Chapter 2
BOT3015L
Introduction to Autotrophs
and Osmotrophs
Organisms able to synthesize nutritive
substances required for growth
(auto=self, troph=feed/grow)
Organisms that take up nutritive substances
required for growth by osmosis
(osmo=take up from external,
troph=feed/grow)
Presentation created by Danielle Sherdan
All photos from Raven et al. Biology of Plants except when otherwise noted
Today
•
Plant cells
– characteristics of plant cells
– plastids
– large central vacuoles
– cell wall
– effects of osmosis on plant cells
– cell division
Microscopy enables the discovery of cells
Slices of cork. Drawing by
Robert Hooke, who coined the
term “cell” in the 1600s
Harvesting cork for
commercial purposes
Modern cell theory
The modern cell theory states that
1. All living organisms are composed of one or
more cells
2. Chemical reactions of living organisms take
place within cells
3. Cells contain the hereditary information of the organisms
of which they are a part, and this information is passed
from parent cell to daughter cell
4. Cells arise from other cells
Generalized diagram of a plant cell
Note: As you will observed, much variation from this
generalized diagram exists.
Cytoplasmic streaming of chloroplasts
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Considering their function, why
would movement of chloroplasts
by cytoplasmic streaming be
advantageous?
Amyloplasts store starch
Today, we will use
staining techniques
(iodine stains
starch) to visualize
amyloplasts in
potato tubers
Amyloplasts
in a bean
root
Observing the vacuole
Put cells in a
bath of
concentrated
solution
What do you
expect?
Osmosis
Plasmolysis
Normal physiological conditions
--Low external solute concentration
--High internal solute concentration,
thus positive pressure inside.
--Positive pressure in the plant cell
pushes against the restricting cell
wall, like a water balloon in a cage.
Under high external
solute concentrations
--External water potential decreases to
below that inside the cell, thus osmotic
water efflux from the cell. This process is
plasmolysis.
Today
•
Plant cells
– characteristics of plant cells
– plastids
– large central vacuoles
– cell wall
– effects of osmosis on plant cells
– cell division
Mitosis and cytokinesis
Mitosis (nuclear division)
simplified diagram
chromosome
replication
during S
phase of cell
cycle
chromosomes
align along
metaphase plate
Homologous and are attached
chromosomes to cytoskeleton
chromosomes
condense and
nuclear
envelope
degrades
nuclear
envelope
forms around
each set of
chromosomes
chromosomes are
pulled apart to
opposite poles,
notice both sets
are identical
Cell division in plants occurs at
meristems
Onion root
meristem located
at tip of root
Compare
mitosis and meiosis
Total number of cell divisions?
Fill in ploidy level in above “cells”
Pairing of homologs?
Crossing over?
Comparison chart II mitosis
meiosis
Centromeres divide?
How many daughter cells are genetically identical to original cell?
or triploid or tetraploid…
or tetraploid or hexaploid…, but
not triploid, why?