Posts Tagged ‘ orchids ’

Issue 97: Floral arms race seduces insects

November/December – 2007
Author: Anne Gaskett

During National Science Week, ANNE GASKETT reported compelling evidence that native Australian orchids use their colour, shape and fragrance to seduce male insects. Her ground-breaking research has important implications for the control of agricultural pests.

Australian orchids are engaged in an arms race, using sensory overload to seduce male insects. Macquarie University PhD student Anne Gaskett has discovered just how they do it. Her work is important to the conservation of orchids and the control of economically important agricultural pests.

Gaskett has been analysing the smells, colours and shapes of flowers from an insect’s perspective. She has found that orchids mimic female insects so well that male insects cannot resist mating with them and accidentally ferrying pollen from plant to plant.

“I have accumulated the first compelling evidence of an ongoing and escalating arms race between orchids and their unwitting insect pollinators,” Gaskett explains.

“Over generations the insects learn to avoid having sex with orchids, and this means only the most persuasive orchids reproduce, which drives the acceleration of orchid subterfuge.”

The Australian bush is rife with such sexual deception, Gaskett says, as native orchids lure pollinators with false promises of romance.

Gaskett has been studying the hardworking orchid dupe wasp (Lissopimpla excelsa), which is fooled into copulating with not just one, but five native tongue orchid species (Cryptostylis) in urban and regional Australia. All the tongue orchid species mimic the female dupe wasp, but to the human eye they look quite different.

By using modern technology to study the physics of the colours of the orchids and the female insects, Gaskett has revealed that they are identical when viewed by male insects. The flowers are also shaped to mimic female insect bodies.

To the human eyes the female wasp looks orange and black and the orchids are pink, maroon and orange-red. However, receptors in human and wasp eyes are very different. Unlike humans, wasps see ultraviolet light. When Gaskett used a spectrometer to study the wavelengths of light reflected from orchids and female wasps, she was amazed to find they were virtually identical.

“The smell is the most important thing for attracting the insect,” she said. “But the colours say this is the source of that alluring fragrance.”

Gaskett is now looking at the impact of the chemical components of orchid perfumes directly on wasp antennae, to understand what makes these fragrances irresistible.

“The key to the orchids’ success is bombarding young male wasps with an extremely compelling sensory overload of irresistible sex signals,” Gaskett explains.

Studying these intimate interactions addresses big questions about nature and evolution and highlights the millions of other unknown interactions crucial for a sustainable and healthy environment.

“These insects might be fools for love, but their role as orchid pollinators makes them indispensable.”

Gaskett’s next step will be to analyse the seductive orchid bouquets to discover which elements mimic the female wasp pheromones.

So what led Anne Gasket down this research path?
“I’ve always enjoyed getting out and investigating nature,” said Gaskett. “In the past, I’ve focused on animals, studying projects such as Antarctic fish diet around Macquarie Island, and spider mating and sex pheromones.

“When I was designing my PhD research I wanted to expand into botany and learn lab techniques useful for applied research in the future. I wanted a topic that would involve local community groups and enthusiasts plus travel and fieldwork opportunities, and avoid nocturnal animals – I didn’t want to be up all night!

“Studying orchids suited all these requirements and since Australia has most of the world’s sexually deceptive orchids, I thought I was well placed to use local native plants to discover interesting results with some global impact,” she said.

To study the orchids’ scents, Gaskett borrowed techniques from agricultural studies for identifying pest insects, usually very specific sex pheromones.

“If you can identify and make synthetic versions of the pheromones, you can use it as bait to trap male insects so they can’t reproduce or get into the crops,” she said.

The identification procedure is called gas chromatography – electro-antennography. It involves sampling the scent of an orchid, or a female of a pest species, and using gas chromatography to break the scent down into its separate components.

