Experiments were conducted in the field, greenhouse, and controlled environment chambers to study the effect of environmental factors on tillering, growth, and carbohydrate content of orchardgrass. Tillers of one genotype were studied with several variable factors (light, temperature, moisture,. nitrogen, and/or defoliation) in each of four experiments. Factorial treatment combinations were used in each of the four experiments to study single factors and interactions.

Tillering declined to 73 and 26% of normal light when light intensity was reduced in the greenhouse and field, respectively. In the controlled environment chambers, tillering rates were higher with an 18-hour than for a 9-hour day with 3100 F.C. in both chambers. Soluble carbohydrates in the stubble were associated with tillering. There was a marked increase in water soluble carbohydrates as light energy increased up to normal sunlight. Ory matter production was associated with tillering and carbohydrate contents of orchardgrass, factors which increased tillering augmented clipping dry weights.

Tillering and foliage growth were much higher when day temperature was 80*F. as compared with 60°F. There was a sharp increase in soluble carbohydrates with low temperature, but at the high temperature carbohydrates did not accumulate as they were apparently utilized for fast growth and tillering. Carbohydrate accumulation per se was not associated with tillering nor yields when temperatures were sub~-optimum for fast growth.

Tillering was increased 30% by irrigation. Tillering of orchardgrass plants, defoliated to 1.5, 3, and 6 inches in combination with other treatments, showed increased tillering and dry matter production as defoliation intensities were relaxed. High tillering rates were associated with the magnitude of carbohydrates in orchardgrass stubble. Root development at the end of the experiment was much poorer for intensive defoliation as compared with lax defoliation.

Nitrogen stimulated tillering and retarded soluble carbohydrate accumulation in orchardgrass stubbles, Nitrozen stimulated the production of new tissue and nitrogen compounds at the expense of stored carbohydrates in the stubbles. With slow orchardgrass growth under low nitrogen, soluble carbohydrates in the stubble accumulated. There was good evidence that soluble carbohydrates are directly associated with tillering and growth of orchardgrass when factors such as light, nitrogen, and water do not limit growth. Carbohydrate accumulatpeiro nse is not associated with tillering, if any environment growth factor is sub-optimum for tillering and growth. sub-optimum for tillering and growth.