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Background and aims: Soil acidification impedes crop growth. Seed pelletization was used to improve crop resistance to various stress environments but not acidic soil. This study aimed to develop rapeseed seed pelletization and to assess the promotional effects of pelletization on rapeseed growth under acidic conditions. Methods: Two main acid-resistant functional agents (Ca(OH)2, and biochar) and a basic formula including sodium carboxymethyl cellulose, H3BO3, nano-silica, brassinolide, sodium naphthalene acetate, indoleacetic acid, and yeast metabolite were used to evaluate the effects on rapeseed growth by seed pelletization. Then, the mechanism of alleviating acidic stress by seed pelletization was investigated. Results: A basic formula were developed by soil test. Three acid-resistant seed pelletization cases (① 0.5% Ca(OH)2 + a basic formula; ② 10% biochar + a basic formula; ③ 0.25% Ca(OH)2 + 5% biochar + a basic formula) were confirmed to have significant plant growth promotion. Compared to the unpelletized treatment, seed pelletization significantly increased root length and dry weight of rapeseed seedling by 67.32%-78.34% and 46.47%-74.12%, respectively. It also increased nutrient uptake and reduced the accumulation of toxic Al by 11.72%-16.23% in rapeseed roots. Moreover, seed pelletization modulated the local soil environment at the sowing site, increased soil pH by 0.88–1.11 in the microzone, thereby reducing the adverse effects of acidic stress. Conclusion: Seed pelletization in rapeseed can enhance its tolerance to acidic stress and promote plant growth. Additionally, our results provide new insights into the strategies to alleviate the inhibitory effects of acidic soil. [ABSTRACT FROM AUTHOR]

Salinity is one of the major constraints in oilseed rape ( Brassica napus L.) production. One of the means to overcome this constraint is the use of plant growth regulators to induce plant tolerance. To study the plant response to salinity in combination with a growth regulator, 5-aminolevulinic acid (ALA), oilseed rape plants were grown hydroponically in greenhouse conditions under three levels of salinity (0, 100, and 200 mM NaCl) and foliar application of ALA (30 mg/l). Salinity depressed the growth of shoots and roots, and decreased leaf water potential and chlorophyll concentration. Addition of ALA partially improved the growth of shoots and roots, and increased the leaf chlorophyll concentrations of stressed plants. Foliar application of ALA also maintained leaf water potential of plants growing in 100 mM salinity at the same level as that of the control plants, and there was also an improvement in the water relations of ALA-treated plants growing in 200 mM. Net photosynthetic rate and gas exchange parameters were also reduced significantly with increasing salinity; these effects were partially reversed upon foliar application with ALA. Sodium accumulation increased with increasing NaCl concentration which induced a complex response in the macro-and micronutrients uptake and accumulation in both roots and leaves. Generally, analyses of macro- (N, P, K, S, Ca, and Mg) and micronutrients (Mn, Zn, Fe, and Cu) showed no increased accumulation of these ions in the leaves and roots (on dry weight basis) under increasing salinity except for zinc (Zn). Foliar application of ALA enhanced the concentrations of all nutrients other than Mn and Cu. These results suggest that under short-term salinity-induced stress (10 days), exogenous application of ALA helped the plants improve growth, photosynthetic gas exchange capacity, water potential, chlorophyll content, and mineral nutrition by manipulating the uptake of Na+. [ABSTRACT FROM AUTHOR]