What, there are three different types of photosynthesis?

As if Photosynthesis was not complicated enough, there are actually different variations of how plants convert CO2 (Carbon dioxide) to C6H12O6 (Carbohydrates).  Plants have various physiologies to adapt to various environments on earth.  Alfalfa for instance can remain persistent and prolific during certain drought episodes due to its deep taproot that can help the plant utilize deep water sources.  In term this causes the Alfalfa legume to be sensitive to poorly drained soils that are not very permeable to surface water.  So the question someone could ask is; do all desert plants have long roots?  The answer is no, but one way desert plants conserve water and grow in a hot and arid climate is by the way they photosynthesize.

The three main types of photosynthesis are C3, C4, and CAM (crassulacean acid metabolism).  In college I had to memorize some of their pathways and mechanisms, but I will highlight what gives one an advantage over another and what types of crops, forages, and weeds have specialized C3 and C4 photosynthesis.  This will tell us why they can do well in certain climates and times of the year and when we can expect certain plants to be more abundant.

Rubisco is the name of the enzyme (protein) that “grabs” the CO2 molecule and puts it into the assembly line that will create the carbohydrates.  It is known as the most abundant protein in the world.  When we examine the quality of feed in our forages, it is rubisco that makes up most of the protein value in the forage analysis.  That is one of the main reasons leaves are desired over stems in hay.

C3 photosynthesis is the predominant way plants will take in carbon dioxide and produce carbohydrates.  In C3 photosynthesis Rubisco takes the CO2 and it is reduced into carbohydrates all in the same place and time.  By that, I mean in the same cell chloroplast and during the day (sunshine) when the stomata are open and the CO2 is entering the cell and the water is leaving through the same opening.  The issue with this is that it has the greatest water loss and during very high photosynthetic times (July) it becomes stressful for the plant.  Another issue is that oxygen is generated during photosynthesis and the oxygen will inhibit rubisco and slow photosynthesis down when the system is running very fast.  It seems counterintuitive, but the slow down allows the plant to deal with too much light that could cause damage.  Ever notice that cool season grasses do not grow too fast in July and August?  Cool season grasses have a C3 photosynthesis mechanism.

Now let us transition to some of the C4 grasses, also known as “warm season grasses” such as corn, sorghum, crab grass, sugarcane, bermuda grass, and foxtail.  These plants have rubisco in one cell and they have a mechanism of pulling the CO2 in a different cell that is connected by openings between the cells called plasmodesmata connecting the two cells together.  So what happens is that the plant can concentrate its CO2 where the rubisco is located and prevent that oxygen inhibition caused in the C3 mechanism.   These plants don’t have that high sunlight, July inhibition.  In addition to that, the specialization of the cells allows for approximately 40% less water usage per weight of CO2 reduction.  This just means that it is 40% more efficient in water usage on average.  There is always variation among species.  C4 plants can also partially close their stomata to prevent water loss and because they concentrate the CO2 in a different area, the oxygen will not inhibit the rubisco enzyme.  This is one of the major reasons why warm season paddocks are desired in a rotational grazing operation.  It allows for growth during the July and August time period, when the cool season, C3 grasses are inhibited and not actively growing.

Here is the misconception; many dicots (broadleaves) are also C4 plants, it is not just the grasses!  Sedges and many of the Amaranthus species are C4 plants, they seem to be the largest plant families in this C4-broadleaf category.  So Palmer Amaranth and Spiny Amaranth, along with the sedges do great in July and August.  The fact that they are C4 plants could be contributing to this phenomenon. Knowing this allows a farmer to possibly tackle a weed before it takes over a field when a desirable cool season crop could be growing slowly or possibly dormant.  Only 1% of all known plant species have C4 metabolism and even less have CAM metabolism.

Finally there is CAM photosynthesis. CAM is found in desert plants.  What these plants do is open up their stomata at night to allow CO2 in to minimize the water loss during the hot days.  The CO2 is stored in the plant vacuole as malic acid during the night.  When the desert sun comes out, the stomatal openings are closed and the CO2 is “removed” from the malic acid to then be introduced to rubisco and make carbohydrates.  By comparison, CAM is even more water efficient than C4 is.  If C4 is 40% more water efficient, CAM is 83% more efficient as compared to most C3 photosynthetic processes.  Cacti, many succulents, and the pineapple have CAM photosynthetic metabolism.

 

Resources:

  1. Taiz and Zeiger, Plant Physiology Ed. 3
  2. Christin and Edwards, The C4 plant lineages of planet Earth, Journal of Experimental Botany

 

CATTLEMEN’S ROUNDUP & OARDC BEEF AND FORAGE NIGHT

Friday, August 26th is OARDC Jackson’s Beef and Forage Night which will be held in conjunction with the Ohio Cattlemen’s Association Roundup on Saturday, August 27th. Both events require registration. Friday’s registration is due by August 23rd and Saturday’s is due by August 15th. Follow the links above to find out more information. Registration for one or both events can be made online by clicking here.

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Farm Science Review 2016

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Farm Science Review (FSR) 2016 will be held Sept. 20-22 at the Molly Caren Agricultural Center near London, Ohio. Farm Science Review offers farmers and other visitors the opportunity to learn about the latest agricultural innovations from experts from the College of Food, Agricultural, and Environmental Sciences (CFAES) at The Ohio State University.

