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Rapeseed meal, a nutritious organic fertilizer (OF), contributes to improving soil environment and crop productivity. However, there are also problems, namely slow fertilizer efficiency and low nutrient utilization during the growing season. This 2‐year field trial was conducted to explore the effect of biochar addition on improving the nutrient availability of OF through a comparative study of various biochar application rates under rice‐rapeseed rotation conditions. The findings revealed that, compared to the individual application of chemical fertilizers (CF), OF alone decreased rice yield (2%/2%) and rapeseed yield (6%/10%) in 2019/2020. Compared with OF, combining biochar (15 t ha−1) with OF (OF + B15) significantly increased rice yield (17%/10%) and rapeseed yield (25%/20%) in the first/second year. Additionally, OF + B15 still increased rice yield (14%/7%) and rapeseed yield (12%/13%) for two consecutive years compared to CF. The co‐application of biochar and OF had positive impacts on soil physicochemical properties and enzymes. Compared to OF, OF + B15 elevated soil organic carbon (SOC) by 57%–81%, soil catalase 19%, invertase 14%–20%, urease 17%–19%, and phosphatase 13%–17% during rice season, and similarly increased SOC by 77%–90%, soil catalase 14%–16%, invertase 14%–20%, urease 18%–24%, and phosphatase 16%–17% in rapeseed season. Biochar addition improved soil conditions and enzymatic activities, and the available nutrient supply of OF. Also, the co‐application of biochar and rapeseed meal surpassed the effect of chemical fertilizer alone on the growth and yield of crops. Therefore, biochar coupling with organic fertilizer is an effective fertilization strategy based on resource recycling, which promotes both crop yield and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Although gibberellic acid (GA3) improves seed germination and seedling growth in stressful conditions, the mechanisms underlying GA3-priming improved drought tolerance have not been defined. To investigate the effects of GA3-priming on physiology and antioxidant enzymes, we primed rapeseed seeds with polyethylene glycol (PEG-6000)-induced stress and quantified the changes in reactive oxygen species (ROS) homeostasis, root morphology, osmotic adjustment, stomatal morphology, and cell ultrastructure analysis. Drought stress reduced the germination rate and the subsequent growth. GA3-priming improved rapeseed germination rate and seedling growth under PEG-6000-simulated drought stress. Our results indicate that the lower germination rate and the inhibition of seedling growth in non-primed seeds under drought conditions were associated with higher production of ROS. However, GA3-primed seedlings accumulated higher activities of superoxide dismutase, peroxidase, catalase, ascorbic acid, and glutathione. They thus developed a stronger antioxidant defense system for scavenging the over-accumulated ROS under drought. GA3-priming also contributed to osmotic adjustments by promoting the accumulation of proline, soluble sugars, and soluble proteins. Ultimately, GA3-priming protected the cell wall from degradation and preserved chloroplast from autophagy. These ameliorative effects of GA3-priming under drought stress were further confirmed by significantly improving the rapeseed root morphology in hydroponic experiments. We conclude that GA3-priming improves seed germination and promotes productivity by regulating physiological and biochemical responses to drought stress. [ABSTRACT FROM AUTHOR]

Low temperature seriously affects the growth of crops and poses a huge threat to food production. The application of wood vinegar can be used as a cost-effective and environmentally friendly strategy to promote crop growth and enhance stress resistance, and the physiological resistance to low-temperature stress of rapeseed still needs further research. The present study investigated the effects of spraying wood vinegar on the growth, photosynthesis, osmotic adjustment, and antioxidant enzymes of rapeseed seedlings under low-temperature stress. The results showed that spraying wood vinegar at normal temperature reduced the stomatal conductance but increased the leaf area and total biomass of rapeseed and enhanced stomatal density and water use efficiency. The leaf area and total biomass of rapeseed sprayed with wood vinegar at low temperature improved by 22% and 31%, respectively, and stomatal density and water use efficiency increased by 14% and 83%, respectively, and intercellular CO2 concentration and stomatal conductance were reduced by 9% and 41%, compared to the low-temperature, respectively. Besides, the application of wood vinegar liquid improved the proline, soluble protein, and soluble sugar content of leaves by 208%, 38%, and 115%, respectively, and the activity of superoxide dismutase increased by 27%, the content of malondialdehyde decreased by 46%, compared to the low-temperature. Spraying wood vinegar could alleviate low-temperature stress by improving the anti-oxidant enzyme content and osmoprotectants, reducing the stomatal conductance, and enhancing water use efficiency. These results provide new insights for wood vinegar to relieve the low-temperature stress of rapeseed, and this strategy can be used for low-temperature rapeseed cultivation and management, and benefit farmers' plant profit. [ABSTRACT FROM AUTHOR]

