Effects of nitrogen, light and wet and dry heat treatments, on the germination of six perennial plant species from western Spain

摘要

Imbibed seed of six common species from the Central West of Spain were placed in Petri dishes in moist soils and heated in ovens set to 30°C, 50°C and 100°C for 0.5, 1, 4, 8 and 16 days. After heating, seeds were incubated for 35 days on a 10/14 dark/light regime and germination was recorded. The same duration of heating treatment was applied to non-imbibed seeds. The effect of nitrogen on germination was also investigated by applying NaNO_2, NH_4NO_3, KNO_3 and NH_4Cl at five increasing concentrations (1, 10, 50 and 100mM). Temperatures of 30°C were the most successful for germination of pre-imbibed seeds. Dittrichia viscosa, Cistus albidus and C. ladanifer increased germination under the wet treatment. Germination was higher after treatment at30°C and 50°C that at 100°C for non-imbibed except for Cynara humilis and Cistus albidus. The maximum temperature required to prevent germination varied among species and was variable with duration of heating. Fertilisation with KNO_3 and NH_4Cl at 25mM and NH_4NO, at 10mM and 100mM increased both level and rate of germination in most species. Continuous darkness inhibited germination in all the species. The increase in temperature activates the germination of non-imbibed seeds and also the increaseof nitrogenous compounds in the field trigger the germination of nutrient-requiring species.