Variation in growth attributes of contrasting populations of Trifolium repens

Abstract

SUMMARYA range of growth attributes was measured in seedlings of 10 Trifolium repens populations, differing in leaf size and origin, grown in three temperature and two glasshouse environments.Growth rates of large leaf types of Mediterranean origin were higher than those of smaller leaf types at 10°C. However, the greater temperature response of the smaller leaf types resulted in higher growth rates for S.100 and S.184 than for a large leaf type from Israel at 20°C.The increase of growth rate with temperature was associated with changes in leaf area ratio and net assimilation rate between 10° and 15°C but only with changes in net assimilation rate between 15° and 20°C. Within each temperature environment, population differences in growth rate were related to differences in net assimilation rate rather than leaf expansion.At low temperature a greater proportion of dry matter was distributed to leaf tissue in large leaf types particularly those of Mediterranean origin but they showed a proportionately smaller increase in allocation to leaves with increasing temperature compared with small leaf types.In the glasshouse environments growth rates in spring were more than double those in the autumn. This difference was associated with net assimilation rates which were about five times greater in the spring environment. However, leaf area ratios in the spring were only half those in the autumn. These differences in leaf area ratio between the glasshouse environments were closely related to differences in specific leaf area but not to differences in distribution of dry matter to leaf tissue which was greater in the spring environment.