Rapeseed has formed three ecological types, namely winter, semi-winter, and spring during the long domestication process. Different ecotypes have different low-temperature requirements for floral initiation. Rapeseed growth has a large demand for nitrogen, and the amount of nitrogen application significantly impacts the number of flowering. Meanwhile, the time of floral imitation determined the quantity of floral bud, the final number of pods, and yield of rapeseed. Therefore, it is of great significance to understand the regulation of temperature and nitrogen on floral initiation. This experiment selected representative semi-winter and spring rapeseed varieties to study the leaf's soluble sugar and protein concentration under different nitrogen supplies and the transcriptome reactions to vernalization for spring and semi-winter varieties rapeseed in transition to floral initiation. The results showed that the soluble sugar content and carbon-to-nitrogen ratio changed due to the different growth processes and nitrogen application rates. The increase of the sugar content to a peak could be regarded as the signal to start floral initiation. Reducing the nitrogen application rate increased the peak of sugar content, but the effect on the appearance time of the peak was not obvious. Under normal (20–25 °C) and low temperatures (10–15 °C), the floral initiation time of spring variety "1358" showed no difference, nor did expression of hub gene SOC1, which is involved in the flowering regulation network. The semi-winter variety "Zhongshuang No. 11" did not commence floral initiation under normal temperature because of the lacking of vernalization requirement. Low temperature promoted the floral initiation of semi-winter variety mainly through the FLC, SOC1, and LFY signaling pathways, and the gibberellin also played a positive factor in this process. In essence, the present study provides valuable information on the gene expression differences of vernalization-driven floral transition for spring and semi-winter ecotypes of rapeseed when the photoperiod is not an unlimited factor. [ABSTRACT FROM AUTHOR]

The amendment of biochar has been proposed to improve soil fertility and crop yield. However, consolidated information lacks explaining the role of biochar on soil and plant enzymatic activities involved in nutrients cycling in soil and accumulation in plants improving utilization of applied inorganic fertilizer and crop growth. In the current study, we evaluated the integral effects of biochar levels (B0:0, B15:15, B3:30, and B60:60 t ha–1) and nitrogen fertilizer levels (N0:0, N75:75, N225:225, and N450:450 kg ha–1) on soil physicochemical properties, enzymatic activities, nitrogen use efficiency (NUE) and grain yield of rapeseed for 2 years in the pots during 2020 and 2021. The findings revealed that compared to control (B0 + N0), a combination of B30 + N450 increased soil urease activity by 73 and 75%, and B60 + N450 increased activities of soil catalase by 17 and 16%, and B60 + N225 increased alkaline phosphatase by 17 and 19%, respectively, in the first and second year. Moreover, a single application of high nitrogen at 450 kg ha–1 reduced the activities of plant nitrogen metabolism-related enzymes, however; the integration of biochar at 30 t ha–1 compensated the high nitrogen toxicity and improved the activities of nitrate reductase (NR), nitrite reductase NIR, glutamate synthase (GS) and glutamine synthetase (GOGAT) at seedling stage (SS) and flowering stage (FS) in both years. The integration of biochar at 30 t ha–1 with nitrogen at 450 kg ha–1 induced synergetic effects on rapeseed growth through sorption of excessive nitrogen in soil and significantly improved the plant height up to 11 and 18%, pods plant–1 39 and 32% and grain yield plant–1 54 and 64%, respectively, during the first and second year. Moreover, biochar at 15 t ha–1 along with nitrogen at 225 kg ha–1 resulted in the highest NUE of 29% in both years suggesting that biochar can also offset the deficiency of lower nitrogen. This study highlighted the ameliorative effect of biochar suppressing high nitrogen toxicity and decreasing lower nitrogen deficiency effects on rapeseed growth by improving nitrogen use efficiency via enhancing soil conditions, enzymatic activities and soil nitrogen utilization potential and thus improving rapeseed growth and yield. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential element for plant growth, and the relationship between leaf N content and photosynthesis has been widely studied in different species under steady‐state light. However, under natural conditions, the light intensity at the leaf level is always changing, inherently heterogeneous in time and space. Therefore, the effect of leaf N content on photosynthesis under dynamic light conditions needs further study. At present, the effects of leaf N content on leaf non‐steady‐state photosynthesis have not been reported in canola (Brassica napus L.). To clarify the relationship between leaf N content and the speed of the response leaf gas exchange to variations in light intensity, eight genotypes of canola varying in leaf N content were used to study the temporal response of gas exchange to a step increase in irradiance. We found there were significant differences in non‐steady‐state photosynthesis, physiological characteristics, and anatomical traits across genotypes (the maximum amplitude was about fivefold), despite the lack of contrast under normal, steady‐state photosynthesis. In addition, initial stomatal conductance to water vapor in the darkness and leaf N content per leaf area were negatively correlated with the time required to achieve 50% and 100% of the maximum photosynthetic rate. Contrarily, the time required to reach 50% of the maximum stomatal conductance was positively correlated with the time required to achieve 90% of the maximum photosynthetic rate across genotypes. It is concluded that the genotypes of canola with higher N content per leaf area show a faster induction of photosynthesis to fluctuating light conditions. [ABSTRACT FROM AUTHOR]

