Photosynthesis in Higher Plants

Kranz anatomy is the special leaf anatomy of $C_4$ plants, in which large bundle sheath cells are arranged like a wreath around the vascular bundles.
The bundle sheath cells may form several layers; they are characterised by a large number of chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.
The thick, gas-tight walls keep the $CO_2$ released from the $C_4$ acid concentrated around RuBisCO, which prevents photorespiration.
Thin walls with intercellular spaces are features of the mesophyll cells.
Hence the bundle sheath cells have thick walls, no intercellular spaces and a large number of chloroplasts.

Photolysis (splitting) of water is associated with photosystem II, on the inner side of the thylakoid membrane: $2H_2O \rightarrow 4H^+ + O_2 + 4e^-$
The electrons released replace those removed from PS II; oxygen is evolved as a by-product.
The oxygen-evolving complex contains manganese; manganese (with chloride ions) is needed for the splitting of water to liberate oxygen during photosynthesis.
Copper is a component of plastocyanin, boron is needed for pollen germination and membrane function, and zinc activates carboxylases and is needed for auxin synthesis.
Hence manganese is essential for photolysis of water.