[smart (OP)]

Is exogenous glucose beneficial to plant growth in the seedling stage?

[chris]

I doubt it; the raw material produced by photosynthesis is glucose; plants use it as the substrate for everything they make and then trade their excess with soil fungi in return for other things they cannot make:

This is a link to a piece I wrote about how the mycorrhizal relationship between plants and fungi follows economic principles.

Adding sugar to the soil is more likely to feed the fungi for free making them less generous to the plants; plants also are likely to have relatively poor uptake abilities for absorbing glucose because that's something they'd never normally do.

[Bored chemist]

A bit of sugar in the water  for a vase full of flowers is supposed to keep them alive longer.

[MarkPawelek]

In the plant science books I have, they grow roots in vitro in 2% sugar solution (plus other nutrients). So (some) roots certainly absorb sugar. The only times I seen sugar recommended for plants is:
1) In the example above - cut flowers kept in sugar water
2) When transplanting root suckers. A sucker is a new shoot which sprouts from the roots of an existing plant. When transplanting suckers, the suckers will often die when one attempts to transplant a sucker with an inadequate root system. So gardening books recommend one cut a circle around the sucker 2 months before transplanting it. This gives the plant time to learn how to survive on its own root system - as the sucker will grow new roots after it's isolated from the mother plant. In practice, cutting holes into ones garden around the suckers will significantly impact the mother plant's root system, and likely as not, cause even more suckers to sprout next year!  A vicious circle. An alternative may be to carefully dig into the soil, avoiding damaging the parent plant's roots until one is able to isolate the sucker with one strategic root cut. Once a sucker is isolated like this it can be transplanted but it has a low survival rate - as its own roots may be almost non-existent. Because of this it's recommended to feed the transplanted sucker on sugar (2% looks good), for a few weeks to help it overcome transplant shock. The best time to transplant suckers seems to be in the the plant's dormant stage; in early winter.

I would not feed seeds on sugar solution.