Like dinosaurs, being huge is not an advantage throughout history and Paris japonica stands a greater chance of extinction because of its large genome, say researchers.

Paris japonica has 152.23 picograms (pg) of DNA, 50 times bigger than the human genome, which is 3.0 picograms. A picogram is one trillionth of a gram.

Why does that matter?  The more DNA there is in a genome, the longer it takes for a cell to copy all of its DNA and divide, thus a key reason why plants living in deserts which must grow quickly after rains have small genomes enabling them to grow rapidly.

The smallest genome?  A parasitecalled Encephalitozoon intestinalis, which has just 0.0023 picograms of DNA.

Reported in the Botanical Journal of the Linnean Society.