BIOL 1030 Lecture Notes - Germination, Endosperm, Vascular Tissue
7 May 2018
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BIOLOGY 1030 - KEVIN SCOTT and CARLA ZELMER - WINTER 2018 - Lectures 27-29!
Lecture 27: Plant Form and Function
Growth of the plant body is an increase in size of the plant body, which is indeterminate and is
continuous throughout the life of the plant, with the addition of new tissues to the root and the
shoot. Growth starts at syngamy with the formation of the zygote, developing into the embryo
and then the mature plant. "
#An organ’s individual growth occurs in the root system and the shoot system (stem and
leaves). "
Cell division occurs through mitosis and cytokinesis, with cell plate formation (future wall that
connects two cells together), and through the stimulation of plant hormones (auxin, a growth
hormone; and cytokinin, hormone controlling cytoplasmic division). "
#Active cell division occurs in a localized region, the meristem, from which permanent
tissue is derived. "
#Meristem is first formed in the embryo and is active for the life of the plant."
•S.A.M. (Shoot Apical Meristem), primary growth: an increase in length of the plant body at
the terminal bud along the shoot-axis. This growth produces primary tissue"
•R.A.M. (Root Apical Meristem), primary growth: an increase in the length of the plant body
along the root-axis. Root hairs have a short lifespan and must be continuously produced
to absorb nutrients from the soil. Dead root hairs serve as anchorage to the plant body
and stabilize the plant, growing both upwards and deeper into the soil. "
•Vascular Cambium, secondary growth: an increase in diameter (girth) of the plant body,
with the production of secondary xylem and phloem in areas of the plant body that have
finished primary growth. This is a characteristic of woody plants, consisting of the wood
and inner bark. "
•Cork Cambium, secondary growth: an increase in girth of the plant body, with the
production of non-living cork cells on the outer diameter (outer bark), creates a water-
proofing (lipid layer) to the inner bark and the protect the plant against water loss. This
production of periderm, a characteristic of woody plants can be seen to offer a fire-
protection function. "
#Secondary growth occurs in woody plants, "
Cell enlargement:
#Increase in cell size through division of the parent cell but not growth "
#Small vacuoles form, which are membrane bound from the Golgi and fuse to form larger
vacuoles."
#the cell wall loses its rigidity and becomes plastic (more stretchable) in certain areas to
allow cell wall elongation."
#The cell elongates, becoming wider with the formation of new wall material in one
direction, with the cap of the old cell wall remaining the same size. "
*Cell differentiation : Morphological vs. physiological changes in the cell; when cells develop
from meristem to mature plant tissue
-Vascular tissue systems: "
•Secondary xylem : transport or water and minerals in areas of secondary growth;
tracheids in gymnosperms, and vessels*"
•Secondary phloem : transport of sugars in areas of secondary growth; cytoplasm
losing its nucleus taken over by companion cell (mitochondria), interrupted by a sieve
plate (open space) *"
-Ground tissue systems:
•Parenchyma: basic, highly vacuolated, with small green chloroplasts. "
•Collenchyma: thick primary cell walls that provide support in young parts of the plant
(stringy material in celery)."
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