Effect of temperature regimes, dormancy break treatments and low hydration on seed germination in barley, tomato and turnip

Germination of surface sterilized seeds of barely, tomato and turnip was tested under different temperature regimes (constant temperatures: 16, 21 and 31°C) and alternate temperatures (10/30°C (16h/8h), 20/30°C (16h/8h), 15/25°C (16h/8h)), in filter paper lined paired petridishes with 12 h/d light inside BOD incubator. Effect of dormancy break treatments on promotion of seed germination and effect of low hydration (−1.5 MPa) maintained by sucrose, mannitol or polyethylene glycol (MW 6000) solutions and abscisic acid (25 mg/l) on seed germination was examined under various temperature regimes in darkness, in 16 h/d or in continuous light provided by fluorescent tubes (400 fc). Each type of seed tested was found to have a specific germination temperature range and most effective dormancy break treatment varied. For barley, it was 15°C, dehusking; in tomato, germination in alternate temperature 20/30°C (16h/8h) in light and for turnip 21°C in light and GA₃ 200 to 400 mg l⁻¹ (co-applied).