The effect of matric and osmotic potential stresses on seed germination of siris (Albizia lebbeck)‎ tree

الملخص EN

Two separate laboratory experiments were conducted to study germination of Siris tree seeds exposed to matric (Ψm) and osmotic (Ψo) potential stresses.

The first experiment comprised 5, 10, 15, 20, and 25 kPa Ψm at 20ºC soil temperature and zero Ψo and the second experiment comprised 0.0, 76.12, 152.3, 304.5, and 609.0 kPa Ψo at 20ºC soil temperature and 12.2 kPa Ψm.

Distilled water was added to sandy soil achieving the desired Ψm levels in the first experiment.

Sodium chloride solution was added to the sandy soil to achieve the desired Ψo levels in the second experiment.

Ten seeds of Siris were sown in each plastic container (0.15 m I.D.

and 0.20 m height).

The seeds were fresh (six months old) and had no pretreatment.

The plastic containers were covered using clear polyethylene bag for maintaining the level of matric potential during germination.

Parameters recorded were, namely, number of germinated seeds, germination percentages, germination rate, and lengths of both radicle and shoot of the emerged seedlings.

The results revealed that significantly great germination percentage and germination rate were associated with the level of 10 kPa Ψm than the other levels used, and tended to decrease drastically as the level of Ψm decreased/increased around this level.

For optimum germination, the calculated Ψm was found to be 12.2 kPa.

The length of both radicle and shoot decreased linearly as Ψm level decreased.

Likewise, both the germination percentage and germination rate decreased linearly as osmotic potential, Ψo, decreased.

The threshold osmotic potential for germination was calculated to be 1154.8 kPa Ψo, below which germination was inhibited.

Lowering the osmotic potential level resulted in delay of seed germination.