AOBPreview published online on January 4, 2007
Annals of Botany, doi:10.1093/aob/mcl271
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© The Author 2007. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Genome Size Evolution in Relation to Leaf Strategy and Metabolic Rates Revisited
1 California Polytechnic State University, Department of Biological Sciences, San Luis Obispo, CA 93407, USA
2 Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK
* For correspondence. E-mail knight{at}calpoly.edu
Received: 10 July 2006 Returned for revision: 27 September 2006 Accepted: 6 November 2006
BACKGROUND AND AIMS: It has been proposed that having too much DNA may carry physiological consequences for plants. The strong correlation between DNA content, cell size and cell division rate could lead to predictable morphological variation in plants, including a negative relationship with leaf mass per unit area (LMA). In addition, the possible increased demand for resources in species with high DNA content may have downstream effects on maximal metabolic efficiency, including decreased metabolic rates.
METHODS: Tests were made for genome size-dependent variation in LMA and metabolic rates (mass-based photosynthetic rate and dark respiration rate) using our own measurements and data from a plant functional trait database (Glopnet). These associations were tested using two metrics of genome size: bulk DNA amount (2C DNA) and monoploid genome size (1Cx DNA). The data were analysed using an evolutionary framework that included a regression analysis and independent contrasts using a phylogenetic tree with estimates of molecular diversification times. A contribution index for the LMA data set was also calculated to determine which divergences have the greatest influence on the relationship between genome size and LMA.
KEY RESULTS AND CONCLUSIONS: A significant negative association was found between bulk DNA amount and LMA in angiosperms. This was primarily a result of influential divergences that may represent early shifts in growth form. However, divergences in bulk DNA amount were positively associated with divergences in LMA, suggesting that the relationship may be indirect and mediated through other traits directly related to genome size. There was a significant negative association between genome size and metabolic rates that was driven by a basal divergence between angiosperms and gymnosperms; no significant independent contrast results were found. Therefore, it is concluded that genome size-dependent constraints acting on metabolic efficiency may not exist within seed plants.
Key words: Leaf mass per unit area, LMA, photosynthesis, Amass, dark respiration, Rmass, genome size, phylogeny, independent contrasts, contribution index
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  C. A. Knight and J. M. Beaulieu Genome Size Scaling through Phenotype Space Ann. Bot., April 1, 2008; 101(6): 759 - 766. [Abstract] [Full Text] [PDF]
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