Sugars and osmolytes
Trehalose, sucrose, mannitol, stevioside and xylose appear across the Boost range. Some are osmoprotectants, some are carbon, and one is a cross-pillar ingredient.
Why sugars appear in crop inputs
Three distinct reasons, often conflated. As osmolytes, certain sugars and polyols accumulate in cells under water stress and protect proteins and membranes. As a carbon source they feed rhizosphere microorganisms, which is a real if indirect effect. And as formulation components sugars act as humectants, stickers and antioxidant stabilisers.
A sugar in a product may be there for any of these, and the label rarely distinguishes them.
Trehalose
The most interesting of the group. A disaccharide of two glucose units, and one of the most effective known protectants against desiccation — the mechanism that allows some organisms to survive near-complete drying and rehydrate intact. It stabilises membranes and proteins by replacing water at their surfaces. In plants it also has a signalling role, with trehalose-6-phosphate involved in carbon status sensing.
It appears in Brix Boost and Cellular Boost. It is also a cosmetic humectant, used in Vegalab's Hydrating NanoSerum and the Youlief Peptiderma cream — a genuine cross-pillar compound, though the mechanisms differ enough that the two pages can reasonably stand separately, each stating its scope.
Mannitol, sucrose, stevioside, xylose
Mannitol is a sugar alcohol and osmolyte, accumulated by some plants under stress, with additional reactive-oxygen-scavenging activity. In Brix Boost.
Sucrose is straightforward carbon and a formulation humectant, in Balance Boost, Calcium Boost and Pollen Boost.
Stevioside, the steviol glycoside from Stevia rebaudiana, and xylose, a pentose sugar, both appear in Brix Boost. Their rationale there is less clear than the osmolytes' and would benefit from being stated: a Brix product containing sugars invites the question of whether measured Brix increase reflects plant metabolism or applied sugar, and an honest page should address that directly rather than leave it hanging.
What does sugars and osmolytes not do?
Applied sugars are not a significant carbon or energy source for the plant at use rates — plants make their own by photosynthesis, and foliar sugar uptake is limited. They do not increase yield potential. And sugar applications can feed pathogens as readily as beneficials, so heavy foliar sugar in humid conditions is not risk-free.