Keeping the blooms alive

Ever the romantic, I bought my beloved a clump of dying plant tissue to put in a vase on the kitchen window. Of course I didn't put it quite like that when I brought them home but it's good to remember what you are buying when you pick up a bunch of flowers.

From the moment they are cut to the time when they end up in your wheelie bin, it's a battle against the inevitable to keep cut flowers alive and Spanish scientists have now shown that sugar and the plant hormones in the flowers themselves are key to keeping them looking their best long enough for your partner to forgive you for whatever you've done to offend.

A flower is a thing of beauty to be enjoyed but from a biological point of view it has a definitive job to do. The huge diversity in flower anatomy, colour and scent is largely related to pollination. Plants have evolved flowers to attract insects, birds and other animals to disperse pollen and fertilise the female reproductive organs.

From the colossal flowers of Rafflesia arnoldii – the largest flowers in the world at up to a metre in diameter, to the minute blooms of Wolffia species – the smallest in the world, the simple goal is the same.

Once fertilisation has occurred, the plant has no need for such gaudy displays and the petals are usually the first parts of the flower to show signs of decay once their job is done.

To counteract the short vase-life of flowers, a packet of 'flower food' is often included when you visit the florist. These products usually contain some sugar to act as an energy source; a compound to alter the acidity of the water to make it more suitable for the flowers; and a disinfectant to kill off any bacteria which could speed up decay in the vase.

Now researchers using lilies (Lilium longiflorum) have shown that adding sugar to the vase speeds up the opening of the flower and slows down its decay but doesn't affect the rate at which the petals drop off the flower - a sure sign your peace offering should have been binned already. The overall effect of these changes is a longer flowering window and a happy customer.

Laia Arrom and Sergi Munné-Bosch found that adding sucrose to the vase accelerated flower opening by 2.4 days and delayed its decay by 24 hours. Their work was published in the journal Plant Science earlier this year.

Further analysis of how the tissues of the flower use this sucrose showed that the petals and the male parts of the flower took up lots of the sugar and used it quickly. The female parts of the flower, on the other hand, took up sucrose and held on to it - a reserve, perhaps, for the female element's new role as a seed-bearer.

So, how did adding simple sugar to the distilled water in the vase increase the length of time the flowers kept their condition? Crucially, the addition of sucrose to the vase seemed to alter the balance of hormones in the flower tissues.

Hormones serve much the same function in plants as they do in animals - acting as chemical signals which can be transmitted over long distances.

It was already known that a particular group of plant hormones called cytokinins can delay the onset of floral decay and, sure enough, this recent study showed that a cytokinin called zeatin riboside was accumulated in the flowers, prolonging their vase-life.

Another plant hormone, abscicic acid, is known to speed-up the decay of petals and the researchers found that flowers treated with sucrose had 57% less absicsic acid compared to control flowers.

The cut flower industry is big business. A recent report (pdf) on the industry described it as being worth over US$100 billion a year worldwide. The UK share alone is worth around £2.2 billion - a 250% increase over the last twenty years. That's a lot of husbands doing a lot of apologising.

Whatever we're buying them for, consumers like flowers that stay alive long enough to enjoy them. This latest research suggests we're doing the right thing by adding sugar. The extra energy source is able to alter the balance of plant hormones enough to get an extra few days of enjoyment out of the blooms. If that doesn’t work, you may need to try a box of chocolates.

World’s first night flowering orchid discovered on the island of New Britain

B. nocturnum (Image: J. Vermeulen)

Botanists from the Royal Botanic Gardens, Kew, and the Netherlands Centre for Biodiversity Naturalis have described the first night-flowering orchid known to science. The discovery is published in the Botanical Journal of the Linnean Society.

The new night flowering species, Bulbophyllum nocturnum, from the island of New Britain near Papua New Guinea, is the first known example of an orchid species with flowers that consistently open after dark and close in the morning. Its flowers last one night only.

