the university of lahore

Slide 1: 

1/14/2010 9:39:45 PM Inflorescence 1 Inflorescence

Slide 2: 

1/14/2010 9:39:45 PM Inflorescence 2 An inflorescence is a mode of flowering.  It is how the plant presents itself in flowering. Two types exist:  determinate and indeterminate.  Determinate inflorescences, like in the picture above, have the oldest flower at the top of the plant with younger flowers under it.  Indeterminate inflorescences, as in the picture bottom left, have the youngest flowers at the top of the plant with older flowers below.  The bottom picture of the coleus indicates how these young flowers are at the top, the older more toward the bottom.

Slide 3: 

1/14/2010 9:39:45 PM Inflorescence 3 Here are three kinds of elongated inflorescences.  The top picture to the left shows a raceme.  The flowers have their own pedicle, or stalk, and they do not branch.  In the middle picture to the left a panicle is seen.  This is when the pedicles do branch.  Finally on the bottom left is an example of a spike.  Here, the inflorescence is obviously elongated, but the flowers have no pedicles at all.  Sometimes the term used here is sessile because the flowers are without stalks, or pedicles.  All of these are indeterminate.

Slide 4: 

1/14/2010 9:39:45 PM Inflorescence 4 There are three kinds of flat-topped inflorescences.  In the picture to the bottom top of a dissected inflorescence, a closer view would reveal that these flowers do not have any pedicles.  The term is capitulum, or head.  In the middle picture to the left, an umbel is shown.  Note that the pedicles visible are all of the same length.  In the picture to the bottom left you see a corymb.  This is a flat-topped inflorescence with pedicles of different length.  All of these are indeterminate.

Slide 5: 

1/14/2010 9:39:45 PM Inflorescence 5 Among the "special" types of inflorescences in plants, two stand out.  In the picture above is a catkin from a birch tree.  Catkins are typically unisexual, spikes, and apetalous.  They are normally involved in wind pollination.  In the picture below of the Jack-In-The-Pulpit, you see a spadix. That is the stalk surrounded by the cup and hood, which is a spathe.  The spadix contains many small flowers, probably sessile, and probably some either male or female flowers.  Members of the The Araceae family routinely present this type of inflorescence Very often the spathe is very showy.  These are all indeterminate.

Inflorescence : 

1/14/2010 9:39:45 PM Inflorescence 6 Inflorescence 1. Racemose inflorescence 2. Cymose inflorescence 3. Special types of inflorescence.

Inflorescence : 

1/14/2010 9:39:45 PM Inflorescence 7 Inflorescence Flowers are the reproductive structures in angiosperms. Each flower is a modified shoot adapted for purposes of reproduction. Flowers may occur either singly or in clusters. When clustered, the flowers are generally arranged on branches, which are quite distinct from the vegetative branches. Such a floral branch system is known as inflorescence. The main axis of the inflorescence is called the peduncle. Individual flowers are attached to this peduncle by stalks of their own. Stalk of each flower is called the pedicel. Stalked flowers are called pedicellate while the flowers without the stalk are called sessile.

Cymose Inflorescence : 

1/14/2010 9:39:45 PM Inflorescence 8 Cymose Inflorescence In cymose inflorescence, the main axis ends in a flower since the peduncle stops growing. The flowers show basipetal succession. The oldest flower is at the apex and youngest towards the base. When the flowers are clustered the arrangement is said to be centrifugal, Here, the oldest flower is at the centre and younger flowers are towards the margin. There are different types of cymose inflorescence.

Different Types of Cymose Inflorescence : 

1/14/2010 9:39:45 PM Inflorescence 9 Different Types of Cymose Inflorescence Solitary Cyme Monochasial Cyme Dichasial Cyme Polychasial Cyme

Solitary Cyme : 

1/14/2010 9:39:45 PM Inflorescence 10 Solitary Cyme This is the simplest type of cymose inflorescence where there is only a single flower. The flower may be terminal on a short peduncle or it may be axillary in position, e.g. Hibiscus, Thespesia.

