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The Negative Effects of Long Summer Daylight on Golf Course Turfgrass

While longer daylight hours during the summer season often bring joy to golf

enthusiasts, they can also have detrimental effects on the health of golf course turfgrass. It is crucial for turfgrass management professionals to understand how extended daylight impacts the intricate biological processes of respiration in the Krebs and Calvin cycles. In this blog, we will delve into the negative effects of long daylight hours in the summer on golf course turfgrass and explore how these conditions affect respiration in the Krebs and Calvin cycles.


Respiration in the Krebs Cycle

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a vital metabolic pathway in plants. During respiration, the Krebs cycle facilitates the breakdown of carbohydrates, producing energy for various cellular processes. However, extended daylight hours can disrupt the delicate balance of respiration in the following ways:

  1. Excessive Energy Production: Longer daylight hours lead to increased photosynthesis and carbohydrate production in turfgrass. When an excess of carbohydrates accumulates, the Krebs cycle may struggle to keep up with the influx of energy. This surplus of energy can potentially disrupt the equilibrium of the Krebs cycle, leading to metabolic imbalances and negatively impacting turfgrass health.

  2. Imbalanced Carbon-to-Oxygen Ratio: The Krebs cycle requires a precise balance of carbon and oxygen to function optimally. Prolonged exposure to intense sunlight, especially during periods of high temperatures, can increase the rate of oxygen consumption in turfgrass. This can create an imbalanced carbon-to-oxygen ratio within the Krebs cycle, inhibiting the efficient breakdown of carbohydrates and compromising the energy production process.


Photoinhibition and ROS in the Calvin Cycle:

The Calvin cycle, also known as the light-independent or dark reaction, occurs in the stroma of chloroplasts within turfgrass cells. It is the second phase of photosynthesis, following the absorption of light energy during the light-dependent reactions. It is essential for the production of carbohydrates, which provide energy for various metabolic processes, including cell division, root and shoot development, and overall turfgrass health. Here are some ways long daylight hours can have a negative effect on the Calvin cycle:

  1. Photoinhibition: Extended periods of intense sunlight can lead to photoinhibition, which occurs when excess light energy overwhelms the capacity of the Calvin cycle. Photoinhibition hampers the enzymatic activity necessary for the efficient functioning of the Calvin cycle, reducing the conversion of carbon dioxide into carbohydrates and impeding overall turfgrass growth and health.

  2. Reactive Oxygen Species (ROS) Formation: Intense sunlight and prolonged daylight hours can increase the production of reactive oxygen species (ROS) within plant cells. ROS are highly reactive molecules that can cause cellular damage and impair the functioning of enzymes involved in the Calvin cycle. This oxidative stress disrupts the normal metabolic activity, adversely affecting carbohydrate synthesis and turfgrass health.



In Canada, we tend not to think of our turf as getting an excessive amount of daylight hours, but in these hot summer months we see turfgrasses of all varieties suffering from respiration stress all the time. To help remedy this, we recommend using a product like SENEX-TG which will not only provide immediate respiration stress relief, but also lay a good foundation for cell division and integrity.


Senex-TG Sales Sheet - 2023
Download PDF • 716KB


While long daylight hours in the summer bring excitement to golf enthusiasts, it is essential to recognize the potential negative effects they can have on golf course turfgrass. The delicate balance of respiration in the Krebs and Calvin cycles can be disrupted by extended periods of intense sunlight. Excessive energy production, imbalanced carbon-to-oxygen ratios in the Krebs cycle, and photoinhibition and reactive oxygen species formation in the Calvin cycle are among the consequences that can impact turfgrass health.

Understanding these negative effects is crucial for turfgrass management professionals to implement appropriate strategies to mitigate the potential damage. Proper shading techniques, careful management of irrigation and nutrition, and implementing stress management practices can help alleviate the strain on turfgrass caused by long summer daylight hours. Additionally, staying informed about advancements in turfgrass research and consulting with experts in the field can provide valuable insights into effective strategies for maintaining healthy turfgrass.

By being mindful of the impact of extended daylight on respiration in the Krebs and Calvin cycles, golf course management professionals can proactively address the challenges associated with long summer days and ensure the optimal health and playability of the turfgrass on golf courses.



- Foyer, C. H., & Noctor, G. (2009). Redox regulation in photosynthetic organisms: Signaling,

acclimation, and practical implications. Antioxidants & Redox Signaling, 11(4), 861-905.


- Ort, D. R., & Baker, N. R. (2002). A photoprotective role for O2 as an alternative electron sink

in photosynthesis? Current Opinion in Plant Biology, 5(3), 193-198. doi:10.1016/s1369-


- Taiz, L., & Zeiger, E. (2010). Plant physiology (5th ed.). Sinauer Associates.

- Salisbury, F. B., & Ross, C. W. (1992). Plant physiology (4th ed.). Wadsworth Publishing.



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