Article Figures & Data
Figures
- Fig. 1.
Comparison of lateral root development with localized application of control agar (left) or agar containing 100 μm NPA (right) to the root-shoot junction. Roots were grown for 4 d after application of agar.
- Fig. 2.
The effect of NPA application at several positions on the Arabidopsis primary root. Five-day-old Arabidopsis seedlings were treated with a line of agar containing 100 μm NPA at several positions along the root. The root was divided into 10-mm zones, with zone 1 beginning at the root-shoot junction. The lines of agar were placed above zone 1, 2, or 3, as indicated. The number and density of lateral roots were determined after 3 d of growth. The data were analyzed by Student's t test, and P values were determined for each sample compared with the controls and are indicated with asterisks (*P ≥ 0.015 and ≤ 0.038; **P ≤ 0.005).
Tables
[NPA] Lateral Root No. Root Length Lateral Root Density-a μm mm 0.0 15.9 ± 1.0 48.6 ± 1.4 0.33 ± 0.02 5.0 12.3 ± 0.8 47.2 ± 0.7 0.26 ± 0.02-b 10.0 10.4 ± 1.1 45.9 ± 1.1 0.23 ± 0.02-b 20.0 8.6 ± 0.7 39.0 ± 1.7 0.22 ± 0.20-b 50.0 6.4 ± 0.6 45.0 ± 0.9 0.14 ± 0.02-b 100.0 1.0 ± 0.3 38.7 ± 1.7 0.03 ± 0.00-b Four-day-old seedlings were treated by application of agar containing NPA at the indicated concentrations to the root-shoot junction. After 6 additional d of growth, lateral roots were counted and the length of the primary roots was measured. The reported values are averages ± se of 10 plants.
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↵F0-a The lateral root density was calculated by dividing the number of lateral roots by the primary root length for each plant, and is reported as the number of lateral roots per millimeter of primary root. The average ± se of the lateral root density calculated for each root is reported.
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↵F0-b Lateral root density was significantly reduced by all concentrations of NPA (P ≤ 0.007).
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- Table II.
Effects of localized NPA application at the root-shoot junction on free IAA concentration
Treatment Free IAA Concentration1-a Lateral Root No.1-b ng/g fresh wt Control agar 25.8 ± 4.7 15.5 ± 0.8 NPA agar 17.6 ± 2.2 5.9 ± 0.5 Seven- or 8-d-old seedlings were treated by application of agar with or without NPA to the root-shoot junction. After 3 additional d of growth, roots were harvested and the free IAA concentration was determined by GC-SIM-MS or the number of lateral roots was determined.
Treatment [3H]IAA Transported cpm fmol Control agar 1501 ± 175 61.4 ± 7.1 NPA agar 1124 ± 52 46.0 ± 2.1 Agar blocks containing [3H]IAA were applied to 4-d-old seedlings with and without NPA-containing blocks, and radioactivity in the roots was determined after 24 h. The reported values are averages ± se of four replicates, each containing five plants.
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F2-a Using a Mann-Whitney U test, the differences in IAA are statistically significant (P ≤ 0.04).
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Agar Lateral Root No. Lateral Root Density3-a Change in Length3-b mm Control3-c 4.4 ± 0.6 0.46 ± 0.07 Control3-d 5.3 ± 1.1 0.14 ± 0.03 30.2 ± 1.0 NPA3-c 1.7 ± 0.5 0.18 ± 0.053-e Control3-d 0.1 ± 0.1 0.00 ± 0.003-e 23.5 ± 1.0 Control3-c 4.4 ± 0.5 0.49 ± 0.06 NPA3-d 1.3 ± 0.6 0.05 ± 0.023-e 12.1 ± 0.7 Six-day-old seedlings were transferred to plates containing 10 μm NPA in the upper or lower half, as indicated. After 4 additional d of growth in the light, lateral roots in the upper and lower halves were counted and new primary root growth was measured. The reported values are averages ± se of 10 plants.
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↵F3-a The lateral root density was calculated by dividing the number of lateral roots by the primary root length for each plant, and is reported as the number of lateral roots per millimeter of primary root.
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↵F3-b The amount of elongation of the primary root after transfer to the indicated plates.
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↵F3-c The compound in agar and the lateral root growth on the upper half of the plate is shown.
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↵F3-d The compound in agar and the lateral root growth on the lower half of the plate is shown.
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↵F3-e Lateral root density decreased significantly (P ≤ 0.002) as judged by Student's ttest.
