Grasses all day, every day, and grasses ever after, amen!

My life, as well as the lives of billions of other people, are intertwined with grasses...we are touched by them....from the time we wake up in the morning, to the time we sleep at night.

This was what I tried to convey during a talk with Matt Candelas of In Defense of Plants.

In my case, when I wake up in the morning, I (like literally billions of other people around the world) encounter members of the grass family, or derivatives of it, throughout the day.

The first thing I do in the morning is eat a bowl of oatmeal, and oatmeal of course is from the grass Avena sativa. 

When I eat my bowl of oatmeal, I put  some sugar into the mix of fruits, and around 80% of sugar in the world is derived from a grass, sugarcane (Saccharum officinarum).

I walk out to my car, and I'll see suburban lawns stretching to the horizon, and the turf grass of course is a mix of various grass species. In Florida it would be Stenotaphrum secundatum (St. Augustine grass), Paspalum notatum (Bahia grass) and maybe Cynodon dactylon (Bermuda grass), while in the Northeast you get various mixes of Poa pratensis (Kentucky bluegrass), Festuca spp, and Lolium spp.

Such species are what people normally think of when you mention the word "grass" to them. Ornamental grasses also fall into this category of grasses that are used in landscaping.

When I drive my car to work, the ethanol in my gasoline tank is likely as not made from Zea mays. In fact, around 40% of all corn production is used as bioethanol!

During lunch, I might go out and get a burger, and where would that be without the bread that frames the delicious ingredients between them? Bread of course is from a grass that we call wheat,  (Triticum aestivum and its ilk).

Maybe I also eat some snacks for lunch, and if you are brave enough to look at the ingredients of your candy or chips, you'll probably find something called high fructose corn syrup in it. This is a very common ingredient of packaged foods, because it adds to the sweetness of the food, and this is of course derived from a grass that we already mentioned above, Zea mays (corn/maize).

In fact, if you live in the USA, your body is probably mostly derived from that single grass species. Here is a great documentary that explores in some depth the ubiquity of Z. mays in American life.  

Finally, during some part of the day, I'll probably eat rice (Oryza sativa) during either lunch or dinner (and sometimes breakfast too!). Rice is, of course, one of those grasses that have been essential in the creation and and molding of entire civilizations (which I'll look into next time).

And I'm not even including all the times we use bamboo implements and tools!

So no matter how you look at it, the family Poaceae is by far the most influential and important plant family in the world. It's grasses all day, every day, and grasses ever after, amen!

Winter is Coming: How Grasses Conquered the Long Freeze

Tundra (By Education Specialist)

There are vast areas of the world where cold temperatures create problems for plants.

Such "cold stress" happens when temperatures that are below what are optimal for plants creates physiological problems for the individual plants. Depending on the species, optimal growing conditions usually hovers between 10℃ and 30℃. 

There are two types of cold stress, depending on the temperatures involved.

Chilling refers to cold stress where the temperatures range between 0℃ and 15℃, whereas freezing refers to cold stress where the temperatures are below freezing (0℃). 

In the case of freezing, plants can respond via two different methods. Freezing avoidance is when the plant is able to delay or even prevent freezing altogether in their tissues. In contrast, in freezing tolerance, the plants do not prevent ice crystal formation, but they avoid damage by controlling the size of the crystals and/or where the crystals are formed. Freeze-tolerant plants can survive even freezing of their tissues, and represent the extreme adaptation to conquering the cold over long time periods.

Deschampsia antartica (c) Lomvi2 - Wikipedia

Grasses initially evolved as tropical plants that loved the warmth. But over time, the grasses have managed to adapt to the cold and have become the most widespread vascular plant family, and present in all continents. Indeed, the grass Deschampsia antartica is only one of two vascular plants that are native to Antarctica, and its optimal growing temperature is an amazing 10℃!

Freezing can kill grasses via the formation of ice crystals. At first, ice crystals form in the extracellular spaces between cells, which causes water to be pulled from the cell interior. The loss of intracellular water (and later solutes) results in dehydration and osmotic stress. As ice crystals continue to form into the interior of the cells, the cell membranes start to degrade and programmed cell death occurs.

The evolution of the ability to tolerate freezing in the Poaceae is fascinating, and is confined mostly to species in two different subfamilies of the Poaceae. Grasses in the subfamilies Pooideae (in the Northern Hemisphere) and Danthonioideae (in the Southern Hemisphere) live in cold temperate continental regions, and they have solved the problem in two different ways. 

