狗牙根根系抗拉性能对水淹时长的响应

为明确水淹胁迫下植物根系对水淹时长的响应特征，该研究以三峡库区消落带优势植物狗牙根根系为研究对象，以未水淹为对照，分析不同水淹时长下（0，15，30，60，90，120，150和180 d）狗牙根根重密度、根系活力及抗拉性能的变化规律，明确根系抗拉性能对水淹时长的响应规律。结果表明：随着时间的增加，对照组根重密度和根系活力基本无明显变化，而淹没组根重密度与根系活力均随水淹时长增加呈先急剧减小后缓慢减小的变化规律，水淹初期（15 d）减小量分别占根重密度和根系活力总减小量的65.15%和75.86%。水淹环境会明显降低狗牙根根系抗拉性能，根系最大抗拉力和抗拉强度均随水淹时长的增加而下降，180 d水淹分别造成根系抗拉系数和抗拉强度系数减小了59.46%和59.48%。不同直径根系对水淹的响应程度有所不同，根系最大抗拉力下降程度随其直径的增加而增加，0.6～0.7 mm直径狗牙根根系最大抗拉力下降幅度最大，达7.56 N，抗拉强度下降程度则随根系直径的减小而增加，0.1～0.2 mm直径狗牙根根系抗拉强度下降幅度最大，达36.42 MPa。因此，水淹显著降低狗牙根根重密度、根系活力和抗拉性能（P<0.05），根系活力能够较好的解释其抗拉性能的变化。研究结果对进一步探究水淹胁迫下根系固土机理具有重要科学意义。

Response of tensile properties in Cynodon dactylon root to submersion duration

Abstract: Plants can significantly alter the physiological and ecological characteristics to adapt to the continuous submersion in the water-level fluctuation zone, thus leading to the performance of root on soil reinforcement. However, it is still unclear on the effects of submersion duration on the tensile properties of plant roots. In this study, the dominant plant in the water-level fluctuation zone of the Three Gorges reservoir area, Cynodon dactylon, was selected as the research object. The seeds were sown at 15 g/m2 on a purple soil field in August 2019, and the maintenance was then conducted more than two years before the beginning of the submersion test. Samples were taken in September 2021 and then submersed in the water tank with a submerged depth of 50 cm. Among them, the water tank was covered with the black cloth to simulate the dark condition during submersion. The unsubmerged condition was used as the control. The root weight density, root activity, and tensile properties were analyzed under eight submersion durations (0, 15, 30, 60, 90, 120, 150, and 180 d), in order to evaluate the response of tensile properties of Cynodon dactylon root to submersion duration. The results indicated that there was a rapid decrease in the root weight density and root activity, followed by a slow but continuous decline with the increasing of submersion duration in the submersion group, compared with the control. The root weight density and root activity decreased by 28.42%, and 55.80%, respectively, for the submersion duration 180 d, compared with at the beginning of the submersion test. The root weight density and root activity decrease in the initial stage of submersion (15 d), accounting for 65.15% and 75.86% of the total decrement, respectively. Meanwhile, the maximum tensile strength of the root was closely related to the root diameter with the power function. The tensile force and tensile strength coefficient a, c decreased with the increase of submersion duration, while the tensile force and tensile strength power coefficient b, d showed no outstanding change. The tensile force and tensile strength coefficient a, c for the relation of root diameter with the maximum tensile strength and tensile strength decreased by 38.42%, 42.86%, 58.27%, 52.48%, 55.95%, 57.03%, 59.46%, and 38.45%, 42.87%, 58.26%, 52.50%, 55.95%, 55.95%, and 59.48%, respectively for the submersion duration15, 30, 60, 90, 120, 150, and 180 d, compared with at the beginning of the submersion test. The initial stage of submersion accounted for 64.61% and 64.64% of the total decrement of fitting tensile force and tensile strength coefficient a, and c, respectively. The response degree of root tensile properties to the submersion also varied with the root diameter. Specifically, the decrement of the maximum tensile strength increased with the increase of root diameter, while the decrement of tensile strength increased with the decrease of root diameter. Moreover, the tensile force and tensile strength coefficient a, c for the relation of root diameter with the maximum tensile strength and tensile strength shared a significant logarithmic relationship with the root activity. Therefore, the submersion environment significantly reduced the root weight density, root activity, and tensile properties. The root activity can be expected to better explain the changes in the tensile properties. The finding can be of great significance to explore the plant root on soil reinforcement under a submersion environment in the water-level fluctuation zone.