Plants contain highly specialized tissues and cells to facilitate growth and transport.
Complete the following sentences:
- The outermost cell layer that forms a protective barrier around a leaf and controls gas exchange is the __________.
- The specialized, undifferentiated tissue responsible for rapid cell division and growth at the tips of roots and shoots is the __________.
Xylem vessels transport water and mineral ions throughout the plant. Apart from cellulose, the walls of these vessels are heavily reinforced with a tough, water-impermeable polymer. Name this polymer.
The diagram below shows a longitudinal section of phloem tissue:
The concentration of dissolved sucrose inside the phloem sieve tube element is higher than the concentration inside Cell X.
Explain how the sub-cellular structures in Cell X help to transport sucrose into the sieve tube element against this concentration gradient.
During cell differentiation, unspecialized cells undergo specific structural changes to form functional sieve tube elements. State one such structural change.