茎 means "stem" and refers to the main structural part of a plant that supports leaves, flowers, and fruit. It is used in botanical and scientific contexts when describing plant anatomy.
这种植物的茎又细又长,容易折断。
zhè zhǒng zhíwù de jīng yòu xì yòu cháng, róngyì zhéduàn.
The stem of this plant is thin and long, and breaks easily.
向日葵的茎可以长到两米多高。
xiàngrìkuí de jīng kěyǐ zhǎng dào liǎng mǐ duō gāo.
The stem of a sunflower can grow to over two meters tall.
你看,水分是通过茎输送到叶子的。
nǐ kàn, shuǐfèn shì tōngguò jīng shūsòng dào yèzi de.
Look, water is transported to the leaves through the stem.