4.2 Xylem, Phloem and Nutrient transport (Part1: Xylem)

What is xylem?

Xylem = the vascular tissue in plants that conducts water and some dissolved minerals up the plant.

Key cellular components: What are Tracheids

i. Tracheids

• possessed by all plants

• pitted end walls allow water to pass slowly

• die in maturity but retain function (form the woody part of plants)

Key cellular components: What are Vessel elements

ii. Vessel elements

• possessed by angiosperms (flowering plants)

• dead, lignified cells

• open ends allow water to pass rapidly up hollow tubes

Key cellular components: What are Fibers

iii. Fibers

• Protein (lignin) glue that structurally supports xylem

• fiber cells die in maturity

Key cellular components: What are Xylem parenchymas

iv. Xylem parenchyma

• store nutrients and immune mechanisms to support xylem

• only living cells in Xylem

what is osmosis

osmosis = water moving toward a region where there is a high concentration of something it can dilute

Where does water enter the plant

water enters the plant through the roots/root hairs via osmosis

What are the two components that allow water to move up the plant against gravity

water moves up the plant because of the cohesion tension theory and root pressure

what is the cohesion tension theory

1) water leaves cells near stomata via transpiration

2) water from adjacent cells moves in to replace it

3) effect continues to xylem where a negative pressure draws water up the plant

4) Adhesion prevents the water from sliding down

Simple Summary

Water is pulled up the plant like a chain, where each molecule pulls the next one up, thanks to evaporation from the leaves.

chat gpt (ask langs)

What is root pressure?

• positive hydrostatic pressure in roots ‘pushes’ water up columb

• this pressure alone can move water several vertical meters

what factors affect transpiration

• temperature

• humidity

• wind

• light sensitivity

know the curves

how do we measure transpiration

a potometer

label Xylem