Plant Biology and Physiology
How Plants Function
Plant organization
Plants have roots, stems, leaves, and specialized tissues such as xylem and phloem. Their growth is modular, allowing continued development from meristems.
Transport in plants
Xylem transports water and minerals upward largely by transpiration pull. Phloem transports sugars from sources to sinks using pressure-flow mechanisms.
Water potential
Water movement in plants is governed by gradients in water potential, not by active pumping of water itself.
Which tissue mainly transports sugars in plants?
Phloem distributes sugars and other organic nutrients.
Correct answer: Phloem
What is transpiration?
Transpiration drives water movement and helps cool leaves.
Correct answer: The loss of water vapor from plant surfaces, mainly through stomata.
Xylem vs phloem
Xylem
- Transports water and minerals
- Flow is mostly upward
- Cells are strengthened with lignin
Phloem
- Transports sugars and signals
- Can move source to sink
- Relies on living sieve tube elements
Stomata primarily regulate:
Stomata allow in and water vapor out, balancing photosynthesis and water conservation.
Correct answer: Gas exchange and water loss