2015). This article describes how the creation of a learning community within a two-course sequence of mathematics content courses for elementary teachers addressed the fears and anxieties of a cohort of prospective female teachers. The learning community was founded on three perspectives: Palmer’s (1989) community of truth, Paul’s description of the church as a human body in 1 Corinthians 12, and Jolliff’s (2009) reinterpretation of Guthrie’s (1963) lonesome valley experience by a solitary traveler. Themes expressed by the students in their reflections after the second course included greater conceptual understanding, an emphasis on both individual and community learning, reduced anxiety, attention to multiple perspectives, and the ability to learn as both a teacher and a student

Understanding the role of knowledge in the practice of expert nephrology nurses in Australia

This paper, which is abstracted from a larger study into the acquisition and exercise of nephrology nursing expertise, aims to explore the role of knowledge in expert practice. Using grounded theory methodology, the study involved 17 registered nurses who were practicing in a metropolitan renal unit in New South Wales, Australia. Concurrent data collection and analysis was undertaken, incorporating participants' observations and interviews. Having extensive nephrology nursing knowledge was a striking characteristic of a nursing expert. Expert nurses clearly relied on and utilized extensive nephrology nursing knowledge to practice. Of importance for nursing, the results of this study indicate that domain-specific knowledge is a crucial feature of expert practice

Do I Dare Disturb the Universe?

This memoir investigates the roots of my core anxiety, the incessant but impossible ability to achieve perfection. It is framed by my experience getting a second tattoo, which is a line from T.S. Eliot\u27s modernist poem, The Love Song of J. Alfred Prufrock, and ties together both my internal struggle and my affinity for physical pain. This memoir draws a line between the past and the present, seeking to find a connection between struggling with anxiety and engaging in self-mutilation as a source of relief