Growth characteristics in Hordeum spontaneum populations from different habitats

Hordeum spontaneum shows a large genetic variation and occupies a wide range of different habitats. The aim of this study was to quantify variation in growth characteristics of H. spontaneum from different sites in Israel and to relate this variation to different environmental conditions. To this end, 84 accessions of 21 populations were grown in a growth chamber in near-optimal conditions and a range of physiological, morphological, allocation-related and chemical characteristics were measured. These parameters included rates of photosynthesis, shoot and root respiration, specific leaf area, biomass allocation and seed mass. Averaged over all traits variation explained by differences between populations was 26%, between accessions 21%, whereas that within accessions was 53%. By contrast with most genetic studies, we found variation between populations larger than between accessions. The largest between-population variation (46%) was for morphological traits. In particular, seed mass, leaf thickness and leaf width differed strongly between populations. Variation in growth characteristics between populations was poorly related to mean annual rainfall, mean humidity or January temperature at the sites of origin. We expect that differences between populations to be larger and correlation with environmental parameters stronger in plants grown in stressful conditions. According to our study, seed mass is more important than relative growth rate in determining variation in early plant biomass in H. spontaneum.