The Arabidopsis vacuolar H + -pyrophosphatase (AVP1), when over-expressed in transgenic (TG) plants, regulates root and shoot development via facilitation of auxin flux, and enhances plant resistance to salt and drought stresses. Here, we report that TG perennial creeping bentgrass plants over-expressing AVP1 exhibited improved resistance to salinity than wild-type (WT) controls. Compared to WT plants, TGs grew well in the presence of 100 mM NaCl, and exhibited higher tolerance and faster recovery from damages from exposure to 200 and 300 mM NaCl. The improved performance of the TG plants was associated with higher relative water content (RWC), higher Na + uptake and lower solute leakage in leaf tissues, and with higher concentrations of Na + , K + , Cl -and total phosphorus in root tissues. Under salt stress, proline content was increased in both WT and TG plants, but more significantly in TGs. Moreover, TG plants exhibited greater biomass production than WT controls under both normal and elevated salinity conditions. When subjected to salt stress, fresh (FW) and dry weights (DW) of both leaves and roots decreased more significantly in WT than in TG plants. Our results demonstrated the great potential of genetic manipulation of vacuolar H + -pyrophosphatase expression in TG perennial species for improvement of plant abiotic stress resistance.

Warm‐season turfgrass quality declines under shade due to reduced photosynthesis, increased disease pressure, reduced carbohydrate production, tree root competition, and reduced lateral stem growth. Another factor limiting turfgrass growth and development under tree shade is variable qualities of light filtered by trees. However, effects of various filtered wavelengths on turfgrass performance are lacking and deserve research. Therefore, a greenhouse project investigated the physiological and morphological responses of ‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.], ‘Sea Isle 2000’ seashore paspalum (Paspalum vaginatum Swartz.), and ‘Tifway’ and ‘Celebration’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] to variable light spectral qualities. Light treatments included a control without any shade cloths and four different color shade cloths filtering wavelengths 560 to 720 nm (blue shade cloth), 360 to 520 nm (yellow shade cloth), 360 to 560 nm (red shade cloth), and 360 to 720 nm (black shade cloth). The percent light reduction for each cloth was about 65% relative to the control. Data collected included visual turfgrass quality (TQ), relative clipping yield, relative chlorophyll concentration, relative shoot width, relative root biomass, relative root length density, relative specific root length, and root and shoot total nonstructural carbohydrates. Diamond was the least affected turfgrass by the color shade cloths, while Celebration and Sea Isle 2000 performed similarly. Tifway was the most sensitive turfgrass with the lowest TQ under color shade cloths. Yellow and red shades were least detrimental, while black shade most negatively inhibited parameters measured, followed by blue shade. This study implies different types of shade significantly impact the TQ of warm‐season turfgrasses.

Managing warm-season turfgrasses with reduced sunlight is challenging due to C 4 plant morphological limitations, such as reduced lateral stem growth. Adjusting cultural management practices, such as N and trinexapac-ethyl (TE) [4-(cyclopropyl-ahydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester], application may benefi t turfgrass performance when sunlight is reduced. Th erefore, a 2-yr fi eld study from 15 June to 15 September in 2006 and 2007 at Clemson University investigated the best management practices for sustaining a high quality 'Champion' bermudagrass (Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davy) putting green maintained at a 3.2-mm mowing height under reduced sunlight. Treatments included fullsunlight, 55% full-day shade, TE (0.02 kg a.i. ha -1 2 wk -1 ), Fe (2.7 kg ha -1 2 wk -1 ), and N as liquid urea at 147, 293, and 440 kg ha -1 yr -1 . Data collection included visual turfgrass quality (TQ), total clipping yield, clipping chlorophyll concentration, root total nonstructural carbohydrates (TNC), thatch accumulation, and thatch depth. Overall, Fe applications minimally impacted parameters measured. Increasing N rates linearly increased TQ when grown under full sunlight. Applying N at ~40% lower (147 kg ha -1 yr -1 ) than the typical recommended rates for ultradwarf bermudagrass putting greens improved Champion TQ under reduced light compared to higher N rates. Applying TE resulted in a linear TQ increase for full sunlight and shade-grown Champion bermudagrass. Under reduced sunlight, a 15% chlorophyll concentration increase was noted for TE-treated plots compared to nonTE-treated plots. Shade reduced thatch accumulation 40% compared to sun-grown Champion, which suggests less aggressive cultivation practices are required for thatch control under reduced light. Champion bermudagrass did not provide an acceptable putting green quality when grown under 55% full-day shade, however, adjusting management practices enhanced Champion bermudagrass quality under reduced light.

Morphological limitations, such as reduced lateral stem growth, reduced stress resistances to unfavorable environments and pests, and overall reduction of carbohydrate synthesis contribute to bermudagrass (Cynodon spp.) decline under shade. Due to shade sensitivity and possible genetic variability of bermudagrasses, a two-year replicated greenhouse study in 2005 and 2006 determined the shade tolerance of 42 bermudagrass cultivars selected from the 2002 National Turfgrass Evaluation Program (NTEP). Cultivars were subjected to 64% continuous artificial shade for 60 days. Data collection included visual turfgrass quality (TQ), shoot chlorophyll concentration, root length, and total root biomass.

Traditional hollow-tine (HT) aerification programs can cause substantial damage to the putting green surface resulting in prolonged recovery. Despite the growing interest in new and alternative aerification technology, there is a lack of information in the literature comparing new or alternative technology with traditional methods on ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)] putting greens. Therefore, the objective of this research was to determine the best combination of dry-injection (DI) cultivation technology with modified traditional HT aerification programs to achieve minimal surface disruption without a compromise in soil physical properties. Research was conducted at the Mississippi State University golf course practice putting green from 1 June to 31 Aug. 2014 and 2015. Treatments included two HT sizes (0.6 and 1.3 cm diameter), various DI cultivation frequencies applied with a DryJect 4800, and a noncultivated control. The HT 1.3 cm diameter tine size had 76% greater water infiltration (7.6 cm depth) compared with the DI + HT 0.6 cm diameter tine size treatment. However, DI + HT 0.6 cm diameter tine size had greater water infiltration at the 10.1 cm depth than the noncultivated control. Results suggest a need for an annual HT aerification event due to reduced water infiltration and increased volumetric water content (VWC) in the noncultivated control treatment. It can be concluded that DI would be best used in combination with HT 1.3 or 0.6 cm diameter tine sizes to improve soil physical properties; however, the DI + HT 0.6 cm diameter tine size treatment resulted in minimum surface disruption while still improving soil physical properties compared with the noncultivated control.