BROMELIAD SEED GERMINATION INDUCTORS, AND INHIBITORS.: A ROLE OF NACL, LOW TEMPERATURES, GIBBERELLIC ACID, AND SULPHURIC ACID ON GERMINATION OF DYCKIA ENCHOLIRIOIDES (GAUDICHAUD) MEZ VAR. ENCHOLIRIOIDES

Dyckia encholirioides (Gaudichaud) Mez var encholirioides is an endangered endemic bromeliad in the Brazilian Atlantic Forest running along the Atlantic Ocean. It is considered vulnerable because it has restricted, discontinuous clusters dispersed throughout central-southern Brazil and is listed as endemic to these regions. In this study, we investigated the role of seed storage in low-temperature gibberellic acid (GA3), as well as the effect of sulphuric acid (H2SO4), to enhance seed germination. Also, it was tested different salt levels (0, 100, 200, 300, 400, and 500 mmol L-1 NaCl) under various temperature regimes (10-20°C, 15-25°C, 20-30°C, and 25-35°C), both in 12 hours of dark and 12 hours of light photoperiod and complete darkness on seed germination. We found that GA3 has little or no effect on seed germination promotion. In contrast, storage of the seeds at low temperatures efficiently promoted seed germination since its germination was delayed. The seed germination was almost 100% in all treatments with GA3 or lower temperatures and 80% with H2SO4 as a promoter. The mean germination time (MGT) in response to GA3 or cold ranged from 6 to 14 days, increasing as cold time increased. Under H2SO4, the MGT ranged from 4 to 9 days, with higher values in intermediate H2SO4 levels. Time exposure to H2SO4 progressively reduced seed germination. Under NaCl as a negative promotor, the highest seed germination rate was obtained at 0, 100, and 200 mmol L-1 NaCl at 20-30°C, and a further increase in salinity resulted in a gradual decrease in germination. Less than 5% of seeds germinated at 500 mmol L-1 NaCl. Salinity treatment at 15°-25°C was slightly inhibitory to the seed germination than the optimal temperature regime, whereas under both 10°-20ºC and 25°-35°C temperature regimes, seed germination was substantially reduced. Few seeds germinated at concentrations higher than 200 mmol L-1 NaCl. Germination rate was fastest at 20°-30°C and slowest at 10°-20°C. A low seed germination rate was obtained in the dark as compared to seeds germinated in a 12-hour photoperiod under saline conditions. Recovery experiments showed that exposure of seeds to various salinity and temperature regimes had little effect on viability, and seeds could successfully germinate after salt stress relief in D. encholirioides seeds.