Essay on Trees: Introduction, Habit and Kinds | Botany

Let us learn about Trees. After reading this article you will learn about: 1. Introduction to Trees 2. Tree Habit – Oldest Habit of Seed Plants 3. Trees: Longest-Lived Organisms 4. Different Kinds of Trees.

Essay # Introduction to Trees:

It is to be noted that a tree starts its life as a sapling growing from a seed as in most angiosperms. Forests are big assemblage of trees and other plants. In tropical rain forests, typically, the forest canopy is composed of three stories characterized by different types of trees.

The trees of the top, or dominant, story form a nearly closed canopy which is frequently 60 metres or more in height. The crowns of the second story are beneath those of the dominant story and like those of the dominant story, frequently form a nearly closed canopy.

The trees of the third or lowest Story are usually small and slender and have small open crowns. The presence of these three stories of different trees is not usually evident on casual observation for the composition of all the stories is very complex and few of the trees present any striking peculiarities.

Moreover smaller trees of a higher story always occur in a lower story as well as between the different stories’ while the different species of a story have different heights. Erect palms are frequently numerous in the lower stories.

Beneath the tree stories there is a ground covering. In dry areas, it may consist largely of woody plants, while in moist situation herbs and ferns are abundant. Some individual tall trees are called emergents which protrude above the general level of the canopy in tropical rain forests.

There are certain forests which are dominated by single species of trees such as oak (Quercus), beech (Fagus), pine (Pinus) or spruce (Picea), etc.

Structural diversity of trees can also be noticed. For example Banyan tree (Ficus benghalensis Linn., Family-Moraceae) is an enormous tree, 70 to 100 feet high, sending down roots from the branches, which enter the ground and form trunks, thus extending the growth of the tree indefinitely. Banyan is a common tree planted near temples and shrines, and an open ground near villages.

The roots of trees reaching ground act as pillars to support the branches. The trees have the biggest crowns of any in the world and with their aerial prop roots, a single tree looks like a small grove. The Banyan tree of botanical garden, Kolkata, has about 3000 trunks of which more than 2000 are 2 to 3 feet in diameter. About ten thousand people can get shelter under this tree at a time.

There are several other trees, e.g., Pipal tree (Ficus religiosa), Shisham (Dalbergia latifolia), Indian coral tree (Erythrina indica), Mahua tree (Madhuca indica), Jamun tree (Syzygium cumini). Tamarind tree (Tamarindus indica). Silk cotton tree (Bombax ceiba), etc., which are commonly found in north Indian plains and peninsular India.

In strict sense, all trees which are not cone bearing are flowering trees (angiosperms) while cone bearing trees are gymnosperms, e.g., Pinus, Cedrus, Cupressus, Picea, Abies, Araucaria, Cryptomeria, Ginkgo and Cycads.

There are several species of palms (Monocots: family palmaceae), such as oil palm (Elaeis guineensis), date palm (Phoenix dactylifera), coconut palm (Cocos nucifera), palmyra palm (Borassus flabellifer), betelnut palm (Areca catechu). Toddy palm (Caryota urens), etc. All palms have unbranched stems and crown of leaves on their tops.

The Baobab tree (Adansonia digitata Linn., Family-Bombacaceae) is known in India for many centuries, particularly along the western coast of this country. This is a strange looking tree. The great size attained by the trunk makes it strange looking. A soft-wooded tree, its trunk is about thickest in the world, suddenly tapering into thick branches.

In those parts of tropical Africa where the tree is indigenous, the trunk reaches 10 metres or more in diameter and this makes the trunk about 30 m in girth. This is an erect tree, seldom going over 20 m high.

Essay # Tree Habit – Oldest Habit of Seed Plants:

Tree habit is oldest habit of seed plants. They are perennial in habit living for many years. Due to secondary growth in dicots and gymnosperms they increase in thickness or girth.

California Coastal – redwood (Sequoia sempervirens) is considered a living fossil, the tallest tree of world, 112.6 m high. California Big Tree (Sequoiadendron giganteum) is also considered a living fossil, popularly known as ‘general sherman’ of 83.82 m height and 24 m girth or circumference.

The tree with greatest girth is sweet chestnut (Castanea sativa) of Mount Etna, Sicily. The tree is about 4000 years old. The girth or circumference is about 60 m or more.

Taxodium distichum var. mucronatum is also a tree with large girth of about 40 m, situated in St. Maria, Oaxaca.

Abies nobilis (noble fir) is another big tree about 84.73 m high and situated in Gifford Natural Forest, Washington.

Among angiosperms Eucalyptus regnans is tallest tree. The tallest tree, 150 m high is situated in Victoria, Australia.

Essay # Trees: Longest-Lived Organisms:

Trees are longest-lived organisms (plants). Some of long lived trees are mentioned here: Shorea laprosula, a tree of Dipterocarpaceae is more than 250 years old. Average age of Parashorea spp., is considered about 300 years. Most trees of tropical rain forests are 100 years old or so. Generally gymnosperms, such as Sequoiadendron giganteum are long-lived having average age of 3000 years.

Betula spp., (Birch tree) about 100-200 yrs; Acer rubrum (red maple) 100 years or more; Fraxinus spp., (Ash tree) about 150 years ; Quercus spp., (Oak tree), 800 to 1000 years; Ficus benghalensis (Banyan tree) 500 years or more; Sequoia sempervirens (California Coastal redwood) more than 2000 years; Sequoiadendron giganteum (California Big Tree) more than 3000 years; Pinus aristata (Bristle cone fern) more than 4500 years; Taxus baccata (Yew) more than 5000 years ; Dragon trees (Dracaena draco) of Sumatra, more than 10,000 years of age.

Taxus baccata (Yew tree) of Scotland is supposed to be of 5000 years age with a girth of about 17 metres. English Yew (Taxus baccata) lives upto 1000 years. English Oak (Quercus ruber) is also a long-lived tree and lives upto 400-500 years. Gymnosperms, such as coast and mountain redwoods of Western United States, some conifers and dragon trees of Sumatra are well established long-lived trees.

In some trees, during process of ageing in natural life cycle the branches and leaves fall off. For example in Dougluss fir or Xmas tree (Pseudotsuga mengies).

The leaves and branches fall off as shown in fig. 33.5. A, 8 year old tree; B, 30-40 years old; C, 50-60 years; D, 100 year old tree and E, 200 year mature tree, which may attain a height of 325 feet; F – G, after about 400 years where branches and leaves fall off and H, shows toppled down tree.

Essay # Different Kinds of Trees:

On the basis of their leaves, trees may be divided into three important categories.

They are as follows:

1. Conifers:

They possess needle and scale like leaves, e.g., Pinus, Cedrus, Cupressus, etc.

2. Broad-leaved trees:

They have flattened simple or compound leaves. Most of Dicotyledons, such as Bombax, Ficus, Butea, etc.

3. Monocotyledonous trees:

They are palms with crown-leaves, feathery in appearance, e.g., Borassus, Roystenia, Phoenix, etc.

Today broad leaved trees are dominant in tropical rain forests. Palms, generally occur in coastal regions. They are supposed to be ancient plants.

Conifers make the gymnospermous trees of today. However, they were dominant 300 million years ago but today they are found only in colder regions. Cycadales and Ginkgoales were dominant in Mesozoic era. Today Cycas revoluta and Ginkgo biloba are typical examples of living fossils.

Tree ferns are now rare and most of them are found in fossilised forms. Tree cacti are common plants of deserts.