Relative growth rate and biomass allocation in 20 Aegilops (Poaceae) species

This paper analyses relationships between relative growth rate (RGR), Seed mass, biomass allocation, photosynthetic rate and other plant traits as wel l as habitat factors (rainfall and altitude) in 20 wild species of Aegilops L. and one closely related species of Amblyopyrum (Jaub. & Spach) Eig., wh ich differ in ploidy level (diploid, tetraploid and hexaploid). The plants were grown hydroponically for 20 d in a growth chamber. The relationships b etween parameters were calculated either using the phylogenetic information (phylogenetically independent contrasts, PIG) or without using the phyloge netic information (trait values of taxa, TIP). The results using the two ap proaches were very similar, but there were a few exceptions in which the re sults were different (e.g. RGR VS. Seed mass). Specific leaf area (SLA) was positively correlated with leaf area ratio (LAR) and negatively correlated with net assimilation rate (NAR), which together resulted in the absence o f a correlation between SLA and RGR. Leaf photosynthetic rates (expressed o n a mass or area basis) showed no correlation with RGR. RGR was positively correlated with the stem mass ratio and negatively with root mass ratio. Sp ecies with a lower d. wt percentage have a higher RGR. Aegilops species fro m locations with higher annual rainfall invested less biomass in roots and more in shoots (leaves and stems) and had a higher RGR. Diploid species had a lower seed mass and initial mass than the hybrids (tetraploid and hexapl oid species), but there was no correlation of RGR With ploidy level. Polypl oid species, which have higher seed mass, occur at a higher altitude than d iploid species. Our results show that variation in RGR in Aegilops and Ambl yopyrum spp. is associated mainly with variation in biomass allocation (pro portion of biomass in stems and roots) and d. wt percentage, and not with v ariation in SLA, leaf photosynthetic rates or seed mass.