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Chromium (Cr) is a serious environmental contaminant that drastically limited the crop yields. Nitric oxide (NO) and spermine (Spm) portrayal significance in improving the plant tolerance against abiotic stresses. Therefore, we investigate the protective efficacy of seed priming with NO (100 μM) and/or Spm (0.01 mM) in minimising the Cr-induced toxic effects in rice (Oryza sativa L.) plants. Our outcomes revealed that Cr alone treatments (100 μM) notably reduced the seed germination rate, plant growth, photosynthetic apparatus, nutrients uptake and antioxidant defence system, but extra generation of reactive oxygen species (ROS). Interestingly, the combine applications of NO and Spm significantly reversed the Cr-induced toxic effects by reducing the Cr-accumulation, maintaining the nutrient balance, improving the germination indices, levels of photosynthetic pigments (chl a by 24.6%, chl b by 36.3%, chl (a + b) by 57.2% and carotenoids by 79.4%), PSII, photosynthesis gas exchange parameters and total soluble sugar (74.9%) by improving antioxidative enzyme activities. As a result, NO + Spm lowered the accumulation of oxidative markers (H2O2 by 93.9/70.4%, O2˙− by 86.3/69.9% and MDA by 97.2/73.7% in leaves/roots), electrolyte leakage (71.4% in leaves) and improved the plant growth traits. Based on these findings, it can be concluded that NO triggers Spm to minimise the Cr-accumulation and its adverse effects on rice plants. Additionally, combined treatments (NO + Spm) were more effective in minimising the Cr-induced toxic effects in comparison to NO and Spm alone treatments. Thus, co-exposure of NO and Spm may be utilised to boost rice tolerance under Cr stress conditions. Chromium (Cr) is a major constraint effecting the growth, yield and quality of rice (Oryza sativa L.). Priming with nitric oxide (NO) and Spermine (Spm) alleviates the negative effects of the Cr on the rice growth and development. Hence, the exogenous supply of NO and Spm possess great potential for the stress tolerance, and can be effectively used to prevent losses in crop plants under heavy metal stress. [ABSTRACT FROM AUTHOR]

The present study was conducted to screen different growth inhibitors i.e. ethephon (125 mM), methyl jasmonate (1 mM MeJA) and their combinations (125mM ethephon + 1mM MeJA) for minimizing the harmful effects of pre-harvest sprouting during hybrid rice seed production. The combination of both growth inhibitors significantly reduced germination and growth attributes with a more prominent decrease in cultivar Zhu Liang You 06 (ZY) as compared to cultivar Qian You No.1 (QY). Moreover, the activities of a-amylase, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and malonaldahyde (MDA) contents were significantly increased with the combination of both growth inhibitors as compared to the control. CAT activity was significantly increased with 1mM of MeJA as compared to the control. The combination of both growth inhibitors resulted in the increase of abscisic acid (ABA) contents and the decrease of gibberellins (GA) contents as compared with the control. Gene expression analysis showed that the transcription levels of ABA genes (OsNCED1, OsNCED3 and OsABA80x1) were up-regulated with the combination of both growth inhibitors. While, GA genes (OsGA3ox1, OsGA20ox1 and OsGA2oox2) were down-regulated by seed soaking with both growth inhibitors and their combination. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the role of different levels of Methyl jasmonate (MeJA) i.e. control, 1, 2.5 and 5 mM to minimize pre-harvest sprouting in rice. The results suggested that MeJA (5 mM) significantly reduced germination percentage, germination energy, germination index, shoot height, root length and seedling biomass in comparison with the control treatment. This reduction was more obvious in cultivar Zhu Liang You 06 (ZY) than in Qian You No.1 (QY). The activity of antioxidative enzymes i.e. catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and malondialdehyde (MDA) contents were significantly increased after treating with 1 mM and 2.5 mM concentrations of MeJA. However, higher concentration of MeJA (5 mM) significantly reduced the activities of antioxidant enzymes, seedling biomass and increased ROS generation. The a-amylase activity was significantly decreased with seed soaking in 5 mM of MeJA as compared to the control. Gene expression analysis suggested a significant up regulation of root Amy2A and Amy3A mRNA in comparison with the shoot, by seed soaking in MeJA. Higher concentration of MeJA (5 mM) improved resistance to pre-harvest sprouting in both rice cultivars. However, little cell damage and higher ROS accumulation were also observed. [ABSTRACT FROM AUTHOR]