. Explain Phyllotaxy? What is Phyllotaxy the arrangement of leaf.


Best Answer

Leaves are arranged in different way to avoid shading one another and to provide sufficient light to the leaves.

There are three important types of Phyllotaxy: (1) Alternate (2) Opposite (3) Whorled

(1) Alternate or spiral

Here only a single leaf arises at each node.

If a string is passed around the stem along the bases of successive leaves at consecutive nodes, a spiral would be formed which is known as Genetic spiral.

On the basis of number of leaves in relation to spirals, alternate phyllotaxy is pided into following types:

(a) Distichous or two ranked or ½ Phyllotaxy:

Here leaves are arranged in two vertical rows.

There are two leaves in each spiral.

Angular pergence =  .

e.g. Ginger, Wheat, Rice, Oat.

(b) Tristichous or three ranked or 1/3 Phyllotaxy: 

Here leaves are arranged in three vertical rows.

There are three leaves in each spiral.

Angular pergence =  .

e.g. Cyperus rotundus.

(c) Pentastichous or five ranked or 2/5 Phyllotaxy:

Here leaves are arranged along five vertical rows.

There are five leaves in 2 spiral.

Angular pergence =  .

e.g. Chinarose, Banyan.

(d) Octostichous or eight ranked or 3/8 Phyllotaxy:

Here leaves are arranged along eight vertical rows.

There are eight leaves in three spirals.

Angular pergence =  .

e.g. Papaya.

(2) Opposite

Here two leaves are present at each node standing opposite each other.

Opposite phyllotaxy may be of two types.

(a) Superposed

Here a pair of leaves at one node stands directly over the lower pair. e.g. Guava, Quisqualis, Ixora.

(b) Decussate

Here leaves at each node stand at right angle to the adjacent pair, above or below. e.g. Calotropis, Mussaenda.

(3) Whorled

Here more than two leaves at each node, are arranged in a circle. e.g. Nerium, Alstonia (Devil’s tree).

 

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