Catkin

Catkins are a flower cluster, it is cylindrical in shape and is quite slim. It usually lacks petals, in some cases, they might have a very small number of petals on them. Catkin is also known as ament. They are unisexual flowers. They have the characteristic feature of attachment of all the flowers to a single stem, these flowers are in close association with each other. Catkin-bearing plants include the following genre of plants Betulaceae, Fagaceae, Moraceae, and Salicaceae. The common examples of catkins are birch catkin, alder catkin, hazel catkin and, pussy willow catkin.

Catkin Diagram

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Evolution of Catkin

The evolution of the catkin based on the molecular phylogeny is traced back to the polyphyletic group called Hamamelididae. Based on the phylogenetic studies it is proved that catkin has a convergent evolution pattern. A convergent evolution pattern has arisen in Fagales and Salicaceae. Catkin is the name that originated from the dutch and german origin word “katteken” which means kitten. It is named so because of the close resemblance with the kitten tail. 

Willow Catkin

Willow catkin belongs to the family Salicaceae family, these family includes willow, poplar, aspen, and cottonwoods, these family include 56 genre, 1220 species, all the members of this family are trees or shrubs with alternate leaf arrangement. Some of the members of these families are found in the temperate region, trees in the temperate region are deciduous. Another characteristic feature of this group is the presence of the scaloid tooth. 

Willow catkins are also generally referred to as the pussy willow, they belong to the genus Salix, pussy willow are normally referred to as the catkin which is in their early developmental stage or young stage. Catkin and willow catkin are used interchangeably. Among various species following are the most widely known willow catkin.

1. Goat Willow -  It belongs to the species Salix capera it is the predominant native species found in northwest Asia and northern Europe.

2. Grey Willow - It belongs to the species called Salix cinerea they are a small population native to northern Europe.

3. American Pussy Willow - It belongs to the species known as Salix discolor, they are native to North America

Birch Catkin

Birch catkin is a subgroup of the family Betulaceae, which is commonly known as the birch family. It includes six genres and around 167 species. Among all of the species of birch, the catkin majority are deciduous. There are six well-known and studied species of the birch family which include, birches, hazels, alder, hornbeams, hazel-hornbeam, and hop-hornbeam. Birch catkins have a distinct feature of the appearance of catkins at first, even before the appearance of leaves. Betulaceae family (birch), all the subgroups within the family belong to the angiosperm category. 

Phylogeny of Betulaceae - The phylogenetic relationship of Betulaceae can be defined as it is divided into two subfamilies which are, Coryloideae and Betuloideae, they are further divided into various sub-groups which causes diversification on the morphological features of the family. 

Uses - Birch family are generally used as ornamental trees because of their smooth bark and bright colours, because of their hardwood they were used to make wheels and furniture in the past.

Alder Catkin

Alder catkin is the subgroup of the Betulaceae family, commonly known as the birch family, they are classified under the genre Alnus. The scientific name of the common alder species is Alnus glutinosa. They are native to Europe with the exception that they are not found in the extreme north and south of the continent. The etymology of the word comes from the old English word “alor”. They are generally deciduous, with both male and female catkins present on the same tree, that is they are monoecious. The only difference between an alder catkin and a birch catkin is that the female catkins of alder are woody in nature and do not disintegrate post maturation rather they open the catkin for seed dispersal. Alder catkins usually follow seed dispersion by wind but sometimes dispersion can be mediated by the bees.

Ecological Importance

Alder trees have huge ecological importance they are mostly found in symbiotic association with nitrogen-fixing bacteria. This symbiotic relationship is mandatory for nitrogen fixation by the microbe. Nitrogen fixation is the prime step of nitrogen cycling, it also ensures that the fertility of the soil is maintained. 

Alder catkins also serve as the food source of various birds including siskin and goldfinch.

Use of Alder Catkin 

There are the following important uses of alder,

1. It is used to make musical instruments such as guitar.

2. Alder wood has high water resistivity that is it can withstand rotting in water, so it is used to make boats and plywoods.

3. Alder wood and bark are traditionally used as tannin in the leather industry.

4. Alder catkins are also used in the food industry as a spice, it is also used to smoke coffee to give it texture.

Hazel Catkin

Hazel also belongs to the family Betulaceae, it comes under the subfamily known as Coryloideae. Hazel belongs to the genus Corylus. They are monoecious angiosperms, that is they have both male and female flowers on the same plant. The fruit of hazel is known as hazelnut and it is predominantly found in Eastern Asia and Europe. They perform self-pollination and also use wind for seed dispersal. Each male catkin is covered by a white scaly layer that bursts open at maturation to disperse the seeds through the wind. After the pollen release, the male pollen dry's off and falls from the stem.

Uses of Hazel - There are the following uses,

1. Hazel fruit is known as hazelnut and all the variety of hazelnut are edible

2. These are used as ornamental trees.