Sex-change tree, Pluto's cryovolcanoes, Sellafield's plutonium, Ant super-organisms

Britain's oldest tree changes sex - The science behind the headlines - this week it was reported that the Fortingall Yew in Perthshire (known to be a male tree, over 2-5000 years old) had started to produce berries (female) on one of its branches. Dr. Max Coleman from the Royal Botanic Gardens in Edinburgh explains that sexuality in plants is more fluid than in animals.

Cryo-volcanoes on Pluto The latest observations from the New Horizons mission to Pluto show possible volcanic-type structures made from ice. The mountains have what appear to be caldera-like depressions in the top. Unlike volcanoes on Earth, that erupt molten rock, the suspected volcanoes on Pluto, would likely erupt an icy slush of substances such as water, nitrogen, ammonia or methane.

Sellafield's plutonium The nuclear reprocessing plant in Cumbria has amassed around 140 tonnes of plutonium on site. This is the largest stockpile of civil plutonium in the world. For now it is being stored without a long-term plan, which is costly and insecure. At some point a decision will need to be taken on how it is dealt with. The estimated clean-up costs are between £90-250 billion, which means the pressure to make the right decision is massive. Should we convert it into useable fuel or get rid of it? And how secure is it in its current state?

Ant super-organisms Ants behave as a super-organism when under predation threat - complex chemical communication in rock ants are key to how they behave as a unit to different threats.

Producer: Fiona Roberts.