Why not glucose?

Sugar is made up of molecules containing carbon, hydrogen, and oxygen. Because plants get their carbon from carbon dioxide in the air, and both hydrogen and oxygen from water taken up through the roots, there is never a scarcity of these elements available to the plant, so sugar provides no nutrients for the plant. Plants make and store their own food, sugar, during photosynthesis.

A tablespoon of sugar in a gallon of water has the same effect on a plants ability to take up water as a tablespoon of table salt. Plants rely on solutes inside their cells to 'pull' water through cell walls (osmosis). As the level of solutes in the solution outside of cells increases, it becomes increasingly more difficult for the plant to take up water and the nutrients dissolved in water. You can see that sugar has no direct benefit to plants, and is more likely to do harm.

What sugar MIGHT do, is provide a carbohydrate source of food for soil organisms that enrich mineral soils. Remember though, that you need to take into account the amount of other solutes in the soil (like fertilizer) because sugar applications oversupplied can cause fertilizer burn as quickly as fertilizer.

Al

Thanks Al, the same principle as avoiding fertilizing a plant when it is under water stress.

Unfortunately we are beset with strong winds here at the moment, so I am just keeping the water trickling and hoping.

Cheers
Eleanor