Unformatted text preview: Mimosa pudica , turgor changes are caused by water potential changes. • The water potential of the apoplast surrounding the pulvinus joint in the petiole of the leaf drops dramatically when sucrose is “dumped” by phloem in response to the pressure signal. (A pulvinus is a special "motor organ" comprised of parenchyma cells surrounding a vascular trace, usually found at the base of the petiole, capable of rapid turgor changes, hence collapsing the tissue.) • K + ions in the pulvinus cells move into the surrounding apoplast in response to the changed water potential. Water follows the solute gradient. • When the pulvinus cells lose turgor, the leaf collapses. This takes just a few seconds at most. Pulvinus structure...
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- Fall '09
- Vascular plant, Tropism, Mimosa pudica, Thigmotropism