The experiment was conducted in the research field of the Department of Agroforestry and Environment, Hajee Mohammad Danesh Science and Technology University (HSTU), Bangladesh. The geographical location field is between 25º 13' latitude and 88º 23' longitude and about 37.5 m above the sea level. The field experimental plot was situated in a medium high land belonging to the Old Himalayan Piedmont Plain Area (AEZ 01). Land was well-drained as drainage system was well developed. The soil texture was sandy loam in nature. The soil pH was 5.1. The climate of the study area was characterized by scanty rainfall during Rabi season (7th October to 15th March). The seeds of test crops were collected from the Bangladesh Agricultural Development Corporation (BADC), Dinajpur. The bark and stem were collected from E. camaldulensis trees of nearby area of HSTU. The collected bark and stem of E. camaldulensis was chipped and air- dried at room temperature. The air-dried materials were soaked in distilled water for five days and were kept into bottles. The bottles were then brought into laboratory for further use. For laboratory experiment, the treatments were consisted of four factors-(i) Test crops: 3 (country bean, bottle gourd, maize), (ii) Exudates: 2 (bark, stem), (iii) Bark exudates concentration: 3 (10%, 25% and 50%) and (iv) Stem exudates concentration: 3 (10%, 25% and 50%). Three different concentrations of bark and stem exudates (50%, 25%, 10%) were prepared. To prepare 50% concentration 50g air-dried material were soaked in 100ml water. Like 50% concentration, to prepare 25% concentration 25g air-dried material were soaked in 100ml water and 10g air-dried material were soaked in 100ml water to prepare 10% concentration. Finally, treatments were replicated 3 times in completely randomized design in the laboratory experiment. Distilled water was used for control treatment. For field experiment, to prepare 50% concentration 50g air-dried materials were soaked in 100ml water. Finally, treatments were replicated 3 times in randomized complete block design in the field experiment. So, the treatment combinations of field experiment were: T1= bark (50% concentration), T2= stem (50% concentration) and T3= control (only water).
Bioassays: In laboratory, the seeds were rinsed in distilled water repeatedly after surface-sterilization with 0.5% mercuric chloride solution. Ten seeds were placed in each sterile petridis (9cm dia) lined with two Whatman No.3 filter papers and 4 ml of test extract was added to each petridis according to treatment. The germination experiment was conducted in laboratory with room temperature.
Seeds were considered germinated when root lengths were 1-2 mm and recorded every 24-hour till seven days. The seedlings of maize, country bean and bottle gourd were removed from the Petridis after 7 days and the length of primary roots and shoots were measured. The effects of extracts on test crops were expressed in percentage (%) of control and were calculated according to T/C, where T is the “treatment” data and C is the “control” data (Zhang and Fu 2010). The effect is stimulatory when the result is greater than 100% and the effect is inhibitory when the result is less than 100%. Germination data were collected on the germination percentage, germination speed, shoot number and days of germination initiation. Germination speed was calculated as under (Chiapusio et al. 1997): S= (N1*1) + (N2–N1)*1/2 + (N3- N2)*1/3 + … + (Nn- Nn-1) *1/n.
Where, N1, N2, N3, …, Nn-1, Nn refers to the proportion of germinated seeds on the first, second, third days, …, n-1, n days.
In field, the seeds of test crops were sown into field to see their root-shoot growth parameters and fine root architecture (length, diameter and number) in field condition. The collected seeds were sown in the field by mixing the bark and stem exudates in soil separately.
All statistics were calculated with Statistix 10 Software and the data were analyzed statistically following ANOVA technique and means separation were adjusted by Tukey’s Range Test and MS Excel 2007. Statistical difference was determined at p<0.05 level of significance.