Rooting depth and root and shoot biomass were measured for seedlings of 20 species in both watered and unwatered sand columns. The species were from habitats of widely varying moisture status, ranging from marsh to de...Rooting depth and root and shoot biomass were measured for seedlings of 20 species in both watered and unwatered sand columns. The species were from habitats of widely varying moisture status, ranging from marsh to desert. Moisture status of the species' habitats was quantified as Ellenberg moisture number. Seedlings were allowed to grow in moist sand for 21 days and were then exposed to the treatments (watered and unwatered) for a further 21 days. Rooting depth of control plants was not correlated with Ellenberg number. Root depth of plants from dry habitats tended to increase in drying sand, while roots of plants from wet habitats decreased in depth. Plasticity of rooting depth (depth in unwatered / depth in watered sand) was significantly correlated with Ellenberg number ( r 2 = 0.56). Plasticity of shoot/root ratio was also correlated with Ellenberg number, but the relationship was weaker than for rooting depth plasticity. Species that showed the greatest plasticity in rooting depth also showed the greatest ability to sustain shoot growth in unwatered sand. There was some evidence that growth of plants from very dry habitats was reduced in the watered treatment. Results of this study suggest that a major, although not the only, adaptation of plants of dry habitats is the ability of their seedlings to exploit deeply buried water resources.展开更多
文摘Rooting depth and root and shoot biomass were measured for seedlings of 20 species in both watered and unwatered sand columns. The species were from habitats of widely varying moisture status, ranging from marsh to desert. Moisture status of the species' habitats was quantified as Ellenberg moisture number. Seedlings were allowed to grow in moist sand for 21 days and were then exposed to the treatments (watered and unwatered) for a further 21 days. Rooting depth of control plants was not correlated with Ellenberg number. Root depth of plants from dry habitats tended to increase in drying sand, while roots of plants from wet habitats decreased in depth. Plasticity of rooting depth (depth in unwatered / depth in watered sand) was significantly correlated with Ellenberg number ( r 2 = 0.56). Plasticity of shoot/root ratio was also correlated with Ellenberg number, but the relationship was weaker than for rooting depth plasticity. Species that showed the greatest plasticity in rooting depth also showed the greatest ability to sustain shoot growth in unwatered sand. There was some evidence that growth of plants from very dry habitats was reduced in the watered treatment. Results of this study suggest that a major, although not the only, adaptation of plants of dry habitats is the ability of their seedlings to exploit deeply buried water resources.
