FRACTAL ANALYSIS FOR MORPHOLOGICAL DESCRIPTION OF CORN ROOTS UNDER NITROGEN STRESS

A means of quantification of plant root branching, specifically under stress, is of importance for evaluating the contribution of plant root s to water and nutrient uptake and subsequently plant growth. An exper iment was conducted to describe the morphology of corn (Zea mays L.) r oot systems using fractal analysis and also to determine if a root's f ractal dimension (D) is altered by N stress. Corn genotypes (B73 x LH1 05 and N74 x Mo17) were planted in peg boxes, 1.2 m long, 1.2 m deep, and 0.05 m wide filled with 20:80 soil to sand mixture and were grown with N rates of 0, 10, 20 and 30 mg kg - 1. Thirty-nine days after pla nting, the mixture was gently washed from the roots and the roots were divided into nine sections (squares of side 304.8 mm) and slide photo graphs were taken from each section. The slides were projected on grid s made up of 12(2), 24(2), and 48(2) squares of sides (r) 25.4, 12.7, and 6.35 mm, respectively. Regression of log of number of squares inte rsected by roots vs. long of r levels was used to determine the slope (-D). Fractal dimension was significantly smaller for zero N compared to applied N with no detectable difference among applied N levels. Fra ctal dimension was highest for the section directly below the crown (D = 1.73) indicating high root branching and was lowest for the section s in deeper soil (D = 1. 19, average of 3 sections in the 0.6 to 0.9-m depth) indicating less branching. The intercept of the regression lin e (log K), which indicates root abundance, was lowest for zero N. Amou nt of roots in the section directly below the crown was 45% of total r oots. Nitrogen stress changed the morphology of corn root system and c aused less root branching. Fractal analysis was a useful method for de scribing the morphology of corn root systems, both quantitatively and qualitatively.