Germination of seeds of huisache (Acacia schaffneri) and catclaw (Mimosa monancistra) as affected by sulphuric acid and mechanical scarification and subsequent growth and survival in a greenhouse and field experiment

Soils in the central highlands of MBxico are heavily eroded reducing soil productivity and deteriorating natural resources. A reforestation program to prevent erosion and restore soil fertility will require large quantities of plantlets so seeds of huisache (Acacia schafieri) and catclaw (Mimosa monancisrra) were scarified mechanically or by submerging in sulphuric acid or water and their germination was monitored for 20 days. Seedlings were inoculated with or without mycorrhizal fungi and their survival and growth were determined in the greenhouse for 120 days and subsequently in the field for 9 months. Seeds of huisache and catclaw mechanically scarified and soaked in water for 24 h or in an extract of Bacillus subrilis gave a > 99% germination compared to 5% and 17% in untreated ones, respectively. Seeds of catclaw submerged in hot water did not show different germination from the untreated ones, while those submerged in 98% H2S04 for 15, 20 or 30 min resulted in > 92% germination. Seeds of huisache submerged in 98% H,S04 for 30 min gave 71% germination. Increasing or reducing the time of submerging or decreasing the concentration of H2S0, reduced the percentage of germination of both seeds. The growth of catclaw seedlings in the greenhouse was significantly faster after scarification with 98% H2S04 compared to the other treatments and after mechanical scarification for huisache. The survival of plantlets in the field derived from seds scarified with concentrated H2S04 were not significantly different after six and nine months for both huisache (69%) and catclaw (68%) and not significantly affected by inoculation with mycorrhizal fungi. We found that although mechanical scarification of huisache and catclaw seeds gave the largest percentage of germination, submerging them for 40 and 15 min, respectively, in concentrated H2S04 might be the best technique as the treatment time is much shorter and less tedious. The propagation of huisache and catclaw in the greenhouse resulted in a high survival rate in the field, but inoculation with mycorrhizal fungi had no significant effect.