Distinguishing the Biomass Allocation Variance Resulting from Ontogenetic Drift or Acclimation to Soil Texture

Biomass allocation is a central issue in plant life history, and it provides the basis for understanding the response or adaptive strategies of plants. Different biomass allocation patterns reflect how plants respond to different selection pressures. Plant biomass allocation patterns depend primarily on genetic differences between species. Adjustments in biomass allocation can also be plastic as a response to varying resource availabilities, or as a result of ontogenetic drift or both. To understand how environmental factors influence biomass allocation or the developing phenotype, it is necessary to distinguish the biomass allocations resulting from environmental gradients or ontogenetic drift.

To determine whether the biomass allocations to different organs were mainly governed by ontogenetic drift, soil texture or both, researchers carried out experiment during the cotton-growing season of 2010 at the Fukang Station of Desert Ecology, Chinese Academy of Sciences, which is located on the southern periphery of the Gubantonggut Desert. 

They compared the development trajectories of cotton plants (Gossypium herbaceum L.), which were grown in two contrasting soil textures during a 60-d period. Those results distinguished the biomass allocation pattern resulting from ontogenetic drift and the response to soil texture. The soil texture significantly changed the biomass allocation to leaves and roots, but not to stems. Soil texture also significantly changed the development trajectories of leaf and root traits, but did not change the scaling relationship between basal stem diameter and plant height. Results of nested ANOVAs of consecutive plant-size categories in both soil textures showed that soil gradients explained an average of 63.64%–70.49% of the variation of biomass allocation to leaves and roots. Ontogenetic drift explained 77.47% of the variation in biomass allocation to stems. The results suggested that the environmental factors governed the biomass allocation to roots and leaves, and ontogenetic drift governed the biomass allocation to stems. The results demonstrated that biomass allocation to metabolically active organs (e.g., roots and leaves) was mainly governed by environmental factors, and that biomass allocation to metabolically non-active organs (e.g., stems) was mainly governed by ontogenetic drift. We concluded that differentiating the causes of development trajectories of plant traits was important to the understanding of plant response to environmental gradients.

The result has been published on PLOS ONE, 2012 7(7): e41502. doi:10.1371/journal.pone.0041502. The paper can be downloaded from http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0041502.