Scientists discover why some roses smell sweeter than others - and how to improve the scent

A Damascus Rose

Not all roses smell that sweet but scientists have found out why some smell sweeter than others and in the process have discovered a way of potentially improving the scent of the gardener’s favourite ornamental flower.

A study into the chemistry of rose scents has found a new biochemical pathway in the petals of the plants which produces a sweet-smelling fragrance that could be re-introduced into rose varieties that have lost their smell.

Scientists have identified an enzyme known as RhNUDX1 which plays a key role in producing the sweet fragrance of roses, which they suggest could be re-introduced into modern varieties that have lost their scent as a result of intensive breeding for better colour and shape.

Jean-Louis Magnard and colleagues from the University of Lyon in St Etienne in France identified the new source of rose scent in a study published in the journal Science that investigated the source of the strong scent in the rose Papa Meilland.

They found that the enzyme was lacking in another rose, called Rogue Meilland, which produces little scent and a genetic analysis revealed key differences in the genes responsible for the biochemical pathway that led to the synthesis of the enzyme.

The researchers found that the RhNUDX1 enzyme, which works in the cells of the flower petals, generates the well-known fragrance substance called monoterpene geraniol, the primary constituent of rose oil.

In the future, it might be possible to exploit the knowledge about the gene for RhNUDX1 in order to breed pleasant-smelling scents back into modern varieties that lack a strong fragrance, they said.

Rose Flower pictures

Scientists believe that the discovery of a new biochemical pathway that can synthesise rose scents is probably due to the independent evolution of chemical attractants designed to advertise flowers and bring pollinators to fertilise them.

It is known that a single constituent of rose oil, such as rose oxide, can impart different scents depending on which 3-D shape they have formed. Rose oxide, for instance, can produce four different scents, sweet, fruity, minty or citrusy, depending on which one of four 3-D shapes it has formed.

A version of this article appeared in the print edition of The Daily Star on July 03, 2015, on page 11.

Summer flowers rapidly appearing: Country diary 100 years ago

In a willow-grown marsh, easier than usual to walk through just now, I found the ragged robin abundantly in flower. With its pale pink and untidy, straggling petals it looks a poor relation of the sturdy red campion, which in the dry wood has been long out and new is the most noticeable flower. The ragged robin is a mid-June flower; why should it be called “floscuculi”? There are several “cuckoo flowers,” but the best known is the bittersweet, which in these parts is usually called the May-flower; it comes out when the cuckoo is calling all day-long, but the bird is getting weary when the ragged robin appears. It is true that yesterday I saw a cuckoo apparently flying for its life because an annoyed tree-pipit was chasing it, and that when it outdistanced the little bird it called many times, but the voice of the cuckoo is not the most noticeable bird-note now.
Summer flowers are rapidly appearing to replace the now seeding blooms of spring. There are open thimbles on a few foxgloves - thimbles of the “little folk” or fairies, - and in another month this tall favourite will line the hedgerows and fill cleared spaces in the woods. There is another very common flower now out, the pink spike of the bistort, known in this district as the “patience dock” and by the farmers “snakeweed,” on account of its trailing roots. Gerarde, the Cheshire herbalist, called it: “passhions” and described it as “an excellent potherbe,” and no doubt, that is the origin of the local name. It was an Easter plant, not because it flowered then, but because its young leaves made a suitable vegetable in spring. It is rather a troublesome plant in pastures, but its flowers and dark green leaves are certainly handsome, if we are capable of seeing beauty in common things.

