Ronald A. Fisher, John B. S. Haldane and Sewall Wright- which showed that mutation and natural selection together cause adaptive evolution.

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Types of Leaf

Simple Leaf

Compound Leaf

The compound leaves may be of two types;

A number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf called Pinnately compound leaf

Ex- Neem 

The leaflets are attached at a common point, such as at the tip of petiole, called Palmately compound leaf

EX- poison ivy, familiar house plant Schefflera sp. (commonly called “umbrella plant”)

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Phyllotaxy

This is usually are of four types – alternate, opposite, spiral and whorled

In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower plants

Phyllotaxy

In opposite type, a pair of leaves arise at each node and lie opposite to each other as in Calotropis and guava plants.

If more than two leaves arise at a node and form a whorl, it is called whorled, as in Alstonia (Devil Tree) Apocynaceae

Spiral phyllotaxy

Fibonacci sequence

Golden Angle

the divergence angle between successively arising leaves is fixed at the golden angle of 137.5°

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Modification of leaves

Leaves are often modified to perform functions other than photosynthesis.

Succulent leaves are also thickened leaves, but they are found above ground, still conduct photosynthesis, and function primarily in water storage

Spines are sharp projections derived from leaves that function in plant defense. Almost all cacti (in the plant family Cactaceae)  barberry and some Acacia species have spines 

Spines can also be formed from stipules (stipular spines) or bud scales.

Tendrils are another structure that can originate from multiple structures, including stems, leaves, or leaflets. 

leaves of glory lily are modified as tendrils

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Phyllode resembles cladodes and phylloclade but refers to a flattened petiole that resembles a leaf blade (rather than a narrow stalk). 

Australian acacias (Acacia) have phyllodes

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Carnivorous plants, in these plants, leaves are modified as traps to capture insects or catch their prey in snap-closing traps made of modified leaf blades. 

Ex- cobra lily (Darlingtonia), various pitcher plants (Nepenthes),  the butterwort (Utricularia),and the best known, the Venus flytrap

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The Inflorescence

The stem holding this whole reproductive portion of a plant is called a peduncle.

The major axis above the peduncle called rachis bears the flowers or secondary branches. Also, each flower stalk in the inflorescence is referred to as a pedicel.

Types of Inflorescence

Based on the mode of branching of the main axis or peduncle, the main groups of inflorescences are: 

simple (single)

2)  compound, 

3)  mixed, and 

4)  special