FEATU RE STO RY
TURFGRASS MANAGEMENT
Water: Functions, Flow and Forms By Tom Samples, Ph.D. and John Sorochan, Ph.D., Department of Plant Sciences Alan Windham, Ph.D., Department of Entomology and Plant Pathology University of Tennessee Institute of Agriculture
It
is estimated that water makes up about 71 percent of the Earth’s surface and that 96.5 percent of all the Earth’s water is salt water contained in the oceans. Only about an estimated 3.5 percent is freshwater, 69 percent of which occurs as ice in glaciers and ice caps. Slightly more than 0.7 percent or 8.6 million acre-feet of the Earth’s freshwater occurs as groundwater, rivers, lakes and streams. Turfgrass industry professionals are very aware that a susceptible turfgrass, a favorable environment and a pathogen with the ability to infect plants are required before a turfgrass disease will develop, and that free water on leaves and optimum temperatures for a certain number of hours are required for most fungal pathogens to cause disease. For example, pythium blight, a common disease of cool-season turfgrasses during hot, humid weather, is especially problematic when the surface of turfgrass leaves remain wet for at least 12 hours, the daytime temperature is greater than 82°F and the night temperature remains above 68°F. Cottony white mycelium is often visible in the morning when the surface of infected leaves are wet after a night of rain or heavy dew.
Pythium disease of tall fescue
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This article is intended to summarize how water functions and flows in a turfgrass plant.
Functions Water is essential for seed germination and plant growth, and usually comprises 75 percent or more of the fresh weight of actively growing turfgrasses. Roots contain the least amount of water, and stems the most. Water moves by way of diffusion from the soil solution into root hairs. Once inside turfgrass plants, water helps protect them from sudden changes in temperature. Both organic and inorganic molecules including sugars and essential mineral nutrients move to plant cells in water. An estimated 1 to 3 percent of the total amount of water taken up by turfgrasses every day is required to support internal biochemical reactions in plant cells, and cell division and expansion. Although this amount appears small compared to the total amount of water turfgrasses use, it is vitally important for plant survival. Without water, turfgrasses would not be able to convert
Bermuda miniverde Pythium blight advanced
TENNESSEE TURFGRASS DECEMBER/JANUARY 2020 Email TTA at: info@ttaonline.org
