A time machine for botanists

MAGNIFICENT TREES SWAY gracefully in the Botanical Gardens near the red brick Botany Building where the Department of Biological and Environmental Sciences is housed. When it rains, the wind drags on their greyish brown branches. The idea that some of these trees were planted more than a hundred years ago fascinates botanist Carl Skottsberg. He was also the founder of Herbarium GB.

Director Claes Persson meets the interviewer at the entrance of the Botany Building with curator Claes Gustafsson.

“We lend material to researchers all over the world and our researchers can lend us material here for safekeeping,” says Claes Persson as he leads the way into the Herbarium, which is housed on two floors of the Botany Building.

600 square metres in three large rooms accommodate more than one million plants, fungi and algae. No small number in comparison to the 390 million samples found in the world’s 3,100 herbariums, where the Herbarium of the University of Gothenburg ranks as one of the 50 largest of these.

“It’s a huge genetic resource that we have here,” says Claes Gustafsson enthusiastically indicating with a sweep of his hand the large number of white cabinets standing in countless rows.

HE OPENS ONE OF them and pulls out a drawer. It is brimming with herbarium specimens preserved on sheets of special paper. All material for specimens comes here unmounted. Each plant specimen is affixed with paper strips to an acid-free herbarium sheets after the specimen has been stored for three days at minus 40 degrees Celsius. The cabinets are completely sealed using silicone strips – a safe barrier against pests. Claes selects one of the sheets and brings out a sprig from the Lauraceae family, of the same genus as the avocado. The collection number and essential data are noted on the sheet: when and where the material was collected, its appearance, the colour and scent of its flowers, and where the tree grew – in this case 930 metres above sea level. The species is called Persea raimondii and is from Ecuador. This can all be read from the small label stapled to the bottom of the sheet on which the sprig is mounted.

“The researcher can use parts of every specimen we have, place them in water and bring it to a boil so that the flower becomes three-dimensional again. Pollen can be picked for pollen studies, scanning electron microscopy can magnify specimens, we can explore what pollen grains look like or examine the fruit if it is present. But the colour disappears over time, so the colour of the flower has to be recorded,” says Claes Persson.

With access to only a tiny piece of it, researchers can sequence the DNA of a specimen. In the past, this was done manually and took considerable time; today the material is sent to specialist labs instead.

“We don’t have museum objects here – the Herbarium functions as a library from which we lend specimens for study.”

MANY PLANTS IN THE Herbarium come from the Nordic countries, but all parts of the world are represented. A major project to map the flora of Ecuador has been going on since 1973. So far 97 volumes have been produced, and Claes Persson is one of the editors.

“We know a lot about plants from our region, but Ecuador, which is half the size of Sweden, has masses of species, 4000 of which are orchids,” says Claes Persson.

PLANT SPECIMENS COME to the Herbarium in a variety of ways. In the 1920s, the Herbarium purchased whole collections of plant specimens. But today collections are donated, and researchers and doctoral students supply material from their expeditions. Others come as gifts or exchanges with other herbariums.

A green box file with worn leather straps sits on a bench. Claes opens it and unsorted specimen sheets stream out; the first shows a pressed stickle wort from 1923. The collector has written his name in a flowery style: George Olsson. Probably a student in a school class.

“We get a lot of school herbariums and collections from people interested in botany. Of course, everything needs to be remounted. But most of the material does come from international researchers.”

COLLECTED AND DOCUMENTED material becomes “a slice in time”. No one knows of course what specimens botany research will need in the future. Mosses are a good example. They reproduce via spores, have no roots, assimilate nutrients from water and air and are insensitive to heavy metals. But they do store heavy metals in their tissue without being significantly affected by them.

“In the 1950s, 60s and 70s, large quantities of PCB and DDT were spread in the environment. Using time series, you can clearly see how the content of heavy metals increased in mosses during that period, to later decline in the 1980s and beyond,” says Claes Gustafsson.

The Herbarium is hugely important in being able to analyse biodiversity and detect climatic changes. This is why we want to start collecting 100 common Swedish plants such as hare bell and wild chervil every five years to be able to study any changes.

BUT UNCOMMON PLANTS also urgently need preservation. Claes opens a new cabinet and pulls out a drawer full of boxes of all sizes. He picks out a smaller casket. Inside it is a slime mould.

“We have a small group of 9,000 slime moulds that we are very proud of. They are actually not moulds, but have a peculiar vegetative stage similar to Amoebozoa. In that state they get compressed into a slime body that can creep several metres up a tree trunk and produce fruiting bodies there,” he says.

 By: Carina Eliasson