The daily dance of flowers tracking the sun is more fascinating than most of us realise


Julien Christ/Unsplash

Gregory Moore, The University of MelbourneWhen I was a child, I was intrigued by the Queensland box (Lophostemon confertus) growing in our backyard. I noticed its leaves hung vertical after lunch in summer, and were more or less horizontal by the next morning.

This an example of heliotropism, which literally means moving in relation to the sun. We can see it most clearly as spring arrives and various species burst into flower — you might even get the feeling that some flowers are watching you as they move.

Many of us probably first got to know of heliotropism at home, kindergarten or primary school by watching the enormous yellow and black flowering heads of aptly name sunflowers, which moved as they grew.

These flowers track the course of the sun spectacularly on warm and sunny, spring or summer days. Sometimes they move through an arc of almost 180⁰ from morning to evening.

So with the return of sunny days and flowers in full bloom this season, let’s look at why this phenomenon is so interesting.

The mechanics of tracking the sun

A number flowering species display heliotropism, including alpine buttercups, arctic poppies, alfalfa, soybean and many of the daisy-type species. So why do they do it?

This is Heliotropium arborescens, named for its heliotropism. They were very popular in gardens a century or more ago, but have fallen from favour as they can be poisonous and weedy.
Shutterstock

Flowers are really in the advertising game and will do anything they can to attract a suitable pollinator, as effectively and as efficiently as they can. There are several possible reasons why tracking the sun might have evolved to achieve more successful pollination.

By tracking the sun, flowers absorb more solar radiation and so remain warmer. The warmer temperature suits or even rewards insect pollinators that are more active when they have a higher body temperature.

Optimum flower warmth may also boost pollen development and germination, leading to a higher fertilisation rate and more seeds.




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So, the flowers are clearly moving. But how?

For many heliotropic flowering species, there’s a special layer of cells called the pulvinus just under the flower heads. These cells pump water across their cell membranes in a controlled way, so that cells can be fully pumped up like a balloon or become empty and flaccid. Changes in these cells allow the flower head to move.

Venus fly trap
Fly traps have somewhat similar mechanics to heliotropism.
Shutterstock

When potassium from neighbouring plant cells is moved into the cells of the pulvinus, water follows and the cells inflate. When they move potassium out of the cells, they become flaccid.

These potassium pumps are involved in many other aspects of plant movement, too. This includes the opening and closing of stomata (tiny regulated leaf apertures), the rapid movement of mimosa leaves, or the closing of a fly trap.

But sunflowers dance differently

In 2016, scientists discovered that the pin-up example of heliotropism — the sunflower — had a different way of moving.

They found sunflower movement is due to significantly different growth rates on opposite sides of the flowering stem.

A sunflower facing a setting sun
Sunflowers move differently to other heliotropic flowers.
Aaron Burden/Unsplash

On the east-facing side, the cells grow and elongate quickly during the day, which slowly pushes the flower to face west as the daylight hours go by — following the sun. At night the west-side cells grow and elongate more rapidly, which pushes the flower back toward the east over night.

Everything is then set for the whole process to begin again at dawn next day, which is repeated daily until the flower stops growing and movement ceases.




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While many people are aware of heliotropism in flowers, heliotropic movement of leaves is less commonly noticed or known. Plants with heliotropic flowers don’t necessarily have heliotropic leaves, and vice versa.

Heliotropism evolves in response to highly specific environmental conditions, and factors affecting flowers can be different from those impacting leaves.

The leaves of Queensland box, Lophostemon confertus, which track the sun.
Krzysztof Ziarnek, Kenraiz/Wikimedia Commons, CC BY-SA

For example, flowers are all about pollination and seed production. For leaves, it’s for maximising photosynthesis, avoiding over-heating on a hot day or even reducing water loss in harsh and arid conditions.

Some species, such as the Queensland box, arrange their leaves so they’re somewhat horizontal in the morning, capturing the full value of the available sunlight. But there are also instances where leaves align vertically to the sun in the middle of the day to minimise the risks of heat damage.

Plants are dynamic

It’s easy to think of plants as static organisms. But of course, they are forever changing, responding to their environments and growing. They are dynamic in their own way, and we tend to assume that when they do change, it will be at a very slow and steady pace.

Heliotropism shows us this is not necessarily the case. Plants changing daily can be a little unsettling in that we sense a change but may not be aware of what is causing our unease.

As for me, I still keep a watchful eye on those Queensland boxes!




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The Conversation


Gregory Moore, Doctor of Botany, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why daily doses of nature in the city matter for people and the planet



File 20181120 161612 jduiq9.jpg?ixlib=rb 1.1
Brisbane’s South Bank parkland isn’t exactly getting out in the wild, but experiences of urban nature are important for building people’s connection to all living things.
Anne Cleary, Author provided

Anne Cleary, Griffith University

The environmental movement is shifting away from focusing solely on raising awareness about environmental issues. Many environmental agencies and organisations now also aim to connect people with nature, and our new research suggests daily doses of urban nature may be the key to this for the majority who live in cities.

Every year in the United Kingdom the Wildlife Trusts run the 30 Days Wild campaign. This encourages people to carry out a daily “random act of wildness” for the month of June. The International Union for Conservation of Nature recently launched its #NatureForAll program, which aims to inspire a love of nature.

This shift in focus is starting to appear in environmental policy. For example, the UK’s recent 25-year environment plan identifies connecting people with the environment as one of its six key areas. Similarly, in Australia, the state of Victoria’s Biodiversity 2037 plan aims to connect all Victorians to nature as one of two overarching objectives.

