磷胁迫条件下北美红杉幼苗生长的适应性反应

采用温室盆栽的方法探讨了不同的P质量浓度(0、0.018、0.036、0.054、0.071、0.108、0.142和0.213g.L-1,以0.071g.L-1作为对照)处理下北美红杉一年生幼苗生物量及根系生长的反应,结果表明,P供应不足时,幼苗将更多的生物量分配到地下以扩大根系的生长,地下/地上生物量比率增加,缺P时为0.47。高水平供P条件下,增加幅度较大,供P水平增加2倍时,达0.66。幼苗细根/叶生物量比率与地下/地上生物量比率变化规律相似。当供P水平较低时,幼苗的一级侧根数增多,根系的分枝密度增加,二级侧根节点之间距离减小,细根的特定根长增加,这些根系结构特征的变化有利于幼苗吸收更多的养分和水分。P养分供应适宜时,幼苗增加了地上部分的分枝数,以争取更多的地上资源空间。

Adaptive response of Sequoia sempervirens seedlings to phosphorus stress

Phosphorus is essential to forest trees for their growth and development. But it is usually deficient or its availability is low in red mountain soil and yellow mountain soil of Yunnan regions. Thus, many trees often suffer from phosphorus stress. In this paper, one-year-old Sequoia sempervirens seedlings were sand-cultured in pots supplied with various P mass concentrations(0, 0.018, 0.036, 0.054, 0.071, 0.108, 0.142 and 0.213 g.L-1, and 0.071 g.L-1 as the control)for six months to study their adaptive response to phosphorus stress. The results suggested that deficient phosphorus supply caused increments of biomass partitioning to roots in order to increase root growth; the ratios of below-ground to above-ground biomass were 0.47 and 0.66 when they were supplied with 0 and 0.213 g.L-1 P respectively. The ratios of fine root/leaf mass were similar to the ratios of below-ground to above-ground biomass. Under the conditions of low P concentrations, the number of first lateral roots and the specific root length of the seedlings increased and the links of second lateral root were decreased, helpful for the seedlings to absorb more nutrients and water. The number of branches of Sequoia seedlings under normal P treatment was increased to exploit more above-ground energy sources. These results are of significance for forest plantation and stand nutrition management.