Determination of malate levels during the swelling of vacuoles isolated from guard-cell protoplasts

Schnabl, H.; Kottmeier, C.

Planta 161(1): 27-31

1984


ISSN/ISBN: 0032-0935
PMID: 24253551
DOI: 10.1007/bf00951456
Accession: 052532843

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Abstract
A method for the preparation of vacuoles from guard cells ofVicia faba L. is described. Vacuoles were released from guard-cell protoplasts by osmotic shock and purified on a Ficoll gradient. Contamination of the vacuoles was examined by assaying marker enzymes, such as fumarase, glucose-6-phosphate dehydrogenase, phosphofructokinase, acid phosphatase and mannosidase. Potassium ions in the incubation medium caused increases in the volume of the vacuoles by a factor of about 2.6, while the malate level remained unchanged. In contrast, malate synthesis was stimulated during the swelling phase when complete guard-cell protoplasts were exposed to K(+). The possible role of K(+) as an efficient osmotic effector is discussed.