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植物根序和径级不仅反映细根的形态结构,而且能反映根系的一些生理特征,如细根寿命和周转等。该文以二年生油松(Pinus tabulaeformis)幼苗根系为研究对象,系统比较了根序分类方法和径级分类方法在描述根系特征上的优缺点,探索了两者之间的内在联系。结果表明:二年生油松幼苗最多可包括6级根序,直径的变化范围为0.169–3.877mm。按根序划分,I–VI级根序的总根长和总根表面积主要集中在前3级根序,这3级根序的根占总根长的78.77%和总根表面积的62.72%。前3级根序的比根长是后3级根序比根长的1.3–3.0倍,比根面积是后3级比根面积的1.0–1.5倍。按常用的径级(以0.5、1.0、1.5和2.0mm为阈值)划分方法,油松幼苗大部分根系直径≤1.5mm,此区间细根的根长和根表面积占总根长的93.76%和总根表面积的84.35%。直径≤1.5mm的细根平均比根长是>1.5mm细根比根长的3–7倍,比根面积的1.5–3.0倍。由于油松根序和径级之间有显著的指数关系,依据径级最大程度反映根序的原则,提出了新的径级划分方法,即以0.4、0.8、1.3和2.0mm为阈值对油松幼苗根系径级重新进行划分。此时,上述区间可分别包括I级、II级、III级、IV级、V级根序中根尖数的93.22%、86.37%、75.96%、70.47%和76.67%。同时也可分别涵盖各径级根长的89.34%–70.83%、根面积的86.01%–76.12%以及体积的87.73%–76.12%。此时,根系不同径级与根序之间可以建立起良好的对应关系。这些结果表明,通过合理划分径级区间可以较好地反映根序特征。
Plant roots and diameter not only reflect the morphological structure of fine roots, but also reflect some physiological characteristics of the root system, such as fine root life and turnover. In this paper, the root system of biennial Pinus tabulaeformis seedlings was studied, and the advantages and disadvantages of root-sequence classification and diameter-class classification in describing root traits were systematically compared, and the intrinsic relationship between them was explored. The results showed that the perennial Pinus tabulaeformis seedlings could include up to 6 orders of root diameter with a range of 0.169-3.877 mm in diameter. According to the order of roots, the total root length and the total root surface area of I-VI roots were mainly in the first three orders, which accounted for 78.77% of the total root length and 62.72% of the total root surface. The specific root length of the first three orders is 1.3-3.0 times the root length of the second three orders, and the specific root area is 1.0-1.5 times of that of the third three grades. According to the commonly used diameter class (0.5, 1.0, 1.5 and 2.0 mm as the threshold), the root diameter of most of the Pinus tabulaeformis seedlings is less than or equal to 1.5 mm, and the root length and root surface area of the fine roots in this range account for 93.76% of the total root length Total root surface area of 84.35%. The average root length of the fine roots with a diameter of less than 1.5 mm is> 1.5 mm. Fine roots are 3-7 times longer than the root length and 1.5-3.0 times the root area. Because of the significant exponential relationship between the order and diameter of Pinus tabulaeformis, a new method of diameter classification was proposed based on the principle that the diameter class can best reflect the order of the roots, that is, with the thresholds of 0.4, 0.8, 1.3 and 2.0 mm, Roots of seedling diameter class re-divided. In this case, the above intervals can respectively include 93.22%, 86.37%, 75.96%, 70.47% and 76.67% of the number of root tips in class I, class II, class III, class IV and class V, respectively. At the same time, 89.34% -70.83% of the root length of each diameter class, 86.01% -76.12% of the root area and 87.73% -76.12% of the volume can be covered separately. At this point, different diameter classes and root sequences can establish a good correspondence between. These results show that the root-sequence characteristics can be well reflected by the reasonable partition of diameter-class interval.