부산대학교 도서관

1. Two laboratory screening experiments tested the juvenile-phase responses of 14 C 3 and 12 C 4 grassland species to pulses of warm temperature and water deficits. The first experiment determined germination response in relation to duration of warm temperature exposure (30/20 °C day/night). The second experiment determined the desiccation tolerance of seedlings immediately following germination. 2. The C 4 species were more dependent on warm temperatures for germination than the C 3 species. However, there was considerable variation within C 3 and C 4 types. In particular, Panicum dichotomiflorum was identified as the C 4 species least dependent on warm temperatures, exhibiting > 50% of maximum germination in continuous cold (7 °C). 3. The C 3 species were generally more desiccation-tolerant than the C 4 species, but there were several exceptions. Trifolium repens (C 3 ) was ranked as the least desiccation-tolerant whereas Setaria geniculata (C 4 ) was the eighth most tolerant species. Large-seeded species were more desiccation-tolerant than small-seeded species. 4. We suggest that poor desiccation tolerance contributes to the observed restriction of C 4 grass invasion into productive grasslands of the wetter regions of New Zealand. On the basis of juvenile-phase attributes, we ranked the C 3 species as more invasive of these grasslands than the C 4 species, and annuals as more invasive than perennials. Having invasive juvenile-phase attributes is an advantageous adaptation for species that rely solely on regeneration from seed.