Plant Biology.pdf

Prepared by: Samuel C. Brillo, MSc-Biology (cand.)
MODULE 1A
ORGANISMAL BIOLOGY:
PLANT BIOLOGY

Plant Biology consists of three subtopics:
• Module 1A.1 Plant Form and Function
• Module 1A.2 Plant Nutrition and Transport
• Module 1A.3 Reproduction and Development of Flowering
Plants

MODULE 1A.1
Plant Form and Function

• define plant anatomy, plant morphology, and plant physiology
• describe diversity of plant forms
• illustrate different functions essential for plant’s survival

Plant Anatomy
deals with structure; in-depth detailed
examination in order to identify
position, relations, structure, and
function of body parts

Plant Morphology
the study of the physical form and external
structure of plants; is the general term for
the study of the morphology (physical form
and external structure) of plants

The Plant Body
1. Root system (the one that we
don’t see; below the ground –
composed of root)
2. Shoot system (the one that we
see; above the ground –
composed of stem, leaves,
flowers, and fruits)

Key Features:
• The outer layer (epidermis) may have
protrusions called root hairs to increase
available surface area for material
exchange
• The central region is called the stele and
is surrounded by an endodermis with a
Casparian strip (controls water transport)
• The pericycle / cambium provides
strength to the root and is also
responsible for the development of lateral
roots
• The vascular bundle is located centrally to
withstand stretching forces and allow for
material transport to be controlled

Key Features:
• The epidermis covers the outer surface and
functions to waterproof, protect the stem and
control gas exchange
• The ground tissue (cortex and pith) is found
internally and assist in the transport and
storage of materials within the stem
• The cambium is a centrally located, circular
layer of undifferentiated cells responsible for
lateral growth of the stem
• Vascular bundles are arranged in bundles
near the outer edge of the stem to resist
compression and bending
• The xylem is located to the interior side of
the bundle and the phloem is on the exterior
side (phloem = outside)

•Anatomy of Leaf
Leaf. It is usually a
green, flattened, lateral
structure attached to a
stem and functioning as
a principal organ of
photosynthesis. This is
also the part where gas
exchange (CO2-O2)
occur.

Key Features:
• Palisade mesophyll is the site of
photosynthesis and hence is located on
the upper surface of the leaf (facing
sunlight)
• Spongy mesophyll is the main site of gas
exchange and is hence located on the
lower surface of the leaf (near stomata)
• Stomata are on the underside of the leaf
(prevents obstruction so as to maintain an
open channel for gas exchange)
• The top surface of the leaf is covered by a
thick, waxy cuticle (prevents water
absorption which would affect
transpiration)
• Vascular bundles (including xylem and
phloem) are located centrally to allow for
optimal access by all leaf cells

PISTIL
Anatomy of Flower
Flower. This organ
is present in
angiosperms only (or
flower-bearing
plants). It possesses
whorls of often
colorful petals or
sepals, and bears the
reproductive parts.

Anatomy of Seed
Seed. This is the
mature ovule of a
flowering plant. It is
considered as the
embryo, which bears
young plant.

Anatomy of Fruit
Fruit. It is a seed-
bearing structure of a
plant which is
formed from the
ovary.

Plant Physiology
deals with ways that
plants function

Plant growth and development
◉ Plant growth = starts from seed
germination and continues to
maturity
◉ Plant growth and development
involves combination of 2
important processes:
1. Cellular responses
2. Molecular interaction

Water uptake
◉ It allows plants to metabolically
utilize the chemical compounds and
micronutrients obtained from soil.
◉ This is possible due to the presence of
root hairs, which increase surface
area of roots for water uptake.

which increase surface area of
roots for water uptake.

