We studied the effects of root container volume on plant growth, carbohydrate concentration, and photosynthesis, and the effects of release from root volume restriction (RVR) on plant growth, carbohydrate concentration, and distribution of photoassimilates in cabbage seedlings. Plant dry weight increased with increasing root container volume from 9 mL to 300 mL. Dry matter allocation to leaves was lower in plants grown in a smaller root container volume. The photosynthetic rate was higher with increasing root container volume. Starch and soluble sugar concentrations in leaves were highest at 9 mL and lowest at 300 mL. Starch was not detected in roots, and the soluble sugar concentration in roots increased with decreasing root container volume. Plant growth was enhanced when plants were released from RVR by transplanting from 9-mL containers to 300-mL containers. The carbohydrate concentrations in leaves and roots decreased after release from RVR. Total activity of ¹⁴C-photoassimilates incorporating into leaves was much higher in released plants than in control plants. The distribution rate of ¹⁴C-photoassimilates from incorporated leaves to stems and roots was higher in released plants than in control plants. These results indicate that carbohydrate metabolism in cabbage seedlings was altered in response to RVR, which is closely associated with plant growth.