Post on 27-Mar-2015
XylemAnd
Phloem
Vascular tissue evolved as an adaptation to life on land. It consists of a series of
elements that form tubes throughout the plant.
Both are vascular tissue (tubes) Both are found in roots, leaves and stems. Both transport materials needed by plants
• Composed of dead cells• Cells are made of thick
cell walls• Found in wood• Carries water and
nutrients• Transports materials up
the stem…capillary action(like a straw)
• Helps support the stem
Phloem• Composed of living cells• Cells don’t have
thick cell walls• Found in bark• Carries food
(sugar-sap)• Transports materials up
and down the stem(like an elevator)
• Does not support the stem
Xylem
LeavesA leaf is an above-ground plant organ
specialized for the process of photosynthesis and transpiration.
A leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works
to expose the chloroplast to more light and to increase the absorption of carbon dioxide at the expense of
water loss.
Stomata – pores where gas exchange takes place.
Guard cells – open and close the stomata to facilitate the exchange of gas and water vapor.
Veins – are the xylem and phloem tubes.
Cuticle – thin waxy covering of plants that prevents water loss.
is the evaporation of water in plants through the stomata.
• Transpiration takes place mainly in the underside of leaves but also occurs through roots and stems.
Water travels up through xylem
tubes
Water enters the roots
Water evaporate
s through stomata
in leaves
Water lost by transpiration.
Capillaryaction
Water absorbed by root hairs.
Turgor Pressure
Transpiration is necessary… • for distributing water,
nutrients, CO2 and O2 throughout the plant.
• the ingredients are essential for photosynthesis and respiration.
• to be able to take up carbon dioxide from the atmosphere
• to maintain plant temperature• to maintain the water cycle
(10 percent of the moisture found in the atmosphere is released by plants through transpiration)
The following parts of a leaf will help in identifying plants.
saw-toothed
smooth
double saw-toothed
lobed
parallel
palmate
pinnate
opposite alternate
simplepalmatelycompound pinnately
compound
v-shapedrounded
flat heartuneven
Dichotomous means “divided into two parts”.
Di = 2
In a dichotomous key two questions are offered; one will direct you to the answer and the other will direct you to a set of two more
questions. By following the key and making the correct choices, you should be able to identify
the name of an unknown organism.For example…we could construct a key using the
following stationary supplies taken from a student's pencil
case.
1. a. long, tubular objects------------go to #2
1. b. short, non-tubular objects-----go to #4
2. a. constructed from plastic--------go to #2
2. b. constructed from wood---------go to #4