“You attach an antenna from the orchid-visiting insect or pest species so that as the scent is separated, it also blows across the antenna. You can detect when the antenna’s chemoreceptors fire and, therefore, which components are attractive to the insect,” Gaskett explains.

“I’ve used this project as an opportunity to promote and improve my skills with these techniques so the future might see me working in a much more applied capacity.”

Gaskett was one of 16 early-career scientists presenting their research to the public for the first time thanks to Fresh Science, a national program sponsored by the Federal and Victorian Governments. Her work has been funded for three years by a 2005 American Orchid Society Fellowship.

For further information contact:
Anne Gaskett
Ph: 0401 009 328

About Fresh Science
Fresh Science is a national competition that identifies new and interesting research being done by early-career scientists around the country. Their stories are released to the media before, during and after National Science Week, which was held in August.

Sixteen scientists were selected from more than 80 nominations. They were flown to Melbourne for a day of media training after which they presented their work to the media, school students, the general public, scientists, government and industry over the course of three days.

Described by some as a boot camp in science communication, previous Fresh Scientists have attracted national and international interest resulting in hundreds of media stories, including national television news. Details of previous winners, their press releases and media coverage can be seen on the Fresh Science website.

Now in its 10th year, Fresh Science is a national event, which brings together scientists, the media and the public. It is designed to:
– Enhance reporting of Australian science
– Highlight and encourage debate on the role of science in Australian society
– Provide role models for the next generation of Australian scientists.

If you are a scientist who was awarded a PhD less than five years ago, have a significant peer-reviewed scientific achievement and think you can tell an interesting story in everyday language, then check out the selection criteria on the Fresh Science website for the 2008 Fresh Science competition.

Issue 96: Barrita Orchids

September/October – 2007
Author: Scott Barrie

Elevated view of the inside of the greenhouse.

Inset: Phalaenopsis.

SCOTT BARRIE gives a commercial grower’s insight into the cultivation of high quality orchids for the retail market Australia wide, including the development of new varieties.

Barrita Orchids is owned and operated by the Barrie family. Founded in1963 by Geoff and Angela Barrie, the nursery was originally established in Mt Hutton, Newcastle. Recently the nursery relocated to the Central Coast of New South Wales and is now under the management of Scott Barrie. Barrita Orchids is a commercial orchid growing business which supplies quality plants to K-Mart stores throughout New South Wales as well as flowers and plants to markets and florists Australia wide. The aim of Barrita is to produce high quality cut flowers and potted orchid plants and to develop new varieties.


There are in excess of 3,000 genera in the orchidaceous family, many of these originating from the jungles of the Americas and Asian region. Mystery and myth seem to surround these delightful beauties and stories of the orchid collectors sent by British gentry into the wilds of the South American jungles add colourfully to this mythology. Today, there are many traits which make orchids popular to collectors and the general public.

There is a long list of popular and well-known orchid varieties including Cymbidiums, Phalaenopsis, Dendrobiums (often referred to as Singapore Orchids), Cattleyas, Paphiopedilum or Slipper Orchids, Sarcochilus, Vandas and Oncidiums. Cymbidiums are grown in great numbers in Holland, and Phalaenopsis, which are one of the most graceful flowers, are one of the biggest pot plant sellers in Europe.

Cymbidium Khan Flame.

Cymbidium Toni McCartney.

Australian native Sarcochilus plants.

Orchid requirements
Orchids come in varieties which are either terrestrial or epiphytic. Epiphytic orchids, which are the focus of Barrita, require an inert media with free-draining characteristics, good air circulation and high light.

Looking across benches of orchid plants.

The Greenhouse
The Barrita greenhouse is located 320m above sea level, is north facing and positioned as to have no light impediments such as surrounding trees or buildings. It is 102m x 57m x 4m (gutter height) in size with a twin-skinned roof to give greater environmental stability. Twin roof vents give maximum air movement and ventilation and 50% shade screens allow maximum light to penetrate without allowing leaf burn.

