Effects of Photoperiod on Germination of Seeds of Talinum triangulare (Jacq.) Willd

Seed germination in Talinum triangulare as affected by photoperiod,with or without previous incubation in the dark in water at25 or 4 °C, was studied. The time course and quantity ofseed germination in photoperiods of 1 h and above were similarwith or without dark pretreatment, but the time to half maximumgermination was reduced from 12 days in non-dark pretreatedseeds to 4 days in seeds given 20 days in the dark at 25°C.A photoperiod of 0·25 h gave a lower rate and total germinationthan photoperiods of 1 h and above. Un-pretreated seeds required17 cycles of 24 h photoperiod for maximum germination as comparedwith 7 or less cycles if the seeds received more than 10 daysdark pretreatment at 25 °C. Both the rate and total germinationin light increased as the length of dark pretreatment at 25°C was increased from zero to 30 days. Incubation of theseeds in water in the dark at 4 °C for 5 to 30 days priorto illumination at 21 °C, reduced both the rate and quantityof seed germination in light as compared with those similarlyincubated in the dark at 25 °C. However, previous incubationin the dark for 30 days at 4 °C partially substituted forthe light requirement. The possible mechanism of breakage ofseed dormancy in Talinumis discussed in relation to these andother findings. Talinum triangulare (Jacq.), Willd, light, photoperiod, seed germination