Hordeum jubatum of the subfamily Pooideae (Northern Hemisphere)

The grasses in subfamily Pooideae in the Northern Hemisphere all use the C3 mode of photosynthesis, and are commonly called the cool season grasses. They include many turf grasses (such as Poa pratensis or Kentucky Bluegrass), as well as food staples such as Triticum aestivum (wheat), Avena sativa (oat), and Hordeum vulgare (barley). 

The ancestors of the Pooideae evolved about 67 million years ago in small niches during the formation of the Eurasian mountain ranges. In this group, ice binding proteins evolved which decreased the rate of the formation of ice, as well as altering the shape of the ice crystals being formed. These anti-freeze proteins prevent the formation of large crystals that can physically damage cells and tissues.

Cortaderia selloana from the subfamily Danthonioideae (Southern Hemisphere)

In contrast, cold-acclimated grasses from the subfamily Danthonioideae in the Southern Hemisphere have evolved a different method for conquering the cold. The members of this group are also C3 grasses, and include the large ornamental grass Cortaderia selloana (Pampas grass). The freeze tolerant members of this subfamily produce ice-nucleation proteins that allow them to control where ice crystals form. Thus, they can prevent damage by limiting crystal formation in the extra-cellular spaces and the leaf surfaces, but not within the cell interiors.

The independent evolution of such mechanisms by the Danthonioideae and Pooideae to tolerate freezing have enabled grasses to dominate large areas where there are extreme seasonal fluctuations in temperature, and contributed to the grassy world we live in today. 

As an interesting aside, at the other end of the temperature spectrum, C4 grasses such as those in the grass subfamilies Chloridoideae and Andropogoneae - which include corn/maize (Zea mays), the bluestems (Andropogon spp), sugarcane (Saccharum officinarum), and cogon grasses (Imperata cylindrica) - have extended the range of environments conquered by the Poaceae to much warmer and drier climes. 

For a quick look at the difference between C3, C4 and CAM photosynthesis in grasses, click here.

Muhlenbergia sericea of the subfamily Chloridoideae, a C4 grass

Finally, to read more about the fascinating topic of cold adaptation in grasses in depth, check out the references below.

Note: In addition to the specialized mechanisms of freezing tolerance above, grasses can deploy other additional mechanisms for coping with the cold that are beyond the scope of this shirt post, such as accumulating fructan in their vacuoles, using supercooling (for shorter cold spells), and increasing anti-oxidant enzymes.

Phalaris arundinacea of the subfamily Pooideae

References:

Timothy J. Gallaher, T. J. Gallaher, Paul M. Peterson, P. M. Peterson, Robert J. Soreng, R. J. Soreng, Fernando O. Zuloaga, F. O. Zuloaga, De-Zhu Li, D. Li, Lynn G. Clark, L. G. Clark, Christopher D. Tyrrell, C. D. Tyrrell, Cassiano A.D. Welker, C. A.D. Welker, Elizabeth A. Kellogg, E. A. Kellogg, & Jordan K. Teisher, J. K. Teisher. (2022). Grasses through space and time: An overview of the biogeographical and macroevolutionary history of Poaceae. Journal of systematics and evolution, 60, 522-569. doi: 10.1111/jse.12857

Schubert M, Humphreys AM, Lindberg CL, Preston JC, Fjellheim S. 2020. To coldly go where no grass has gone before: A multidisciplinary review of cold adaptation in Poaceae. In: Annual Plant Reviews online.Wiley.523–562.

Let Them Grow Cake! Climate Change and The Wheat Crises

by Bluemoose

Triticum  aestivum (common wheat) and a few other species in the grass genus Triticum  (T. durum and T. compactum) are the source of one of the most important staple foods in the world. These grasses are grown in more than 200 million ha of land worldwide, and in 2020 world annual production of wheat stood at 760 million tons. But now an unfortunate combination of climate change and war have threatened our food supply.

Extreme weather events in almost all the wheat producing regions in the world have been causing chaos in the food supply. India, one of the top three wheat exporting countries,  has seen record high temperatures that have severely impacted their crops, so much so that the Indian government just declared limits on wheat export. In China, floods have also potentially compromised wheat supply, and in the EU, US, and Canada various combinations of drought and unseasonably warm temperatures have also threatened wheat crops. Meanwhile, Russia seems relatively unaffected by the extreme weather events going on elsewhere, but the war in Ukraine has limited its role in at least helping to dampen the growing impact of climate change on this year's food supply. Some estimates have declared that the world has only 10 weeks supply of wheat left, and this will be sure to create increases in the prices of bread and other staple foods going forward.

In the end, we owe it to ourselves and to our children to makes sure we address the growing impact of climate change, not only on other species, but on our own, before it becomes too late.