April 8, 2020 | David F. Coppedge

Botanical Marvels: How Plants Catch Light and Take Flight

Land plants enhance our world in many ways, but some of the most amazing ways are at the micro level and atomic level.

Here are some amazing facts about plants. But avoid the temptation to scroll down to the Grand Finale!

How Fast Is a Plant?

The light-collecting chloroplasts in plant leaves can respond in a fraction of a second, claims a press release in eLife. An international collaboration of scientists used ultra-bright X-ray bursts to measure the reaction time.

“The phytochrome allows organisms to distinguish between two colours of light, giving plants, fungi and bacteria primitive two-colour vision,” explains lead author Elin Claesson, a doctoral student at the University of Gothenburg, Sweden. “Key to its function is the initial response to light, where the light signal is translated into structural changes over a fraction of a second….”

One motion they observed was a twisting motion of the D-ring, a portion of the chromophore. This D-ring operations like a gear or switch. It “causes displacement of the neighbouring rings as well as changes of atoms around the chromophore.” Why is this important to us humans?

“These findings demonstrate that the initial response to light is highly collective and that many parts of the chromophore and phytochrome protein play an important role,” concludes senior author Sebastian Westenhoff. “Our study confirms a previous working model of the twisting motion of the D-ring and suggests that the pyrrole water molecule is also important in this process. We propose that both chemical events work together enabling phytochrome proteins to translate light into structural signals, guiding the growth and development of plants, fungi and bacteria on Earth.”

How Plants Stay Young

At the tip of a plant stem, and along points where branches develop, there are clusters of stem cells. When these stem cells divide, one daughter maintains its young ‘stem-ness’ properties while the other differentiates to form tissue. The Chinese Academy of Sciences found that “Genetic self-activation maintains plant stem cells,” reports Phys.org. “The study … describes how a key shoot stem cell-promoting gene activates its own expression, thus maintaining a stem cell lineage in the leaf axil that enables branching.”

How Plants Sense Temperature

A specific protein named Phytochrome B acts like a thermostat, allowing plants to adjust their behavior to temperature. Researchers found at the University of California, Riverside (Phys.org) sought to understand how this thermostat works by studying proteins called phytochromes.

Phytochromes switch between active and inactive forms like a binary switch controlled by light and temperature. In direct sunlight, such as in open fields, phytochromes switch “on,” absorbing far-red light. This active form inhibits stem elongation, which limits how tall plants in direct sunlight can grow.

In shade phytochromes are less active, absorbing red. This “off” form releases the inhibition of stem growth, so plants grow taller in shade to compete with other plants for more sunlight.

Phytochrome B proteins cluster into collections called photobodies.

Photobodies are large, dynamic protein complexes. Our results suggest that each of them could have a different composition,” Chen said. “What we think is that the unique composition of individual photobodies make them react to temperature differently.”

Molecular biologists used to think that the photobodies appeared in sunlight (the “on” position) and vanished in the shade (the “off” position). The scientists at UCR found this to be incorrect; a “completely unexpected” mechanism operates the switch instead. The photobodies cluster outside the nucleus for the “off” position, but inside for the “on” position. Moreover, this mechanism provides more of a rheostat than a thermostat to finely tune the response to light. They say, “individual photobodies could be sensors for specific temperature ranges.”

The team found increasing the temperature did not cause all the photobodies to disappear at once. Instead, specific photobodies disappeared in specific ranges of temperature. Increasing the temperature incrementally reduced the number of photobodies as they disappeared selectively.

The response of the plant, therefore, is finely tuned at the molecular level. Phytochrome B can sense and respond to temperature “from two different locations on the molecule,” providing even more elegant regulation of the response.

The Best for Last

After hearing details of molecules, here’s a treat that will wake you up! two years ago (25 Oct 2018), we reported findings about dandelion seeds. We showed what scientists learned, using wind tunnels, about how they stay aloft. Illustra Media has just released another dazzling “2-Minute Wonder” short film that explains the mechanism with beautiful photography and stunning animation. We don’t need to say anything more: just watch this “Uplifting Story” —

Isn’t that amazing? You can share this short film on social media using the paper-airplane icon at the end of the film, or the following link to The John 10:10 Project. Your friends will love it!

 

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