Abstract
Hydrocotyle bonariensis is a rhizomatous perennial herb with wide distribution along the southwestern Atlantic coast, typically growing in wind exposed areas of dunes and in sandy places where water table is near soil surface. Temperature requirements for germination of this plant were investigated at five different constant temperatures (10, 15, 20, 25 and 30oC) and at three different thermoperiods (15-20, 15-25 and 15-30oC), and cold stratification at 5oC during 10, 15 and 30 days. Additional others treatments were tested: leaching, addition of KNO3, GA3 and mechanical scarification with sand. Seeds showed no germination at constant temperatures, except at 15oC with 8%. The effect of thermoperiods showed an increase of germination with the amplitude of the fluctuation of temperatures, from 54% to 82%. Cold stratification did not show significant effect on the final germination, but it, resulted in a significantly faster germination rate between the control and cold-treated seeds. The effects of GA3 (91%) and leaching (93%) on germination significantly increased the germination in relation to the control (78%). Seeds of H. bonariensis can reach higher germination under alternating temperatures suggesting an adaptative value for better timing and position in the soil by the seeds. Hormone inhibition may regulate this process.
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