Silicon (Si) application has great potential to improve salt tolerance in a variety of crop plants. However, it is unclear how Si influences the responses of contrasting rice cultivars when exposed to excessive salt. Here, we investigated the functions of Si in alleviating the negative effects of salt stress on two contrasting rice cultivars, namely BRRI dhan48 (salt-sensitive) and Binadhan-10 (salt-tolerant). Rice seedlings was pre-treated with three doses of Si (as silicic acid; 0, 1 and 2 mM) for 14 days at one-day interval before being exposed to salt stress (10 dSm⁻¹) in a sustained water bath system. The results demonstrated that the seedlings of BRRI dhan48 and Binadhan-10, respectively exhibited substantial reductions in shoot height (16 and 9%), shoot fresh weight (64 and 43%) and shoot dry weight (50 and 39%) under salinity. Intriguingly, BRRI dhan48 pre-treated with 1 and 2 mM Si, respectively, showed a higher increase in shoot height (SH) (by 25.90 and 26.08%) as compared with Binadhan-10 (by 3 and 8%) under salt stress compared with their respective controls. Data revealed that a comparatively higher improvement in the growth performances of the salt-induced Si pre-treated BRRI dhan48 than that of Binadhan-10. For example, 1 and 2 mM of Si treatments significantly attributed to elevated leaf relative water content (RWC) (13 and 22%), proline (138 and 165%), chlorophyll a (42 and 44%), chlorophyll b (91 and 72%), total chlorophyll (58 and 53%) and carotenoids (33 and 29%), and recovery in the reductions of electrolyte leakage (13 and 21%), malondialdehyde content (23 and 30%) and shoot Na⁺/K⁺ ratio (22 and 52%) in BRRI dhan48 compared with Si-untreated control plants under salt stress. In addition, we found salt-tolerant Binadhan-10 also had enhanced RWC (9 and 19%), proline (12 and 26%) with pre-treatment with 1 and 2 mM of Si, respectively, under salt stress, while no significant differences were noticed in the case of photosynthetic pigments and Na⁺/K⁺ ratio. Our results showed that Si supplementation potentiated higher salt-tolerance ability in the salt-sensitive BRRI dhan48 as compared with salt-tolerant Binadhan-10. Thus, Si application could be highly beneficial in the growth recovery of the salinity-affected salt-sensitive high yielding rice cultivars in the saline-prone areas.

Water pollution is a significant problem stemming from several causes, with the contamination of heavy metal(oid)s being a primary concern. This is especially concerning because of the poisonous characteristics of these metal(oid)s and their effects on the aquatic ecosystem. This research is distinguished by its unique methodology for assessing metal(oid)s in the surface water of Bangladeshi rivers over a period of sixteen years, from 2007 to 2022. This work seeks to elucidate recent results on metal(oid) concentrations, contamination levels, multivariate statistical analyses, source identification using positive matrix factorization models, and probabilistic health risks. The findings reveal that the concentrations of chromium, nickel, arsenic, cadmium, and lead exceeded the acceptable limits for drinking water established by the World Health Organization (WHO) by factors of 4.64, 2.25, 22.51, 45.60, and 10.13, respectively. Our meta-analysis, subsequent to a Principal Component Analysis, indicated that increased concentrations of hazardous metals account for 85.47% of the variation from both anthropogenic and natural causes. Ecological risk indicators, including the metal index (84.06) and the Nemerow pollution index (10.55), indicated significant metal contamination. Ecological risk indicators, like the metal index (84.06) and the Nemerow pollution index (10.55), indicate substantial metal contamination. The positive matrix factorization (PMF) model detected the following sources of metals in water: industrial (22%), mixed (32%), agricultural activities (27%), and natural sources (19%). Furthermore, Monte Carlo-simulation-based assessments of health hazards indicated that the mean hazard index (HI) and cancer risk values for adults (301.89 and 422.76) and children (51.56 and 39.45) significantly exceeded the recommended limits, suggesting that both adults and children are vulnerable to potential non-carcinogenic and carcinogenic health risks. The immediate execution of control measures and regulations is essential to avert escalating pollution in surface water, protect ecosystems, and mitigate health hazards.

The transplanting of over-aged seedlings is an important adaptive strategy for rice cultivation during the monsoon season in the coastal areas of Bangladesh. This study aimed to identify promising hybrid rice varieties that can be transplanted as over-aged seedlings in the south-central tidal coastal ecosystem of Bangladesh. Three elite hybrid varieties, namely, AZ7006, Dhani Gold, and INH-16019, along with a popular local cultivar, Moulata (as the control), were used in this field study, and seedlings at two different ages (e.g., 50- and 60-day-old) were transplanted. The results showed that Dhani Gold had the highest grain yield (5.47 t/ha) with the maximum number of tillers (17) and effective tillers (15) per hill for the 50-day-old seedlings as compared with the 60-day-old seedlings. In addition, the hybrid variety INH-16019 also yielded 5.20 t/ha grain with the highest number of spikelets/panicle (191), filled grains/panicle (174), and unfilled grains/panicle (17) for 50-day-old seedlings. However, the local cultivar, Moulata, had the highest plant height (149 cm), required the maximum time for 50% flowering (75 days after transplanting, DAT) and harvesting (104 DAT), and also produced the lowest number of spikelets/panicle (114) and filled grains/panicle (108), leading to the lowest grain yield (3.57 t/ha) considering both ages of the seedlings. Our data further revealed the significant influence of seedling age (50- and 60-day-old seedlings) on the straw yield. Interestingly, this study revealed that the hybrid variety Dhani Gold showed a remarkable decrease in straw yield (by 36%) but obtained the highest (56.3%) harvest index when transplanted as very over-aged (e.g., 60-day-old) seedlings. Moreover, we recorded a higher grain nitrogen content in the hybrid varieties than in the local cultivar, Moulata. Among the hybrids, AZ7006 showed the highest nitrogen content (1.72%), which was statistically similar to INH-16019 (1.67%) and Dhani Gold (1.57%) for 50-day-old seedlings. Importantly, the grain yield of Dhani Gold was 50% higher than Moulata for 50-day-old seedlings, and the benefit–cost ratio of Dhani Gold was also the highest (1.34) for the same seedling age. Hence, the over-aged Dhani Gold hybrid rice seedlings would be a good choice for increasing Aman rice productivity during the monsoon season in the south-central coastal ecosystem of Bangladesh.