Physio-Morphological Characters of F1 Hybrids of Rice (Oryza sativa L.) in Japonica-Indica Crosses

Abstract

A pot experiment was conducted to study photosynthetic rate in terms of carbon dioxide exchange rate (GER), chlorophyll meter reading (SPAD value) and specific leaf area (SLA) of 12 Fj hybrids from crosses between japonica and indica rice and their parents, and to estimate the heterosis in Fx hybrids at active tillering, flowering and dough ripe stages. In all Fx hybrids and parent cultivars, CER was high at the active tillering stage with a small heterosis value. A positive heterosis for this trait was found at the flowering stage. The magnitude of heterosis for CER depended on the cross combinations. Although a positive heterosis for SPAD value was found at the active tillering stage, there was no correlation between heterosis for SPAD value and that for CER at the flowering stage, at which heterosis for CER was positive. Heterosis for SLA was high at the active tillering stage and gradually decreased thereafter. Heterosis for CER might be dependent not only on negative heterosis for SLA but also on other photosynthetic factors such as N content, soluble protein content and Rubisco activity.