Relation between maize ( Zea mays L.) leaf area and root density observed with minirhizotrons

Abstract

The shoot and the root system are functionally closely related. This study describes the correlation between leaf area and root density of maize over the entire crop season to contribute to the understanding of shoot-to-root relationships. The crop was planted for three years in drainage lysimeters in repacked soil. Leaf area was estimated from non-destructive, morphometric measurements of individual leaves. Root density (roots cm −2) was determined from observations made with horizontally placed minirhizotrons (60 mm outer diameter with an image size of 2.43 cm 2), positioned perpendicularly to the maize row at ten soil depths between 5 and 100 cm. Relationships between leaf area and root density were determined by the non-parametric Kendall rank correlation coefficient for different depths, positions relative to the plant row, and maize developmental stages. During crop development significant correlations between leaf area and root density were observed successively at deeper soil layers, a pattern not observed for increasing distances from the plant row. Closest and most frequent correlations were found for shoot and root growth rates between leaf developmental stages 09 and 12, as well as for maximum leaf area and maximum root density. For other phases of the crop development leaf area and root density were weakly correlated. The spatial pattern of these correlation coefficients may indicate a compartmentation of the root system. Improving root data quality from minirhizotron observations and correction of the raw data for root clustering and shoot variability at the plot level may contribute to improve the interpretation of data from similar studies.