BFG Ch 3: stems Flashcards
6 clearly defined areas of herbaceous stems
epidermis cuticle (made of waxy cutin) cortex pith vascular bundle vascular cambium
epidermis
single layer of outer boundary cells
cuticle
layer of waxy cutin superimposed on and impregnating the outer walls of epidermal cells
stems can be _____ or ______
smooth or hairy
pith
center of the stem
composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant.
pith is encircled by a ring of xylem
cortex
outermost layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of differentiated cells, usually large thin-walled parenchyma cells of the ground tissue system.
The outer cortical cells often acquire irregularly thickened cell walls, and are called collenchyma cells. Some of the outer cortical cells may contain chloroplasts. It is responsible for the transportation of materials into the central cylinder of the root through diffusion and may also be used for food storage in the form of starch.
Vascular bundle
consists of large, water conducting cells of the xylem tissue
toward the outside are food-conducting phloem cells that are smaller.
primary xylem and primary phloem
Vascular cambium
a meristematic tissue whose cells divide laterally and so result in an increase in the stem’s diameter during its secondary growth process
Primary tissues
all cells in an herbaceous stem; established by the apical meristem
secondary phloem, secondary xylem formed by what?
formed by the vascular cambium
What gives the stem its flexibility?
the softness of the pith and cortex cells
what arrangement of xylem/phloem allows them to branch into leaves?
their arrangement into small bundles
How to tree trunks become so thick?
two lateral meristems:
vascular cambium
cork cambium
what side of the vascular cambium becomes secondary xylem?
the inner side; the protoplasm dies and they become wood cells.
The tree trunk is always thicker than what?
its bark