Greenhouse operations are run by a Galcon computer with a PC interface. This program controls the timing and operation of the entire hydroponic system including all overhead watering, fertilization and pH adjustment in addition to vent and screen functions regulated by temperature, wind and light sensors.

There are two different growing areas within the greenhouse where the plants can be housed in either a heated or non-heated environment. In the heated section, tropical Phalaenopsis grow to be sold as pot plants and to supply cut flowers for use in florist bridal work. This section is also used to house deflasked plantlets. This environment receives a greater frequency of irrigation giving plants a high rate of growth, achieving maximum size in the pot in the shortest time possible.

The non-heated area, which is the bulk of the greenhouse, contains Vandas, Cymbidiums and Sarcochilus growing towards maturity and flowering. This section’s environmental control is set to achieve the lowest temperatures attainable and allow the maximum air exchange with the outside environment.

Benefits of greenhouse production
While it is not necessary to grow orchids in a greenhouse environment, there are many outstanding benefits to this system of production. As is the case in many horticultural pursuits where a crop may be grown outside or in a greenhouse, greenhouse produced orchids are of a higher quality due to the ability to limit variables such as wind damage and rain spoilage, ensuring delivery of a high quality product. Cut flower markets require the highest level of quality assurance. This is only achievable in a greenhouse.

Angela packing flowers.

There are also economic benefits to greenhouse production. Since moving to the greenhouse environment, previously high employment input has fallen due to computer system control drastically reducing the need for many manual tasks, a more worker-friendly environment and the elimination of wasted days lost to wet weather.

Finally, the complete control of conditions made possible by this type of production allows for much greater control of pests and disease. Reliance on fungicide is reduced simply by regulating the wet time of the plant and a bio-control program has been implemented to control two spotted mites All methods combine to reduce chemical input whilst ensuring optimal growth and healthy plants.

Traditionally, Australian Cymbidium orchid producers have relied heavily on cross-pollination for the bulk of their production. This method is the cheapest in regards to the cost of plantlets, however this can lead to irregularity in flower production. This may lead to another year of growth pre-flowering, and unproven keeping qualities as a cut flower giving rise to poor customer satisfaction.

Orchid flowers are renowned for longevity as a cut flower. Failure to meet this expectation damages supplier/customer relationships. For these reasons, whilst a small breeding program at Barrita exists to produce new cultivars to fill stock gaps, the majority of production is derived from clones from Barrita’s own breeding programs proven for their ease of growth and flowering.

This cloning process, which is undertaken on site, requires plants begin their lives in the Barrita laboratory. The cloning of plants produces corms which multiply into plantlets. The new plantlets are grown in sterile, tissue culture jars for up to 12 months to a height of approximately 10cm, at which point they are planted out into individual 50mm tubes and relocated to the heated greenhouse environment.

Looking across benches of orchid plants.

Although the heated environment is unnecessary for the growth of the cold-growing varieties, these new plants do require the increased water supply this area of the greenhouse receives. The plants will then continue to grow in this environment until they are ready to move onto 125mm pots. At this point the cold varieties will be transferred to the main growing area, while those requiring heat will move into another area of the heated environment.

Once in the main growing area, plants spend as much as 12 months in the 125mm pot before being transferred to a 175mm pot. Some plants will flower in this size pot in the next flowering season, although it is usual to grow the plant into the next season in a 200mm pot. This 200mm pot is the finished product, and provided the plant flowers it will be sold. All going to plan, this process has taken five years from the time the initial clone was cut to the time the plant has its first opportunity to be sold. This is why orchids generally are regarded as expensive plants and a reason why there are not many large commercial orchid producers.

Flower spikes about to open.

Cymbidium flowers ready to harvest.

The hydroponic system at Barrita
Given that the orchids grown at Barrita are epiphytic in nature, they require a specialist hydroponic system in which to grow to their maximum potential. This involves a high quality soilless growing medium, plenty of air circulation, and the right amount of water and water-based fertilizers.

