Experimental Site The experiment was conducted at Field and Plant Systematics Laboratories of the Department of Crop Botany, Bangladesh Agricultural University during April to July, 2016 to find out the variability in morphology and physiological features of four Sesbania genotypes. Geographically it is located at 240 75´ N latitude and 900 50´E longitudes at the elevation of 18 m above the sea level (UNDP and FAO, 1988). The initial soil of the Field was analyzed and had the following characters: pH 5.82, organic matter 1.53%, total nitrogen 0.09%, phosphorus 3.66 ppm, potassium 0.15 meq/ 100g, Sulfur 2.51 ppm.
Laboratory Experiment and Germination Test A total of four genotypes from four Sesbania species viz. S. cannabina (Accession #28), S. bispinosa (Accession #71), S. sesban (Accession #81) and S. rostrata (Accession #105), were used as experimental materials. The observations like seed length and width, 1000-seed weight, germination percentage, vigor index, seedling length and biomass yield were recorded. The experiment was laid out in a completely randomized design with four replications. From each genotype, 50 healthy seeds were spread uniformly on each Petri-dish using filter paper as medium of growth. Cumulative germination (CG) percentage of seeds was counted daily up to 10 days.
Field Experiment, Design and Crop Establishment The experiment was laid out in randomized complete block design with three replications. Sesbania seeds were sown in four lines of 2. 5 m × 2.0 m plots with a spacing of 50 cm (row-row) × 15 cm (plant-plant) to maintain 200 plants m–2 . Data on different morphological and physiological growth parameters were recorded at every 10-day intervals up to 60 days after sowing (DAS).
Data Measurement on Plant Growth Parameters Plant morphological descriptors were collected from 60 days old plants. Morphological attributes were measured with a ruler and using digital slide callipers with a precision of 0.1 to 150 mm. The morphological descriptors viz. length of shoot, root, base diameter, number of leaves plant–1, internodes number plant–1, inter-node length, leaf length and leaf width were measured.
Data Collection on Biomass Production Ten plants from each plot were carefully uprooted and roots were cleanly washed in water. The root and shoot portions were separated. The samples were air dried and subsequently, oven dried at 720±20C for 72 hours to constant weight. Biomass accumulation study was carried out at 10 days interval from 10 DAS to 60 DAS. Following growth studies were made using the prescribed formulae: The biomass accumulation of the crop per unit area per unit of time is referred to crop growth rate (CGR), expressed as g m–2 d –1. The mean CGR values for the crop during the sampling intervals were computed using the formula of Brown (1984).
Data analysis The collected data were analyzed with Excel application to determine the arithmetic mean, standard deviation, coefficient of variance and range among the accessions.