Spatiotemporal patterns of enzyme activities in the rhizosphere: effects of plant growth and root morphology

Lentil and lupine, having contrasting root morphologies, were chosen to investigate the effects of plant growth and root morphology on the spatial distribution of β-glucosidase, cellobiohydrolase, leucine aminopeptidase, and acid phosphomonoesterase activities. Lentil kept as vegetative growth and the rhizosphere extent was constant, while the enzyme activities at the root surface kept increasing. Lupine entered reproductive growth in the seventh week after planting, the rhizosphere extent was broader in the eighth week than in the first and fourth weeks. However, enzyme activity at the root surface of lupine decreased by 10–50% in comparison to the preceding vegetative stage (first and fourth weeks). Lupine lateral roots accounted for 1.5–3.5 times more rhizosphere volume per root length than taproots, with 6–14-fold higher enzyme activity per root surface area. Therefore, we conclude that plant growth and root morphology influenced enzyme activity and shape the rhizosphere as follows: the enzyme activity in the rhizosphere increased with plant growth until reproductive stage; lateral roots have much larger rhizosphere volume per unit root length and higher enzyme activity per root surface area than the taproots.