London, Sep 26: The world's botanic gardens contain at least 30 per cent of all known plant species, including 41 per cent of all those classed as "threatened", a new study revealed on Monday. Through analysing datasets compiled by Botanic Gardens Conservation International (BGCI), the team led by researchers from the University of Cambridge cross-referenced the working list of known plant species -- currently sitting at 350,699 -- with the species records of a third of botanic gardens on the planet, some 1,116 institutions. This provides a "minimum estimate" for the plant diversity held in botanic gardens, Xinhua quoted the team as saying. The study found that the global network of botanic gardens conserves living plants representing almost two-thirds of plant "genera" (the classification above species) and over 90 per cent of plant families. But the team also pointed out that there is a significant imbalance between temperate and tropical regions. Some 60 per cent of temperate plant species were represented in botanic gardens but only 25 per cent of tropical species, despite the fact that the majority of plant species are tropical, according to the study. "Currently, an estimated one fifth of plant diversity is under threat, yet there is no technical reason why any plant species should become extinct. Botanic gardens protect an astonishing amount of plant diversity in cultivation, but we need to respond directly to the extinction crisis," said senior author Samuel Brockington from the University of Cambridge. "If we do not conserve our plant diversity, humanity will struggle to solve the global challenges of food and fuel security, environmental degradation, and climate change," Brockington added. The study has been published in the journal Nature Plants.