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.




Read more:
Why there’s a lot more to love about jacarandas than just their purple flowers


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.




Read more:
The secret life of puddles: their value to nature is subtle, but hugely important


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!




Read more:
It is risen: the story of resurrection ferns and my late colleague who helped discover them in Australia


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.

Environmental activism goes digital in lockdown – but could it change the movement for good?



Greta Thunberg talks with Professor Johan Rockström about the coronavirus and the environment at the Nobel Museum in Stockholm, Sweden, April 21 2020.
EPA-EFE/Jessica Gow

William Finnegan, University of Oxford

The environmental movement’s past recently collided with its future. April 22 marked the 50th anniversary of the first Earth Day, a milestone for environmentalism. A few days later, a global school strike was organised by Fridays for Future, the international coalition of young people inspired by Greta Thunberg’s protests against climate change. But after months of careful planning, both occasions were upended by the COVID-19 pandemic – and went online instead.

So when social distancing measures are eased, will protests return to the streets, or do these events mark a turning point?

In 1970, an estimated 20 million Americans (10% of the US population at the time) participated in the first Earth Day. Back then, US senator Gaylord Nelson conceived of a national “teach-in” to raise environmental awareness and recruited Harvard law student Denis Hayes to organise the event.




Read more:
Earth Day at 50 – what the environmental holiday means today


Teach-ins had emerged in the mid-1960s as a hybrid of student sit-ins and informal lectures in opposition to the Vietnam War. Rather than going on strike, teachers and students occupied classrooms instead. According to environmental historian Adam Rome, 1,500 universities and 10,000 schools held Earth Day teach-ins in April 1970, “nurturing a generation of activists.”

A postage stamp issued to commemorate the first Earth Day, April 1970.
Michael Rega/Shutterstock

In the decades that followed, the environmental movement grew into a political and cultural force. Yet subsequent Earth Days failed to capture the urgency and grassroots passion of the original.

The 50th anniversary Earth Day sought to address this by going back to its roots. Teach-ins were planned for classrooms and campuses across the world, but COVID-19 closed schools. The day of action evolved into a 12-hour live-stream during which actors, athletes, musicians, politicians, and even Pope Francis shared messages of environmental stewardship and climate action.

The school climate strikes originated in August 2018, when 15-year-old Greta Thunberg skipped school to protest inaction on climate change outside the Swedish parliament.

Within little more than a year, seven million students and their supporters were joining school strikes around the world and Thunberg was making headlines for her scathing speeches at the UN climate conference in Poland and [World Economic Forum in Davos]. Another global strike was scheduled for April 2020, but COVID-19 again pushed the event online.

The school strikes and annual Earth Day celebrations reflect different generations of environmental activism and different philosophies of protest. Yet both have been guided by the environmental slogan “think globally, act locally”. During the pandemic, environmental activists are now thinking globally and acting digitally.

‘Clicktivism’ and digital natives

I’m researching climate change education and youth climate activism in the UK. Like the protesters, I’ve been forced to adapt my plans and have been exploring the digital side of climate activism.

Online activism has been called “clicktivism”, or, disparagingly, “slacktivism”. It’s been characterised as impulsive, noncommittal and easily replicated, emphasising the lower risks and costs of political expression on social media versus protest and political engagement in the real world. But the relationship between digital technology and social movements is more complicated.

Researchers are split on the precise role of digital activism. From one perspective, campaigners can use social media to “supersize” their public engagement. This helps them to reach more people and bypass traditional media channels. Other researchers emphasise the power of the internet to help activists self-organise. Without the structure or hierarchy of traditional organisations, digital platforms can allow completely new forms of activism to flourish.




Read more:
Beyond hashtags: how a new wave of digital activists is changing society


A recent study found that climate advocacy groups that started on the internet, such as 350.org, have different online strategies, tactics and theories of change compared to older environmental groups such as Greenpeace. Founded in 2008, 350.org (which is both a URL and reference to the safe level of 350 parts per million carbon dioxide in the atmosphere) led the first wave of internet-savvy, youth-driven environmental organisations.

Successful digital campaigns at 350.org have been described as a virtuous cycle where online tools spur offline action – the results of which can be documented and shared online to inspire further action.

Modern activists can film demonstrations using smartphones and share them online, reaching a much wider audience.
Rachael Warriner/Shutterstock

It’s too early to say how the school climate strikes of 2019 have influenced the broader movement, but current research is exploring how climate strikers are using Instagram and how collective identities on social media may drive collective action. As “digital natives”, these young climate activists grew up with the internet, smartphones and social media. Their movement uses memes and hashtags across YouTube, Instagram and Twitter, where Thunberg has more than four million followers.

While COVID-19 prevents offline action, thousands of #ClimateStrikeOnline social media posts show solitary protesters around the world armed with handmade signs, a virtual echo of where the movement started. When it comes to climate activism, digital natives are now leading the way. The revolution will be live-streamed.The Conversation

William Finnegan, PhD Candidate in Climate Education and Activism, University of Oxford

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

A current affair: the movement of ocean waters around Australia



File 20181219 27776 1jdhree.jpg?ixlib=rb 1.1
Where do the ocean waters that wash the Gold Coast come from?
Flickr/LJ Mears , CC BY-NC-SA

Charitha Pattiaratchi, University of Western Australia; Ems Wijeratne, University of Western Australia, and Roger Proctor, University of Tasmania

Many people in Australia will head to the beach this summer and that’ll most likely include a dip or a plunge into the sea. But have you ever wondered where those ocean waters come from, and what influence they may have?

Australia is surrounded by ocean currents that have a strong controlling influence on things such as climate, ecosystems, fish migrations, the transport of ocean debris and on water quality.

