Tech Notes Issue 7

Drought Resistance and Its Component

Severe moisture stress or drought causes negative effects on turfgrass growth and development. The major components of drought resistance are avoidance and tolerance.

Avoidance is the ability of a turfgrass plant to postpone plant water loss by reducing transpiration and/or increasing water uptake. Turfgrass plants can reduce transpiration through early stomatal closure, leaf rolling, presence of hairs on the leaf blade that reduce evaporation from the leaf surface, and a thicker cuticle layer. Most importantly a deep root system helps turfgrass avoid a moisture deficit by extracting water from deeper in the soil profile.

Tolerance is the ability of the plant to experience the moisture stress and survive. Usually, grasses go dormant, leaves shrivel and die, but the crown dehydrates but survives to give rise to new growth. Additional internal adjustments including osmotic enhance the drought resistant turfgrasses. A measurable characteristic of a turfgrasses drought tolerance is the potential to recover, grow, and spread once the plant comes out of dormancy with the arrival of rain or irrigation.

Table: Relative drought resistance (Avoidance + Tolerance), avoidance (maintain quality during moisture stress), and toler-ance (ability to recover from drought stress) of a few selected turfgrasses (source: Fry and Huang, 2004).