Understanding Turf Health by Bayer Research Manager, Jyri Kaapro

To turfgrass managers there is an ever increasing range of products being promoted with claims of various plant health benefits. The purpose of this article is not to examine the science (or lack of) behind these products, but to explain some of the terminology being used in a “Glossary of Turf Health”.

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Abscisic acid – ABA is one of hormones that help turfgrass adapt to stress. It does this is several different ways. When soil water uptake isn’t able to keep up with transpiration ABA triggers the closing of stomata. ABA can stimulate root growth and hence the plants ability to take up water.

Antioxidants – We regularly hear about the benefits of various antioxidants to human health. Antioxidants also play a role in plant health. As the name suggest antioxidants prevent the oxidation of other molecules. Oxidation is a chemical process in which free radicals are produced. There are many chemicals which have beneficial antioxidant properties.

Amino acids – There are many different amino acids with varied roles in plants. All amino acids have a basic structure made of carbon, oxygen, hydrogen and nitrogen. Proteins and enzymes are made from amino acids and are important to many aspects of plant growth and function. Some amino acids have a key role in stress management. Amino acids can also be used as a fertilizer (they contain nitrogen) and some have been evaluated for nematode control in turf.

Auxin – Auxins are plant hormones which are important in plant cell growth. The herbicide 2,4-D is a synthetic auxin which produces uncontrolled cell growth in weeds. Auxins play a role in root development and growth.

Biostimulants – This is a term which includes many different products. The term is used to describe chemically complex compounds like seaweed extracts, humic acids, fulvic acids, compost teas etc. It is also used to describe more basic components like amino acids and cytokinin. By definition many products which produce a growth response in plants can be called biostimulants.

Cytokinin – These are another group of hormones and this time they affected cell division. The ratio of cytokinin to auxin in plants has an important effect on shoot vs root growth. Cytokinin encourages shoot growth and auxin root growth.

Free radicals – Free radicals are produced in plants in certain chemical processes. These free radicals cause damage to other plant parts. Photosynthesis is a process which can produce free radicals that can be very damaging to plant health.

Gibberellic acid – GA is a plant hormone which causes cell elongation in turfgrass. The common turfgrass growth regulator trinexapac-ethyl affects GA production and hence the growth of turfgrass. Applying excess GA to plants encourages elongated growth and is currently being evaluated for a potential role in weed control. GA is also used in some turf situations to maintain winter colour and to encourage early spring growth.

Induced systemic resistance & Systemic acquired resistance – ISR and SAR occur where plants are pre-conditioned to stress by stimulating their own defence processes. The biochemicals involved are different for the two mechanisms. ISR and SAR can help plants reduced the damage from various pathogens and pests.

Mycorrhizae- A group of soil fungi which form a symbiotic relationship with plant roots. The fungi colonise the roots and through their filament network provide nutrients and water to the plant and in return obtain carbohydrates which the plant has manufactured.

Photorespiration – This is a chemical process in plants which involves the utilisation of energy made from photosynthesis. The process can be damaging to plants because it is not efficient and can result in the production of free radicals which then damage plant cell components. Managing photorespiration will help plants manage stress periods.

Phytoalexin – These are chemicals made by plants in response to attack by pathogens. They are toxic to the pathogen and can help reduce disease infestation. Some chemicals help increase the levels of phytoalexin production in plants.

Of course there are many more terms that need explanation and no doubt new ones will come into common use. When next reading labels, testimonials, marketing information or listening to presentation I hope you are clearer on the terminology being used.