EFFECT OF PRE-SOWING TREATMENTS ON SEED GERMINATION AND SEEDLING GROWTH OF CALLIANDRA HAEMATOCEPHALA HASSK. SHRUB

The present investigation was conducted at the nursery of Hort. Res. Inst., ARC, Giza, Egypt during 2013 and 2014 seasons to study the effect of different pre-sowing seed treatments, viz., untreated seeds (control), soaking in tap water for 24 h at room temperature, soaking in previously boiling water for 24 h at room temperature, boil/cold water dipping (thermal shock treatment), soaking in concentrated H2SO4 for either 2 or 4 min (chemical scarification) and abration testa with rough emery paper (mechanical scarification) on seed germination and seedling growth of Powder Puff (Calliandra haematocephala Hassk.) shrub. The obtained results indicated that most of the used treatments improved germination % and velocity, mean germination rate, germination rate and vigour indices, seed viability and epicotyl length of germinated seeds, as well as seedling growth with various significant differences compared to control in the two seasons, except for thermal shock treatment which completely failed to induce germination. It was also noticed that seed viability markedly decreased as a result of mechanical scarification with emery paper to reach the least values at all. Content of total indoles and phenols in the untreated seeds was stable as they were not subjected to any treatment, but in treated seeds, it was increased where total indoles reached the maximum by soaking in either concentrated H2SO4 or boiling water, while these two treatments caused a nil increment in seed content of total phenols relative to control and other pre-sowing treatments. In addition, content of chlorophyll a, b, carotenoids and total soluble sugars in the leaves of seedlings raised from the treated seeds was greatly increased, especially by chemical and thermal scarification. Generally, the mastery in all previous measurements was for soaking in either concentrated H2SO4 for only 2 min or boiling water for 24 h, as they recorded the utmost high means in the majority of measured traits in both seasons. Hence, it is recommended to treat seeds of Calliandra haematocephala pre-sowing by soaking in either previously boiling water for 24 h. or in concentrated H2SO4 for only 2 min. to obtain the best germination and seedling growth.