Rashi: Aros is an expression of something rooted well, like "Rasha Aritz u'Mis'areh k'Ezrach Ra'anan" (Tehilim 37:35). Also Menachem explained in his Machberes 'seeds that took root.'

Radak: Aros is an adjective, for moist vegetation. The same applies to "u'Mis'areh k'Ezrach Ra'anan."

Malbim: Egypt was financed by the abundance of grain that grew in their land. It was called the storehouse of grain. People came to there from afar to buy grain and bread.

Rashi: It is Al ¹ the Nile, and even Al Pi Ye'or (on its banks); all will dry.

Malbim: It is even what people seeded. Its roots are stronger, and it lasts - also it will dry.

Malbim: The wind will uproot it, "and it is not."