Primary and secondary growth

Primary Growth
and

Secondary Growth

Group members:
Abel Goh Zhe Wei

Chai Xiang Jun
Khong Chee Leong

Teh Haween
Wong Jia Xuan

Introduction

• Primary growth is a result of rapidly dividing cells in the apical meristems at the shoot tip
and root tip. Subsequent cell elongation also contributes to primary growth. The growth of
shoots and roots during primary growth enables plants to continuously seek water (roots)
or sunlight (shoots).

• Secondary growth is the growth that results from cell division in the cambia or lateral
meristems and that causes the stems and roots to thicken, while primary growth is growth
that occurs as a result of cell division at the tips of stems and roots, causing them to
elongate, and gives rise to primary tissue.

Aim

• To gather information on the necessary of primary and secondary growth

Discussion

1. The necessity of primary in terms of height, support and transportation
✔ Allow 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

Discussion

2. The need of secondary growth to increase support and transportation
✔ Secondary growth is important to woody plants because they grow much taller than other

plants and need more support in their stems and roots. Lateral meristems are the dividing
cells in secondary growth, and produce secondary tissues.
✔ In secondary growth, cambium ring divide inwards to form secondary xylem and outwards
to form secondary phloem. The primary xylem tissues are compressed to form stronger
layer because the walls of xylem are thickened with lignin. This provides mechanical
support to the plants. Secondary growth in plants also provide stability by increasing the
stem and root diameters. As a result, the amount of water, mineral and food transported by
xylem and phloem to every part of the plant will increase.

Discussion

3. The importance of plants undergoing secondary growth economically
✔ Secondary growth is one of the most important biological processes on Earth. Its product,

wood, is of primary importance to humans as timber for construction, fuelwoods, and
wood‐pulp for paper manufacturing. It is also the most environmentally cost‐effective
renewable source of energy
✔ Plants that undergo secondary growth have strong and hard woods which are suitable to be
used as structures for houseboats, furniture, fences, doors and others.
✔ The presence of annual rings makes furniture look attractive and they can be made as
decorative items.

Discussion

3. The importance of plants undergoing secondary growth economically
✔ The woods and barks of some plants such as Hopea sp. (merawan) and meranti can

produce resin and oil. The substances can be commercialised as varnish, adhesive
substance, perfume and medicine.
✔ Flowering plants can be made as decorative plants.
✔ Commercialised fruits such as mangoes and mangosteen, are products of plants that have
undergone secondary growth and they are able to generate income as well as boost
economic growth.

Photographs

Photographs

Conclusion

• Primary growth and secondary growth are the two types of mechanisms that plants use to
increase the size.

• The primary growth occurs by the action of the apical meristem while the secondary
growth occurs by the action of the cambium.

• The primary growth increases the length of the plant while the secondary growth increases
the diameter of the plant.

• The main difference between primary and secondary growth is the type of tissues involved
in each growth and the type of growth

Source of reference

• Jariah binti Khalid, Rodiah binti Abdul Wahid, Sudani binti Sudin. Biology Form 5 Textbook.
Publisher: IMS Books Trading SDN.BHD.

• https://www.google.com/
search?q=the+need+of+secondary+growth+to+increase+support&rlz=1C1ONGR_enMY974MY
974&oq=the+ne&aqs=chrome.0.69i59j69i57j0i131i433i457i512j46i131i433i512j46i131i175i199i43
3i512j69i60l3.9958j0j7&sourceid=chrome&ie=UTF-8

• https://www.google.com/
search?q=importance+of+secondary+growth+economically&rlz=1C1ONGR_enMY974MY974&
sxsrf=APq-WBtud1gcDPq0HTwN-e_XINx8Bk4ANA%3A1648630145123&ei=gRlEYpiOB-
Go4t4PqLaboAg&oq=importance+of+secondary+growth+&gs_lcp=Cgdnd3M

Source of reference

• https://organismalbio.biosci.gatech.edu/growth-and-reproduction/plant-development-ii-
primary-and-secondary-growth/

• https://labs.plb.ucdavis.edu/rost/Tomato/Stems/secstem2.html#:~:
text=Secondary%20growth%20involves%20the%20thickening,
and%20the%20transport%20of%20nutrients.

• https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/
Book%3A_General_Biology_(Boundless)/30%3A_Plant_Form_and_Physiology/30.2%3A_Ste
ms/30.2C%3A_Primary_and_Secondary_Growth_in_Stems#:~:
text=Primary%20growth%20is%20a%20result,)%20or%20sunlight%20(shoots).

• https://en.wikipedia.org/wiki/Secondary_growth#:~:
text=In%20botany%2C%20secondary%20growth%20is,
gives%20rise%20to%20primary%20tissue.