Gardens: plants in their natural habitat

I remember the day I first I saw a dog’s tooth violet. It was April in the garden my parents moved to in the mid-70s and the find was just one of many treasures that emerged after we cleared 50 years’ of undergrowth. The plant was part of a tightly clustered colony in a little clearing under the shade of a liquidambar. The leaves emerged first, pushing up and then opening out in a splay of blue-green paddles that were curiously mottled. Pointed buds soon flung the petals back to reveal a push of green stamens. It was a mystery how something so exquisite had survived the neglect.
It was several more years before I came to meet Erythronium dens-canis in the wild. It was a June trip and my first plant-hunting venture in the Picos de Europa in northern Spain, aged 19. I had no idea that you could see summer astrantia in the morning and narcissus in the afternoon through making the ascent. We moved through nut woodland, where moody mourning widow combined with Lilium martagon, and through orchid-filled meadows mounded with wild peas. Gaining altitude, we saw the turf shorten and the season move backwards as we approached snowmelt. It was here that I found the very same erythronium. Once again they were alone and ahead of the summer competition.
Seeing plants growing in the wild takes some of the mystery away from how to grow them. The mountainside erythroniums had all the water and light they would need while they flowered, seeded and retreated below ground again before the slopes dried in their dormancy. Our domesticated dog’s tooth violets had survived there in the moss, with spring moisture and light while the liquidambar was dormant.
I’m guessing our hearty soil and lush grass will overwhelm them at the farm, but the dog’s tooths are not difficult bulbs as long as they do not have too much competition. Winkling them into the beds among later-emerging perennials, such as peony, is the best bet. I will also try some of the other species. Plants adapt in the wild by evolving their genus – and we can use this to our advantage.

Perfect partner: the violet head of mourning widow (Cranesbill). Photograph: Arco Images GmbH /Alamy

Erythronium also occur in North America and the American species offer up several good varieties. E tuolumnense stands about 18in high with apple-green foliage and starry yellow flowers. ‘Pagoda’ is a fine and vigorous selection for open woodland or a border that allows it time to settle in. Plant it among pulmonaria for a springtime combination and the cover of foliage once they become dormant.
Erythronium californicum ‘White Beauty’ s smaller in stature, with marbled foliage and ivory flowers. I like to mingle them through a low carpet of wild strawberries and for the carpet to sweep among epimedium, which enjoys the same conditions. If you find them a place that they like and where they can be left alone, you may well be planting them for future generations.

Get growing

Buy dog’s tooth violet plants now while in full growth or order for delivery in the autumn as dormant rhizomes. Keep rhizomes damp if you are waiting to plant them by storing in compost, as they will not recover from dehydration.

No room in the park? Why not use next door’s back garden?

Open gardens usually conjure up images of older, well-to-do people admiring each others’ chrysanthemums. But now, with a shortage of public space in cities, overcrowded parks and young people increasingly living in rented accommodation with little outdoor space, a new drive by the National Gardens Scheme is aiming to make private gardens more inclusive.
The scheme has already begun opening up gardens to allow users to enjoy early snowdrops and will continue until late October. It wants to encourage young people to use private outdoor space as they would a public park. Private garden owners can register their gardens with the NGS and open them up to the public, charging a fee of about £4, with all proceeds going to nursing and caring charities.
“Gardening is generally regarded as an occupation for old retirees but there has been a steady movement towards it among young people keen on environmental issues, or growing their own produce for cooking, or just looking for some quiet space,” said George Plumptre, chief executive of the NGS.
“In urban areas, we want to encourage more young people to turn up, sit on a bench with a book or have a cup of tea with friends and spend a couple of hours in a green space, particularly if they have not got that at home.” The NGS is increasing its use of social media and has created a free app that gives precise details about garden openings.
Experts welcomed the move. Les Back, 52, professor of sociology at Goldsmiths, University of London, said: “People in their 20s and early 30s are increasingly living in rented accommodation with no garden and very little room. This is true of Bristol, Birmingham, Manchester and particularly London. The amount of space people do have is increasingly pressured.”
Back said public parks, which were traditionally conceived as being the lungs of a city, were being besieged as the population of the UK increased and outdoor areas were shrinking or becoming overcrowded. “Schemes such as this are showing that, at last, those with more land – older, middle-class people – are thinking about sharing their space. It’s not before time,” he said.
Clare Elliott, 29, a film-maker who rents a shared house in Walthamstow in London, agreed. She said that for people living in a city where houses were being sliced up into flats and outdoor space is a luxury, it could be difficult to find a peaceful place out of doors.
“Right now, if you choose to live in London, you’re basically deciding that you won’t have any green space. None of my friends can afford their own gardens or outdoor areas,” she said.
“In the summer, many of the parks near me don’t even have green grass because it’s been trampled on. There’s certainly a demand for more access to nature in the capital – quiet places where young people can go to read, hang out, have a coffee or even go on a date.” She added: “Some cities are better than others but there’s a lack of designated green areas and these really great garden societies are making a difference.”
The NGA opens up more than 3,500 private gardens across the country each year, with the peak time being in the summer, when there are 250-400 gardens open every weekend from late May until early July. Founded in 1927 by the Queen’s Nursing Institute, the district nursing movement, the NGA raises more than £3.25m a year, with proceeds going to charities such as Macmillan, Marie Curie, Carers Trust, Hospice UK and Perennial.

