Leaf blade dimensions of rice (Oryza sativa L. and Oryza glaberrima Steud.). Relationships between tillers and the main stem

The effects of genotype and environment on the leaf area index of rice are well documented, but the rules governing leaf area distribution among main stem and tillers are less well understood. This study investigated the onto genetic patterns of leaf blade area and dimensions on the main stem and til lers of three rice cultivars, IAC47, Java (Oryza sativa L.) and CG14 (O. gl aberrima Steud.) grown in pots without competition among plants. No differe nces in phyllochron were observed among calms, but leaves on tillers appear ed 0.5 to 0.8 phyllochrons earlier than the genealogically corresponding le aves on the main stem (system of Katayama). Cohorts were thus not fully syn chronized. All culms produced their largest leaves soon after panicle initi ation (PI), despite differences in tiller age. Leaves that appeared subsequ ently were smaller owing to reduced length but not width, which remained co nstant. Three different hypothetical rules governing the behaviour of culms were tested: (1) tillers behave as clones of the main stem; (2) cohorts be have uniformly, and (3) behaviour is determined by leaf position (sum of ge nealogical leaf and tiller indices). The results were best explained by hyp otheses (2) and (3), with leaf blade width and length showing markedly diff erent patterns. (C) 2001 Annals of Botany Company.