Salt stress is one of the major adverse factors affecting plant growth and crop production. Rapeseed is an important oil crop, providing high-quality edible oil for human consumption. This experiment was conducted to investigate the effects of salt stress on the phenotypic traits and physiological processes of rapeseed. The soil salinity was manipulated by setting three different levels: 0 g NaCl kg−1 soil (referred to as S0), 1.5 g NaCl kg−1 soil (referred to as S1), and 3.0 g NaCl kg−1 soil (referred to as S2). In general, the results indicated that the plant height, leaf area, and root neck diameter decreased with an increase in soil salinity. In addition, the biomass of various organs at all growth stages decreased as soil salinity increased from S0 to S2. The increasing soil salinity improved the distribution of biomass in the root and leaf at the seedling and flowering stages, indicating that rapeseed plants subjected to salt stress during the vegetative stage are capable of adapting their growth pattern to sustain their capacity for nutrient and water uptake, as well as leaf photosynthesis. However, as the soil salinity increased, there was a decrease in the distribution of biomass in the pod and seed at the maturity stage, while an increase was observed in the root and stem, suggesting that salt stress inhibited carbohydrate transport into reproductive organs. Moreover, the C and N accumulation at the flowering and maturity stages exhibited a reduction in direct correlation with the increase in soil salinity. High soil salinity resulted in a reduction in the C/N, indicating that salt stress exerted a greater adverse effect on C assimilation compared to N assimilation, leading to an increase in seed protein content and a decrease in oil content. Furthermore, as soil salinity increased from S0 to S2, the activity of superoxide dismutase (SOD) and catalase (CAT) and the content of soluble protein and sugar increased by 58.39%, 33.38%, 15.57%, and 13.88% at the seedling stage, and 38.69%, 22.85%, 12.04%, and 8.26% at the flowering stage, respectively. In summary, this study revealed that salt stress inhibited C and N assimilation, leading to a suppressed phenotype and biomass accumulation. The imbalanced C and N assimilation under salt stress contributed to the alterations in the seed oil and protein content. Rapeseed had a certain degree of salt tolerance by improving antioxidants and osmolytes.
Abstract Increasing planting density is a common practice to enhance rapeseed ( Brassica napus L.) yield via an increase in pod quantity. However, excessive density may lead to a deterioration in pod quality. Therefore, we hypothesized that improving pod quality based on a certain level of pod quantity could further increase seed yield. A randomized block experiment was conducted with five density levels (2.4, 3.6, 4.8, 6.0, and 7.2 × 10 5 plants ha −1 , referred to as D1, D2, D3, D4, and D5) using two hybrid varieties of Qinyou10 and Ningza1838. The plot seed yield reached the maximum value in D2 or D3, and there was no significant difference between these two density levels. An increase in planting density resulted in a decrease in canopy thickness, but an increase in lodging angle and pod density. According to the number of seeds per pod, the pods were categorized into low‐productive pod (≤14), middle‐productive pod (15‒17), and high‐productive pod (≥18). The number of high‐productive pod in D2 and D3 ranged from 48.15 × 10 6 to 54.22 × 10 6 ha −1 , accounting for 53.76%‒63.28% of the total pod number and 76.89%‒82.83% of the total seed yield. With the planting density increasing from D3 to D5, there was a significant transition from high‐productive pod to middle‐productive and low‐productive pods, causing a decrease in seed yield. Therefore, when the seed yield was targeted as 4500 kg ha −1 , the suitable planting density ranged from 3.6 × 10 5 to 4.8 × 10 5 plants ha −1 , and the optimal number of pods in population ranged from 83.0 × 10 6 to 94.0 × 10 6 ha −1 , and the quantity proportion of high‐productive pod maintained >50%. This study provides a guide for high‐yield cultivation of rapeseed in China and presents a novel approach to promoting a potential yield of rapeseed.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)