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Difference in germination rate of Baobab (Adansonia digitata L.) provenances contrasting in their seed morphometrics when pretreated with concentrated sulfuric acid

Marème Niang 1,2 *, Macoumba Diouf 1 , Samba Arona Ndiaye Samba 3 , Ousmane Ndoye 4 ,
Ndiaga Cissé 1 and Patrick Van Damme 2, 5, 6
Received 9 December, 2014 ; Accepted 11 March, 2015

Baobab (Adansonia digitata L.) is considered an under-utilized species even though it is an economically
useful tree often used daily in the diet of rural communities in West Africa. Baobab seeds do not germinate
immediately after they are released from ripe fruits due to dormancy imposed by hard seed coats. A study was
carried out to assess (1) best soaking duration for seed pretreatment in concentrated sulfuric acid (96%) to
increase germination rate of baobab seeds ; and (2) relationships between seed morphometric traits as varying
with provenances and germination rate. Length, width, thickness and weight of baobab seeds collected from
seven provenances spread across an agro-climatic gradient of 250 to 1100 mm in Senegal were first
measured. Then, seeds were pretreated by soaking them in distilled water (control) and concentrated H 2 SO 4
(96%) for 12 min, 30 min, 1, 3, 6, 8 and 12 h, respectively. Pretreated seeds were placed on moistened filter
paper in 16 cm diameter Petri dishes in an incubator at 25°C for germination. Highest germination rates were
obtained for seeds that had been soaked for 6, 8, and 12 h in concentrated sulfuric acid as evidenced by
germination rates at 3, 7 and 10 days after sowing, respectively, although we did not find any significant
differences among these three soaking durations. Significant variation among provenances was observed in
seed morphology traits and seed germination rates. Highest seed trait and germination rate values were
observed for Sudano-Sahel and Sudan agro-ecological provenances. This study has shown a significant
variation in these characters mainly related to geographical origin. Overall, results could be useful for a
further domestication and integration of baobab in the agro-productive system in Senegal as knowledge on
seed germination requirements is a critical factor in seedling production for subsequent planting and
reforestation.

Key words : Agro-ecology, baobab seed, dormancy, germination physiology, germination rate, non-timber forest
product (NTFP), under-utilized species.


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