Potassium permanganate fixative and the electron microscopy of sieve tube contents

Sieve tube "slime" is probably fibrillar as suggested by other workers. The granular material seen in electron micrographs of sieve tubes "fixed" with potassium permanganate is mostly a precipitate produced by the reaction of the permanganate with the sieve tube contents, particularly with sucrose, and with reagents used in the fixing, dehydrating and embedding process. Potassium permanganate is not therefore a good fixative for the electron microscopy of sieve tube contents. Neither is it suitable for the study of fine structure in vacuoles or vesicles containing precipitable solutes in other kinds of cells nor for examining the fine structure of their ground cytoplasm.

The conduction of sap : II. Detection of vibrations produced by sap cavitation in Ricinus xylem

An apparatus has been constructed for the detection of vibrations generated within plant tissue. This can detect vibrations due to water cavitation within fern sporangia. Using this detector 'clicks' have been obtained from Ricinus petioles and leaves in a condition when, from previous work, water cavitation might be expected.Evidence is provided to show: 1. That 'click' production is correlated with the water status of the plant tissue. 2. There are reasons for opposing the possibility that 'clicks' result from tissue fracture alone. 3. The 'clicks' may be detected in a wide range of plants. The implications of the apparent vulnerability of water conducting systems in plants are discussed.

Effects of atelectasis on pulmonary surfactant and quasi-static lung mechanics

The effects of unilateral atelectasis on pulmonary surfactant activity and lung mechanics have been studied in rabbits. Total left lung collapse was produced by pneumothorax and maintained from 90 min to 8 days. Quasi-static pressure-volume relationships were determined with air and saline after varying intervals. Surface activity of minced lung extracts and of dried foam obtained by tracheal washings was measured on a surface balance. A marked decrease in lung inflatability progressing with duration of collapse was noted during air and saline pressure-volume studies. However, deflation characteristics of all atelectatic lungs were normal. Extracts from minced, in vitro reinflated atelectatic lung showed a variable but significant loss of surface activity compared to the right (normal) lung of the same animal. However, highly surface-active material could be demonstrated in the collapsed lungs by the more efficient extraction procedure of tracheal foaming. Correlation exists therefore between normal volume stability of alveoli after initial inflation and presence of surfactant activity in atelectatic lungs.

pressure-volume relationships; rabbit lung surface activity

Submitted on July 27, 1964