Low temperature is a main adverse factor affecting successful seedling establishment in the Yangtze River basin, and thus low‐temperature stress tolerance at the germination and seedling emergence stages is an important attribute for rapeseed (Brassica napus L.) production. The present study was conducted to evaluate the low‐temperature stress tolerance indices (STIs) of a large conventional rapeseed genotype population at the germination and seedling emergence stages. Twelve seed germination‐ and seedling emergence‐related indices were investigated under normal and low‐temperature conditions, and the broad‐sense heritability of these indices ranged from 25.4 to 57.6%. Therefore, the selection of genotypes with strong low temperature tolerance is a feasible way to guarantee seedling establishment. Using principal component analysis, the STIs during the seed germination and seedling emergence stages have been divided into three main categories: dry matter weight, germination speed and final germination percentage, and root length with a seedling vigor index. The top three genotypes ranked by comprehensive STI score were Huayou No. 2, SWU44, and 2012‐K8053; the bottom three genotypes ranked by comprehensive STI score were Chuanyou18, wx1025, and 97096. The results of the present study could provide valuable information for breeders to utilize the rapeseed germplasm resources in the Yangtze River basin to achieve the goal of low‐temperature resistance breeding. [ABSTRACT FROM AUTHOR]

Chitin hydrogels were successfully prepared from chitin solution dissolved in NaOH/urea aqueous solution at low temperature by crosslinking with epichlorohydrin. The experimental results indicated that the chitin hydrogels were hydrophilic, had a microporous structure, and had a large surface area, leading to excellent water uptake ability and water-retention properties. Moreover, they exhibited good mechanical properties and a high equilibrium swelling ratio. The growth indexes of rapeseed, including the germination rate, root length, shoot length, fresh weight and dry weight, for chitin hydrogel (CG2) were not significantly different from those of soil and significantly higher than agar. Chitin hydrogel as a plant growth regulator could promote seed germination and growth when applied to Brassica napus rapeseed sowing. Moreover, chitin was safe and biodegradable so it would be suitable to use as soilless culture media for plant growth. This work provided a new pathway for the application of chitin hydrogels in the agriculture field. [ABSTRACT FROM AUTHOR]

