Alfalfa Root Growth, Cambial Activity, and Carbohydrate Dynamics during the Regrowth Cycle1

Abstract

Anatomical studies of the alfalfa (Medicago sativa L.) taproot during three regrowth cycles revealed a close relationship between cambial cell division activity, subsequent growth patterns, and total nonstructural carbohydrates. Narrow, band‐like patterns of cambial cells occurred with greatest frequency 2 to 3 weeks after cutting, indicating a flush of coordinated cell division. The narrow bands of cells were observed more often in fascicular than interfascicular cambial zones; this is indicative of greater cell expansion rates in the interfascicular zones. Radial expansion of the wood (xylem) occurred in all regrowth cycles during the season. Radial expansion of the bark (phloem) was limited, probably due to the crushing and centrifugal expansion in that tissue resulting from wood growth. Areas of both wood and bark increased during the second half of the regrowth cycle with the concurrent accumulation of carbohydrates.