What is the earliest fossil record of a plant?

Answer 1

"The oldest indications for the existence of real land plants have been found in cores from boreholes in Oman. They contained fours of mutually connected spores (tetrads) enveloped by remains of the spore sac in which they had been formed. Research on the spore walls point to a relationship with the liverworts. The fossils have been found in the Middle Ordovician and are about 475 million years old."

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Answer 2

Rhynia gwynne-vaughanii, oldest know true plant. From the early Devonian 390 000 000 years back!