[Hilary]

I saw this in the Evrotas river bed, near Sparta at the end of March Last year.
The river was running in a narrow channel and this plant was growing among the pebbles of  what would be covered in water earlier in the year when there would be more water in the river
I am afraid I don't have a good photo of its leaves

[John]

I'm pretty sure it's Lunaria annua, Honesty. Interestingly it appear to have the virus that afflicts it in many gardens in Britain which causes the white streaking.

[ezeiza]

Bad news. What could prevent it from infecting other plants in the same family (or others, alas)

[John]

Only elimination!

[Hilary]

Thanks for the identification.
Looking at the original photo there is even one of the seed pods somewhere around.
Also the leaves and stalk are the same.
This was the only plant in the river gravel.
Photos I have of Lunaria annua at Mystras and other places on Taygetus don't have the white streaks.
I suppose that is what put me off identifying it in the first place, that  and not taking my time to note all the points which help in identifying plants