Allocation, plasticity and allometry in plants

doi:10.1078/1433-8319-00083

2004-01-01

963

PRE

Jacob Weiner

DOI：10.1078/1433-8319-00083

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Allocation is one of the central concepts in modern ecology, providing the basis for different strategies. Allocation in plants has been conceptualized as a proportional or ratio-driven process ('partitioning'). In this view, a plant has a given amount of resources at any point in time and it allocates these resources to different structures. But many plant ecological processes are better understood in terms of growth and size than in terms of time. In an allometric perspective, allocation is seen as a size-dependent process: allometry is the quantitative relationship between growth and allocation. Therefore most questions of allocation should be posed allometrically, not as ratios or proportions. Plants evolve allometric patterns in response to numerous selection pressures and constraints, and these patterns explain many behaviours of plant populations. In the allometric view, plasticity in allocation can be understood as a change in a plant's allometric trajectory in response to the environment. Some allocation patterns show relatively fixed allometric trajectories, varying in different environments primarily in the speed at which the trajectory is travelled, whereas other allocation patterns show great flexibility in their behaviour at a given size. Because plant growth is often indeterminate and its rate highly influenced by environmental conditions, 'plasticity in size' is not a meaningful concept. We need a new way to classify, describe and analyze plant allocation and plasticity because the concepts 'trait' and 'plasticity' are too broad. Three degrees of plasticity can be distinguished: (1) allometric growth ('apparent plasticity'), (2) modular proliferation and local physiological adaptation, and (3) integrated plastic responses. Plasticity, which has evolved because it increases individual fitness, can be a disadvantage in plant production systems, where we want to optimize population, not individual, performance.

Keyword:

allometric growth

biomass allocation

partitioning

size-dependence