Download Transport in Plants Lesson 10 Biology 10

Transport in Plants
Lesson 10
Biology 10
Objective: You will be able to
-identify the xylem and phloem in plants
-describe their function
Xylem
The xylem transports water and soluble mineral nutrients
from the roots throughout the plant. It is also used to
replace water lost during transpiration and
photosynthesis.
The transport is passive.the most important cause of
xylem flow is the evaporation of water from the surfaces
of mesophyll cells to the atmosphere. This flow is called
transpirational pull.
Xylem Vessels
Xylem vessels are a long straight chain made of
tough long dead cells known as vessel elements. The
cells are arranged end to end and the cell walls which
would normally surround the whole cell dissolve
where ever they are touching another cell wall.
Phloem
In vascular plants, phloem is the living tissue that
carries organic nutrients, in particular, sucrose, a
sugar, to all parts of the plant where needed.
At their "source" — the leaves — sugars are pumped by
active transport into the companion cells and sieve elements
of the phloem.
Comparing Xylem and Phloem
Transpiration-cohesion-tension
1. Water is constantly lost through transpiration from
the leaf (stomata).
2. When one water molecule is lost another is pulled
along by the processes of cohesion and tension.
Cohesion: the attraction (sticking together) of different
substances.
Adhesion: the attraction (sticking together) of the same
substance. Water forms drops because of this!
3. Transpiration pull, utilizing capillary action and the
inherent surface tension of water, is the primary
mechanism of water movement in plants.
Guard Cells and Transpiration
Read page of notes, use textbook and label diagram .
(text p.309)
Assignment
Read p. 315-322
Do Check and reflect #1-8