Do Trees Grow From The Top Or Bottom?

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Trees are a stunning feature of our environment. They are not only beautiful and relaxing to look at, but they also offer a haven for creatures, oxygen and shade to humankind and are vital to our ecosystem’s survival.

The seed primarily depends on the nutrients it carries from the parent tree to grow into a tree. The seed sprouts and sends out its first root and stem after it has found the ideal location to begin the growth process, transforming into a seedling with the perfect combination of water, light, temperature, soil, and nutrients.

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Meanwhile, the seedling’s roots attach to the soil and absorb water and nutrients to fuel further development. The stem of the seedling bursts through the soil surface after it has grown enough strength. When the seedling’s leaves are big enough, it may begin to manufacture its food via photosynthesis and the meristem development process continues.

Trees do not grow like humans, where each part or organ grows as humans evolve. New cells proliferate under the bark and the branch tips grow extensively, but not the trunk. The trunk grows as well but much in diameter, not in height. This happens because trees develop by making new cells in a restricted number of locations across the tree, known as meristems.

Apical meristems grow from the tree’s roots and branch tips and allow them to expand in length/height. Each year, the vascular cambium generates new xylem and phloem, increasing the diameter of the trunk, branches, and roots.

The trunk of a tree grows by one annular ring per year as it grows from the roots up. The upper branches and leaves flourish, but the lower branches die off unless someone or something prunes them and stimulates new growth.

Where Does Growth In A Tree Take Place?

Meristems responsible for tree growth are a kind of tissue containing cells that can divide and produce new cells. In general, cells divide, lengthen, and differentiate into structures like roots and shoots throughout development. Primordia are meristems that may generate new meristems from their meristems. Apical meristems in a bud, for example, are responsible for the formation of new meristems known as leaf primordials. Each leaf primordium will eventually develop into a new leaf of its own.

Tree branches are made up of live cells that cause branches to grow longer and the tree to grow higher as it takes on the height and shape of its species.  A thin layer of cells under the bark causes the tree’s circumference to expand. It develops from the bottom up rather than from the top down. 

Growth in the Broadest Sense

Trees grow primarily in the reverse direction, from the top down. However, for a tree to grow, there are two ways it may do so. Every branch’s tip produces new sprouts, allowing the tree to grow taller and quickly spread outwards. Trunk, roots, and twigs grow as the tree grows, making them fatter. The tips of branches may grow faster. The increase in circumference is less noticeable but not insignificant. 

Every year, the tree’s height and width expand, necessitating an increase in the trunk’s thickness to support the growing tree. Each year, the trunk adds a new ring to its structure. The number of rings on a tree depicts its age.

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Below-Ground Development

The length, diameter, and several roots may all increase. The root cap is located at the root’s tip. As a root pushes through the earth, this cap protects it and must be changed regularly. A meristem is located behind the root cap and creates new cells for the root cap and root elongation. These new cells expand, divide, and develop into root sections as it pushes through the soil.

The vascular cambium generating wood (xylem) and bark produces root diameter growth identical to that of the stem (phloem). The distinction between root and shoot diameter growth is that a root cambial development is substantially more irregular, resulting in oval or irregular roots in cross-section, and horizontal roots have a higher fluctuation in diameter with age than vertical roots.

Roots may also sprout and branch off the primary root, forming additional lateral roots. A new root primordium is produced by specific cells in a layer within the root. The root is pushed out through the parent root by this new meristem, which splits and elongates.

Development Above-Ground

Growth of the Sprouts

At the terminals of the branches, the sprouts lengthen or increase in height. The final buds at the terminals of the shoots contain apical meristems. The apical meristem’s cells divide, extend, and develop in discrete steps, the bud at the branch’s tip opens, leaves grow and get more prominent and the space between the leaves becomes wider. 

Similarly, the peripheral buds too develop; however, they are generally inactive and do not emerge until pruning.

Growth Of The Leaves

A new meristem forms on the surface of the apical meristem in the bud. A leaf primordium is a new meristem where cells divide and develop into a leaf. A new bud primordium (meristem) forms at the base of each leaf stem. Once established, this auxiliary bud can become a branch, although it may remain dormant for many years.

Growth In Diameter

The vascular cambium is a thin layer of dividing meristematic cells between the wood and the bark. The cambium splits, resulting in new wood on the inside and bark on the tree’s exterior. The diameter of the trunk and branches grows due to the additional cells. The xylem, or new wood cells, transport water and minerals from the roots to the leaves.

The outer bark of all woody trees is continually renewing and protects the tree against insect assaults and environmental factors such as fire and mechanical injuries. Some trees have thick, abrasion-resistant bark. Others are vulnerable to damage due to their thin bark. The exterior section of the tree has to yield as it develops in thickness, resulting in ridges and fractures in the bark. The outer bark eventually sloughs off.

The Concluding Thought

A tree’s life depends on sunshine, water, and nutrients. The crown of the tree, the trunk, and the roots are the three essential components of a tree that utilise light, water, and nutrients. The bulk of a tree’s trunk is deadwood, but the activity occurs just under the rough bark. Straw-like cells transfer water and nutrients from the roots to the crown, whereas sugar-transporting cells transport sugars to the roots.

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