A.K. Fazlul Hoque*
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Imam Hossain
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Sharif Hasan Limon
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Md. Khairuzzaman
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Aegiceras corniculatum, Salt tolerance, Mangrove, Germination, Seedling growth
Sundarbans Reserved Forest
Risk Management in Agriculture
The experiment was carried out in hydroponic culture as it permits efficient control of the salinity of the growth medium and nutrient supply to experimental plants. Mature propagules of A. corniculatum were collected from the plants in the Sundarbans Reserved Forest in September 2004. Experiments were carried out using CRD. Germination of propagules was studied using 10 salinity levels (0 to 45 ppt at 5 ppt intervals) with 3 replications, each replication containing 30 propagules. Seedling growth in constant salinity was carried out in four salinity levels (0 to 15 ppt at 5 ppt intervals) and that in gradually increasing salinity was conducted in seven salinity levels (0 to 36 ppt at 6 ppt intervals). Each treatment was applied with seven replications, one seedling representing a replication. Details of the germination and seedling growth experiment are presented below.
Effect of salt on the propagule germination: A 100 ppt stock solution of common salt (NaCl) was prepared. Using this stock, working solution of 0 to 45 ppt salinities at 5 ppt interval were prepared. Salinity of the working solution was checked with a hand held temperature compensated salinity refractometer. One third of a plastic bowl (diameter 30 cm and depth 14 cm) was filled with sand. Salt solution was poured into the bowl until a thin layer of water on the sand surface was visible. Following this process for 10 salinity levels (0 – 45 ppt at 5 ppt intervals), each with 3 replications, a total of 30 plastic bowls were prepared. In each bowl 30 propagules were sown in September 2004. The water level in bowls was checked and corrected once daily by adding tap water. Initiation of root was considered as the indicator of germination. The germination of the propagule was recorded at 2 days interval until there was no fresh germination.
Effect of salt on the seedling growth: Containers for seedling growth study was prepared as in Fig-1. Nutrient solution was a modified Hoagland’s solution, MnSO4.H2O and (NH4)6Mo7.4H2O being used instead of MnCl2.4H2O and H2MoO4. H2O. Such modifications are widely accepted (Jones, 1997). Growing seedlings in nutrient solution with salinity corresponding to that of germination media: This study had to be kept limited to 4 salinity treatments viz., 0, 5, 10 and 15 ppt as germination in salinities ≥20 ppt was poor or absent. For a known volume of nutrient solution with a particular salinity, required volume of nutrient solutions was determined. Stock solutions of nutrients and salt were taken in a graduated container and tap water was added to make desired volume nutrient solutions with 0, 5, 10 and 15 ppt salinities. For each salinity level, 700 ml of nutrient solution was poured into each of the seven containers. Level of solution was marked on the bottle. Seven healthy seedlings from each salinity treatment (0, 5, 10 and 15 ppt) for germination were uprooted carefully, washed in running tap water, blotted dry and weighed for initial biomass with a digital top loading balance. Each seedling, representing a replication, was transplanted in a container having nutrient solution with salinity corresponding to that of germination substrate. To maintain uniform salinity, level of solution was checked and corrected by adding tap water once daily. Nutrient solution was flashed out and renewed weekly. This study was carried out over a period of six months from November 2004 to May 2005.
Growing seedlings in gradually increasing saline conditions: Firstly, nutrient solution without salt was prepared. From this, 700 ml solution was poured into each of 63 containers. Biomass of 63 healthy seedlings (germinated in fresh water condition) was measured as described above. Each of these seedlings was transplanted in a container. Salinity of the solution was increased by 2ppt on every third day to produce nutrient solution with 0-36 at 6 ppt intervals. To do this required volume of stock solution for increasing salinity of 700 ml nutrient solution by 2 ppt was determined. On the third day after transplanting seedlings, this volume of stock salt solution was added in 56 containers. In the other seven containers seedlings were grown without salt. The procedure was repeated on the every third-day. Thus, after nine days 56 containers had nutrient solution with 6 ppt salinity. In the following third-day stock salt solution was added in 49 containers to increase the salinity. By this procedure over a period 54 days nutrient solutions with salinities 0 to 36 ppt at 6 ppt intervals were produced. In each salinity level there were seven seedlings growing- each representing a replication. Throughout the study period, salinity was maintained by daily checking and replenishing water loss by adding tap water. Nutrient solution was flashed out and renewed weekly. This experiment was carried out over a period of five months from December 2004 to May 2005.
At the end of the experiment seedlings were uprooted and green biomass was measured using a top loading digital balance. Seedling growth during the experimental period was calculated by subtracting initial biomass from the final biomass and was converted into percentage of the initial biomass for further analysis.
Khulna University Studies, Special Issue (1st Research Cell Conference): 135-140, 2006
Journal