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The purpose of this paper is to explore the effects of acid treatment on root morphology and architecture in seedlings of Malus hupehensis var. pingyiensis. The rootstock seedlings were cultured in 1/2 Hoagland nutrient solutions of different pH (pH 4, pH 4.5, pH 5 and pH 6), respectively. The parameters of root architecture were measured in the day 4, 8 and 12 with the professional WinRHIZO 2007. Compared with the control (pH 6), the treatments significantly decreased the fractal dimension, length, diameter, surface area and volume of roots in day 8 and 12, and they kept decreasing followed the increase of the acidity and treatment time. The growth of lateral roots was more susceptible to acid treatment than taproots. In addition, the acid treatment mainly inhibited the growth of rootlets, significantly decreased the proportion of rootlets that changed the composition of roots, and then simplified the space structure of roots.

Soil acidification is one different form of soil degradation, the form resulted from many factors such as agricultural measures became more and more serious in recent decades [

Because the difference between the seedling Malus hupehensis var. pingyiensis is very small, it is an ideal material for researching the fruit roots [

According to the experiment method [

According to the test method [

The parameters were measured according to the test method [

The data in the article were handled through Excel statistical software 2003 and SPSS 17.0 statistical software package, the significant difference was conducted by Duncan’s new multiple range method.

It was shown in

Treatment | Days of treatment | Total root length/cm | Taproot length/cm | Lateral root length/cm |
---|---|---|---|---|

pH4 | 4 | 145.32 ± 6.10a(a) | 7.62 ± 0.73a(a) | 137.10 ± 4.88a(a) |

8 | 153.52 ± 2.54b(a) | 8.29 ± 0.17a(a) | 144.72 ± 2.42b(a) | |

12 | 159.26 ± 0.99b(a) | 8.78 ± 0.76a(a) | 150.05 ± 0.91b(a) | |

pH4.5 | 4 | 154.39 ± 1.19a(b) | 8.14 ± 0.64a(a) | 145.93 ± 0.58a(b) |

8 | 166.42 ± 3.57b(b) | 8.85 ± 0.57ab(a) | 156.73 ± 3.21b(b) | |

12 | 174.85 ± 2.31c(b) | 9.63 ± 0.61b(a) | 163.34 ± 1.38c(b) | |

pH5 | 4 | 159.38 ± 0.97a(bc) | 8.51 ± 0.29a(a) | 150.88 ± 0.49a(c) |

8 | 177.31 ± 1.75b(c) | 9.36 ± 0.27b(b) | 167.12 ± 1.50b(c) | |

12 | 189.63 ± 0.51c(c) | 10.53 ± 0.46c(b) | 178.88 ± 0.44c(c) | |

pH6 | 4 | 164.58 ± 2.43a(c) | 8.78 ± 0.43a(a) | 155.23 ± 2.15a(c) |

8 | 187.62 ± 1.50b(d) | 9.85 ± 0.92b(b) | 177.09 ± 0.48b(d) | |

12 | 208.96 ± 1.49c(d) | 11.25 ± 0.40c(c) | 197.96 ± 1.59c(d) |

Duncan’s multiple test, different letter outside the brackets indicated the significant differences among days of treatments in the same treatment, different letter in the brackets indicated the significant differences among the different treatments in the same day, small letter stand for 5% level.

time, the sequence of length reduction in the following decreasing order: lateral roots > total roots > taproots.

The mean diameter of the seedling roots became smaller under acid treatment (

At day 4, the surface area of the seedling roots had no significant changes (

The changes of volume of roots were consistent with that of surface areas of the seedling roots, the volume of the seedling roots had no apparent variations (

Composition of roots in seedlings was analyzed according to the diameter (

Root diameter (mm) | pH | 4d | 8d | 12d | |||
---|---|---|---|---|---|---|---|

Length (cm) | Percent (%) | Length (cm) | Percent (%) | Length (cm) | Percent (%) | ||

