Think of it this way, if you donated a pint and then got into an accident severely cut your arm, would your survival be increased or decreased because you have less blood? The answer is the for you and plants, decrease.

montane1, roots take up water; leaves transpire water. Here is a thought. "Pruning plants can help by reducing the amount of foliage that is losing water. However, trimming should be done carefully. Severe pruning opens up the plant to more sunlight and, consequently, more water loss during midsummer". From Water efficient Gardening and Landscaping. Denny Shrock. Dept. of Horticulture. University of Missouri.
Hope this helps.

I started to write a long response to this tread because there are many factors that go into this, but I'm going to end up with just the summary:

Pruning newly transplanted plants is almost never a good idea. Pruning a plant initiates a response (including an attempt to replace the foliage lost) by the plant that takes energy away from the plant's ability to recover from its root loss. It will almost always adds to the stress experienced by the plant and increase the time required for the plant to become established rather than decreasing stress or improving the odds that the plant will survive. The need to match the top-growth/foliage to the root mass when transplanting is an old theory long ago proven to be wrong. Even some nurseries resist changing what they were taught years ago, but all modern research strongly indicates a need not to prune healthy wood/foliage at transplant.

Using the term 'plant'instead any specific plant makes many answers possible. Al