1989;White et al., 1993;Marcum et al., 1995; Carrow, 1996b;Huang and Fry, 1998). Although total root length Knowledge of root traits associated with drought tolerance is important for further understanding drought tolerance mechanisms of influences water and nutrient uptake, maintenance of the whole plant. The experiment was designed to investigate effects roots that are viable and active in water and nutrient of drought stress on root physiological activities of six cultivars (Kenuptake during drought may be more important for plant tucky-31, Falcon II, Houndog V, Phoenix, Rebel Jr., and Bonsai) of tolerance to drought (Huang et al., 1997). Drought has tall fescue (Festuca arundinacea Schreb.) varying in drought resisbeen among the main causes of root death in the field tance. Grasses were grown in well-watered or drying (nonirrigated) (Smucker et al., 1991). Persistent root growth of perensoil for 35 d in a greenhouse. Drying reduced root length and dry nial grasses is a characteristic that greatly enhances the mass in the 0-to 20-cm layer for all six cultivars. Root length and dry mass in the 40-to 60-cm layer was enhanced for Houndog V, adaptation of a grass to semiarid and arid climates Falcon II, and Kentucky-31; was not affected for Phoenix and Bonsai; (Weaver and Zink, 1955). and was reduced for Rebel Jr. by soil drying. Water uptake rates forUnderstanding the mechanisms of root tolerance to Falcon II and Kentucky-31 decreased with soil drying in the 0-to 20drought stress may further our understanding of root cm layer but increased in the 40-to 60-cm layer. Soil drying limited physiological traits associated with drought tolerance. water uptake by Rebel Jr. in both layers. Drought stress increasedSuch traits could be incorporated into breeding proroot mortality in the 0-to 20-, 20-to 40-, and 40-to 60-cm layers, but the increase was most dramatic in the surface soil layer. The increaseThe experiment consisted of two soil moisture treatments: (i) well-watered control (plants were irrigated every other day until drainage occurred) and (ii) drought stress (irrigation was

High temperature is a major factor limiting growth of creeping bentgrass (Agrostis palustris Huds.). Physiological causes of turf growth and quality decline with increasing temperature is not well understood. The objective of the study was to examine responses of growth and carbohydrate metabolisms to increasing temperatures in three creeping bentgrass cultivars. Sods of ‘Penncross’, ‘ISI‐AP‐89150’, and ‘SR 1020’ were grown in growth chambers and exposed sequentially for 20 d to each of the following temperatures: 20, 24, 30, 34, and 38°C. Evaluation and measurements were made at 10 and 20 d after each sequential temperature increase. Decreased root viability and root dry matter production of all cultivars was observed after a 10‐d exposure at 30°C and continued to decline with increasing temperatures. A decline in turf quality and leaf chlorophyll content (Chl) was observed at a 20‐d exposure to 30°C. Turf quality, Chl content, and root viability of SR 1020 were higher than those of Penncross after a 10‐d exposure at 30°C and 20 d at 34°C, and 10 d at 38°C, respectively. Canopy net photosynthetic rate (Pn) decreased with temperature in all cultivars. Dark respiration rates of whole plants (Rplant) increased with temperature up to 34°C, and then declined at 38°C. Daily carbon consumption to production ratio increased dramatically with temperature after 30°C, and Rplant exceeded Pn when temperature increased to 34 or 38°C in all cultivars. Plants grown at 30, 34, and 38°C had lower total nonstructural carbohydrate than those grown at 20 or 24°C. Results suggest that a decline in root activity of creeping bentgrass occurred before a decline in turf quality at temperatures above 30°C, and could be related to the imbalance between photosynthesis and respiration, and limited carbohydrate availability.

Background: Recently, perfluorooctanoic acid (PFOA) has become a significant issue in many aspects of environmental ecology, toxicology, pathology and life sciences because it may have serious effects on the endocrine, immune and nervous systems and can lead to embryonic deformities and other diseases. Human serum albumin (HSA) is the major protein component of blood plasma and is called a multifunctional plasma carrier protein because of its ability to bind an unusually broad spectrum of ligands.

Drought is among the most limiting factors for turfgrass growth. Understanding genetic variations and physiological mechanisms in turfgrass drought resistance would facilitate breeding and management programs to improve drought resistance. The experiment was designed to investigate shoot physiological responses of six tall fescue (Festuca arundinacea Schreb.) cultivars representing several generations of turfgrass improvement to drought stress. Grasses were grown in well-watered or drying (nonirrigated) soil for 35 days in the greenhouse. Net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), relative water content (RWC), and photochemical efficiency (Fv/Fm) declined during drought progression in all cultivars, but the time and the severity of reductions varied with cultivar and physiological factors. The values of Pn, RWC, gs, and Tr decreased significantly for `Rebel Jr', `Bonsai', and `Phoenix' when soil water content declined to 20% after 9 days of treatment (DOT) and for `Houndog V', `Kentucky-31', and `Falcon II' when soil water content dropped to 10% at 15 DOT. A significant decrease in Fv/Fm was not observed in drought-stressed plants until 21 DOT for `Rebel Jr', `Bonsai', and `Phoenix' and 28 DOT for `Houndog V', `Kentucky-31', and `Falcon II'. The decline in Pn resulted mainly from internal water deficit and stomatal closure under mild drought-stress conditions. After a prolonged period of drought stress (35 DOT), `Falcon II', `Houndog V', and `Kentucky-31' maintained higher Pn than did `Rebel Jr', `Bonsai', and `Phoenix', which could be attributed to their higher Fv/Fm. This study demonstrated variation in drought resistance among tall fescue cultivars, which was related to their differential responses in photosynthetic capacity and water relations.

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