なぜ一種の植物が一年生の草本になったり、多年生の木本になったりするのでしょうか。

、。

Why is it that some plants become annual herbs while others become perennial woody plants?

Literal

Why one-kind [gen-の] plant [subj-が] one-year-life [gen-の] herbaceous [become-になった] [or-たり], many-year-life [gen-の] woody [become-になった] [or-たり] do [explanation-のでしょうか].

Formal botanical vocabulary: 一年生草本 'annual herb' and 多年生木本 'perennial woody plant' — both sinitic compound terms that productively use the ~生 'life' suffix and the 草本/木本 botanical-classification pair. The ~たり~たりする frame lists alternative possibilities. のでしょうか softens the question into a reflective 'I wonder why?' appropriate for a scientific curiosity.