0 | 4 | 95.35 ± 2.19* | 65.6 | 99.64 ± 1.98** | 64.9 | 101.56 ± 0.84** | 63.6 |

4.5 | 107.52 ± 2.08* | 69.6 | 115.11 ± 1.44* | 69.2 | 120.03 ± 1.32** | 68.6 | |

5 | 117.63 ± 1.01 | 73.6 | 130.99 ± 2.19* | 73.8 | 139.36 ± 2.68* | 73.6 | |

6 | 129.18 ± 1.78 | 78.3 | 149.24 ± 1.51 | 79.8 | 170.42 ± 1.38 | 81.2 | |

0.5 | 4 | 35.21 ± 1.14* | 24.2 | 36.28 ± 1.90* | 23.6 | 36.89 ± 0.56* | 23.1 |

4.5 | 33.28 ± 0.55* | 21.5 | 34.67 ± 1.58* | 20.9 | 35.42 ± 0.79* | 20.3 | |

5 | 27.79 ± 0.79 | 17.4 | 29.72 ± 1.13 | 16.8 | 31.36 ± 1.07 | 16.6 | |

6 | 21.95 ± 0.83 | 13.3 | 23.75 ± 0.79 | 12.7 | 26.39 ± 1.00 | 12.7 | |

1 | 4 | 9.71 ± 0.66 | 6.7 | 13.61 ± 0.82 | 8.9 | 15.41 ± 0.66 | 9.6 |

4.5 | 11.55 ± 1.39 | 7.5 | 12.62 ± 0.88 | 7.6 | 14.79 ± 1.08 | 8.5 | |

5 | 10.05 ± 0.97 | 6.3 | 11.26 ± 1.92 | 5.8 | 12.23 ± 0.42 | 6.5 | |

6 | 8.98 ± 0.66 | 5.5 | 9.91 ± 1.54 | 5.3 | 10.65 ± 0.69 | 5.1 | |

1.5 | 4 | 4.64 ± 1.02 | 3.2 | 4.83 ± 0.24 | 3.1 | 5.25 ± 0.47 | 3.3 |

4.5 | 1.69 ± 0.47 | 1.1 | 3.28 ± 0.40 | 1.9 | 3.83 ± 0.55 | 2.2 | |

5 | 4.06 ± 0.76 | 2.5 | 5.13 ± 0.24 | 2.9 | 5.46 ± 0.52 | 2.9 | |

6 | 3.62 ± 0.46 | 2.2 | 4.11 ± 1.27 | 2.2 | 4.98 ± 1.28 | 2.4 |

*Indicate significant difference (P < 0.05), **Indicate extremely significant difference (P < 0.01).

however, the percentage of length of 0.5 < D ≤ 1.5 mm middle roots became larger with an increase of acid concentrations. At day 12, the percentage of length and length of 0 < D ≤ 0.5 mm fine roots significantly decreased (P < 0.01). These results showed that percentage of length of 0 < D ≤ 0.5 mm fine roots had a decreasing trend, the percentage of length of 0.5 < D ≤ 1.5 mm middle roots had an increase. In all, growth of 0 < D ≤ 0.5 mm fine roots was restrained, percentage of length of 0 < D ≤ 0.5 mm fine roots declined, composition of roots in seedling was affected by the acid treatment.

It was shown from

day 12, their fractal dimension of the seedling roots also reduced by 42.77%, 30.84%, 12.99% compared with the treatment pH 6, respectively. The decrease of fractal dimension of roots in seedlings under acid treatment showed that acidification resulted in the reduction of branch and structure simple.

1) Length of total roots, taproots and lateral roots in seedlings of Malus hupehensis var. pingyiensis had apparent decrease under the increase of acidity and treatment time in the experiment, the reduction of lateral roots was the largest among the researched roots. The lateral roots were easily damaged compared to the taproots.

2) The parameters of the seedling roots in the different treatments such as diameter, surface area, volume of roots and fractal dimension obviously reduced under acidification treatment, had apparent decrease under the increase of acidity and treatment time in the experiment, it also demonstrated a dose effect relationship with acid concentrations. Those parameters of the seedling roots such as diameter, surface area, volume of roots and fractal dimension became much smaller than that of the treatment pH 6 with much higher concentration acidification.

3) Composition of roots in seedlings was changed significantly with the increase of acid concentrations and treatment days under acid treatment. Percentage of length of 0 < D ≤ 0.5 mm fine roots had a decreasing trend, percentage of length of 0.5 < D ≤ 1.5 mm middle roots had an increase. Growth of 0 < D ≤ 0.5 mm fine roots was restrained, percentage of length of fine roots declined, composition of roots in seedling was affected by the acid treatment.

This work was supported by “five-twelfth” Nation Science and Technology Support Program of China (Grant No. 2014BAD16B02).

Zhang, Z., Fan, W.G., Yang, H.Q., Chen, J.X., Dong, J.W., Han, K.J., Li, P.F. and Wang, L. (2017) Effect of Acid Treatment on Root Architecture in Seedlings of Malus hupehensis var. pingyiensis. Agricultural Sciences, 8, 1082-1088. https://doi.org/10.4236/as.2017.810078