Abstrakt
Brassinosteroids are phytohormones that regulate various plant metabolic processes including photosynthesis. However, it is not yet clear which part of photosynthesis is the main site of brassinosteroid action.
One possibility is brassinosteroid involvement in the regulation of primary photosynthetic processes. The data obtained from brassinosteroid-treated plants or mutants clearly suggest that both the function and organization of the photosynthetic complexes located in thylakoid membranes are affected by these phytohormones.
Some plant families or species are perhaps more sensitive to brassinosteroid imbalance than others and plant development is probably also an important factor. Although the studies dealing with this topic seem to indicate that the role of brassinosteroids in the regulation of the photosynthetic electron-transport chain is a secondary one, the evidence for brassinosteroids acting as direct regulators of the stability of the oxygen-evolving complex of Photosystem II exists.
Moreover, Photosystem I seems to also be somehow regulated by these compounds.