Developmental basis of interspecific differences in leaf size and specific leaf area among C3 grass species

Abstract

Summary Leaf size and specific leaf area (SLA) are major traits in determining a plant's ecological functions. Differences in these leaf traits are characterized by cell division, expansion and maturation processes during leaf development. In this study, 16 C3 grass species were grown under controlled environments, and various cell division and elongation parameters in the leaf growth zone were obtained by a kinematic method to examine cellular mechanisms underlying interspecific differences in leaf length and specific leaf area. Leaf length showed a threefold difference among species. This difference in leaf length was closely associated with the number of dividing cells in the leaf meristem. Cell division activity in the leaf meristem also influenced mature cell length. Species with high levels of cell division activity had smaller mesophyll cells, mainly caused by a short cell elongation period. The fact that 70% of the variation in mature cell length was explained by cell division activity suggests that cell size determination is more strongly influenced by the developmental processes than by specific genes affecting cell size. Cell division and elongation activities did not have clear effects on SLA. However, species with high levels of division activity had higher leaf water content and lower leaf dry matter concentration than did species with low levels of division activity. The results of this study reveal the importance of cell‐cycle regulation in the leaf meristem in determining interspecific differences in leaf size and SLA among grass species.