Climate change is disrupting flower pollination, research shows

The early spider orchid and miner bee, that depend on each other for reproduction, have become increasingly out of sync as spring temperatures rise, research has shown.
Sexual deceit, pressed flowers and Victorian bee collectors are combined in new scientific research which demonstrates for the first time that climate change threatens flower pollination, which underpins much of the world’s food production.
The work used museum records stretching back to 1848 to show that the early spider orchid and the miner bee on which it depends for reproduction have become increasingly out of sync as spring temperatures rise due to global warming.
The orchid resembles a female miner bee and exudes the same sex pheromone to seduce the male bee into “pseudocopulation” with the flower, an act which also achieves pollination. The orchids have evolved to flower at the same time as the bee emerges.
But while rising temperatures cause both the orchid and the bee to flower or fly earlier in the spring, the bees are affected much more, which leads to a mismatch.
“We have shown that plants and their pollinators show different responses to climate change and that warming will widen the timeline between bees and flowers emerging,” said Dr Karen Robbirt, at the Royal Botanic Gardens, Kew and the University of East Anglia (UEA). “If replicated in less specific systems, this could have severe implications for crop productivity.”
She said the research, published in Current Biology on Thursday, is “the first clear example, supported by long-term data, of the potential for climate change to disrupt critical [pollination] relationships between species.”
Three-quarters of all food crops rely on pollination, and bees and other pollinators have already suffered heavily in recent decades from disease, pesticide use and the widespread loss of the flowery habitats on which they feed. In the UK alone, the free fertilisation provided by pollinators is estimated to be worth £430m a year to farmers.
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Professor Anthony Davy, also at UEA and part of the research team, said: “There will be progressive disruption of pollination systems with climatic warming, which could lead to the breakdown of co-evolved interactions between species.”
Scientists have already identified a few timing mismatches caused by global warming between species and their prey. Oak tree buds are eaten by winter moths, whose caterpillars are in turn fed by great tits to their chicks, but the synchronicity of all these events has been disrupted.
Suspected mismatches have occurred between sea birds and fish, such as puffins and herring and guillemots and sand eels. The red admiral butterfly and the stinging nettle, one of its host plants, are also getting out of sync.
The new study focused on the early spider orchid Ophrys sphegodes, found in southern England, and the solitary miner bee species Andrena nigroaenea because they have a very close relationship. Other plants can be pollinated by many insects and other insects can pollinate many plants, making it very hard to determine the effect of changing temperatures.
Female solitary miner bee ( Andrena nigroaenea ) The solitary miner bee is affected more by rising temperatures than the early spider orchid that it pollinates. Photograph: Oxford University
Another challenge is that the temperature effects can be subtle, meaning data has to be collected over a long period. Robbirt and her colleagues realised that the natural history museums in London and Oxford and Kew Gardens had dated specimens of both the orchid and the bee stretching back to 1848.
Analysing all the data, and checking it against recent surveys, revealed that the orchid flowers six days earlier for every 1C increase in spring temperatures. But the effect on the male miner bee was greater, as it emerged nine days earlier.
The female miner bees, which usually emerge later than the male, emerged 15 days earlier. The latter effect meant the male bees were less likely to visit the orchid flowers for pseudocopulation. “The orchids are likely to be outcompeted by the real thing,” said Robbirt.
The UK government published its national pollinator strategy on Tuesday. It was welcomed by the pesticide trade body, the Crop Protection Association and the National Farmers Union. But Joan Walley MP, chair of parliament’s Environmental Audit Committee, said: “I am disappointed the government seems stubbornly determined to keep open the possibility of challenging the EU ban on neonicotinoid pesticides, which have been linked to pollinator declines.”