Effets du substrat et du traitement avant semis sur la germination des semences du Fagara (Zanthoxylum zanthoxyloides (Lam.) Watermann)

Abstract

Zanthoxylum zanthoxyloides (Lam.) Watermann seeds excised from ripe and fresh fruits were evaluated for their germination capacity under different pre-sowing and substrates conditions. Initial moisture content (iMC) of seed lots was assessed using 4x10 seeds while initial germination was evaluated on three different substrates: agar 1% concentration, river sand and a composite substrate of soil, sand and manure, using 4x25 seeds per assay. In a second experiment, seeds were subjected to three pre-treatments prior to sowing. Seeds iMC varied between 7 and 8% suggesting that they are likely orthodox. Seed started to germinate between 24 and 45 days after sowing. This minimum incubation period is rather long if one considers that the usual duration for tree seeds germination testing is 28 days. An improvement of germination was observed when combining the best substrate with the best pre-sowing treatments. Highest percentage, recorded on the composite substrate, rose from 42±0.71% when seeds were sown intact, to 59±0.70% when rubbed with sand and to 61±1.41% when washed with soap prior to sowing. We concluded that Z. zanthoxyloides seeds exhibit dormancy due to impermeable and/or oily seed coat. For seedlings production, seeds should be previously washed with soap or polished with sand and sown on a mixture of soil, sand and manure in a ratio of 3v/1v/1v.