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Agar4-a Lateral Root No. Lateral Root Density Upper Lower Control Control 6.7 ± 0.85 0.19 ± 0.02 IAA Control 10.0 ± 0.56 0.43 ± 0.03 Control NPA 0.33 ± 0.14 0.02 ± 0.01 NPA IAA 4.25 ± 0.73 0.24 ± 0.04 IAA NPA 1.72 ± 0.46 0.08 ± 0.02 After the indicated treatments, lateral root number and root length were determined after 4 d of additional growth in the light. The reported values are averages ± se of 10 plants.
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↵F4-a Two, thin (1-mm), parallel lines of agar either with or without 10 μm IAA and 100 μm NPA were applied to the root-shoot junction of seedlings that were 4 d old. This technique allowed for the simultaneous application of two compounds to seedlings. Although both lines were over the root-shoot junction of the seedlings, one line was closer to the plant shoot (the Upper line) and the other was closer to the root (the Lower line).
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Agar Lateral Root No. Lateral Root Density5-a Change in Length5-b mm Control5-c 4.6 ± 0.4 0.62 ± 0.06 Control5-d 5.3 ± 0.9 0.14 ± 0.02 43.7 ± 1.8 IAA5-c 7.2 ± 0.5 0.98 ± 0.275-e Control5-d 9.1 ± 1.8 0.33 ± 0.065-f 37.8 ± 1.8 Control5-c 4.3 ± 0.4 0.47 ± 0.065-e IAA5-d 10.1 ± 0.9 0.30 ± 0.035-f 42.4 ± 2.5 Six-day-old seedlings were transferred to plates containing 0.1 μm IAA in the upper or lower half, as indicated. After 4 additional d of growth in the light, lateral roots in the upper and lower halves were counted and new primary root growth was measured. The reported values are averages ± se of 10 plants.
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↵F5-a The lateral root density was calculated by dividing the number of lateral roots by the primary root length for each plant, and is reported as the number of lateral roots per millimeter of primary root.
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↵F5-b The amount of elongation of the primary root after transfer to the indicated plates.
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↵F5-c The compound in agar and the lateral root development on the upper half of the plate is shown.
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↵F5-d The compound in agar and the lateral root development on the lower half of the plate is shown.
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↵F5-e These values are not statistically different from the control values (P ≥ 0.06).
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↵F5-f These values are statistically different from the control values (P ≤ 0.004).
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Treatment [IAA] Lateral Root No. Root Length Lateral Root Density6-a μm mm Intact plants6-b 0.0 28.6 ± 2.3 51.9 ± 3.1 0.56 ± 0.04 Shoot excised6-b 0.0 6.4 ± 0.4 45.7 ± 1.9 0.14 ± 0.01 Root tip excised6-b 0.0 20.8 ± 0.8 27.7 ± 0.8 0.76 ± 0.03 Shoot excised6-c 0.0 6.0 ± 1.0 42.4 ± 2.1 0.14 ± 0.02 Shoot excised 0.1 6.3 ± 0.9 46.7 ± 2.0 0.13 ± 0.02 Shoot excised 1.0 9.3 ± 1.2 43.5 ± 1.6 0.21 ± 0.03 Shoot excised 10.0 13.1 ± 1.3 36.7 ± 1.5 0.36 ± 0.03 Plants were treated by shoot or root-tip excision and application of agar containing IAA at the indicated concentrations to the root-shoot junction. After 3 additional d of growth, lateral roots were counted and the length of the primary roots was measured. The reported values are averages ± se of 10 plants.
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↵F6-a The lateral root density was calculated by dividing the number of lateral roots by the primary root length for each plant, and is reported as the number of lateral roots per millimeter of primary root.
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↵F6-b Five-day-old seedlings were treated and grown for 3 additional d in the light.
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↵F6-c Eight-day-old seedlings were treated and grown for 3 additional d in the dark.
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- Table VIII.
Effects of localized IAA application on lateral root development in dark-grown plants
[IAA] Lateral Root No. Root Length Lateral Root Density7-a μm mm 0.0 0.1 ± 0.1 33.5 ± 2.5 0.00 ± 0.00 0.1 0.7 ± 0.4 31.7 ± 1.4 0.02 ± 0.01 1.0 2.1 ± 0.4 27.6 ± 4.1 0.09 ± 0.027-b 5.0 6.0 ± 0.5 15.4 ± 0.8 0.40 ± 0.027-b 10.0 9.3 ± 0.7 13.0 ± 0.6 0.70 ± 0.077-b Seven-day-old seedlings were treated by application of agar containing IAA at the indicated concentrations to the root-shoot junction. After 3 additional d of growth, lateral roots were counted and the length of the primary roots was measured. The reported values are averages ± se of 10 plants.
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↵F7-a The lateral root density was calculated by dividing the number of lateral roots by the primary root length for each plant, and is reported as the number of lateral roots per millimeter of primary root.
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↵F7-b The increase in lateral root density was statistically significant, as judged by Student'st test (P ≤ 0.0008).
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