Effective breaking of dormancy of Scaevola sericea seeds with seawater, improved germination, and reliable viability testing with 2,3,5-triphenyl-tetrazolium chloride

Abstract

Scaevola sericea (Gaertn.) Roxb., which is a semi-mangrove halophyte, displays low seed germination (SG) and poor development. A model system was established to assess seed viability (SV) and enhanced SG in response to 2,3,5-triphenyl-tetrazolium chloride (TTC), and to detect SV under different storage conditions and duration to establish an optional storage method for seeds. Percentage SG (SG%) was also tested with different periods of soaking in water, gibberellic acid (GA3) and seawater after removing fruit pulp. Optimal detection of the percentage of SV (SV%) was possible when seeds were soaked for 3 h in 0.4% TTC. In these conditions, after 15 d, SV% exceeded 90.0%. This indicates that low SG was not related to SV under natural conditions. The nutritious epicarp (pulp) of intact fruit is easily infected by mildew, rotting rapidly in high relative humidity (60–90%). When pulp was removed from fruits, germination period was speeded up by almost 8 d (seeds germinated after sowing for 28 d). This also increased SG%. Seawater broke seed dormancy more efficiently than GA3. The SG% (59.0%) of seeds with their epicarp removed then soaked in seawater for 24 h was higher than seeds soaked in distilled water (24.0%) or in 200 mg/L GA3 (33.7%) after sowing for 40 d The SV% of seeds stored at 4 °C was higher than seeds stored at room temperature (25±3 °C), but when storage period was extended to 180 d or longer, their SV% declined rapidly. In natural conditions, S. taccada seeds have a high SV%. The low SG% is caused by easily rotting pulp and the physiological dormancy of fruits. By removing the pulp and soaking naked seeds in seawater can break seed dormancy and achieve ideal SG which would benefit ecorestoration and landscaping projects.