In fact, like any other living thing, they go through four crucial stages of development: birth, growth, reproduction and death. “But with some adaptive peculiarities that increase its life expectancy”, says biologist Solange Mazzoni, from the University of São Paulo (USP). First, trees perform so-called modular growth: since each part of the tree functions relatively independently, damaged tissue can be replaced by new tissue without the plant dying.
Second: unlike most other vegetables, trees also grow in thickness. The living part is concentrated in the outer region – in the core of the trunk, a rigid structure supports the plant. In addition, its chemical composition protects it from some of the most frequent enemies, such as fungi and insects. No wonder these big plants have been on the planet for so long. The first trees appeared 390 million years ago.
Some primitive species, such as Ginkgo biloba, which appeared 180 million years ago, cover China and Japan even today. But the lifespan of a tree varies greatly. A peach tree does not live longer than 30 years, while a giant sequoia, a species of American conifer, is over 3,000 years old. However, anyone who thinks that longevity is synonymous with a peaceful life is wrong. To give you an idea, 95% of seeds die before germinating.
Of the small percentage that overcome this first stage, only 5% survive the first year of life. There are dangers along the way: lack of water or nutrients in the soil, unexpected temperature variations, strong winds or even pollution – which can reduce the growth rate of a plant by up to 40%. The biggest problem, however, is still predatory deforestation. In Brazil alone, 0.5% of forests have been eliminated each year.
– (shih/iStock)
From seed to dust
A tree can last for millennia before it dies.
1 – CHILDHOOD
With a few days to live, the baby tree already has the essentials to survive: a root, which sucks water and mineral salts from the soil; the xylem, set of vessels that take the solution to the leaves, responsible for making food for the other parts of the tree; and the phloem, tissue that distributes nutrients from the leaves to the rest of the plant2 – ADOLESCENCE
The young tree stretches both upwards and downwards. At the tip of the stem and root is the meristem, tissue that promotes growth. Unlike what happens with other plants, the stem of the tree also thickens: the tissue called cambium creates new cells and fattens the plant.
3 – ADULT AGE
The tree becomes mature when it is ready to reproduce. Minerals and sugars are used to develop flowers – where fertilization of the ovules generate seeds – and fruits, which protect the seeds until they germinate. A tree like teak blossoms in just three weeks; oak takes more than 40 years
4 – ELDERLY AGE
In old age, growth slows down, regeneration processes are increasingly slower and the roots are no longer able to extract water and mineral salts from the soil in sufficient quantity. In the trunk, the vessels that carry nutrients stop working. The leaves fall, the branches lose their vigor, the bark comes off and the trunk can fall. It’s the end of life
LEAFY CANOPY
The leaves proliferate in the adult stage, when food production increases. An apple tree can have 100,000 of them. In general, tropical trees have leaves all year round. Species from temperate zones, such as oak and chestnut, called deciduous, lose their leaves in winter to combat water shortages. Thus, the plant transpires less and retains more liquid.
LIFE IN FLOWER
In species called gymnosperms, such as pines and cypresses, the flowers have no petals: the reproductive organs are uncovered. In angiosperms – ipê and paineira, for example – the colorful flowers attract insects, which carry the pollen to the flower’s ovule, fertilizing it. There are even species whose petals change color to warn that the egg has already been fertilized.
PRINCIPLE OF EVERYTHING
The seed has a protective shell and a reserve of nutrients to feed the embryo until the plant leaves. For germination to occur, the seed absorbs water and the embryo increases in size until it breaks the shell.
UNDERGROUND BASE
In the forest, most roots do not go deep into the soil: they stay close to the surface, where water and mineral salts are concentrated. They are very resistant: in general, the tree remains alive even after cutting up to 50% of the root.
BODY ERECT
The trunk has two sections: one live and one dead. The first focuses on the outer layers, where the tissues that transport nutrients and make the tree fat are located. The second (the heartwood) is in the core and it is this dead tissue that constitutes solid wood – which feeds the annual consumption of 2.3 billion cubic meters by the timber industry, equivalent to the felling of more than one billion trees
FRUITFUL STRATEGY
Fleshy and juicy food, the fruits attract animals that end up taking the seeds to germinate away from the parent tree. This is one of the main dispersal techniques in tropical forests. In cold regions, part of the trees have small fruits, which are scattered by the wind.