Plant Histology 5: Secondary Vascular Tissues

cambium

gives rise to the primary plant body

vascular cambium

meristem whose presence results in the development of woody tissues; responsible for plant’s secondary growth

primary growth

What type of growth is shown on the figure on the left?

dicotyledons

The figure on the left is a cross section of what group of flowering plant?

secondary growth

What type of growth is shown on the figure on the right?

pith

a

phloem

b

xylem

c

sclerenchyma, fibers

d

vascular cambium

e

primary xylem

f

secondary xylem

g

cork cambium

h

epidermis

i

cortex

j

bark

k

cork

l

primary phloem

m

secondary phloem

n

procambium

present in herbaceous plants, which remain herbaceous all throughout

parenchyma

What type of tissue is found at the pith?

procambium

positioned between xylem and phloem

first

primary cells refer to cells that were formed ______.

last

secondary cells refer to cells that were formed ______.

secondary, secondary

vascular cambium is positioned between ________ xylem and__________ phloem.

primary phloem

very first tissue to form

secondary phloem

very last tissue to form

epidermis

will eventually be sloughed off and replaced with bark

secondary cortex

associated with bark

secondary phloem

a

sieve tube member

b

vascular cambium

c

secondary xylem

d

flattened

in procambium and vascular cambium, the cells are usually __________.

sieve tube member

main component of phloem that transports or translocates sugar

procambium and interfascicular parenchyma cells

gives rise to the vascular cambium

monocots, monocotyledons

some of these may increase in height and diameter, but its “wood” is not a product of the vascular cambium

dicots, dicotyledons

produce true wood

anomalous secondary growth

in place of vascular cambium, other tissues are responsible for wood found in monocot families; caused by active parenchyma cells give rise to wood or girth increase (example: palm family)

interfascicular parenchyma

“between” + “fascicle”; tissue located in between two vascular bundles

epidermis

a

cortex

b

phloem

c

interfascicular parenchyma

d

procambium

e

xylem

f

vascular bundle

g

cortical region

cortex; usually includes parenchyma, collenchyma, and fibers

periclinal

What is the interfascicular cambium’s manner of division?

Multiplicative division

What kind of division is portrayed as the red line?

Additive division

What kind of division is portrayed as the blue line?

Phloem

What mother cell is portrayed through the light pink boxes?

Xylem

What mother cell is portrayed through the light blue boxes?

outward, inward

In reference to the figure presented, the vascular cambium and procambium are positioned in such a way that phloem develops _______ and xylem _________.

mother cells, initial cells

According to the figure, cells which are produced periclinally become ____________ while those produced anticlinally become what?

meristem

One of its characteristics is being constantly mitotically active.

specialized, meristematic cell

Parent cells divide into two— one becomes _______ and the other will continue to function as a __________.

smaller

Upon the development of the secondary vascular tissues, the pith becomes __________.

continuous

For as long as the cells of the vascular cambium are alive, the development of secondary xylem and phloem is _____________.

tangential section of vascular cambium

What is shown in the image presented?

ray initials

a

ray initials

may give rise to upright, procumbent, tile, and square cells parenchyma cells

ray initial

a

upright cell

b

procumbent cell

c

tile cell

d

square cell

e

fusiform initials

b

secondary xylem

technical term for wood

transverse section or cross section

A

radial longitudinal section (RLS)

B

tangential longitudinal section (TLS)

C

initials

meristematic cell; origin

fusiform initials

elongated in tangential section; taper; give rise to tracheary elements (vessels and tracheids)

ray initials

isodiametric (almost equal in diameter) in tangential section; give rise to ray parenchyma and axial parenchyma

axial parenchyma

vertical arrangement

ray parenchyma

horizontal arrangement

pith

a

heartwood

b

sapwood

c

growth rings, annual rings

d

inner bark

e

outer bark

f

tangential longitudinal section (TLS)

What is the type of sectioning in A?

transverse surface

What is the type of sectioning in B?

radial longitudinal section (RLS)

What is the type of sectioning in C?

heartwood

water can no longer enter this part of the tree, causing it to run out of minerals and eventually die, losing its function of transport; main function is storage of organic substances, some of which imparting color

sapwood

functional in terms of transporting water and minerals; small pit due to occupation of secondary xylem;

outer bark

primarily made out of cork cells (dead cells)

inner bark

still considered bark; secondary phloem is present; functions at translocation; the plant will die if this is removed

translocation

transport of photosynthetic products (example: sugar)

girdling

severing the inner bark from the woody plant to keep them from growing further without cutting down the plant

absent

vessels are ________ in gymnosperms, with the exception of Gnetophyta.

tracheids

Conifers only have ______ in their xylem; it is said that around 90-95% of cells in their wood are represented by this, with the remaining 5-10% being ray parenchyma.

fibers

There are almost no _________ in conifer wood, hence why they are occasionally called soft wood.

tracheids and vessels or tracheary elements, parenchyma

Dicot wood (hard wood) includes different kinds of cells such as _________. These transport water and minerals and impart support and hardness to the plant due to presence of secondary cell wall. It also includes __________.

fibers

In addition to tracheary elements, dicot wood (hard wood) also includes _________. The absence of this is what causes conifer wood to be called soft wood, even if it isn’t actually soft.

transverse section and radial section

In reference to the image, in which sections are resin ducts highly prominent?

resin ducts

____________ are present in all parts of a conifer.

early wood or spring wood, resin duct

The thickness of tracheid’s cell walls may vary. They are thinner at the _________ and thicker when closer to the _________.