36


The complexity of colours


Blueberries. Mangos.


Peaches. Strawberries. Apples. Pineapples. Plums. Figs. Grapes.


Research by MARGARET EVANS


Delicious fruits come in a


rainbow of colours and we take it all for granted. But we undoubtedly get reminded of their appeal every time we drift through the produce department at the grocery store.


Theories as to why fruits are so colourful have been floated for decades. Back in the 1800s, scientists promoted the idea that fruit colours attracted animals that would carry off the fruit, dropping seeds and stones along the way and successfully dispersing the plant. The idea makes sense to us, but it also assumes that animals see fruit colours the same way we do. The problem is, most of them don’t. What looks red to us


doesn’t look red to many mammals. That’s because humans have three colour- sensing cone cells in the retina, each sensitive to red, blue or green wavelengths of light, giving us trichromatic colour vision. Those three cones let us see all the colours of the rainbow. But most other mammals only have two types of cone cells. Birds have


four, giving them a range of colours that we can’t see, including ultraviolet rays. Fruit colour, of course, can be hereditary and some plant species may simply take after their closest genetic relatives. Fruit colour is also influenced by geography and the environment, including factors such as latitude,


temperature and soil properties. To better understand the


relationship between plants and animals, Kim Valenta, visiting assistant research professor at Duke University in Durham, North Carolina, has been studying plant- animal co-evolution for more than 10 years. “When I started to work in Uganda as part of my postdoctoral research, I realized it would be a really great system to compare to Madagascar,” she said. With her research colleagues, she collected reflectance data on ripe fruits and leaves from 97 plant species in Uganda and Madagascar, including yellow hackberries, bluish-black soapbush berries and whitish Weinmannia fruits. They found that the fruit colors of closely related species were no more similar than expected by random chance. However, fruits eaten


mainly by mammals such as monkeys and apes have higher reflectance in the green part of the spectrum,


Tree Fruit Competitiveness Fund


The Province of BC has provided funding to enhance the competitiveness of the tree fruit sector.


The fund is open to tree fruit growers, producers, and processors to support three key areas of priority: ● Research: cultivar, disease and pest research. ● Marketing: export market opportunities and market development research.


● Infrastructure: sector-based infrastructure modernization such as new equipment.


The Tree Fruit Competitiveness Fund is jointly delivered by the BC Fruit Growers’ Association and Investment Agriculture Foundation BC.


For details about the Tree Fruit Competitiveness Fund, including eligibility, deadlines and application forms, please visit www.bcfga.com or iafbc.ca/tree-fruit, or contact funding@iafbc.ca.


A preliminary report on project selection criteria and priorities is available at the BCFGA website, www.bcfga.com/322/Tree+Fruit+Competitiveness+Program


  The Investment Agriculture Foundation of BC (IAF) Board of Directors is looking to recruit talented, energetic, industry leaders who are passionate about helping to build a competitive, sustainable and resilient agriculture and agri-food sector in British Columbia.


BC FRUIT GROWERS’ ASSOCIATION 1-800-619-9022 (ext 1) email: replant@bcfga.com www.bcfga.com


We are currently looking for four (4) Directors, one from


each the following sectors:


• Post Farm Gate (agri-food processing sector)


• Other Livestock (pork, sheep, horse)


• Greenhouse and/or Floriculture and/or Nursery


• Dairy For more information on how to apply: iafbc.ca/director-call FILE PHOTO


whereas fruits dispersed by birds reflect more in the red. This could be because birds tend to rely more heavily on their keen colour vision than many other animals and reds are easier to spot against the green foliage. The findings support the idea that animal dispersers helped drive the evolution of fruit colours in tropical plants. In temperate regions, birds are major influencers in dispersing seed. “Fleshy fruits in both the


tropics and temperate regions are animal-dispersed,” says Valenta. “Vertebrate diversity is higher in the tropics, and there tend to be many more seed dispersing mammals in the tropics in particular, compared to temperate regions, where most seed dispersing animals are birds.” Researchers found that plants with fruits reflecting ultraviolet light also tend to have UV-reflecting leaves. Plant UV-reflectance may also function to reduce water loss in plant parts. This might


suggest that fruit colour is a response to environmental factors affecting the whole plant, such as protection from the sun’s damaging rays. UV reflectance has been found to increase the likelihood of ripening in experiments, and reflectance of red colours increases fruits’ contrast with leaves, allowing visually oriented birds to locate ripe fruit. The study supported previous studies that confirmed mammals exert weaker selective pressure than birds and may rely on scent or touch in their interactions with plants. However, other subtle influencers may play a role, too.


“I've found evidence that


both size and hardness of a fruit husk are highly correlated with mammal-dispersed versus bird-dispersed fruits,” says Valenta. “Mammals tend to eat larger, harder fruits. I've also found that fruit odour is quite important to mammals, and this is something we're


working on now.” Research plans going


forward include odour, size and texture of fruits. Visually bright fruits attract birds, but scent may be more important for other animals whose olfactory senses are keener than sight. In addition, soils and local weather patterns may also be influential. To what extent, and how, is a huge question that Valenta’s team is starting to look at. “This is a very big and complex question,” she says. “I am currently starting a controlled experiment to see if increased UV light exposure leads to increased plant reflectance in the UV part of the spectrum. I've recently published something showing that ENSO (El Niño Southern Oscillation) predicts African phenological patterns. But no one has looked at these questions systematically and across large scales yet.” Valenta and her team’s


report on fruit colours was published in Scientific Reports.


COUNTRY LIFE IN BC • DECEMBER 2018


JOIN IAF’S BOARD OF DIRECTORS CALL FOR EXPRESSIONS OF INTEREST


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52