Diamonds on the leaves of my cukes

Every morning when I go into my greenhouse I see rows of tiny sparkling droplets hanging off the edge of the cucumber leaves.

I thought it was something to do with transpiration but I find that it's a phenomenon common in many plants and known as guttation. It's a way of removing excess water overnight via tiny structures called hydathodes.
(I was already familiar with the same phenomenon in fungi, see here for example.)

Apparently these 'night sweats' are valuable to insects,  acting as  handy mini-bars but uh-uh... they can contain insecticide residue if the plant has been  treated with such:


 "It was found that when bees consume guttation drops collected from plants grown from neonicotinoid-coated seeds, they die within a few minutes."