Monochasial Cyme : 

1/14/2010 9:39:45 PM Inflorescence 11 Monochasial Cyme In this type of inflorescence, the peduncle ends in a flower. Subsequently one branch of the peduncle develops at a lower level and ends in a flower. This type of branching is repeated. If the branches are produced on the same side, the inflorescence is said to be a monochasial helicoid cyme. e.g. Hamelia, Drosera. If the branches are produced alternately in a zigzag manner, the inflorescence is called a monochasial scorpioid cyme. e.g. Heliotropium.

fig. Monochasidal Cyme : 

1/14/2010 9:39:45 PM Inflorescence 12 fig. Monochasidal Cyme

Dichasial Cyme : 

1/14/2010 9:39:45 PM Inflorescence 13 Dichasial Cyme In this type of cymose inflorescence, the peduncle produces a flower at its tip, subsequently the peduncle produces two branches simultaneously at a lower level. They also end in flowers. This type of branching is repeated. If the inflorescence has only three flowers, where the central flower is the oldest and the side ones are younger, it is called a simple dichasial cyme, e.g. Jasmine. If the inflorescence is branched it is called a compound dichasial cyme, e.g. Clerodendrom, Wrightia.

fig. Dichasial Cyme : 

1/14/2010 9:39:45 PM Inflorescence 14 fig. Dichasial Cyme

Polychasial Cyme : 

1/14/2010 9:39:45 PM Inflorescence 15 Polychasial Cyme In this type of inflorescence the main axis ends in a flower. Subsequently the peduncle produces many branches and each branch ends in a flower. The flowers show centrifugal arrangement. e.g. Hamelia

fig. Polychasial cyme : 

1/14/2010 9:39:45 PM Inflorescence 16 fig. Polychasial cyme

Racemose Inflorescence : 

1/14/2010 9:39:45 PM Inflorescence 17 Racemose Inflorescence In racemose inflorescence the main axis is capable of continuous growth and it does not end in a flower. The flowers show acropetal succession on the main axis. The older flowers are towards the base and younger flowers are towards the apex. Sometimes the main axis becomes shortened and the flowers become clustered. In such cases the flowers are said to show Centripetal succession. Here, older flowers are towards the margin and younger flowers are towards the centre. Racemose inflorescence may have elongated peduncles or shortened peduncles.

Racemose Inflorescence with Elongated Axis : 

1/14/2010 9:39:45 PM Inflorescence 18 Racemose Inflorescence with Elongated Axis

Simple Raceme : 

1/14/2010 9:39:45 PM Inflorescence 19 Simple Raceme It has a long peduncle on which a number of pedicellate flowers are produced in acropetal succession. e.g. Crotalaria, Erythrina

Panicle : 

1/14/2010 9:39:45 PM Inflorescence 20 Panicle It is a branched receme. Here, the peduncle produces a number of branches in acropetal succession. On these branches pedicellate flowers are again produced in acropetal succession. e.g. Mango.

Spike : 

1/14/2010 9:39:45 PM Inflorescence 21 Spike It has a long peduncle on which a number of sessile flowers are produced in acropetal succession. e.g. Amaranthus.

Catkin : 

1/14/2010 9:39:45 PM Inflorescence 22 Catkin It is a type of spike with a pendulous peduncle. The flowers are generally unisexual. e.g. Acalypha, Mulberry.

Spadix : 

1/14/2010 9:39:45 PM Inflorescence 23 Spadix It is also a type of spike with a fleshy peduncle. The flowers are generally unisexual. The inflorescence is always accompanied by a big bract called spathe, which almost covers it. e.g. Aroids. In Coconut and Areca nut the spadix is branched and is called a compound spadix

Racemose Inflorescence with Shortened Axis : 

1/14/2010 9:39:45 PM Inflorescence 24 Racemose Inflorescence with Shortened Axis Corymb Umbel

Corymb : 

1/14/2010 9:39:45 PM Inflorescence 25 Corymb The inflorescence axis is slightly shortened. The older flowers have the longer and the younger have the shorter pedicels. As a result of this, all the flowers of the inflorescence are found more or less at the same level. e.g. Caesalpinia

Umbel : 

1/14/2010 9:39:45 PM Inflorescence 26 Umbel In this type of inflorescence, the main axis is shortened and bears at its tip a whorl of bracts. From the axil of each bract a flower arises. All the flowers are more-or-less at the same level. The flowers show centripetal arrangement. When the peduncle is unbranched and bears a cluster of flowers showing centripetal arrangement, the inflorescence is called a simple umbel. e.g. Hydrocotyle. When the peduncle is branched, from the tip of each branch a cluster of flowers may be produced in an umbellate manner it is called a compound umbel. e.g. Coriander, Carrot.

