Some Observations on Invertase Activity in Roots of Vicia faba L.

Invertase activity has been determined at intervals along primaryroots of Vicia faba as they elongated from 0·5 to 8 cm.Little activity was evident in 0·5–1·0 cmlong primaries but in those 2–8 cm in length the mainpeak of enzyme activity was associated with the region of cellelongation. Changes took place in the pattern of invertase activityalong the primary roots as they lengthened and these changeshave been correlated with fluctuations in both the rate of rootelongation and the supply of sucrose to the root from the cotyledons.The presence of a root cap did not increase the activity ofthis enzyme in the apical 1 mm of these roots. Invertase activity was higher in lateral root primordia thanin most parts of the primary root basal to the meristem, presumablybecause of the presence of sucrose in the adjacent cavity inthe cortex of the primary root. The peaks of invertase activityfound basal to the region of cell elongation in 3–8 cmlong primary roots probably resulted from the development ofroot pnmordia in these parts of the root.