Wednesday, November 10, 2010

Helping Plants Move onto Land

At the University of Sheffield, a group of scientists is making advances on learning how the Earth's first plants moved onto land over 470 million years ago. Their breakthrough: soil fungi.

The research provides some missing evidence that an ancient plant group formed a partnership with soil-dwelling fungi to help spread green plants across the land nearly 500 million years ago. Several groups provided input to the research, including the Royal Botanical Gardens, Kew, Imperial College London and the University of Sydney. The evidence sheds some light on the evolving relationship between the Earth's land plants and fungi.

It has been suspected that soil fungi played an essential role in assisting early land plants colonize terrestrial environments by forming mutually beneficial relationships, but there has been no evidence demonstrating how this worked. To show exactly how this happened, the team studied a thalloid liverwort plant (below), which is among the most ancient of land plants that still exists and also shares many traits with its original ancestors.

These plants were placed in controlled-environment growth rooms that simulated the conditions of the Palaeozoic era, which is when the plants were believed to have originated. Under these conditions, the benefits of the fungi for the plant's growth were significantly amplified and this favored the early association between the plant and its fungal partners. When the thalloid liverwort was colonized by fungi, its photosynthetic carbon uptake, growth, and asexual reproduction were all significantly enhanced. These factors have a clear beneficial impact on the plant's fitness.

Why does this happen? The fungi provide the plants with essential soil nutrients. This helps them grow and reproduce better, and in exchange, the fungi benefit by receiving carbon from the plants. This symbiotic relationship resulted in each individual plant being colonized by fungi that could take up the area of 1-2 times that of a tennis court.

Again, this idea has been floating around for a while, but this group was the first to provide hard evidence of the process. Professor David Beerling, from the University of Sheffield, said that "[this] shows that plants didn't get a toe-hold on land without teaming up with fungi. ... [This] will require us to think again about the crucial role of cooperation between organisms that drove fundamental changes in the ecology of our planet." This is true, and given that fungi inhabit every type of habitat in the world, it would be interesting to see if there are any other of these associations that may have shaped the Earth as we know it.

1 comment:

  1. this is really cool and makes sense because i think all plant roots are associated with fungi. however, what was it that actually triggered plants to come onto land? perhaps the first land plants began in tidal areas in which they had to deal with fluctuations between water and no water and eventually evolved to live without water completely and that fungi helped to do this. this is a complete guess though and i don't know what we know about the first plants. do fungi live in intertidal regions i wonder? do fungi live in the ocean anywhere?