Soil clod size is an important factor affecting seedling growth; besides, cultivation of strong seedlings is important to improve yield and benefit of direct-seeding rapeseed. To simulate the open field conditions, two rapeseed cultivars were grown in different clod sized soil to study morpho-physiochemical responses at five leaf stage, beside applying metabolite profiling. Moreover, foliar application via alpha-linolenic acid (ALA) was applied to improve the adaptability of rapeseed to large clod sized soil. Our results showed that soil water content was decreased in large clod sized soil (K2) versus small clod sized soil (K1), which decreased seedling weight, shoot length and root vitality, while increasing root length. Furthermore, osmolyte contents and peroxidase (POD) and catalase (CAT) activity were decreased with increasing malondialdehyde content in studied rapeseed cultivars under K2 conditions. Moreover, phospholipase A2 (PLA2) of phospholipid metabolism and its related enzymes were decreased, while its content and gene expression were increased. Besides, ALA metabolism was up-regulated, while lipoxygenase (LOX) activity, content and its gene expression were elevated under K2 conditions. Metabolic profiling showed that lipid metabolism was significantly changed than other identified components, which is synthetic precursors of various secondary metabolites. Compared with K1, the metabolic pathways of ALA and pyrimidine were up-regulated, while the metabolic pathways of glycerophospholipids and purines were down-regulated in both studied cultivars under K2 conditions. Moreover, ALA application enhanced seedling growth by improving root length, shoot and root dry weight, root vitality, ALA and proline contents, while reducing the malondialdehyde (MDA) content of two rapeseed cultivars under K2 conditions. Taken together, our study provided a theoretical basis and technical support for the soil tillage and cultivation of direct-seeding rapeseed.

中文翻译：

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形态理化性状和代谢分析揭示了油菜在大块土壤条件下的反应


土壤土块大小是影响幼苗生长的重要因素；此外，培育壮苗对于提高直播油菜的产量和效益也具有重要意义。为了模拟露天条件，在不同土块大小的土壤中种植两个油菜品种，除了应用代谢物分析外，还研究五叶期的形态-生理化学反应。此外，通过叶面喷施α-亚麻酸（ALA）来提高油菜籽对大块土壤的适应性。我们的结果表明，与小土块大小的土壤（K1）相比，大土块大小的土壤（K2）的土壤含水量降低，这降低了幼苗重量、芽长和根系活力，同时增加了根长。此外，在 K2 条件下，所研究的油菜品种的渗透剂含量以及过氧化物酶 (POD) 和过氧化氢酶 (CAT) 活性随着丙二醛含量的增加而降低。此外，参与磷脂代谢的磷脂酶A2（PLA2）及其相关酶减少，而其含量和基因表达量增加。此外，K2条件下ALA代谢上调，脂氧合酶（LOX）活性、含量及其基因表达升高。代谢分析表明，脂质代谢比其他已鉴定的成分发生了显着变化，这些成分是各种次生代谢物的合成前体。与K1相比，K2条件下两个研究品种的ALA和嘧啶代谢途径上调，而甘油磷脂和嘌呤代谢途径下调。 此外，在 K2 条件下，施用 ALA 可提高根长、芽和根干重、根活力、ALA 和脯氨酸含量，同时降低两个油菜品种的丙二醛 (MDA) 含量，从而促进幼苗生长。综上所述，本研究为土壤耕作和直播油菜栽培提供了理论依据和技术支撑。