Integrated Biosciences Program, University of Minnesota Duluth, 1035 Kirby Dr, Duluth, MN 55811, USA.
Oecologia. 2012 Sep;170(1):65-76. doi: 10.1007/s00442-012-2296-x. Epub 2012 Mar 10.
Separating plastic from ontogenetic and growth-limiting responses of plants to changes in resource availability can be challenging because there are a total of eight combinations of these three types of responses. These can, however, be uniquely distinguished on plots of root:shoot ratios against total biomass through time. We used this approach to separate ontogenetic, plastic, and growth-limiting responses of wild rice (Zizania palustris L.) to changes in nitrogen, phosphorus, and light availabilities. Relative growth rate was limited primarily by nitrogen but responded to increased light and phosphorus after nitrogen limitations were alleviated. Nitrogen addition increased relative growth rate because it simultaneously increased unit leaf rate, specific leaf area, and leaf weight ratio. Increased light did not change relative growth rate because decreased specific leaf area and leaf weight ratio compensated the increased unit leaf rate. Phosphorus did not change either relative growth rate or its underlying components. Plants responded ontogenetically to increased nitrogen and light availabilities by accelerating their developmental rate, and plastically by decreasing or increasing their root:shoot ratios, respectively. Plants did not respond either ontogenetically or plastically to increased phosphorus availability. Ontogenetic changes in growth can be separated from plastic and growth-limiting responses by plotting root:shoot ratio against total biomass in the context of the eight possible responses identified above, and also by examining how the underlying components of relative growth rate respond.
将植物对资源可利用性变化的分离出由个体发育和生长限制引起的反应可能具有挑战性，因为这三种反应共有八种组合。然而，通过随时间变化绘制根冠比与总生物量的关系图，可以将它们独特地区分开来。我们使用这种方法来分离野生稻（Zizania palustris L.）对氮、磷和光照可利用性变化的个体发育、可塑性和生长限制反应。相对生长率主要受氮限制，但在氮限制缓解后，对光照和磷的增加有反应。氮的添加增加了相对生长率，因为它同时增加了单位叶速率、比叶面积和叶重比。光照的增加并没有改变相对生长率，因为比叶面积和叶重比的降低补偿了单位叶速率的增加。磷既没有改变相对生长率，也没有改变其基础组成部分。植物通过加速其发育速度来表现出个体发育对氮和光照可利用性的增加的反应，通过分别降低或增加根冠比来表现出可塑性的反应。植物对增加的磷可利用性既没有表现出个体发育也没有表现出可塑性的反应。通过在上述确定的八种可能反应的背景下，将根冠比与总生物量作图，以及通过检查相对生长率的基础组成部分的反应方式，可以将生长的个体发育变化与可塑性和生长限制反应区分开来。
