Response of creeping bentgrass to salinity and mowing management: Carbohydrate availability and ion accumulation

Salt problems in turfgrass sites are becoming more common. The effects of mowing height on salinity tolerance and associated mechanisms are not well understood. The objective of this study was to examine the effects of mowing height and the level of salinity on turf quality, canopy photosynthetic rate (Pn), total nonstructure carbohydrate (TNC) content, shoot reducing sugar content (RSC), Na(+) and K(+) content in shoots and roots of creeping bentgrass (Agrostis palustris Huds.). Sod pieces of 'L-93' were grown in a greenhouse for over 7 months. Plants were subjected to three mowing heights: 6.4, 12.7, and 25.4 mm, and to four salinity levels of irrigation water: control, 5 dS(.)m(-1), 10 dS(.)m(-1), and 15 dS center dot m(-1) prepared using ocean salts. Increasing salinity resulted in reduced turf quality, increased shoot Na(+), reduced K(+), and reduced K to Na ratio, to a greater extent for bentgrass mowed at 6.4 mm mowing height. Reducing sugar content in shoot increased with increasing salinity level except at 15 dS(.)m(-1) and 6.4 mm mowing regime where RSC declined. Compared to the 25.4 mm mowing height, mowing height at 6.4 mm caused 32-39% reduction in TNC, a 25% to 37% increase in Na(+) content, and 45% to 51% decrease in K content in shoots, which resulted in substantial decrease in K/Na ratio. These results demonstrated that the reduction of creeping bentgrass salt tolerance under low mowing height was associated with carbohydrate depletion that reduced the plant's genetic abilities to generate osmo-protectants (such as reducing sugar), to reduce N(+) accumulation in shoots, and to selectively uptake and transport K(+). Therefore, a moderate increase in mowing height could improve salinity tolerance of creeping bentgrass.