Carbohydrates in Grass Growth

The main function of a grass plant is to utilize sunshine to make food (carbohydrates). Carbohydrates are needed during the growing season when the plant must maintain itself, to continue growing after defoliation or dormancy, and for maintenance during the winter. The perennial plant must survive winter and renew growth in the spring. Carbohydrate storage organs become extremely important when they are the only available source of energy. Carbohydrate storage organs include stem bases, roots, rhizomes and/or stolons.

Grass plants can utilize the sun's energy only during daylight. When the leaves produces more carbohydrate than is needed for growth and maintenance, some of the production can be shipped (translocated) to the storage organs. When production is insufficient to meet the demands of the plant, the stored carbohydrates are called on for continued growth. This situation causes no problem unless the stored carbohydrates are depleted.

Growth has priority over storage for carbohydrate use. This is why uncontrolled grazing can totally deplete a plant's stored carbohydrates. As grazing managers, we must allow storage to occur for future use since there are occasions when plants are not able to produce enough carbohydrate to meet growth requirements, i.e., periods of non-growth (dormancy) and periods of extensive defoliation.

Proper grass management must consider the demands of growth and their impact on stored carbohydrates. And, even when there are sufficient carbohydrates, the growing points must remain intact to utilize them.

Carbohydrate storage increases when the growth rate slows and leaf area is large. Conversely, carbohydrate storage decreases when leaf area is small and growth rate is fast. It also decreases when the plant is defoliated and there is demand for energy to support growth of new shoots.

Carbohydrate storage increases when:

  • Leaf area is more than adequate to meet growth demands.
  • Growth rate is slow (cool autumn temperatures).

Carbohydrate storage decreases when:

  • Leaf area is inadequate to meet growth demands.
  • Growth rate is rapid (spring).
  • Carbohydrate reserves are depleted.