| dc.description.abstract | Tall fescue (Festuca arundinacea Schreb.) is one of the commonly used cool-season
turfgrass species. Despite the many advantages of tall fescue, there are some properties
that restrict its use as turf grass. Recent efforts on selection of turf-type tall fescue focus on
fine leaf texture, darker green color, seedling turgor, overall density, tolerance to extreme
temperatures, and other stresses. The objectives of this research were to develop
techniques in screening salinity tolerant tall fescue and to investigate the leaf senescence
process, growth and nutrient uptake of tall fescue under salinity stress induced by different
types of salt. Two tall fescue cultivars, Tar Heel II (salt tolerant) and Wolfpack (salt
sensitive) were grown in silica sand as growth medium and fertilized with Hoagland
solution. Salt treatments were added to the medium along with Hoagland solution. At least
three indices calculated based on single leaf spectrum showed promise as sensitive means
to differentiate salinity stress from untreated plants. Those indices also are strongly
correlated to many physiological parameters that have been shown to be reliable measures
of salinity tolerance in many plant species including tall fescue. Tall fescue leaf senescence
was accelerated by salinity stress which was different from the aging process under shade.
Tall fescuc had several adaptation strategies in order to conserve water under salinity stress,
while the plants under shade had adaptation mechanisms centered on light harvesting. Tall
fescue accelerated old leaf senescence, whereas under shade conditions, tall fescue showed
slowing down in the new leaf development as well as mature leaf aging. Tall fescue
growth responded to salinity stress differently from shade stress, a fact that has to be taken into consideration when selecting for stress tolerant traits, such as leaf length, root to shoot
ratio. Leaf appearance rate may be different with stress tolerance levels and mediate the
tiller number and shoot density. By comparing and contrasting the effects on nutrients
uptake, it was shown that K, Ca, Mg may be very important in the ion balance and salinity
stress tolerance. Tall fescue leaf firing was mainly caused by an alkaline condition with pH
higher than 9 as in Na2C03, or moderate pH combined with high salinity (high EC) as in
CaC}i. Plant growth was more affected by sodicity which was high in Na2C03 and Na2S04•
Osmotic adjustment also played an important role in tall fescue salinity stress in chlorides.
Chloride effects were closely related to RWC of the leaves. The combination of different
salts along with the variation of their physical and chemical properties, such as EC, pH, and
osmotic potential, made the differentiation of their influence on tall fescue stress rather
difficult. Multiple properties, such as growth, morphological, and physiological, should be
measured to better understand the effects of different salts. | en_US |