Wood vinegar is formed by the condensation of smoke produced during the production of biochar. It mainly contains acetic acid, butyric acid, catechol, and phenol. Wood vinegar has a compound effect of promoting crop growth similar to plant growth regulators and is environmentally friendly. Moreover, it can enhance the biological and abiotic resistance of crops. In this study, foliar spraying was carried out systematically in the field with the hybrid variety of Huayouza 9 for two years to study the effects of wood vinegar and its compounds on the growth of rapeseed (Brassica napus L.). We applied four treatments with tap water as a control (CK), namely wood vinegar diluted 400-fold (M), M mixed with gibberellin (T1), M mixed with sodium D-gluconate (T2), and M mixed with melatonin (T3). They were sprayed in the seedling stage and overwintering stage, respectively. The results showed that the seed yield, the leaf area index, and the number of pods per plant of rapeseed treated with M increased by an average of 9.58%, 23.45%, and 23.80% in two years as compared to the CK, respectively. Compared with M, the seed yield of rapeseed treated with T1, T2, and T3 increased by an average of 7.88%, 6.90%, and 1.32% in two years, respectively. The treatments also improved the quality of rapeseed. In particular, the glucosinolate content of rapeseed treated with T2 and T3 decreased by an average of 12.83% and 6.72% in two years compared to the CK, respectively. The four treatments selected in the current study improved the resistance of rapeseed at the low temperature of 2–6 °C by increasing the activity of superoxide dismutase and proline and soluble protein contents, as compared to the CK. Besides, all treatments containing M reduced the incidence of Sclerotinia sclerotiorum and Peronospora parasitica (downy mildew) in rapeseed. More specifically, the T3 treatment significantly decreased the infection rate of these two diseases mentioned above by an average of 17.33% and 12.14% in two years compared to the CK, respectively. Therefore, the study and application of wood vinegar due to its compound effects on crop growth and yield is of great importance to sustainable agriculture, crop ecology, and environmental protection. [ABSTRACT FROM AUTHOR]

Compensating nitrogen input and increasing nitrogen utilization efficiency (NUtE) are necessary for sustainable crop production. Research studies on the co-application of biochar and nitrogen to promote rapeseed growth, soil fertility, and improve nutrient utilization efficiency are found to be limited. This study aims to examine the integral effects of biochar and nitrogen over soil fertility, rapeseed growth and nitrogen utilization efficiency. The experiment was conducted in a completely randomized design to assess various morphological, physiological and biochemical traits of rapeseed and soil chemical properties under the application of four nitrogen levels (0, 75, 225, and 450 kg ha−1 equivalent to 0, 133, 400 and 800 mg nitrogen pot−1) and four biochar levels (0, 5, 10, and 15 MT ha−1 equivalent to 0, 10, 20 and 30 g biochar pot−1 soil by weight basis). The results of this study showed that the integral application of biochar at 30 g pot−1 and nitrogen at 800 mg pot−1 at 45 days after sowing (DAS) and 60 days after sowing (DAS) compensated the amount of nitrogen and increased soil organic carbon (SOC 69%), total nitrogen accumulation (TNA) (93% and 62%), leaf biomass (60% and 33%), stem biomass (20% and 22%) and photosynthesis (20% and 17%) at 45 DAS and 60 DAS, respectively as compared to a single application of nitrogen. However, under the conditions of no nitrogen or 75 kg ha−1 nitrogen application, the application of biochar to promote the growth of rapeseed plants is limited due to the less nitrogen supply. In contrast, the application of nitrogen at 800 mg pot−1 and biochar at 10 or 20 g pot−1 showed that the growth of early seedlings was adversely affected due to high nitrogen concentration in soil. The findings of the present study imply that within the appropriate nitrogen application range, the interaction of biochar and nitrogen might have an economical approach towards better utilization of nitrogen and sustainable crop production. [ABSTRACT FROM AUTHOR]

