Cardinal Temperatures and Thermal Time for Germination of Sarawak Traditional Rice

Germination of two rice landraces, namely Bario Sederhana and Biris, was determined from twelve temperatures (12.5 – 40 ºC) in a series of incubation experiments. The cardinal temperatures and thermal time for germination were estimated from a ‘broken-stick’ linear model. Both landraces had a Tb of 10 ºC, Topt between 32 – 33 ºC, and Tmax of 43 ºC. At the sub-optimal temperatures, the thermal time for germination was 62 ºCd for Bario Sederhana and 53 ºCd for Biris. Within the supra-optimal range (Topt to Tmax), both landraces required 27-29 ºCd for seed germination. The maximum final germination for Bario Sederhana was 93% at 30 ºC while Biris had 100% seeds population germinated at 27.5 ºC.