Impact of Heat on Shoot and Root Function in Bentgrass.

Summer decline in bentgrass (Agrostis stolonifera L.) is one of the greatest challenges in golf course management in many parts of the world. Bentgrass is native to cooler climates and the grass stands suffer substantial injury during the hot months of summer that impairs plant health for an extended period each year. Creeping bentgrass plants experience a series of physiological injuries when exposed to temperatures above 30 °C. Multiple systems begin to breakdown and the overall effect is a decline in tillering density, shoot and root growth are inhibited, and canopy photosynthetic rate is reduced. Root function also may be directly affected by heat and the decline of the root system under these conditions will ultimately impact turf quality by limiting water and nutrient supply. When subjected to high root-zone temperatures, root number, length, biomass and viability all decline. Experiments were conducted in growth and hydroponic chambers to study heat effects on shoot and root growth, carbohydrate content, root function, and canopy photosynthetic rates. Initial results indicate that when temperatures increase above 30 °C, plants are sharply weakened - growth of shoots and roots and turfgrass quality markedly decrease. The research shows that any increase in root temperature above 21 °C leads to a substantial decline in above and below ground growth. This research also has revealed that above 30 °C, substantial net CO₂ release occurs, greatly overshadowing photosynthesis. Our research suggests that summer bentgrass decline likely involves some direct effects on the plant, but also interactions between the plant and soil microbial population.