The growing medium
Epiphytic orchids prefer a soilless medium with an air-filled porosity of above 45%. Traditional growers have used sand/peat mixes or bark based composts to grow in. Good quality peat has become difficult and expensive to source, and a reliable grade of bark which will not break down is just as difficult to find.

Barrita chose to turn to the stability of Growool [an Australian-made rockwool product] as a base for the growing media. A mix of Growool, styrene and perlite has been used since the early 1990s. This change away from traditional composts has proven to be a revolution in the growing system used at Barrita. The total stability and regularity of the media allows mature plants to develop into massive plants over 10 years in the same pot, a feat difficult to attain in traditional bark-based media. The revolution came in the form of a greater need to understand the nutritional requirements of the plants, and the use of leaf analysis has provided a base line from which to reference these requirements. The benefits of this mix include a readily available supply in bulk quantities, ease of handling and the recyclable nature of a totally inert media.

Media. Growool, Perlite and Styreen.

The water used in the hydroponic system is derived from two sources. Firstly, the greenhouse roof run-off water is collected and mixed with the second source which is bore water. Bore water in the area is of exceptional quality with an EC of 0.16, giving plenty of scope for the addition of nutrients. The pH of the water is quiet low at pH 3.15. While such a low pH is damaging to the long term growth of the plant, it is easily corrected using potassium hydroxide solution injected via the computer-monitored injection system.

Plants are watered and fertilized through an overhead sprinkler system, which delivers an even misting of nutrient enriched water to the plants. This process is carried out twice a week during the cooler months and increased to three times a week during the warmer seasons. The overhead sprinklers also contribute to the cooling of the greenhouse. A short burst from the sprinklers produces a mist which raises the humidity.

Air circulation
Air movement is considered to be one of the most important aspects of growing orchids and is a major concern in a greenhouse environment. There are a number of ways to increase ventilation including roll-up walls, benching plants, circulation fans and roof vents.

Roll-up sides were included in the original design of the Barrita greenhouse, however, although air circulation is increased, these roll-up sides create variation in the overall environment. In the areas immediately adjacent to the open wall, the plants dry out much faster than the ones in the centre of the house. For these reasons Barrita has found this type of ventilation to be unsuitable.

Benching plants at a height of 300mm off the ground on mesh stands allows air to circulate throughout the plants more evenly and prevents waterlogging. Circulation fans are used in the heated area as the roof is often closed while the heating process is underway. This enables air to circulate freely without loss of heat and environmental fluctuation. Twin roof vents throughout the house are monitored and controlled through the computer, based on wind speed readings. These give excellent air exchange in an even flow all over the growing area. Even on days when there is no breeze the leaves of the plants can be seen to slightly move.

As the growing medium is simply a stabilization method for the plants, no nutrition is received from the growing media. The plants nutritional needs, therefore, are met through the watering system.

Barrita utilize a four injector system delivering A, B and C nutrient solutions and a pH adjustment solution. Typically, solution A contains Calcium Nitrate and Potassium Nitrate, solution B contains Mono Potassium Phosphate, Magnesium Sulphate, Potassium Nitrate, and solution C contains trace elements and Iron Chelate.

Barrita uses variations in the Nitrogen/Potassium ratio to induce flower initiation. These changes are confirmed through leaf analysis. At the time of flower initiation, the Nitrogen level should be lower than 1.8% and rise to 2.5% during the growing phase. This process has been refined over the last 10 years.

While Barrita has an efficient system of production featuring many useful and outstanding cultivars, many years of refining lay ahead. The production of high quality cut flowers and potted orchid plants remains the focus of the nursery, whilst developing new varieties is an ongoing source of excitement and challenge.

Scott Barrie.

For further information contact:
Scott Barrie, Barrita Orchids Pty Ltd,
121 Barnes Road, Kulnura, NSW Australia.