Wakehurst Place Botanical Garden

Millennium Seed Bank

/ Benologist / Leave a comment

During my school trip to the Wakehurst Place Botanic Gardens, in which I learned about DNA extraction and performed surveys, the highlight was the visit to the Millennium Seed Bank, the largest collection of wild plant seeds in the world. The seed bank plans to prevent extinction of endangered, endemic or economically useful plant species by collecting a variety of genetically diverse seed samples, which can be stored for use in medical and biological research as well as replenishment of damaged species. In 2009 the Millennium Bank achieved its goal of storing 10% of all the world plant species, gathered from over 150 different countries, using their connections to 80 organisations across the globe. If they continue to progress at the rate they have been, they hope to have gathered a staggering 25% of all wild plant species by 2020.

The Millennium Seed Bank building, created to look like the Sea Bean, one of my favourite plants, and like the seeds they keep underground, capable of lasting years without germinating.

Once inside the building, we were taken through the intricate process that the seeds go through in order to last hundreds, or possibly thousands of years while still remaining capable of germination when needed by future generations. Orthodox seeds can be preserved through a slow drying, sucking the moisture out of them in order to slow down the metabolic rate of the seed, and thus allow it to live for much longer than normal. The seeds are taken to a drying room, kept at a constant 15°C and 15% air humidity, and left in small brown cloth bags until they are completely dry. The variety of seeds in the room is astounding, and looking at one stack of boxes alone, I see seeds from Mexico, Japan, Scotland, America and a colourful myriad of other exotic locations, showing the scale and depth of the project at Wakehurst Place. It is a simple yet effective procedure, with each percent of moisture lost lengthening the seed’s life by nearly a decade. We couldn’t stay long in the drying room however, as our mere presence was enough to send the humidity up, potentially damaging future seeds.

Bags of seeds and grasses, left out to dry.

After the seeds are dry and ready, the extra chaff and husk are gleaned away, using a variety of sieves and shakers, separating out the actual germinating segment of the plant. These seeds are then x-rayed to check for internal attack from grubs and moulds, which, if released into the seed bank vault, could do a lot of damage the chances of future plants germinating. Recently, a new species of insect was discovered in the seeds here, a creature that survived and lived most of its life inside the seeds of this one particular plant, and had been caught when they examined the dried seeds for signs of attack. The now tested seeds can then be stored in the vault, a huge refrigerator kept safely behind colossal vault doors, underneath the Millennium building. The vault is like a bank, not only to protect the seeds from damage by the elements, but also because the net cost to replace the seeds in the bank is in the millions of pounds. Kept at -20 degrees to slow metabolic reactions further, and shielded behind concrete capable of withstanding a plane crash from nearby Gatwick airport, the seeds are in capable hands.

Sadly, not all of the seeds at Wakehurst are willing to be dried and frozen away, especially tropical plants, which are considered unorthodox, or recalcitrant. The act of drying these seeds would kill them, making them useless for experimentation and growth, and so more extreme measures must be taken. In a process known as cryopreservation, the seeds have their embryos removed and stored in liquid nitrogen, at -196°C. If even this fails, there is always room in Wakehurst Place’s extensive botanical gardens for the more stubborn plants, that must be grown to preserve for future generations.

It was a true privilege to be allowed a behind the scenes tour of the Millennium Seed Bank, looking into the ingenious ways samples are preserved, and glancing into the freezing vaults where the hope for thousands of endangered and rare plants are being stored, ready to be used in the next medical breakthrough, or cultivated to preserve dying species of plants all across the world.

Gel Electrophoresis

/ Benologist / 1 Comment

At the labs of the Wakehurst Place Botanical Gardens, I was given the chance to separate and identify DNA strands using a method known as gel electrophoresis. At Wakehurst, it is important that they can identify and recognise DNA from different species of plant, both to uphold the rules of CITES, an international initiative for the preservation of biodiversity, and to help with research and identification of their own specimens. Given the DNA samples of two types of timber, that the lumber companies claimed were cut in a particular forest approved by CITES, and a known sample from that certified forest, we were asked to determine if the two lumber samples had indeed come from the woodland they were supposed by be from.