Farm Science Review offers visitors nearly 180 educational presentations and opportunities presented by educators, specialists and faculty from Ohio State University Extension and the Ohio Agricultural Research and Development Center (OARDC).  Annually FSR draws between 110,000 and 130,000 farmers, growers, producers and agricultural enthusiasts from across the U.S. and Canada and offers more than 4,000 product lines from 630 commercial exhibitors. To view the full schedule of events and presentations click here.

Advance tickets for the Farm Science Review are $7 at all OSU Extension county offices, many local agribusinesses and online (click here). Tickets are $10 at the gate. Children 5 and younger are admitted free. Hours are 8 a.m. to 5 p.m. Sept. 20-21 and 8 a.m. to 4 p.m. Sept. 22.

If you plan to visit FSR for more than one day, there are many lodging options available in the London area. Some offer discounts for FSR attendance, be sure to mention it when making reservations. Golf carts will be permitted on the grounds for visitors with a documented disability or a doctor’s excuse. Privately owned carts are permitted on the grounds, but must be checked in with a $10 fee and rentals will be available from The Golf Cart Company. Call 1-800-589-8833 to make reservations or fill out the reservation form online.

Farm Science Review tickets are available until September 18th at the following Noble County locations:

Noble County OSU Extension OfficeL & H TractorAgland Co-opJones Feed, and M&M Feed and Supply

Container Gardening class at Hocking Valley Community Hospital Wednesday September 7th at 6pm

I am working on a really neat project right now that I am excited about.

A few weeks ago I was contacted by Latricia Johnston, Director of HVCH Foundation and Community Relations for the Hocking Valley Community Hospital about helping them design a project to celebrate their upcoming 50th anniversary.  They have an event upcoming and wanted to show off the hospital which they are rightfully proud of.   We bounced some ideas on the phone to come up with something cool.

They have a really neat courtyard in the middle of the hospital.

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The plan is to plant a container vegetable and herb garden with 5 different stations of containers that will be used as a display of healthy produce with a collaboration from HVCH Nutrition and Food Services.  The timeline was to have this done by the end of September.  That was not a ton of time to get a veggie garden fully planted, but with some awesome donations from Rick Webb of Webb’s Perennials and two runs to get dirt in my truck I got the herbs, tomatoes, and peppers in.  More veggies will follow in late summer.

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The garden is coming along nicely and should make a great display for their 50th anniversary event.  I wish it would rain so the Master Gardener Volunteers and myself did not have to make so many watering trips but what can you do about that?  I will be teaching a class on container gardening in concert with Denise Kiamy, Director of Nutrition and Food Services in September.   Info is below courtesy of the HVCH weekly newsletter.  It is free and open to the public and will showcase how anyone can have a garden even if you do not have a yard.

Gardening class at HVCH Sept. 7

 

Hocking Valley Community Hospital in partnership with Ohio State University Extension presents: Successful Strategies & Healthful Benefits for Growing Herbs and Vegetables in Containers.

Growing in containers can let the home gardener have a successful gardening season even if they have limited space and time. Come learn the basics of container gardening with a presentation as well as hands-on display of a container herb and vegetable garden. Gardeners of all skill levels are welcome to attend this free class taught by Tim McDermott, Agriculture and Natural Resources Educator, Ohio State Extension.

Denise Kiamy, Director of Nutrition & Food Services will share the nutritional benefits of eating the fruits of your own labor! Join our guest speakers in the HVCH Courtyard on Wednesday, September 7th at 6 p.m. Please call 740-380-8336 to register for this FREE event. Limited seating is available. Snacks to be served made from the container produce.

Horseflies Are Back

Horseflies are building in population here in Southeast Ohio. There are several species of horse flies in Ohio ranging in size from 3/8″ – 1 1/8″ in length. All are aggressive and vicious biters. Horse flies have specialized vision that allows them to see heat; they literally use thermal imaging to locate their hosts. The flies are also able to track large moving objects, particularly dark colored objects, even while the flies are in fast flight. Taken together, their visual acuity allows them to effectively zero in on large, savory, warm blooded animals like cows, deer, people, and of course, horses. Unfortunately for the flies, their visual perception may also cause them to be fooled. A dark colored moving car or tractor that has been warmed by the summer sun looks to a horse fly like a dark, galloping horse, which is why they sometimes chase me when I am on the tractor!

There are a number of things you can do to keep yourself off the horse fly menu. If possible, avoid horse fly habitat. Their larvae feed on decaying organic matter in moist soil, so horse flies are frequently found in swamps or near streams and ponds. If you can’t avoid their habitat, schedule your activities to avoid the flies. Horse flies are active during the day; they can’t find their hosts at night. So, evening pool parties will be free of horse flies. If you must venture into horse fly habitat during the day, remain alert and take precautions. Most flies are silent flyers while horse flies produce a loud, buzzing sound. When you hear the buzz, locate the fly because horse flies love to land stealthily for a quick bite. However, avoid running; remember that horse flies are attracted to moving objects! Wear light clothing. Finally, while insect repellents may provide some protection, horse flies are very good at finding unprotected skin. Long sleeves, long pants, and neckerchiefs can help to thwart the flies.