Which of the following is not a function of root growth bio-stimulants?

Root growth bio-stimulants are substances that enhance the growth and function of plant roots through various mechanisms. They are well known for their ability to improve nutrient uptake, increase the number of fibrous roots, and enhance water uptake.

When it comes to increasing respiration, this is generally not a direct function of root growth bio-stimulants. While respiration is a critical process for plant health and is essential for energy production within the plant cells, root growth bio-stimulants primarily focus on promoting root development and improving the efficiency of nutrient and water absorption. They do not specifically enhance the respiratory rate of roots or the plant as a whole.

In summary, the primary roles of root growth bio-stimulants revolve around optimizing root architecture for better nutrient and water uptake rather than directly influencing respiration rates, which makes the option regarding increasing respiration the correct answer in this context.