Today we are going to talk about what we could call the wisdom of plants in the face of death, at least in the face of the annual death of one of its most important parts: the leaves.
I was talking about this matter back in November 2002. This program belongs, therefore, to the Quilo Vintage series and, as usual in this series, we are going to visit what was known at that time about the mysterious phenomenon of color change that numerous species of trees experience in their leaves in autumn, just a few weeks before their death and their falling from the branches.
As you can listen to on the podcast and read here, the matter deserved an intense debate fifteen decades ago among scientists interested in the biology of deciduous trees.
There was no shortage of hypotheses to try to explain the reason for the increase in anthocyanins in the run-up to the death of the leaves of many trees. However, those mentioned in that article are not the only hypotheses, and some more have been postulated. The reason is probably that several of the proposed hypotheses do not hold up very well. For example, the hypothesis that anthocyanins shield from sunlight to allow photosynthesis when chlorophyll content is declining has the inconsistency that if chlorophyll is missing, photosynthesis is not possible. On the other hand, it is difficult to explain why, under conditions of less solar radiation, chlorophyll decreases if what the plant wants is for photosynthesis to continue. In conditions of less sunlight it seems more sensible to increase rather than decrease chlorophyll to maximize photosynthesis. Yet science has shown time and again that what once seemed sensible actually wasn’t so, or not at all, and that things often have deeper reasons than meets the eye.
One of the new hypotheses that have been postulated over the past two decades is that anthocyanins may serve to trap heat and allow higher functioning of plant metabolism, including photosynthesis, to still occur. This hypothesis also seems sensible, since darker pigments, such as red or purple anthocyanins, can generally heat up more efficiently when exposed to sunlight. Obviously, in the height of summer, capturing heat would not be necessary and the plants would not produce anthocyanins.
Yet another of the most interesting hypotheses, in my humble opinion, is that anthocyanins play a role in the reabsorption of nutrients stored in the leaves before the plant finally sheds them. Indeed, recovering the maximum amount of nutrients from the leaves and storing them in other parts of the plant, such as the trunk and branches, is important before deciduous trees finally go into hibernation. These nutrients can be essential to generate new leaves in spring. This hypothesis has evidence that supports it, but also with others that deny it.
The hypothesis that anthocyanins would protect plants against certain animals, particularly against certain insects, has also received support in the last two decades. Autumn migration is an important part of the life cycle of many insects, particularly various species of aphids, a family of insects to which aphids belong, which feed by sucking sap from plants. Some studies have shown that the red leaves of certain trees attract fewer commensal insects than the green ones.
As we can see, the mystery of the color change of the leaves of many tree species in autumn has not yet been solved. What does seem to be clear is that anthocyanin production has a strong genetic basis that is little influenced by the environment, as experiments in which trees have been transplanted from their usual environment to a different environment have shown. This strong genetic base indicates that the production of anthocyanins has an evolutionary raison d’être, and that the genes responsible for their production have been selected during the evolution of the plant species that require them. However, the exact reason or reasons remain unknown. Let’s hope it doesn’t take another two decades to discover them.
Works by Jorge Laborda.
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Your defenses against coronavirus
Your defenses against coronavirus
Deflamed immunology: An introduction to the immune system and its pathologies
Deflamed immunology: An introduction to the immune system and its pathologies
Deflamed immunology: An introduction to the immune system and its pathologies
Kilo of Science Volume XII eBook
Kilo of Science Volume XII Paper
Kilo of Science Volume I. Jorge Laborda
Kilo of Science Volume II. Jorge Laborda
Kilo of Science Volume III. Jorge Laborda
Kilo of Science Volume IV. Jorge Laborda
Kilo of Science Volume V. Jorge Laborda
Kilo of Science Volume VI. Jorge Laborda
Kilo of Science Volume VII. Jorge Laborda
Kilo of Science Volume VIII. Jorge Laborda
Kilo of Science Volume IX. Jorge Laborda
Kilo of Science Volume X. Jorge Laborda
Kilo of Science Volume XI. Jorge Laborda
Matrix of homeopathy
Chained circumstances. Ed.Lulu
Chained circumstances. Amazon
One moon, one civilization. Why the Moon tells us that we are alone in the Universe
One moon, one civilization. Why the Moon tells us that we are alone in the Universe
One Moon one civilization why the Moon tells us we are alone in the universe
The thousand and one bases of ADN and other science stories
Adenius Fidelius
The intelligence funnel and other essays
The gods have been cloned