Flowering Plant

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This is a Biology Article
Flowering Plant
Subject	Biology
Section	The Organism
Note

The Angiosperms are flowering plants. Angio means covered in, which tells us that the seeds are found enclosed in a special structure. Angiosperms are divided into a root, stem and leaf and posess a clear vascular system. They are sub-divided into two groups;

• Dicotyledons which produce seeds with two cotyledons(seed lobes)
• Monocotyledons which produce seeds with one cotyledon

These can either be Herbaceous or Woody. Herbaceous plants lack woody tissue.

Contents 1 The Life Cycle 2 The Herbacious Plant 2.1 The Root 2.1.1 Root Types 2.1.2 Functions 2.2 The shoot 2.3 The Leaf 2.3.1 Venation 2.3.2 Shapes 2.3.3 Phylotaxy 2.3.4 Functions 3 Seeds 4 The Flower 4.1 Layers 4.2 Functions 5 Woody Angiosperm(the horse-chestnut) 5.1 Appearance in winter 5.2 Appearance in summer

The Life Cycle

The life cycle of the angiosperm involves three key steps:

Germination -> Growth -> Production of seeds

• Empherals complete the life cycle several times in one year. E.g. Shepards purse
• Annuals complete the life cycle within one year. E.g. the sweet pea
• Biennals complete the life cycle once every two years. E.g. the carrot
• Perennials live for many years and produce seeds every year. E.g the rose

The Herbacious Plant

The Root

Root Types

1. The Tap Root: Many lateral roots growing away from the main road, which developed from the radical. This is found in Dicotyledons
2. The Fibrous Root: Any root that does not develop from a radical root, such as those found in grass. This is also known as an adventitious root and is found in Monocotyledons.

Functions

1. To anchor the plant in the ground
2. To absorb water and minerals
3. To store food (in some plants)

The shoot

• Leaves are attached to the stem at the 'nodes
• The gap between the two nodes is called the internode
• The bud at the tip is called the 'apical bud.
• Lateral' buds are found in the axil of a leaf

LAURENCE

The Leaf

A typical leaf consists of the flattened blade or lamina, a leaf stalk, the petiole and a leaf base. The petiole is wider where it joins the blade. On the lamina veins are visible. These canals transport food and water.

Venation

The arrangement of veins is called venation, of which there are two main types;

1. Netted/Reticulate: In this type, there is one or more veins (the midrib) from which smaller veins branch off. These smaller veins often branch off smaller and smaller again. Reticulate venation is typical of dicotyledons.
2. Parallel: Several veins of more or less the same side run side by side, mostly found in monocotyledons.

Shapes

• Simple: A single lamina
• Compuund
  • Pinnate: When the lamina is divided into leaflets all aranged along a central rachis, eg. the fern
  • Palmate: When leaflets radiate from the top of the petiole.

Phylotaxy

Phylotaxy is the arrangement of leaves

• Whorled: Two or more leaves in a circle around the same node
• Opposite: Pairs of leaves opposite each other the same node
• Alternate: Leaves singly at a node. Alternating 1st below third, second below fourth.

Functions

1. Photosynthesis
2. Transpiration of water in the form of vapour
3. Gaseous exchange

Seeds

• Through evolution, seeds have replaced spores for dispersal.
• They can resist harsh environments
• They are multicellular and more complex than a spore
• They contain food supply and a protective coat
• The can be monocotyledon or dicotyledon

The Flower

The flower can be born singly on a stem or grouped as an inflorescence. It consists of whorls or layers. In monocotyledons the parts (e.g. petals, stamen and carpels) are usually found in multiples of 3. In dicotyledons they are usually in multiples of 3 or 5.

Layers

• The Calyx: The outermost whorl. It consists of small green sepals. It protects the flower when it's a bud.
• The Carolla: The next whorl. It consists of brightly coloured petals which attract insects. A nectary, containing nectar, is found at the base.
• The Androecium: The third whorl, which consists of the stamen(which in turn consists of the anther and filament.) Male gametes are formed from pollen grains on the anther.
• The Gynecium: This is the innermost whorl. It consists of Carpels(Stigma, Style and Ovary.) The ovary holds ovules which in turn hold the female gametes

Functions

To produce seeds. The flower is the area of the plant involved in reproduction. It produces the male gaments on the stamen, and the female gametes on the carpel. The bright colours then serve to attract insects which help with pollenation.

Woody Angiosperm(the horse-chestnut)

An example of the woody angiosperm is the horse-chestnut. It is decidious and begins producing fruit in it's 20th year. It's leaves are shed in winter.

Appearance in winter

• The terminal and lateral buds are covered in bud scales
• The bud scales secrete resin which prevents a loss of moisture
• The lateral buds are in pairs at the node, opposite each other and at a 90degree angle to the pair above and below.
• In spring, bud scales fall off, leaving a scale scar. A group of these scale scars form a girdle scar. A twigs age can be determined by the number of girdle scars (equal to number of years)
• When leaves fall in autumn they leave behind leaf scars, on which are vein scars
• The twig is covered with tiny lenticles which are pores used for gaseous exchange.

Appearance in summer

• The Leaf: A compound palmate, with 7 leaflets of varied size
• The Flower: Candles grouped in an inflorescence. Pure white with splashes of dark red or yellow
• The Fruit: One or two seeds form inside the spikey green shell and form conkers