White Patches On Geranium Leaves

Had I not seen it with my own eyes, I never would have believed geraniums (pelargoniums) could catch sunburn (sun scorch). Apparently so. This raises an interesting question; what has happened to the thick cuticle (see 'Plant tissues') which protects against the sun?

Kept in low light conditions for a long time, the plant will have adapted itself to these - probably reducing (or even almost removing) its waxy cuticle (sun and water-loss protection). It would be interesting to confirm this by taking a leaf section and viewing under a magnification. I say this because leaf size has also increased in low light (leaves do this, and vice versa). It might be that the cuticle is still in tact, but the plant has itself jettisoned some chlorophyll and perhaps mesophyll tissue for reasons best known only to itself. In other words, this reaction is the plant's way of reducing its leaf area.