Adaptability And Physiological Responses Of Tall Fescue And St.Augustinegrass To Drought Stress

Two different photosynthetic pathway turf-grasses: C3 plant/Houndog' tall fescue (Festuca arunginacea (Shreb.)) and C4 plant, 'Bitter blue' St.Augustinegrass (Stenotaphrum secundatum (Walt) Kuntze.) were used to study the physiological responses of progressive drought stress on the leaves, crowns(or stolons), roots and the effects of different irrigating treatments on shoot and root growing characteristic with its relation to drought resistance in two turf-grasses.Three water irrigating treatments (T1, T2, T3 referring to plants irrigated to field capacity every 3, 6, 9 days) were setted, which the data showed: tall fescue had deeper rooting distribution and more total rooting length than Auguestinegrass; Prolonging irrigating interval had no impact on shoot dry matter production of tall fescue but increased that of Augustinegrass, root length density (RLD) of any soil layers below 15cm in two turf-grasses increased, especially appeared in tall fescue; Shoot/root ratio (S/R) of tall fescue reduced, but that of Augustinegrass increased. In subsequent soil drought treatment after 144 days interval irrigation, soil water potential in tall fescue depleted more swiftly, but its diurnal fluctuations showed greater, especially in T3 treatment; Emergence of apparent permanent wilting symptom in Tl were earlier than that in T2 and T3, and that in tall fescue were earlier than that in Auguestinegrass; According to changing data of shoot dry matter production, relative water content and leaf chlorophyll content, prolong irrigating interval could increase drought tolerance. Integrated the above data, the results indicated: moderately prolonging irrigation interval could avail root growth and increase deeper rooting distribution, which would avail turf-grasses to enhance drought resistance. Although rooting distribution of tall fescue was deeper that that of Auguestinegrass, depletion of soil water potential in tall fescue was more swifter that in Augustinegrass, which showed drought resistance was lower than that of Augustinegrass.Under unartificial drought conditions, the soil volumetric water content and leaf relative water content of tall fescue decrease more remarkably than that of St.Augustinegrass; Relative to that in Augustinegrass, depletion of root vitality in tall fescue were swifter in early phase of drought, but were slower in later phase of drought. During drought stress, plasma membrane permeability was keeping increasing in remarked correlations with the malondialdehyde (MDA) content; Soluble protein content and activities of SOD, POD and CAT shows an increase in the early phase of drought and then a decrease with further increase in magnitude of water stress, these physiological responses in roots were more sensitive than those of in leaves, and these changes occurred in tall fescueprior to those of in St.Augustinegrass. The results suggest that water stress alters the equilibrium between free radical production and enzymatic defense reactions in two turf-grasses, and changing time of three protective enzyme activities, caused by plant water-losing speed, may be an important reason of drought resistance mechanism difference between two turf-grasses under potted condition.Under unartificial drought conditions, content of TSC, sucrose and fructose in leaf, root and crown (or stolon) of tall fescue and Augustinegrass showed a sustaining increase with the deepening degree of drought stress. In which TSC accumulated most in crown (or stolon) than in leaf and root; the ratio of sucrose and fructose to TSC was 77.6% ~ 93% and 6.6% ~ 18.7% respectively; Content of starch in leaf and root change unremarkably, but declined steadily in crown (or stolon), which correlated negatively to change of TSC.Content of amino acid and proline increased steadily with the deepening drought stress in leaf, root and crown of tall fescue, especially in crown, while content of these substances did not appear regular change in Augustinegrass. In crown(stolon) of tall fescue(Augustinegrass), content of K+, Ca2+, Mg2+ trended to su...