Pulvinus

Cross-section through a pulvinus in the petiole of a cotyledon of Oxalis rosea , from: Charles Darwin (1880): The Power of Movement in Plants .
p - petiole
f - vascular bundle
b - leaf attachment

As pulvini (singular: pulvinus) thickened places in the stems or at the base of the leaflets are of plant leaves referred to as joints act. They allow relatively fast, growth-independent movements ( nastia ), such as day-dependent leaf movements , which occur among other things in umbrella acacias and mimosas .

Anatomically, they consist of a central vascular bundle surrounded by thin-walled parenchymal cells . By taking up or releasing mainly potassium ions , the latter cells can change their turgor pressure and thereby expand or contract. An expansion of the parenchyma on top of the pulvinus leads to a downward movement of the associated organ and vice versa.

swell

Peter H. Raven, Ray F. Evert, Susan E. Eichhorn: Biology of plants . 3. Edition. de Gruyter, Berlin, New York 2000, ISBN 3-11-015462-5 .

Web links

Pulvinus in the compact lexicon of biology (www.wissenschaft-online.de)