We did a study, published in April 2018, that helps to give us a better understanding of those ocean currents.

Surface currents around the Australian continent.
Ems Wijeratne/Charitha Pattiaratchi/Roger Proctor



Read more:
New map shows that only 13% of the oceans are still truly wild


Go with the flow: Indian Ocean

Our 15 year simulation indicates that water from the Pacific Ocean enters the Indonesian Archipelago through the Mindanao current (north) and Halmahera Sea (south).

It then enters the Indian ocean as the Indonesian Throughflow between many Indonesian Islands, with flow through the Timor Passage being the most dominant.

Most of this water flows west as the South Equatorial Current. Re-circulation of the SEC creates the Eastern Gyre that contributes to the Holloway Current. This in turn feeds the Leeuwin Current – the longest boundary current in the world (Ocean currents that flow adjacent to a coastline are called boundary currents)

The Leeuwin Current is the major boundary current along the west coast and as it moves southward. Indian Ocean water is supplied by the South Indian Counter Current increasing the Leeuwin Current transport by 60%.

The Leeuwin Current turns east at Cape Leeuwin, in Western Australia’s south-west, and continues to Tasmania as the South Australian and Zeehan Currents.

The Leeuwin Current passes the lighthouse at the Cape Leeuwin in WA.
Flickr/Cheng, CC BY-NC-ND

There is a strong seasonal variation in the strength of the boundary currents in the Indian Ocean with a progression southwards of the peak transport along the coast.

The Holloway Current peaks in April/May (coinciding with changes in the monsoon winds), the Leeuwin Current reaches a maximum along the west and south coasts in June and August.




Read more:
Climate change is slowing Atlantic currents that help keep Europe warm


Go with the flow: Pacific Ocean

In the Pacific Ocean, the northern branches of the South Equatorial Current are the main inputs initiating the Hiri Current and East Australian Current.

At around latitude 15 degrees south the currents split in two: southward to form the East Australian Current, and northward to form the Hiri Current which contributes to a clockwise gyre in the Gulf of Papua.

The East Australian Current is the dominant current in the region transporting 33 million cubic metres of water per second southward.

At around 32S, the East Australian Current separates from the coast and 60% of the water flows eastward to New Zealand as the Tasman Front. The remaining 40% flows southward as the East Australian Current extension and contributes to the Tasman Outflow.

The Tasman outflow is the major conduit of water from the Pacific to Indian Ocean and contributes to the Flinders Current, flowing westward from Tasmania and past Cape Leeuwin into the Indian Ocean.

Along the southern continental slope, the Flinders Current appears as an undercurrent beneath the Leeuwin Current and a surface current further offshore. The Flinders Current contributes to the Leeuwin Undercurrent directly as a northward flow, flowing to the north-west of Australia in water depths 300 metres to 800 metres.

Impact of the currents

Understanding ocean circulation is a fundamental tenet of physical oceanography and scientists have been charting the pathways of ocean currents since the American hydrographer Matthew Maury, one of the founders of oceanography, who first charted the Gulf Stream in 1855.

One of the first maps of circulation around Australia was by Halliday (1921) who showed the movement of “warm” and “cold” waters around Australia. Although some of the major features (such as the East Australian Current) were correctly identified, a more fine scale description is now available.

Ocean surface currents around Australia by Halliday 1921.

The unique feature of ocean currents around Australia is that along both east and west coasts they transport warmer water southwards and influence the local climate, particularly air temperature and rainfall, as well as species distribution.




Read more:
Explainer: how the Antarctic Circumpolar Current helps keep Antarctica frozen


For example, the south west of Australia is up to 5C warmer in winter and receives more than double the rainfall compared to regions located on similar latitudes along western coastlines of other continents.

Similarly many tropical species of fish are found in the southwest of Australia that hitch a ride on the ocean currents.

The Pacific Ocean is the origin of waters around Australia with a direct link to the east and an indirect link to west.

Ocean water from the Pacific Ocean flows through the Indonesian Archipelago, a region subject to high solar heating and rainfall runoff, creating lower density water. This water, augmented by water from the Indian Ocean, flows around the western and southern coasts, converging along the southern coast of Tasmania.

So next time you head for a dip in the coastal waters around Australian, spare a thought for where that water has come from and where it may be going next.The Conversation

Time for a plunge in the water at Bondi Beach, NSW.
Flickr/Roderick Eime, CC BY-ND

Charitha Pattiaratchi, Professor of Coastal Oceanography, University of Western Australia; Ems Wijeratne, Assistant Professor, UWA Oceans Institute, University of Western Australia, and Roger Proctor, Director, Australian Ocean Data Network, University of Tasmania

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

Earth Hour 2012: Tonight


The link below is to an article on Earth Hour 2012, which is being held tonight. The article below includes a history of the event, which is now a global movement for ‘change.’ However, just how much change is brought about by Earth Hour is still a matter of debate. There seems to be more of an emphasis on going beyond the hour this time round, which is a far better way of drawing awareness to the need of green energy for the future and the major issue of climate change that is facing the planet. If the event is to is bring lasting change, we need to move beyond the hour as just a fun thing to do and actually bring about change to the way we live our lives the world over. There is a long way to go, as can be seen with the great difficulty of reaching any useful agreements on CO2 emission reductions and the like. Hopefully awareness can bring about real change through this event.

For more visit:
http://www.kleenexmums.com.au/sustainability/earth-hour/the-hour-of-no-power/

Earth Day (April 22): Today is Earth Day


April 22 is Earth Day. The first Earth Day was celebrated in 1970 and heralded the environmental movement. How will you celebrate Earth Day? Will you be doing something to raise awareness of issues that impact on the earth?

For more visit:
http://www.earthday.org/