A Mechanistic Model of Carbohydrate Dynamics During Adventitious Root Development in Leafy Cuttings

Abstract

The rooting of vegetatively propagated leafy cuttings involves the complex interaction of many processes. For this reason, the influence of carbohydrate status, nutrition, water and hormonal factors on root formation is poorly understood at a mechanistic level. We present a mechanistic model of the growth of pre-formed root initials on a cutting consisting of leaf, internode and roots. The processes represented are leaf photosynthesis, starch mobilization, sugar transport, and sugar utilization for root growth. The model provides a quantitative scheme for understanding how root development depends on properties of cuttings such as leaf area, internode length and initial carbohydrate content. The potential of the model to interpret rooting experiments on a whole-cutting basis is illustrated using published data for cuttings of Triplochiton scleroxylon (a West African hardwood) with different leaf areas. Observed rooting times are reproduced in the model by varying the leaf photosynthetic rate per unit area. The simulated starch and sugar dynamics during root growth are in qualitative agreement with observations. A sensitivity analysis is performed to examine the effect of key parameters on the timing or success of rooting. The model provides a framework for examining the role of other factors known to affect rooting, such as nutrient and water status, but requires further parameterisation before it can be used as a predictive tool in vegetative propagation.