EFFECTS OF SEDIMENT TYPE ON STEM MECHANICAL PROPERTIES OF THE SUBMERGED MACROPHYTE HYDRILLA VERTICILLATA (L.F.) ROYLE
EFFECTS OF SEDIMENT TYPE ON STEM MECHANICAL PROPERTIES OF THE SUBMERGED MACROPHYTE HYDRILLA VERTICILLATA (L.F.) ROYLE
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发表时间：
2012
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通讯作者：
Guorong Zhu;Meng Zhang;T. Cao;L. Ni;Aiwen Zhong;H. Fu
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作者：
Guorong Zhu;Meng Zhang;T. Cao;L. Ni;Aiwen Zhong;H. Fu
富营养化过程中沉水植物的减少部分归因于肥沃的沉积物对植物形态和生理的不利影响。然而，尽管这一点已在陆地植物中得到证实，但人们对它对机械性能的影响知之甚少。在这项研究中，对生长在不同营养水平的三种沉积物（沙子、粘土和壤土）上的轮叶黑藻的形态特征、力学性能（拉力、拉应力和弯曲指数）和纤维素含量进行了实验研究。结果表明，植物的机械特性在三种沉积物之间以及沿茎部均存在较大差异，其中粘土沉积物的数值最高，并且从下段到上段呈下降趋势，特别是在壤土沉积物中生长时，这表明中营养沉积物有利于茎的机械阻力高于其他两种沉积物，并且植物在其他两段而不是下段更容易折断。茎横截面积和节间长度与拉伸力显着相关，拉伸应力是茎纤维素含量的线性函数。在粘土沉积物中生长的植物表现出最短的株高和最多的分枝数，这在形态上有利于降低水力。总之，肥沃的沉积物刺激了植物生长，但牺牲了轮叶轮藻的机械抗性性能。富营养化过程中机械阻力的降低可能导致沉水植物的减少和沉积物养分的富集。
The decline of submerged macrophytes during the eutrophication progress can be partly attributed to the adverse effects of fertile sediment on morphology and physiology of plants. However, little is known about its effects on mechanical properties, although this has been confirmed in terrestrial plants. In this study, the morphological traits, mechanical properties (tensile force, tensile stress and bending index) and cellulose content of Hydrilla verticillata grown on three types of sediment (sand, clay and loam) with different nutrient levels, were examined experimentally. Results showed that considerable variations in mechanical properties of plants were observed among the three sediments and along the stem, with the highest values in clay sediment and a decreased trend from the lower to upper segment, especially when grown in loam sediment, indicating that mesotrophic sediment benefits to higher mechanical resistance of stems than the other two sediments, and plants were prone to break at the other two segments, rather than the lower segment. Stem cross sectional area and internode length were significantly correlated with tensile force, and tensile stress was a linear function of stem cellulose content. Plants grown in clay sediment showed the shortest plant height and the maximum branch numbers, which are morphologically advantageous to reduce the hydraulic force. In conclusion, fertile sediment stimulated the plant growth at the expense of H. verticillata performance with respect to mechanical resistance. Decrease of mechanical resistance could contribute to the decline of submerged macrophytes with the enrichment of sediment nutrient during the process of eutrophication.