First, I removed 20 micrometres of the known DNA sample from the sample given, using a very precise pipette designed specifically for this purpose. I then placed the sample in a small vial, already containing a naturally occurring enzyme called DNA helicase, that is used in the body to unzip DNA while transcription is taking place. The enzyme unzipped the antiparallel strands of nucleotides that form the DNA molecule and cut them into smaller pieces that we can use to identify where the DNA is from. Having given the mixture a firm shake to ensure that it is fully reacted, I stained the DNA to make sure I could see where it was during the electrophoresis segment of the procedure, that would follow.

We then submerged a piece of extremely even and well textured agar jelly into a buffer solution, which the DNA would move through in a process somewhat similar to chromatography. Injecting the DNA into a hole in the agar, and then running an electric current through the buffer caused the pieces of DNA to separate into identifiable bands. This happens because DNA is a negatively charged molecule, due to its phosphate groups, and so will travel towards the anode of the electric currect, the smaller and faster pieces going further.

We all put our developed samples into the gel, and after about 20 minutes of sitting in the electric current, we were able to compare the results. The known sample from the approved forest showed three distinct bands of DNA, while the 2 samples from the lumber companies showed 2 and 1 respectively, meaning with wood was illegally taken from forests that may well be endangered or declining. The wood would be confiscated, and the companies fined, and any usable lumber will be distributed freely in order to ensure that nobody profits from damaging the threatened woodland.

It was very interesting to see how DNA is extracted and compared, as well as learning about its practical application when dealing with the illegal import and export of endangered species across the world. I hope that I have another chance to sample DNA again in the future.

Wakehurst Meadow Survey

/ Benologist / Leave a comment

The Wakehurst Place Botanical Gardens are one of the last places in Britain where it is possible to find natural meadow or forest. Most meadows across the country are scoured of their native inhabiting grasses and flowers through centuries of management, farmers choosing to plant crops or new, often Italian, grasses that take more easily to fertilisers and provide a healthy and easy to grow feedstock for their animals. This makes true natural meadow, with actual British wildlife very rare, so it was interesting to see what species lived in one of the last preserved meadows.

Using measuring tape and a set of quadrats, we created a transect leading from the middle of the meadow towards the managed treeline of the neighbouring forest. A quadrat is a square metal frame, 1m by 1m in area, used by Biologists to take a sample of a habitat and measure the diversity and species abundance of the whole area. It would be ridiculous and time consuming to search the whole field and note down what lived there, but by taking this sample, I could get an idea of what lived in the rest of the field, while also seeing how the species abundance changed as I approached the forest.

In the centre of the field the field grass coverage was near absolute, with gaps in the green breaking out where moles had previously tunnelled to the surface, and apart from the occasional buttercup or ribwort plantain, not many larger plants lived there. As we approached the forest line, however, we found a greater abundance of different plants, the biodiversity increasing as the shade of the forest made it harder for the grass to dominate the land. Species like knapweed, devil’s-bit scabious, a flower that acts as home to larvae of Marsh Fritillary butterflies, and Birdsfoot Trefoils, sometimes referred to as ‘Bacon and Eggs’ due to the red and yellow colouration of their flowers. Interestingly, the Trefoil releases dangerous cyanide when it is chewed, although it is in such small amounts it is unlikely to be harmful to larger mammals such as humans.

The Birdsfoot Trefoil sitting within my quadrat.

At the edge of the oak woodland, the ground gave way to ferns, before dying out to woodland plants, such as violets and archangels, covered in tiny white spots, that act as magnifying  glasses to focus light onto their leaves. Just before the meadow became forest, we found a group of three tiny Common Frogs, freshly transformed from tadpoles and making their way from the lake at the base of the meadow deeper inland. It was great to see the variety of interesting plant species that grow in our native meadows, especially as it is so easy to forget how amazing our own country is, when shown the brightly coloured rainforests of Brazil, or the volcanic tundra of Greenland. Even such a short way from home I am able to stand in an incredibly rare environment.