Root growth and dry matter partitioning of cauliflower under drought stress conditions: measurement and simulation

Abstract

Field and container experiments were carried out in order to quantify root growth and dry matter partitioning of cauliflower under drought stress conditions. Drought stress did not influence allometric relationships between leaf and stem dry matter and shoot and tap root dry matter. Drought stress, however, had an impact on the sink strength of the curd, thereby curd growth was delayed and curd dry matter production was more seriously depressed by a limited water supply than total dry matter. Drought stress did not modify a linear relationship between shoot dry matter and total root length, however, the specific root length of cauliflower was lower under drought stress conditions leading to a higher dry matter deposition in the fine root fraction. Also the vertical increment of rooting depth per degree day almost doubled under drought stress conditions. An existing model for dry matter partitioning in cauliflower was adopted to include the effects of drought stress on dry matter partitioning to the curd. Therefore, the initial increase of the curd's sink strength was made dependent on the plants relative growth rate during the vernalisation period. Furthermore, a simple descriptive root growth model was adopted to include drought stress impact on root growth. For this purpose the increase of rooting depth per degree day and the specific root length were made dependent on the average soil water potential in the rooted soil profile. The modified model modules predicted dry matter partitioning and described the root length distribution of cauliflower sufficiently well using total dry matter production rate as input values.