Biology Activity 1.2 & 1.3

Title :

Chapter 1.2: Meristematic Tissues and Growth

Aim :

(i) To investigate the information about the
necessity of primary and secondary growth.

(ii) To investigate about the types of monocots that
undergo anomalous secondary growth.

- Introduction -

Meristematic Tissues and
Growth

Meristematic Tissues Cell Growth Zones Growth Types

Apical Lateral -Division -Primary Growth
Meristem Meristem -Elongation [Begins after germination]
- Vascular Differentiation
- Shoot cambium -Secondary Growth
tip [Increase in circumference
- Cork
- Root tip cambium and diameter of plant
stem and root, occurs in

dicot]



Necessity of Primary Growth

• Allows maximum elongation of plants to absorb
sunlight for photosynthesis

• Primary phloem can transport the products of
photosynthesis from the leaves to other parts
of the plants.

• Primary xylem can transport water and mineral
salts from the soil via the roots to the leaves.

• Primary xylem provides support to herbaceous
or young plants.

Need of Secondary Growth

In Terms of Support

❏ Provides stability to plants by increasing the
stem and root diameters to suit the height
of plant

❏ Thickness of stem and root increase

❏ Provides mechanical support to plants

Need of Secondary Growth

In Terms of Transportation

❏ Produces more xylem and phloem tissues
to replace old and damaged xylem and
phloem tissues

❏ Produces stronger and thicker bark to
provide protection to the plants from
excessive water loss, physical injuries
and pathogen infections

❏ Able to live longer by increasing the
chances of seed production and
reproduction

THE IMPORTANCE OF PLANTS UNDERGOING
SECONDARY GROWTH ECONOMICALLY

Have high commercial value This plants have strong and hard
as this plants can produce woods which are suitable to
valuable timber make building, furniture and
door

The presence of annual
rings make furniture looks
attractive and can be made
as decorative items

The woods of Hopea sp. and This substances can be
meranti can produce resin and oil commercialised as varnish, perfume
and medicine.
Resin
A sticky flammable organic
substance produce by some
plants

Commercialised fruits such as Hopea sp.
mangoes and durians are products
of secondary growth plants
They are able to generate income
as well as boost economic growth







Anomalous Secondary Growth in Dracaena

● The secondary growth usually absent in monocots plants because monocots
do not have vascular cambium.

● However, Dracaena shows the anomalous secondary growth in monocot
stem.

● The secondary growth in Dracaena is due to the abnormal activity of
cambium

*doesn't follow normal secondary growth in which vascular cambium produces xylem on inside and phloem on outside.

During Secondary Thickening:

● Formation of secondary cambium occur in the inner region of 01
parenchymatous cortex.

● The activity of cambium is abnormal

02 ● Secondary vascular bundles is produces on its inner side and
parenchymatous cells on the outer side.

● After more parenchymatous is produce by cambium,vascular
bundles formed to the centre

● The vascular bundles keep on changing the position and alternating 03
in position with first ring.

● The last inner ring are embedded in lignified conjunctive tissue.
● Cork cambium activities normal, cork and secondary cortex are

produce at the outer region.

Anomalous Secondary Growth in Palm

Palm trees increase their trunk diameter due to division and enlargement of parenchyma
cells, which is termed "primary gigantism" because there is no production of secondary
xylem and phloem tissues, or sometimes "diffuse secondary growth".

*in palm, there is no vascular cambium, vascular bundlesare
scattered throughout the central cylinder,usually in greater
density at the periphery, and last the life of the palm.

- Conclusion -

Importance of Necessity of Primary Necessity of
Secondary Growth Growth: Secondary Growth:

Economically 1. Produce new cells 1. Provides
for elongation – mechanical
1. Timber – photosynthesis support
furniture, door,
2. Produces primary 2. Produces new and
decoration xylem and secondary xylem
2. Resin – perfume, and phloem
primary phloem.
vanish 3. Produce stronger
3. Fruit and thicker bark

4. Prolongs lifespan

Examples of
monocot plant

undergo
anomalous
secondary

growth :
Dracaena, palm

1. Books:

(i) Biology Form 5 KSSM Textbook
(ii) Focus Biology SPM Form 5 KSSM

2. Internet :

(i) https://ms.m.wikipedia.org/wiki/Meranti_Paang
(ii) https://ms.m.wikipedia.org/wiki/Balak
(iii) https://www.sciencedirect.com/topics/materials-science/resin
(iv) https://www.assignmentpoint.com/science/biology/secondary-growth-plants.html
(v) https://www.pinterest.com/pin/257057091203344427/
(vi) http://www.cas.miamioh.edu/~meicenrd/mudescd/dendrology/scdrygth/1&2gwrtp2.html
(vii) https://plantlet.org/anomalous-secondary-growth/
(viii) https://d2r6h7ytneza1l.cloudfront.net/title/81bc83ee-44db-4e41-8152-

d34c9e595826/broschat_excerpt.pdf
(ix) https://en.wikipedia.org/wiki/Secondary_growth
(x) https://tardigrade.in/question/assertion-no-secondary-growth-takes-place-in-monocots-reason-

5mkld1s5#:~:text=These%20tissues%20are%20formed%20by,in%20between%20the%20vascular%20b
undles.
(xi) https://www.shutterstock.com/image-vector/picture-showing-stem-palm-cross-section-1367767538