GERMINATION BEHAVIOR OF 3 POPULATIONS OF PERIPLOCA-LAEVIGATA-AIT IN PRE-SAHARAN TUNISIA

Germination behaviour of the seeds of three populations of Periploca l aevigata Ait. has been studied at various temperatures and water poten tials. The use of certain indices to qualify germination has shown a r elationship between the biotopes of the populations and the germinatio n behaviour of the seeds. At the optimal temperature of germination (2 5-degrees-C), the germination capacity is high (73-93%). The minimal g ermination temperature is relatively high (8-degrees-C) and could limi t the extension of this species by direct sowing in arid mediterranean areas. P. laevigata seeds tolerate water stress up to a water potenti al of about-9 bars.