Changes in germination and glyoxylate and respiratory enzymes of Pinus pinea seeds under various abiotic stresses

This study examined Pinus pinea seeds for their tolerance to osmotic potentials of - 0.30 MPa (10% polyethylene glycol [PEG]), - 0.58 MPa (18% PEG), -0.80 MPa (21% PEG), -1.05 MPa (24% PEG), pH values of 4, 5, 6, 7, 8, 9, 10, and different calcareous solutions (5, 10, 20 and 40% CaCO3). The main enzymes of glyoxylate cycle and respiratory pathway were tested. Pinus pinea seeds under no stressful condition (Control) and 5% CaCO3 reached 100% of germination. Higher concentrations of CaCO3 (20, 40%) and lower pH (4-5) adversely affected seed germination percentage, glyoxylic and respiratory enzyme activities. PEG caused the most detrimental effects on Pinus seeds; increasing the osmotic potential the germination was completely inhibited. These results suggest that Pinus pinea is able to germinate in calcareous and alkaline soils rather than in soils with lower water availability and acidic conditions.