Dynamics of leaf mass per unit leaf area and root mass per unit root volume of young maize plants: implications for growth models

Leaf dry mass per unit leaf area (LMA) and root dry mass per unit root volume (RMV) are key variables in many growth models because they link the dimension of acquisition organs to their dry mass and development cost. In order to analyse intra-plant and time variations in both LMA and RMV, two experiments were carried out in growth chambers using maize plants grown in rhizotrons and supplied with a hydroponic circulating solution. During the first 37 days after sowing, LMA and RMV of individual organs or organ parts changed with the organ type and development stage: they increased about two-fold for LMA (laminae and sheaths) and about four-fold for RMV (first order and second order roots). Our results confirm that estimating leaf area from leaf dry mass and constant LMA values measured on fully expanded leaves of different ages may introduce serious bias in growth models. They also show a bias in estimating root length from root dry mass and constant RMV values.