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Perennial ryegrass (Lolium perenne L.) is a cool-season turfgrass species that can exhibit significant freezing injury in northern climatic regions. The objective of this study was to quantify major physiological and biochemical changes occurring during the cold acclimation period in four perennial ryegrass accessions varying in freezing tolerance (two freezing-tolerant accessions, TOL-1 and TOL-2, and two freezing-susceptible accessions, SUS-1 and SUS-2). Plants were subjected to a cold acclimation period of 2[degrees]C for 21 d in a controlled environment chamber. Crown tissues were harvested at 0, 7, 14, and 21 d of acclimation for determination of proline, water soluble carbohydrates (WSC), and lipid composition. Leaf photochemical efficiency (Fv/Fm) was also measured weekly before plant sampling for biochemical components. In general, proline levels increased and Fv/Fm decreased during cold acclimation; however, there were no differences in proline accumulation or Fv/ Fm among the accessions in response to cold acclimation. Water soluble carbohydrates significantly increased in response to 2[degrees]C, with TOL accessions (TOL-1 and TOL-2) accumulating higher WSC than SUS (SUS-1 and SUS-2) by 21 d of acclimation. There were also significant changes in major phospholipids classes at 2[degrees]C. Specifically, TOL-2 exhibited a higher ratio of membrane stabilizing lipids and unsaturated fatty acid content compared to SUS-1, SUS-2, and TOL-1 by 21 d of cold acclimation. doi: 10.2135/cropsci2009.06.0293

This study was designed to determine the effects of deficit irrigation on water use traits of colonial (Agrostis capillaris L.), creeping (A. stolonifera L.), and velvet (A. canina L.) hentgrasses and to compare their water use. Field experiments were conducted from July to November in 2002 and 2003. Plots were irrigated at four levels of irrigation based on the percentage of actual evapotranspiration (E[T.sub.a]): 100, 80, 60, and 40% E[T.sub.a] replacement. The influence of deficit irrigation on water use was evaluated by measuring soil water depletion (SWD) and water use efficiency (WUE). The WUE was quantified by the ratio of canopy net photosynthetic rate to transpiration rate and carbon isotope discrimination (CID). Evapotranspiration (ET) rates were compared among the three species under nonlimiting moisture conditions (100% E[T.sub.a]). Our results demonstrated that water use characteristics varied with species, irrigation regime, and climatic conditions. Irrigating at either 60 or 80% E[T.sub.a] had no significant effects on WUE compared with 100% E[T.sub.a] irrigation; however, plots irrigated at 60% E[T.sub.a] exhibited higher SWD compared with plots at 80 and 100% E[T.sub.a]. Velvet bentgrass exhibited lower SWD, higher WUE, and lower CID compared with colonial bentgrass during the summer treatment period, and creeping bentgrass exhibited intermediate water use characteristics among the three species. These results suggest that irrigating bentgrass species at 60 to 80% E[T.sub.a] could be practiced to increase WUE during summer and 40% E[T.sub.a] during fall months under the conditions of this study.

Knowledge of water use requirements of various grass species is important for identifying grasses that persist with reduced water inputs and also for developing efficient irrigation management practices. This study was designed to examine minimum water requirements for maintaining acceptable quality fairways established to creeping (Agrostis stolonifera L.), colonial (A. capillaris L.) and velvet (A. canina L.) bentgrasses. Field experiments were conducted from July to November in 2002 and 2003. Plots were irrigated at four levels of irrigation on the basis of the percentage of actual evapotranspiration determined with minilysimeters (ETa): 100, 80, 60, and 40% ETa replacement. Turf performance was evaluated by measuring visual turf quality (TQ), canopy spectral parameters, canopy photosynthetic rates (Pn), and soil moisture status. Results generally demonstrated that irrigating at 100% ETa was not necessary to maintain acceptable TQ and physiological processes and that the minimum water requirements depended on species and time of year. Colonial bentgrass required irrigating at 80 to 100% ETa, while creeping and velvet bentgrasses required 60 to 80% ETa to maintain acceptable turf performance in the summer of 2002. During the summer treatment period in 2003, however, irrigating at 60% ETa was sufficient for all three species. Irrigating at 40% ETa in the fall treatment period in both 2002 and 2003 was sufficient to maintain acceptable TQ, canopy Pn, and comparable canopy growth parameters to plots receiving 100% ETa. The results from this study demonstrate the potential for significant water and monetary savings by utilizing deficit irrigation practices on bentgrass species used for golf course fairways., WATER AVAILABILITY for irrigation of turfgrasses is becoming increasingly limited, making water conservation a prime concern of turfgrass growers and managers across many areas of the country. Knowledge of water [...]

This study was designed to investigate effects of surface soil drying (SD) on water relations, gas exchange, growth characteristics, and abscisic acid (ABA) content of leaves and roots for Kentucky bluegrass (Poa pratensis L.), and to examine whether physiological adaptation to SD is associated with hydraulic or chemical regulation. 'Award' and 'Nuglade' were subjected to three soil moisture treatments in a growth chamber: (i) well-watered control; (ii) SD (0-20 cm); and (iii) full soil profile (0-40 cm) drying (FD). Under SD, turf quality (TQ), relative water content (RWC), photosynthesis, and cell membrane stability remained the same as the controls, but stomatal conductance ([g.sub.s]) declined by 35 and 45%, and shoot growth rates were reduced by 50 and 40% for Award and Nuglade, respectively. Root DW decreased in 0- to 20-cm dry soil, but increased compared with controls in the 20- to 40-cm wet soil under SD. The ABA content increased by four to sixfold in roots at 0- to 20-cm drying soil and did not change in the 20- to 40-cm wet soil under SD conditions. The ABA content was also higher in leaves of SD plants. The results suggested Kentucky bluegrass adapted to localized soil drying by maintaining TQ, photosynthesis, leaf water status (WS), and root growth using water in the deeper soil profile. Decline in [g.sub.s] and shoot growth was independent of leaf WS, and could be hormonally controlled, which could help maintain favorable WS in leaves by reducing water loss under SD conditions., WATER DEFICIT is one of the most widespread abiotic stresses limiting plant growth. This issue is becoming increasingly important for turfgrass management as water availability for irrigation in urban areas [...]