Maintain Optimum Plant Metabolism During Water Deficit
Scouting Notes: Turf managers should consider key technologies to maintain optimum plant metabolism during a wide range of environmental conditions or during peak playability requirements.
Most agronomists would consider the following cultural practices key to maintaining turfgrass health on high maintenance turfgrass swards like golf course putting greens,
- Sand topdressing
- Mowing practices
- Water management.
Changing environmental conditions or mandated water restrictions will put pressure on otherwise healthy turfgrass plants – leading to oxidative stress, compromised cell and membrane functioning, and reduced growth and vigor. Turfgrasses have evolved with built-in defense mechanisms (secondary metabolism) designed to reduce stress in order to carry out the most important, primary, metabolic processes necessary for survival. Certain compounds called elicitors, when applied to turfgrass, can work to upregulate these vital defense mechanisms. Elicitors, also known as metabolic enhancers, include:
- Plant hormones
- Signaling molecules
The Brandt Discovery and Innovation group routinely evaluates experimental formulations of nutrient and metabolic enhancers designed to maintain turf vigor under adverse environmental conditions OR to improve turf performance during peak playability requirements. For example, to produce firm and fast playing conditions on golf course putting greens when irrigating with a self-imposed water deficit strategy (60-80% ET replacement).
Did you know that osmoprotectants (compatible solutes) accumulate in the cytoplasm of plant cells to maintain water potential equilibrium? Examples include proline and glycine betaine and the mode of action is illustrated in Figure 1. In addition, potassium (K) plays an important role in the osmoregulation in plants.
Figure 1. Illustration of how compatible solutes work inside plant cells. Under water deficit, water moves passively, by diffusion, out of the cell. As proline, or other solutes, accumulate the water potential decreases – allowing water to enter the cell. This mechanism offers plants better water balance across cell membranes and thus better turgor – producing improved turf quality and performance under water deficit conditions.
Figure 2. Turfgrass (right) treated with osmoprotectants compared to untreated turfgrass (left). Both were maintained under a rainout shelter where 60% of ET water loss was replaced and photo taken 25 days after initiation of water deficit. Treatments were made every two (2) weeks, including increased frequency before the onset of water deficit (Huang and Chapman, 2018; Rutgers University).
We tested the effect of one experimental formulation containing a small amount of nutrient and a suite of osmoprotectants on creeping bentgrass (Agrostis stoloniferous) performance under water deficit conditions – replacement of 60% evapotranspiration (ET) water loss. Photos from one replication in the trial are shown in Figure 2.
When considering the mode of action that generated these visual results, we measured relative leaf water content (RLW%) and stress index (S.I.). A trend occurred, where the BRANDT experimental treatments offered better turf quality, increased RLW%, and lower stress index during the water deficit condition (60% ET replacement) and during post stress recovery.
Interestingly, in another trial we found that this experimental formulation significantly increased polyphenol concentrations in creeping bentgrass when soils were dried down to 11-13% volumetric water content (VWC) (Figure 3). In addition, this treatment significantly improved turf quality as a measured by normalized difference vegetation index (NDVI) analysis (data not shown). Increased polyphenol concentrations indicate an uptick in plant defense and better NDVI a subsequent reduction in oxidative stress, including better primary metabolic functioning.
Figure 3. Polyphenol concentration in Agrostis leaf tissue under water deficit (11-13% VWC) and after routine treatment with an experimental formulation containing suite of osmoprotectants, nutrient, and untreated controls (Dempsey, 2018).
*Means followed by a different letter are significantly different (P=0.05)
As a turfgrass manager, consider using all options, including routine applications of nutrient formulations that contain important metabolic enhancers, including osmoprotectants. Apply as part of an integrated and preventative maintenance program. With these tools, you’ll be better equipped to encourage the competitiveness and playability of those turfgrass swards you’re charged with maintaining under less than ideal conditions and improve playability in the process.
*For more information about this or other research trials, please contact T&O Technical Manager, Gordon L. Kauffman III, Ph.D. (firstname.lastname@example.org)