To understand the influence of temperature on floral initiation and to reveal the relationship between floral bud development and yield potential of rapeseed ( Brassica napus L.), early- (“1358”), intermediate- (“Zhongshuang No.11”) and late- (“Zheshuang No.8”) maturity genotypes were sown on different sowing dates under field conditions during four crop seasons. A multiplicative model was introduced to distinguish and quantify the effects of photoperiod and temperature on pre-floral initiation phase. Parameters in this model showed that early-maturity genotype was more sensitive to photoperiod; while late-maturity genotype was more sensitive to vernalization. The relationships between cumulative temperature and mean temperature of pre-floral initiation phase could be well descried by exponential equation. The developmental rate of pre-floral initiation phase against mean daily temperature displayed an asymmetrical distribution, and it decreased rapidly when the mean temperature exceeded the optimum. Leaf primordia differentiated from the shoot apical meristem showed significant linear relationship with the thermal time at pre-floral initiation phase; dynamic change of floral bud differentiated from the shoot apical meristem robustly fitted to a sigmoidal logistic curve. According to the fitted logistic equation, the maximum differentiation rate varied from 1.7 to 4.1 per 10 °Cd due to different sowing dates and genotypes. Averaged across growing seasons, sowing dates and genotypes, bud degeneration rate was 33% on the main raceme, and varied from 58% to 99% on the seven primary branches. The yield showed a significant correlation with floral bud number although the latter showed serious degeneration. In conclusion, the floral bud quantity largely determines rapeseed yield, and thus the genotypes with strong vernalization requirement should be planted early to extend the vegetative stage to achieve more fertile floral buds while the genotypes with weak vernalization requirement should be planted late to avoid flowering in chilling environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Drought stress negatively affect the sustainable crop production in various ways. • Moisture deficits drastically reduced crop yields and regional economies. • Understanding the drivers of yield levels under deficient water is required. • Biochar with high carbon is being recognized by scientists for its potential role. • Biochar improve soil status and enhance utilization of soil water and nutrients. The depletion of soil fertility and freshwater reservoirs in dry and arid conditions of the world are alarming for food and crop productivity. Although many research studies have explored the effect of biochar on plant growth and soil fertility, however, information on the role of biochar on rapeseed under drought stress is limited. The current study was conducted to investigate the effect of biochar on photosynthesis, antioxidants activities, osmolytes contents, growth and yield of rapeseed under drought stress. Rapeseed plants at the flowering stage were subjected to two moisture conditions, no stress (NS) and drought stress (DS) along with four biochar treatments (B0:0, B15:15, B30:30 and B60:60 t ha−1). Drought stress negatively affected rapeseed growth due to the over-production of hydrogen peroxide (H 2 O 2) by increasing 45 %, malondialdehyde (MDA) 21 % and electrolyte leakage (EL%) 40 % in (BO + DS) treatment as compared to control (BO + NS). However, the addition of biochar at 30 t ha−1 alleviated the hostile effects of drought stress in rapeseed to reduce the contents of MDA, H 2 O 2 , EL by increasing the activities of superoxide dismutase (SOD) by 63 %, peroxidase (POD) 48 %, and catalase (CAT) 62 % compared to stress-controlled treatment (BO + DS). The results revealed that biochar could alleviate the harmful effects of drought stress by enhancing the activities of antioxidants, osmoprotectants, soil fertility, and the physiological processes of rapeseed which indicate that the biochar application might be a sustainable strategy to enhance rapeseed growth under drought stress. [ABSTRACT FROM AUTHOR]

• Melatonin-priming improved seed germination under the drought stress. • Melatonin-priming detoxified the ROS activities through enhancement of antioxidants. • Melatonin-priming potentially regulated stomatal traits coping with drought stress. • Seed priming with melatonin prevented chloroplasts autopepsia and cell wall degradation. Water stress encumbers the rapeseed growth and development primarily by oxidative alteration to biological membranes and interrupted tissue water status. Seedling tolerance to water stress is vital for better crop development through the entire period under drought stress condition. The enhancement of plant stress tolerance due to melatonin application is already known; however, the specific underlying mechanisms are still not fully understood. The current study was done to investigate the effect of melatonin-priming on rapeseed germination and subsequent seedling growth under PEG-6000 simulated drought stress. Drought stress significantly inhibited germination and seedling growth, led to oxidative stress from excessive H 2 O 2 generation, and reduced the chlorophyll content. Melatonin-priming alleviated the oxidative damage and the amount of chlorophyll reduction in rapeseed seedlings under the drought stress. The stomatal traits such as number, stomatal length and width were greatly improved in melatonin-primed treatment. Melatonin-priming also preserved the chloroplast structure, maintained cells expansion and strengthened the cell wall in response to drought stress. The results revealed that the ameliorative effects of melatonin-priming may be ascribed to enhancement of antioxidant enzymes activities, increase in the content of non-enzymatic antioxidants, and increase in the amounts of osmo-protectants. The present data suggest that priming seeds with melatonin can be a prime strategy regarding the development of crop drought resistant in crop production. [ABSTRACT FROM AUTHOR]