How does the lack of cytoplasm in xylem vessels aid passage of water in them?

The following hormone had their receptors in the cell membrane except a-insulin b-tsh c-gh d- cortisol

How does natural selection change thephenotypes within a population over time?

What is the importance of having the us forest service, the bureau of land management, the us fish and wildlife service, and the national park service? to manage land resources for conservation and the development of natural resources to manage land resources for conservation and the development of urban areas to preserve historical landmarks and manage the development of urban areas to preserve historical landmarks and manage the development of rural areas