Have you ever noticed that trees don’t grow taller after reaching a certain height? You can see the similar height of trees, especially those of the same species. But, why don’t they reach hundreds of meters into the sky – even though they live for a very long time?
Same with human beings, the growth of trees slows down as they age and ceases at a certain height. For instance, the Rowan tree grows around rapidly each year as a young tree. But once it reaches 90 years old, it will start to rise slowly around a foot and a half each year. Then, by the age of 150, it will no longer increase in height, even if the tree may live for another 50 years.
Various factors can affect a tree from growing, such as the climate, abundance of rainfall, nutrients found in the soil, and the presence of other trees. However, there are many theories concerning other factors on why they don’t reach skyrocketing heights.
One theory suggests that the cells of a tree act like animal cells, meaning they will cease growing once they reach a specific number of cell divisions. If the cells in the tree stop dividing, it will longer get any taller. There are many experiments done about this theory, though, nothing has been conclusive yet.
Another theory talks about the two opposing forces that impact a tree’s height. One force pulls and holds the tree downward, while the other force pushes it upward. Biologists infer that the theoretical maximum height a tree can grow is the point where these two forces balance each out.
Researches also found that trees in the forests have an innate desire to grow the highest they could to surpass other trees and get the maximum. However, gravity causes resistance, making it harder for the tree to transport water and nutrients from the roots to the canopy. That is also why leaves tend to grow smaller as a tree grows taller.
Moreover, the cells inside the leaves and branches of the trees are brimmed with water themselves, seemingly kike how air inflates a bicycle tire. Scientists believe that as trees increase in height, leaf water stress or resistance also increases, limiting the ability for further height growth.
While a tree wants to overtake other trees, it comes to a certain point that longing for sunlight is no longer cost-efficient for itself. That is because the energy it consumes to bring water onto the top for photosynthesis surpasses the amount it gains in the process, offsetting the effort to do so.
The tallest trees in the world are the Coast Redwoods (Sequoia sempervirens), which can reach more than 350 feet. The world’s largest known ever recorded is the ‘Hyperion’ from California, which stands around 379 feet and 4 inches. It trumped the previous record-holder, Stratosphere Giant,’ which stands at 369 feet. Scientists estimated that trees could only grow just above 400, due to the given challenges of transporting water from the roots up to the canopy.
But while trees stop getting taller after reaching a specific height, they never really stop ‘growing’ per se. Instead, they add width on their trunks, make new branches and sprout fresh leaves throughout their lives.
More Readings:
- Tree (Wikipedia)