primary rachis branch

• 第一次枝梗

primary rachis branch的用法和样例：

例句

1. There is a significantly linear relation between secondary branch grain number and grain number per panicle, and they have the same changing tendency.
   穗粒数与二次枝梗粒数随品种的变化是一致的，二者有极显著的线性相关。