Spikelet production efficiency per unit biomass at physiological maturity was generally higher in hybrids than
indica inbreds or NPTs (Table 5). The difference between
indica inbreds and NPTs in spikelet production effi ciency
per unit biomass at physiological maturity was not consis-tent. Spikelet production effi ciency per unit N uptake at
physiological maturity was slightly higher in hybrids than
in indica inbreds and NPTs, but the difference was not
always significant. Spikelet production effi ciency per unit
N uptake at physiological maturity was greater in the WS
than in the DS, which was due to the lower N uptake at
physiological maturity in the WS than in the DS (data not
shown). The product of harvest index and plant height at
physiological maturity was significantly higher in hybrids
than indica inbreds or NPTs in all four seasons.