Turgor Potential and Osmotic Constituents of Kentucky Bluegrass Leaves Supplied with Four Levels of Potassium
- Mark J. Carroll *,
- Leon H. Slaughter and
- John M. Krouse
Solute accumulation is one mechanism by which plants are able to sustain positive leaf turgor potentials (ψt). Potassium, the cation most often found in greatest concentration in Kentucky bluegrass (Poa pratensis L.), can influence accumulation of solutes. A 2-yr glasshouse study was conducted to determine the effect of K availability on accumulation of six osmotically active solutes and ψ1 within leaves of Kentucky bluegrass. Four nutrient solutions containing 0, 10, 100, or 124 mg K L−1 were applied three times weekly to plants grown in silica sand. Small increases in K (0 to 10, or 100 to 124 mg L−1) had no effect on ψt, but increasing K from 0 or 10, to 100 or 124 mg L−1 increased leaf ψt 0.19 to 0.35 MPa. Increasing K from 10 to 100 mg L−1 caused leaf osmotic potential (yn) to decline by 0.17 to 0.23 MPa. Potassium was the only measured osmotically active solute that could account for most of the decline in ψЛ. When the supply of K was increased from 10 to 100 mg L−1, the resulting increase in leaf K concentration caused the calculated contribution of K alone to depress leaf ψ, by 0.29 to 0.31 MPa. Conversely, the combined calculated osmotic contribution of Ca, Mg, glucose, fructose, and sucrose increased leaf ψЛ by 0.12 to 0.13 MPa when K was increased from 10 to 100 mg L−1. The calculated osmotic contribution of all six osmolytes accounted for 46 to 60% of the measured ψπ. Increasing Kentucky bluegrass K tissue concentration appears to have a small but positive influence in increasing leaf turgor.
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