Macadamia (Macadamia integrifolia and M. tetraphylla) is a typical evergreen nut crop with a large amount of racemes. During the development of its racemes, two infructescences of different growth potential, bearing the distinctly different fruit-setting ability and rachis size, can often be found in the trees. However, knowledge about the formation mechanism of these two types of infructescences is still unknown. In the present research, two different sized macadamia infructescences, namely the strong and the weak infructescence, were subjected to analyze the primary metabolites and endogenous hormones in their fruit and rachis by an ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Result showed that the strong infructescences presented a significantly greater fruit set and thicker rachis than the weak ones. Based on widely targeted metabolomics analysis, a total of 151 and 122 primary metabolites with differential accumulation were identified in the fruit and the rachis, respectively. Among these, the lipids were the largest group, followed by the amino acids and derivatives. Accompanied by the infructescence growth, a large proportion of the differential accumulated metabolites (DAMs), including lipids, saccharides and alcohols, amino acids, organic acids and nucleotides, were significantly decreased in the fruit, while most of the DAMs were significantly increased in the rachis except the amino acids. Compared with the weak infructescence, some DAMs, mainly the lipids, showed a greater accumulation in the fruit of the strong infructescence, as well as the lipids, nucleotides and sugars in the rachis. Furthermore, the higher levels of IAA, Me-IAA, IP, tZ, and GA₁ were invested to the fruit and rachis of the strong infructescence, while the contents of the JA, Me-JA, SA, and ABA in the fruit and of the JA, JA-Ile, and H2JA in the rachis were opposite. Notably, the ABA was observed to increase and decrease significantly in the rachis and the fruit of the strong infructescence, respectively. Jointly, these are the first results showing the essential role of these significantly accumulated primary metabolites and endogenous hormones during the formation of the strong infructescence in macadamia.

澳洲坚果 ( Macadamia integrifolia和M. tetraphylla)是典型的常绿坚果类作物，有大量总状花序。在其总状花序的发育过程中，常在树体中发现两个具有不同生长潜力的果序，其坐果能力和轴大小明显不同。然而，关于这两种果序的形成机制的知识仍然未知。在本研究中，采用超高效液相色谱-串联质谱法（UPLC-质谱/质谱）。结果表明，与弱果序相比，强果序的座果率和轴粗明显。基于广泛靶向的代谢组学分析，在果实和花轴中分别鉴定出 151 种和 122 种具有差异积累的初级代谢物。其中，脂质是最大的一组，其次是氨基酸及其衍生物。伴随着果序的生长，大部分差异积累代谢物（DAMs），包括脂质、糖类和醇类、氨基酸、有机酸和核苷酸，在果实中显着减少，而大部分DAMs在果实中显着增加。轴除了氨基酸。与弱果序相比，一些DAMs，主要是脂质，在强果序的果实中表现出更多的积累，以及在轴中的脂质、核苷酸和糖类。此外，更高级别的 IAA、Me-IAA、IP、其次是氨基酸及其衍生物。伴随着果序的生长，大部分差异积累代谢物（DAMs），包括脂质、糖类和醇类、氨基酸、有机酸和核苷酸，在果实中显着减少，而大部分DAMs在果实中显着增加。轴除了氨基酸。与弱果序相比，一些DAMs，主要是脂质，在强果序的果实中表现出更多的积累，以及在轴中的脂质、核苷酸和糖类。此外，更高级别的 IAA、Me-IAA、IP、其次是氨基酸及其衍生物。伴随着果序的生长，大部分差异积累代谢物（DAMs），包括脂质、糖类和醇类、氨基酸、有机酸和核苷酸，在果实中显着减少，而大部分DAMs在果实中显着增加。轴除了氨基酸。与弱果序相比，一些DAMs，主要是脂质，在强果序的果实中表现出更多的积累，以及在轴中的脂质、核苷酸和糖类。此外，更高级别的 IAA、Me-IAA、IP、果实中的 DAM 显着减少，而除氨基酸外，大部分 DAM 在轴中显着增加。与弱果序相比，一些DAMs，主要是脂质，在强果序的果实中表现出更多的积累，以及在轴中的脂质、核苷酸和糖类。此外，更高级别的 IAA、Me-IAA、IP、果实中的 DAM 显着减少，而除氨基酸外，大部分 DAM 在轴中显着增加。与弱果序相比，一些DAMs，主要是脂质，在强果序的果实中表现出更多的积累，以及在轴中的脂质、核苷酸和糖类。此外，更高级别的 IAA、Me-IAA、IP、t Z 和 GA ₁被注入到强果序的果实和轴中，而 JA、Me-JA、SA 和 ABA 的含量在果实中，JA、JA-Ile 和 H2JA 的含量在轴中是相反的。值得注意的是，观察到 ABA 在轴和强果序的果实中分别显着增加和减少。共同地，这些是第一个结果，显示了这些显着积累的初级代谢物和内源激素在澳洲坚果强果序形成过程中的重要作用。