Chapter 24: Kingdom Chapter 24: Kingdom PlantaePlantae

Leaving Certificate BiologyLeaving Certificate Biology

Higher LevelHigher Level

Structure of Flowering PlantStructure of Flowering Plant

• The flowering plant (also called angiosperm) is an example of a living organism that has organisational complexity– Root– Stem– Leaf– Flower– Seed– Vascular (transport) structures

Structure of Structure of Flowering Flowering PlantPlant

Structure of Flowering PlantStructure of Flowering Plant

• Function of root and shoot system:– Roots:

• Anchorage• Absorb water and minerals• Transport water and minerals up plant• Some root store food

– Shoot:• Transport water, minerals, food• Sexual reproduction• Photosynthesis

RootsRoots

• Types:– Tap roots: main root that originates from the

radicle at germination• Lateral: emerge from the primary root

– Fibrous roots: equal size roots that emerge from the stem – common in monocotyledonous plants, e.g. grass

Root ZonationRoot Zonation

• Protection: root cap protects growing tip• Meristematic tissue: region of high cell

production (mitosis) and growth• Elongation: new cells formed within the

meristem then elongate under the influence of growth regulators

• Differentiation: elongated cells differentiate into specialised cells (dermal, ground, vascular)

MeristemMeristem

• The meristem is the region of the shoot tip or root tip where there is rapid mitosis occurring and is responsible for the growth of the plant– The meristematic regions are present in the

root and shoot tips and in peripheral regions such as in the axillary buds, leaves and fruits

StemsStems

• The stem supports the plant and carries the leaves, flowers and fruits of the flowering plant

• Depending on the plant species the stem is either herbaceous (soft, green stem) or woody (hard, usually brown stem)

• The leaves and branches emerge from points on the stem called nodes – whereas the section in between the nodes is called the internode

• Woody stems also have lenticels present on their surface – which are responsible for gas exchange

Functions of the StemFunctions of the Stem

• Support

• Transport of water, minerals and food

• Herbaceous stems carry out photosynthesis

• Some store food

LeafLeaf

• The leaf is an organ of food production – the site of photosynthesis

• The leaf of a plant is attached to the stem or branch by the petiole located at the node

• The leaf is a flattened structure (blade/lamina) designed to capture sunlight

• The leaf has a midrib and veins which are continuations of the petiole and which contain vascular tissues

Leaf VenationLeaf Venation

• Leaf venation depends son the plant species and can be either parallel or net/reticulate– Parallel: veins run parallel to each other and

are most common in monocotyledonous plants such as grasses

– Reticulate: veins form a network of veins by branching out filling the leaf structure and are most common in dicotyledonous plants such as horse chestnut (see leaf structure on previous slide)

Function of the LeafFunction of the Leaf

• Photosynthesis and food production

• Gas exchange

• Transpiration – process of losing water

• Food storage

Flower StructureFlower Structure

Function of the FlowerFunction of the Flower

• The flower function in sexual reproduction by attracting insects (presence of nectar) and animals (seed and fruit formation after fertilisation)

Types of Plant TissueTypes of Plant Tissue• Dermal:

– Functions in protection by having a thick cuticle– Also has stomata and controls gas exchange– Also has root hairs and controls absorption of water

and minerals

• Ground tissue:– Is responsible for photosynthesis, food storage and

gives strength and support to the plant

• Vascular tissue:– Xylem: transports water and minerals– Phloem: transports food

XylemXylem

• Xylem is a vascular tissue made up of two different types of cell:– Xylem tracheids– Xylem vessels

• Tracheids: long, tapered, hollow and dead cells whose walls contain pits that allow water movement

• Vessels: they are strong (supported by lignin), long, hollow, dead, tubular cells with their end walls broken down to form a continuous tube throughout the tissue

TracheidTracheid

VesselsVessels

PhloemPhloem

• Phloem is a transport system running alongside xylem that allows products of photosynthesis to be redistributed by the plant

• Phloem consists of sieve tubes that transport the sugars and companion cells that help in transferring the sugars to the sieve tubes

Structure of Structure of PhloemPhloem

Xylem versus PhloemXylem versus Phloem

Transverse Section of the RootTransverse Section of the Root

Structure Structure of Leafof Leaf

Monocots versus DicotsMonocots versus Dicots• Monocotyledonous plants:

– 1 cotyledon (storage leaf) in seed– Mostly herbaceous plants – soft, green stem– Long, narrow leaf with parallel venation– Vascular bundles arranged randomly in stem– Petals, leaves arranged in 3s or multiples of 3

• Dicotyledonous plants:– 2 cotyledons (storage leaves) in seed– Herbaceous or woody– Broad leaves with network or reticulate venation– Vascular bundles arranged in ring in stem– Petals, leaves arranged in 4s or 5s or multiples of 4s

or 5s