Experimental assessment of salinity tolerance of Ceriops tagal seedlings and saplings from the Indus delta, Pakistan

Propagules of Ceriops tagal (C. tagal) collected from the Indus delta were grown in pots containing sandy soil sub-irrigated with 0, 25, 50, 75 and 10 0% seawater fortified with nitrogen. Seedlings were experimentally grown fo r 6 months and saplings for 12 months. Maximum growth was observed in 50% s eawater and declined with increasing salinity. Water relations data showed that this species progressively adjusted its internal water potential in re sponse to change in external water potential, i.e. responded as an osmoconf ormer. C. tagal is also a non-secretor and accumulated a larger quantity of sodium and chloride ions while availability of other ions were severely re stricted. Our result suggests that C, tagal is almost as salt tolerant as A vicennia marina but would not be able to tolerate a sudden major shift in s alinity. This species could, thus, probably be used to rehabilitate inter-t idal areas, which receive a regular supply of fresh water. (C) 2001 Elsevie r Science B.V. All rights reserved.