From Musser Forests .com on their water gel
"Musser Water Gel is designed to increase the moisture of plants and soil. It is gelatinized starch-hydrolyzed polyacrylonitrile graft copolymer (non-toxic). It comes in the form of small, dry flakes, which when mixed with water, absorb and retain 200 times their weight in water, as swollen gel particles. Acting like hundreds of tiny sponges, Musser Water Gel has the ability to absorb, release and re-absorb water again and again for several months. The dry gel should be mixed with water to create a thick slurry. Plant roots should be dipped in and out of the mix immediately prior to planting or carried to the planting site in a bucket of the mix. Musser Water Gel will retain the moisture around the roots at planting time and for several months. It will continue to attract and retain moisture at the root zone every time it rains or plants are artificially watered. Dry water gel is also used to coat seeds prior to planting. As adequate moisture is the important key factor to plant survival; combined with the drought conditions of the 1990's, we strongly recommend this product. BENEFITS: 1. Fewer losses in new plantings. 2. Faster growth rate. 3. Better moisture retention."
And on the Root Dip
"Musser Root Dip is a combination of: five live spores of Endo and Ectomycorrhizal fungi found in nature to promote root growth; Terra-Sorb Water Gel-absorbs 200 times its weight in water; Dry, Soluble Yucca Plant extract; and Soluble Sea Kelp extract and Humic Acids. The spores in this product are natural and environmentally safe. MUSSER ROOT DIP CANNOT BE FOUND AT YOUR LOCAL GARDEN CENTER, HARDWARE, OR DISCOUNT STORE."
It seems the biggest benefit is keeping terrestial roots wet more evenly.