A relatively small number of plant species have flowers that open at night and close during the day. Until now, no orchids were known among them. This in spite of the fact that many orchids are pollinated by moths. But these moth-pollinated orchids all have flowers that remain open during the day, even if they are mainly pollinated after dark.

Bulbophyllum nocturnum was discovered by Dutch orchid specialist Ed de Vogel on a field trip to the island of New Britain, where he was allowed to collect some orchids in a logging area for cultivation at the Hortus Botanicus in Leiden, the Netherlands.

Under the care of garden manager Art Vogel one of these plant soon produced buds. Their opening was eagerly anticipated as de Vogel and his colleagues had already established that this plant was a member of the Epicrianthes group of orchids of the genus Bulbophyllum. Epicrianthes contains many rare and bizarre species, most of which have only been discovered recently as they occur in some of the remotest jungle habitats on earth.

Frustratingly, however, the buds all withered once they had seemingly reached the size at which they should open. Wanting to get to the bottom of this, de Vogel took the plant home with him one evening in order to find out exactly what happened to the buds.

B. nocturnum (Image: A. Schuiteman)

To his surprise, the bud that was then present opened up at ten in the evening, long after dark, revealing the flower of an undescribed species.

Observations on subsequent buds confirmed that they all opened around 10pm, and closed the next morning around 10am. The flowers lasted only one night, which explained why the buds were seemingly about to open one day and withered the next.

Royal Botanic Gardens, Kew orchid specialist, André Schuiteman, and Leiden Bulbophyllum expert, Jaap Vermeulen, teamed up with de Vogel to investigate and describe this remarkable new species.

Says André Schuiteman of the discovery, “This is another reminder that surprising discoveries can still be made. But it is a race against time to find species like this that only occur in primeval tropical forests. As we all know, such forests are disappearing fast. It is therefore increasingly important to obtain funding for the fieldwork required to make such discoveries.”

Why Bulbophyllum nocturnum has adopted a night flowering habit is unknown and requires further investigation. However, it may be speculated that its pollinators are midges that forage at night.

In February 2012 Kew’s Tropical Extravaganza festival (4 February – 4 March 2012) will celebrate the beauty and diversity of orchids. Orchids make up what is probably the largest plant family on earth, with an estimated 25,000 species. Their flowers show a tremendous range of variation in size, colour and shape.

Wildflowers in Bloom

Some wonderful flowers in bloom on my way to work this morning:

Musk Mallow (Malva moschata)

Common Poppy (Papaver rhoeas)

Corn flower (Centaurea cyanus)

Corpse flower blooms in Basel

The Swiss city of Basel witnessed a rare flowering of the corpse flower, Amorphophallus titanum, over Easter.

The carrion flower is also known as the titan arum and and produces a scent which is not unlike that of a decomposing mammal. The scent is used to attract pollinating insects, in particular carrion flies and beetles, to the flower to transfer pollen. The flowers deep-red colouration also contributes to this carrion-like illusion.

The flower can reach over 3 metres in height but dies back quickly before it is replaced with a single large leaf. The underground corm (swollen plant stem) is the largest in the plant kingdom - around 50 kg.

Found growing in the wild in the rainforests of Indonesia, it is cultivated in many botanical collections around the world but it is notoriously difficult to get to flower.

Interestingly, the popular name titan arum was invented by David Attenborough when he famously filmed the plant for his 'The Private Life of Plants' BBC series. Apparently, he felt that continually referring to the plant by its Latin name on TV would be inappropriate. See video at the end of this post.

The Swiss flower was visited by more than 10,000 people on Saturday alone, each adult paying 10 Swiss Francs for a quick two-minute viewing. All the money raised was going towards funding events at the botanical garden.

Custodian of the Basel Botanical Gardens Heinz Schneider told Swiss TV, "It's crazy! Plant fans from all over Switzerland want to see the titan arum."

By Monday, the flower had wilted but the event was captured on webcam, from which the following series of images were taken (31st March - 27th April).

David Attenborough visits the titan arum in the wild:

(Ignore the title of the video - titan arum is not the biggest flower in the world!)