The aim of the study was to determine the effect of seed production environment in Sri Lanka on seed development, maturation, and subsequent seed quality. The experiment was conducted at six production environments, three locations (Mahailluppalama (M1), Polonnaruwa (POL), and Aluttarama (ALU), over two planting cycles (P1, P2). Seed development and maturation, seed and seedling quality characteristics were evaluated at five reproductive (R6, R7, R8, R8 + 5 and R8 + 10) maturity stages. The study infers that production environment at the late reproductive (LR) stage (R6–R8) was critical in determining the seed quality. If the LR stage coincided with cumulative rainfall (RF) over 100 mm or above 75% relative humidity (RH), categorized as wet environment, around 27.5 days was required for the completion of seed maturation compared with only 17.5 days in dry environment. Seed lots from dry environment during LR stage surpassed the minimum quality standards (75% final germination, germination index of 300, germination rate index of 25% per day, seedling vigor index of 2500 and 15 µmol/min/mg FW catalase activity) at maturity stage R7 onwards, while this only occurred at maturity stage R8 for wet environment. A significant negative correlation (r = −0.50 **) was observed between glucose content, antioxidant enzyme activities and germination percentage. In conclusion, the findings provide useful information for the expansion of areas for seed production in Sri Lanka.

Soybean seed vigour declines with increase in storage duration, due to ageing, which can be alleviated through seed priming. The objective of this study was to investigate the effects of Humic acid (HA) priming on germination, vigour and seedling performance under laboratory and greenhouse conditions with two soil moisture level [50% and 80% field capacity (FC)]. Seeds stored for 12 months having 60% germination were primed either with 0.2 g/L HA solution or distilled water (hydro-primed) at 25 °C for 1, 3, 5 and 7 h. Non-primed dry seeds were used as control, giving nine treatment combinations. Various germination traits [mean germination time (MGT), final germination percentage (FG%), germination rate index (GRI), seedling emergence percentage (SEP)], mean emergence time (MET), seedling quality traits [seedling vigor index (SVI), shoot length, root length, root volume], antioxidant enzyme activities [catalase (CAT), peroxidase (POD)], lipid peroxidation [malondialdehyde (MDA)] and electrical conductivity (EC) were determined. A germination test in the laboratory was conducted as single factor (nine priming treatments), while the greenhouse experiment was conducted as two factors [2 soil moisture level (50 and 80% FC) and 9 priming treatments]. The results indicated that seeds primed with HA for 5 h was able to reinstate the CAT activities (25%), POD activities (50%) and reduced EC (51%) and MDA content (40%) compared with non-primed seeds, reduced the MET (from 4.3 to 3.5 days), increased FG% (from 62 to 71%), GRI (15.6–21.1) and SEP (from 35 to 54%) and (from 60 to 72%) at 50% FC level and 80% FC level, respectively. A strong negative correlation (r = −0.80 **) was found between MDA content and GRI, while CAT and POD activities had positive correlation with GRI r= 0.67 ** and r = 0.56 **, respectively. Thus, priming with 0.2 g/L HA for 5 h improved the vigour of minimally deteriorated soybean seeds resulting in increased emergence with more uniform field establishment.

Parthenium weed is an invasive weed species of economic importance worldwide. Native to the American tropics, the infestation ability of Parthenium weed to a new habitat is largely influenced by environmental factors. Despite Parthenium weed invasion in Malaysia dated back to 2013, investigation on its ecological behavior is still lacking. Hence, extensive studies on the ecological behavior of two predominant Malaysian Parthenium weed populations were executed. In the Petri dish seed bioassay, germination of Parthenium weed seeds was evident at temperatures up to 80 °C. Parthenium weed was also germinable in saline condition of up to 250 mM, osmotic pressure ranging from −1.2 to 0 MPa, and a wide range of pH (4–9), thus these abiotic conditions are by no means the limiting factors for the Parthenium weed. The pot trial observed that this invasive weed grew readily in various Malaysian soil textures. Parthenium weed successfully emerged from 0 cm to not beyond 2 cm soil burial and retained its emergence capacity under different submergence periods in water. The most favorable soil moisture condition for Parthenium weed emergence was saturated (0 kPa), followed by field capacity (−30–−50 kPa), while no emergence occurred in drought (−70 kPa) as well as flooded soils. These indicate that both Parthenium weed populations possess high tolerance to various abiotic conditions in Malaysia. Results obtained in the current study have crucially become guidelines for the local government authorities in predicting wide spread of Parthenium weed in diverse ecological zones, to further manage this pernicious weed efficiently.

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