How to prevent WMS caching on client side with OpenLayers

Question

I have created a WMS object like this:

var wms_Layer = new OpenLayers.Layer.WMS("Plant Date", "http://vmap0.tiles.osgeo.org/wms/vmap0", {
    layers: 'test',
    datasource: 'WMS',
    format: 'image/png',
    transparent: true,
    visibility: true
});

and for drawing I tried both wms_Layer.redraw(); & wms_Layer.redraw(true);

After launching the web browser I can retrieve the layer data, but the problem is the layer data is getting cached by default, which means until a new layer date comes from server the client hold the older data, is there a way to prevent the caching?