This subject of chromosome doubling came up at the Rose Hybridizers Forum, so I had to go digging through CDs to find some old pictures. Still haven't found all of the ones I wanted, but found this one and a bunch of other old images that were "a walk down memory lane". So, since there isn't a whole lot going on outside right now, I'll probably recycle those old images in the next couple of weeks or so - January might just end up being "MAPRC history month" LOL
Now back to chromosome doubling... this image shows the old sterile rose hybrid, Rosa X paulii, that had been treated with trifluralin in an attempt to induce chromosome doubling (and hopefully restore fertility as an amphidiploid). The branch on the left grew from one of the surviving leaf axil buds of a treated shoot tip. It was showing great potential with relatively stable changed morphology (hallmarks of polyploidy) - rounder leaflet shape, rumpled leaf surface texture, and more coarsely toothed edges compared to the normal untreated branch on the right. All other buds that regrew from treated shoot tips would at best show some transient effects from the trifluralin that disappeared gradually as the new shoots grew out.
Sadly, I lost this one, so we'll never be able to check it microscopically or know how it might have behaved as a parent.