The thinking behind such efforts is simple: connecting people to nature will motivate them to act in ways that protect and care for nature. Evidence does suggest that people who have a high nature connection are likely to display pro-environmental attitudes and behaviours.

Looking beyond the park

What is less clear is how to enhance an individual’s nature connection – that is feeling that they are a part of nature. Over half of all people globally, and nine out of ten people in Australia, live in urban environments. This reduces their opportunities to experience and connect with nature.

Our new study may offer some answers. A survey of Brisbane residents showed that people who experienced nature during childhood or had regular contact with nature in their home and suburb were more likely to report feeling connected with nature.

The study used a broad definition of urban nature to include all the plants and animals that live in a city. When looking to connect urban residents with local nature we need to take a broad view and look “beyond the park”. All aspects of nature in the city offer a potential opportunity for people to experience nature and develop their sense of connection to it.

Raffles Place, Singapore – all urban nature should be seen as an opportunity for nature connection.
Anne Cleary, Author provided

The study also looked at the relationship between childhood and adult nature experiences. Results suggest that people who lack childhood experience of nature can still come to have a high sense of nature connection by experiencing nature as an adult.

There have been focused efforts on connecting children to nature, such as the Forest Schools and Nature Play programs. Equal effort should be given to promoting adult nature experiences and nature connection, particularly for people who lack such experiences.

The benefits of nature experience

We still have much to discover about how an individual’s nature connection is shaped. We need a better understanding of how people from diverse cultural and social contexts experience and connect to different types of nature. That said, we are starting to understand the important role that frequent local experiences of nature may play.

In addition to boosting people’s sense of nature connection, daily doses of urban nature deliver the benefits of improved physical, mental and social wellbeing. A growing evidence base is showing that exposure to nature, particularly in urban environments, can lead to healthier and happier city dwellers.

Robert Dunn and colleagues have already advocated for the importance of urban nature experiences as a way to bolster city residents’ support for conservation. They described the “pigeon paradox” whereby experiencing urban nature, which is often of low ecological value – such as interactions with non-native species – may have wider environmental benefits through people behaving in more environmentally conscious ways. They proposed that the future of conservation depended on city residents’ ability to experience urban nature.

As new evidence emerges we need to build on this thinking. It would seem that the future of our very connection to nature, our wellbeing and conservation depend on urban people’s ability to experience urban nature.The Conversation

The pigeon paradox: interactions with urban nature – here in London’s Hyde Park – may help make city dwellers more environmentally conscious.
Anne Cleary, Author provided

Anne Cleary, Research Fellow, School of Medicine, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The ‘Waterfall Tour 2010’


The ‘Waterfall Tour 2010’ is the name of the latest holiday/trip that I’m currently on. It’s not as well organised as my previous holiday around the state which came with a Google Map, Blog updates and photos, etc. However, this one will end up being fairly well represented. Already I have some content on the web and more will follow tonight – more photos and videos. I doubt that I will get everything ‘up to the minute’ as I did last time, as I expect most to be done in the aftermath of the actual trip.

I only decided this morning that I would go on this trip and then left half an hour later – forming the route of the trip as I went along. It is now fairly well formed in my head – I think.

When I finally get everything together, there should be content on Flickr (photos), YouTube (videos), Google Maps (map of the route), Blog posts on Kevin’s Walk on the Wild Side (my wilderness and travel Blog) and Kevin’s Daily (a Blog on which I post either a photo, video, link or quote each day), as well as content on my website at kevinswilderness.com . For Facebook and Twitter followers, you would already be getting updates from both Flickr and YouTube I think, as these sites are getting the photos and videos fairly quickly after they are ready. However, video preparation may take me a little longer now as well – I have a bit to edit and piece together.

Anyhow, as it comes together and is ready to share you can catch it all here on the Wild Side Blog and/or updates on progress in both Facebook and Twitter.

To keep you interested (perhaps), tomorrow I am probably going to see something like 4 or 5 waterfalls, if not more. I saw two today and 1 yesterday.

 

Copenhagen Summit Fails to Deliver


In news that has delighted the ears of climate change sceptics the world over, the Copenhagen summit on climate change has failed to deliver anything of real value that will actually make a difference. It is truly disappointing that even in the face of a massive environmental disaster that will affect the entire planet, global leaders have failed to lead and work together in finding solutions to the major issues we face over the coming decades and century.

Newspapers in Australia have reported the failure of the summit and are reporting on the leader of the opposition gloating over the failure of the summit. His solution is to ignore the real issue and hope that the Australian people prove to be as oblivious to climate change as the coalition he leads.

Typically, the usual anti-Kevin Rudd biased journalists and climate change sceptics of the newspaper (The Sunday Telegraph) I read this morning, were also quick to pour further scorn on the Prime Minister and the problem of climate change itself (which they deny). One particular vocal climate change sceptic in the Sunday Telegraph has very little credibility with me and I find his obsessive anti-Rudd tirades more than a little tiring. This self-opinionated buffoon is little more than an embarrassment for both the Sunday Telegraph and the Daily Telegraph for which he also writes. His columns are becoming more of a personal vendetta against Kevin Rudd than anything resembling real journalism.

I’ll be finding a better way to become acquainted with the daily news than continuing to read the biased diatribes that continue to be put forward by these papers in future. I’ll also be hoping that our leaders can overcome the various preoccupations each have with self-interest (whether it be personal or national) in order to reach a real workable agreement on dealing with the growing threat of climate change