Physiological, morphological, and spectral reflectance characteristics of Kentucky bluegrass, Texas bluegrass, and their hybrids in response to water stress
Date
2002
Authors
Ploense, Mary Rebecca, author
Qian, Yaling, advisor
Hoffer, Roger, committee member
Koski, Anthony, committee member
Cardon, Grant, committee member
Wallner, Stephen J., committee member
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Abstract
Demands on fresh water resources, especially throughout the arid and semi-arid western USA, have resulted in escalation of government regulations to force water conservation. Such measures have included limitations on the permissible area devoted to turfgrass, restrictions on the quantity of potable water relegated to turfgrass irrigation, and mandates on the types of turfgrass permitted. As a result, identification and development of turfgrasses exhibiting improved drought resistance as well as those able to withstand secondary irrigation waters high in soluble salts has become paramount. Towards this end, three studies were conducted. In Study 1 Kentucky bluegrass (Poa pratensis L.) (KBG), Texas bluegrass (Poa arachnifera Torr.) (TBG), and their hybrids (HBG) were evaluated for salt tolerance. A broad range of variability in leaf firing and shoot and root growth reduction in response to salinity was found to exist within and among these Poa spp. and their hybrids, indicating that improvement in the salt tolerance of bluegrasses may be possible. In study 2 HBG and KBG water use characteristics and response to drought were compared. Hybrid bluegrass exhibited a lower inherent ET rate, as well as the ability to moderate its ET as evaporative demand increased, relative to KBG, thereby reducing water loss. Hybrid bluegrass also exhibited lower leaf water content and slower shoot growth than KBG under non-limiting soil moisture conditions, characteristics advantageous to reduce water use. Additionally, HBG possesses a significantly deeper, more extensive root system than KBG enabling water extraction from a greater volume of depth when surface soil water is depleted. These factors combined contributed significantly to the drought avoidance ability observed in HBG. In study 3 we found spectral reflectance within the far-red region of the visible portion of the spectrum to be most sensitive to, and highly correlated with, progressive dehydration. These wavelengths might effectively be used as an irrigation management tool in nondestructively monitoring leaf water status. Computation of reflectance difference between non-stressed and dehydrated leaves of HBG, KBG, and perennial ryegrass (Lolium perenne L.) revealed consistent differences in their reflectance sensitivity to dehydration. This sensitivity ranking was comparable with previous reports of drought resistance among these grasses, suggesting that the magnitude of reflectance change may be used as an indicator of drought resistance.
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Subject
Bluegrasses
Plants -- Effect of drought on