Hoefenagels, M. Biology: Concepts and Investigations. McGraw-Hill, 2017.
Hopkins et. al., Introduction to Plant Physiology. Fourth Edition. Wiley Publishing, 2008.
Mader, S.S. Concepts of Biology. McGraw Hill Publishing, 2014.
Rea, M.A. & Dagamac, N.H. General Biology 2. REX Book Store, 2017.
http://www.houstonisd.org/cms/lib2/TX01001591/Centricity/Domain/26047/Plant%20Anatomy%20and%20
Physiology.pdf
Physiology.pdf
Physiology.pdf

MODULE 1A.2
Plant Nutrition and Transport

 define plant nutrition and transport
 describe the structure of organs and tissues involved in plant
transport
 illustrate pathways of nutrients throughout plants

VASCULAR BUNDLE IN ROOTS
In monocotyledons, the stele is large and vessels will form a radiating circle around the central pith
• Xylem vessels will be located more internally and phloem vessels will be located more externally
In dicotyledons, the stele is very small and the xylem is located centrally with the phloem surrounding it
• Xylem vessels may form a cross-like shape (‘X’ for xylem), while the phloem is situated in the surrounding gaps

VASCULAR BUNDLE IN STEM
In monocotyledons, the vascular bundles are found in a scattered arrangement throughout the stem
• Phloem vessels will be positioned externally (towards outside of stem) – remember: phloem = outside
In dicotyledons, the vascular bundles are arranged in a circle around the centre of the stem (pith)
• Phloem and xylem vessels will be separated by the cambium (xylem on inside ; phloem on outside)

MODULE 1A.3
Reproduction and Development of
Flowering Plants

 define plant growth, plant development, and plant reproduction
 explain how plants develop through primary and secondary
growth
 illustrate how flowering plants reproduce

MERISTEMS
Meristems are tissues in a plant consisting of
undifferentiated cells capable of indeterminate
growth.

PRIMARY AND
SECONDARY GROWTH
An irreversible increase in the size of the plant;
Size increase by cell division and enlargement,
including synthesis of new cellular material and
organization of subcellular organelles.

PLANT HORMONES
Plant growth and development are
controlled by plant hormones
(phytohormones).

Summary of the Main Classes of Plant Hormones

PLANT
REPRODUCTION
Sexual reproduction in flowering plants involves
the transfer of pollen (male gamete) to an ova
(female gamete).

• The transfer of pollen grains from an anther
(male plant structure) to a stigma (female
plant structure)
• Many plants possess both male and female
structures (monoecious) and can potentially
self-pollinate
• From an evolutionary perspective, cross-
pollination is preferable as it improves
genetic diversity
• Fusion of a male gamete nuclei with a female gamete
nuclei to form a zygote
• In plants, the male gamete is stored in the pollen grain
and the female gamete is found in the ovule
• Fertilization of gametes results in
the formation of a seed, which
moves away from the parental plant
• This seed dispersal reduces
competition for resources between
the germinating seed and the
parental plant
• There are a variety of seed
dispersal mechanisms, including
wind, water, fruits and animals
• Seed structure will vary depending
on the mechanism of dispersal
employed by the plant

Cross-pollination involves transferring pollen
grains from one plant to the ovule of a
different plant
Pollen can be transferred by wind or water,
but is commonly transferred by animals
(called pollinators)
Pollinators are involved in a mutualistic relationship with the
flowering plant – whereby both species benefit from the
interaction
The flowering plant gains a means of sexual reproduction
(via the transference of pollen between plants)
The animal gains a source of nutrition (plants secrete a
sugar-rich substance called nectar to attract pollinators

SEED GERMINATION
Germination is the process by which a seed
emerges from a period of dormancy and
begins to sprout.

The first step in the germination process is the metabolic
activation of a dormant seed
Germination begins with the absorption of water, which
causes gibberellin to be produced
Gibberellin triggers the synthesis of amylase, which
breaks down starch into maltose
Maltose is either hydrolyzed (to glucose) for energy, or
polymerized (to cellulose) for cell wall formation
This energy and cellular building blocks is used to
promote cell division and the growth of a nascent shoot
Once the seed is metabolically activated,
germination proceeds according to the following
stages:
•The seed coat (testa) ruptures and the embryonic
root (radicle) grows into the ground to extract key
nutrients and minerals
•The cotyledon emerges and produces the growing
shoot’s first leaves
•The growing plant can be divided into the epicotyl
(embryonic shoot), hypocotyl (embryonic stem)
and developing roots

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