- Racemose Inflorescence with Shortened Peduncle : 

1/14/2010 9:39:45 PM Inflorescence 27 - Racemose Inflorescence with Shortened Peduncle

Racemose Inflorescence with Flattened Axis : 

1/14/2010 9:39:45 PM Inflorescence 28 Racemose Inflorescence with Flattened Axis Head or Capitulum. This type of inflorescence is characteristic of the family Asteraceae. The peduncle is shortened and flattened into a structure called the receptacle. At the margin of the receptacle an involucre of bracts is present. From the top surface of the receptacle a large number of small, sessile flowers commonly referred to as florets are produced. The florets are of two types ray florets, arising from the margin, are zygomorphic and unisexual, and disc florets, present throughout the surface of the receptacle. They are actinomorphic and bisexual. The florets also show centripetal arrangement. e.g. Helianthus (sunflower).

- Head or Capitulum of Sunflower : 

1/14/2010 9:39:45 PM Inflorescence 29 - Head or Capitulum of Sunflower

A catkin : : 

1/14/2010 9:39:45 PM Inflorescence 30 A catkin : This is a spike-like inflorescence (i.e. the flowers do not have a pedicel and the main axis is elongated and unbranched) which has only male or female flowers. They occur in many woody trees such as the hazelnut and the willow.

A willow catkin (Salix sp) : 

1/14/2010 9:39:45 PM Inflorescence 31 A willow catkin (Salix sp)

A raceme : : 

1/14/2010 9:39:45 PM Inflorescence 32 A raceme : A raceme : This inflorescence has an unbranched main axis and all the pedicels of the flowers are more or less the same length.

Sweet pea (Lathyrus odoratus) : 

1/14/2010 9:39:45 PM Inflorescence 33 Sweet pea (Lathyrus odoratus)

Spanish broom (Spartum junceum) : 

1/14/2010 9:39:45 PM Inflorescence 34 Spanish broom (Spartum junceum) Chinese hat (Holmskioldia sp.)

An umbel : : 

1/14/2010 9:39:45 PM Inflorescence 35 An umbel : The peduncle of  this type of inflorescence bears all of the pedicels at its apex.

Slide 36: 

1/14/2010 9:39:45 PM Inflorescence 36 Hydrangea (Hydrangea macrophylla) Lantana (Lantana sp)

A compound umbel : : 

1/14/2010 9:39:45 PM Inflorescence 37 A compound umbel : A compound umbel : This is an example of a compound inflorescence type. The peduncle bears a number of primary pedicels at its apex. These do no bear flowers but a number of secondary pedicels at their apices which in turn bear the flowers.

Frangipani (Plumeria rubra) : 

1/14/2010 9:39:45 PM Inflorescence 38 Frangipani (Plumeria rubra)

A spike : : 

1/14/2010 9:39:45 PM Inflorescence 39 A spike : This inflorescence type has a long, unbranched main axis which bears flowers which have no pedicels or very short pedicels.

Silver oak (Grevillea robusta) : 

1/14/2010 9:39:45 PM Inflorescence 40 Silver oak (Grevillea robusta) Quiver tree (Aloe dichotma)

Gladiolus (Gladiolus sp.) : 

1/14/2010 9:39:45 PM Inflorescence 41 Gladiolus (Gladiolus sp.) Red hot poker (Kniphofia sp.)

A head (capitulum) : : 

1/14/2010 9:39:45 PM Inflorescence 42 A head (capitulum) : The flowers of this inflorescence type, which do not have pedicels, are grouped together on the top of a peduncle which may be flattened or rounded. Daisies (Asteraceae) are a good example and here the outer flowers may have one very large petal as in some members of this family. In other families the whole inflorescence may be surrounded by bracts e.g. the Proteas. This gives the impression that the whole structure is a single flower but it may in fact be hundreds of flowers grouped together.

Slide 43: 

1/14/2010 9:39:45 PM Inflorescence 43