Heat Stress

When temperatures are high, typically in the region of 30˚C, grasses become stressed and physiological activity reduces to prevent plant exhaustion. Plants can effectively become dormant to enable surviving extreme conditions. Syringing and regular irrigation of turfgrass surfaces, shading, reducing the frequency of cut and raising the height of cut, as well as providing a light top-dressing to protect the basal crown of a grass can help to reduce heat stress to some degree, at least for short periods of time.

Some of the effects on a grass plant of heat stress can include:
• A reduction in photosynthesis, reduced leaf production and growth as the plant gradually responds to the increased stress of the environment. Grass colour will often turn light green to yellowish, straw colour and then brown as the tissue dies.
• Evapo-transpiration can increase, assuming sufficient available water is present, producing a plant which wilts.
• Some diseases may be more prevalent in attacking heat stressed plants.
• Plant cell structure can deteriorate and be damaged reducing the effectiveness of physiological processes.
• Root growth can be impaired, reducing potential water and nutrient uptake. However, with the typical reduction in vegetative growth of plants under heat stress this is effectively a natural counter balancing act to prevent excess nutrients and water being taken up by a plant.