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Plants have evolved to adapt to fluctuations in water supply

ON THE FARM

Hello, Trumbull County. Is it just me or does it seem like Mother Nature is hitting the wine bottle a little too much this year? We had a very wet spring and early summer, followed by a cold and wet August, and now a hot and dry September.

We have had just a little more than three-quarters an inch of rain for the month so far, and although cooler temperatures are on the way, there isn’t much relief in sight for rain in the next several days.

This hot and dry weather is perfect for getting grain dried down in the field, and some fields of soybeans are being harvested this week. Most of corn for silage is already in the bunks or silos, and soon corn will be harvested for grain.

We’ve gone from oversaturated soils to overly dry soils in the span of a couple of weeks. Animals have the luxury of finding a more suitable location for the current weather, but plants are literally stuck in the ground and have to deal with whatever comes their way. Fortunately, they have evolved many different mechanisms to deal with extreme fluctuations in water availability.

Water-use efficiency in plants starts with little openings on the bottom sides of the leaves called stomata. The stomata take in carbon dioxide that is needed for photosynthesis, but when they are open, they allow water to escape.

Plants need to photosynthesize, but they also need water so it becomes a balancing act of resources, and many plants will shut down photosynthesis during the hottest part of the day to conserve water.

Around the stomata are two cells, called guard cells, that expand and contract with the available water. When water is plentiful the cells fill with water opening the stomata, but when water becomes scarce they lose water pressure and the stomata close.

That’s a simplistic view of the process, but you get the idea.

Soil with sufficient water in normal temperatures will allow the stomata to stay open for maximum photosynthesis. The more photosynthesis, the more sugar the plant will produce, and ultimately a larger and more flavorful crop.

In situations where there is simply too much water, like we had this spring and summer, the stomata will stay open, but there is too much water preventing oxygen from reaching the roots. Plants use oxygen for cellular respiration just like we do, and they will drown if too much water is present.

Poorly drained soils are less productive for this reason, as plants can’t grow in the absence of oxygen so they have to wait until the water reaches a favorable saturation point.

Drought conditions, like we are currently experiencing, will also limit productivity but for different physiological reasons. When soils are dry, the roots have as much oxygen as they need, but the lack of water keeps the stomata closed shutting down photosynthesis.

Crop yields can vary depending on when drought conditions occur. Pollination and grain fill are the two most critical times for sufficient water. Flower production (tassel and silk for corn) take a lot of energy and water to produce, and water shortage can severely limit the success of pollination. Without pollination, there will be no corn kernel, bean or fruit.

Grain fill is just as it sounds, it is the period of time after pollination that the grains begins to increase in size and at this point it is mostly water. Lack of water will result in smaller grain and ultimately, a lower yield.

Many seed companies are beginning to offer hybrids that are drought-resistant and genetic modification has the potential to lower the water requirements of some crops. The result of these advances will be more grain with less water ­­– or at least that is the plan.

Farming in the age of climate change will be interesting to say the least as weather patterns become more extreme. Farmers will need to adopt crop varieties and practices that fit the environmental conditions.

The Master Gardeners will be offering a training class for new Master Gardeners starting in February 2018.

Becoming a Master Gardener is a great way to increase your gardening knowledge and volunteering to help fellow gardeners in the community. You can also download an application from trumbull.osu.edu. Applications must be received in office by Dec. 13.

The Trumbull County Master Gardeners will be wrapping up their Wednesdays in the gardens series 6 p.m. Oct. 11 with “Winterizing the Garden.”

Come learn the best ways to put your gardens “to bed” at this free program at the gardens behind the Ag Center in Cortland.

For information about plant physiology, Master Gardener program, or any other program call the OSU Trumbull County Extension Office at 330-638-6783 or visit trumbull.osu.edu.

Beers can be reached at beers.66@osu.edu or 330-638-6738.

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