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Description
This programme illustrates sections of the text of Unit 3 and is in three parts. The speakers are Dr. Helen Adamson and Dr. Don Adamson, visiting lecturers in Biology at the Open University. The fi...rst part of the programme contrasts the negative pressure which commonly occurs in the xylem of transpiring plants with the positive pressure that is usual in the phloem. The tension in the xylem is demonstrated using a Scholander pressure bomb and the pressure in the phloem is demonstrated as exudate from the cut mouth parts of the aphids. The treatment concentrates on showing the two techniques, not on discussing results obtained from them. The wider question of the mechanism of cytoplasmic movement in plants is then considered. This question is presented in a speculative way, using film sequences showing movement of cytoplasm from giant algae cells. The possible connection between this process and the movement of substance in the phloem is then discussed. In the second half of the programme the difficulties of investigating the mechanism of phloem transport are discussed and film of living phloem is examined.
Metadata describing this Open University video programme
Module code and title: S22-, Comparative physiology
Item code: S22-; 03; 1972
Series: Comparative physiology
Episode 3
First transmission date: 19-02-1972
Published: 1972
Rights Statement: Rights owned or controlled by The Open University
Restrictions on use: This material can be used in accordance with The Open University conditions of use. A link to the conditions can be found at the bottom of all OUDA web pages.
Duration: 00:24:15
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Producer: Tony Laryea
Contributors: Don Adamson; Heather Adamson
Publisher: BBC Open University
Keyword(s): Cytoplasmic movement; Giant algae cells; Negative pressure; Phloem; Scholander pressure bomb; Xylem
Footage description: Heather Adamson cuts a leaf from a transpiring plant to show that the water in its xylem is under tension. She uses a Scholander pressure bomb to demonstrate the negative pressure in the xylem using specimen with wilted and turgid leaves. Tension in the two is markedly different. Film shots of an experiment which demonstrates the existence of positive pressure in the phloem. Exudates from the cut mouth parts of aphids are shown under magnification. Commentary by Heather Adamson. Heather Adamson sums up the two experiments above. Don Adamson explains the difficulties of examining, microscopically, organic movement in phloem, particularly living phloem. He explains the techniques necessary to make it possible. Adamson uses a diagram to aid his discussion. Film shots under magnification, of living phloem showing longitudinal movement of organic matter. Commentary by Don Adamson. Don Adamson goes on to examine cytoplasmic streaming and discusses the possible connection between it and movement in phloem. He explains why giant algal cells are suitable for the study of cytoplasmic streaming. Shot of a giant algal cell. Don Adamson with a model of a section of giant algal cell wall. He peels back the various layers and explains the composition of each. Film shots of a section of giant algal cell under magnification showing cytoplasmic streaming. The various layers of the cell wall can also be seen. Don Adamson introduces another film sequence. Film shots of a several section of giant algal cell under magnification showing the sol streaming out. The vacuole content of the sol is held in. Don Adamson discusses the possibility of the existence of fibrils in the sol which could be responsible for the movement. Several film shots of rotating fibrils in the sol (under magnification). Don Adamson discusses the possibility of fibriloid proteins being present in phloem sieve tube elements. He shows a microphoto-graph of the ends of two sieve tube elements showing fibriloid material. Adamson sums up the difficulties of investigating the mechanics of phloem transport.
Master spool number: 6LT/70364
Production number: 00521_2121
Videofinder number: 3577
Available to public: no