The shoot of a plant is responsible for two major functions: photosynthesis and reproduction. In most plants, the leaves carry out photosynthesis, while the stems provide stability to elevate those leaves above potential competition. In annual plants, whose entire life cycle from germinate to death is completed in a single year, the epidermis on the stem is often photosynthetic, as well.
Tissues in the shoot are derived from the shoot apical meristem (SAM). Just like in the root, the SAM produces three primary meristems, which produce the primary tissues:
- Protoderm → Epidermis
- Ground meristem → Cortex and pith (simply ground tissue in monocots)
- Procambium → Primary xylem and primary phloem
These primary tissues will then either differentiate into specialized cells or, as is the case in many eudicots, become meristematic and produce secondary tissues. More on this in Lab Secondary Growth.