How plants conquered land: evolution of terrestrial adaptation, study published in the Journal of evolutionary biology, makes a beautiful retrospective on this interesting issue, which directly concerns the history of the planet, with future implications related to the climate crisis and its problems.
The researchers explain: "The transition of plants from water to land is considered one of the most significant events in the evolution of life on Earth. The colonization of land by plants, accompanied by their morphological, physiological and developmental changes, resulted in plant biodiversity.
Besides significantly influencing oxygen levels in the air and on land, plants manufacture organic matter from CO2 and water with the help of sunlight, paving the way for the diversification of nonplant lineages ranging from microscopic organisms to animals.
Land plants regulate the climate by adjusting total biomass and energy flow. At the genetic level, these innovations are achieved through the rearrangement of pre-existing genetic information.Advances in genome sequencing technology are revamping our understanding of plant evolution.This study highlights the morphological and genomic innovations that allow plants to integrate life on Earth."
The primordial atmosphere began to be enriched with gaseous oxygen, which subsequently favored the evolution of all living beings.
The first organisms to develop were some unicellular eukaryotic forms, about 1.5 billion years ago. Starting from them, the first multicellular algae differentiated (700 million years ago) and slowly these autotrophic life forms gave rise to a great variety of living beings.
Among them, almost 300 million years later, simple pedunculate plants appeared capable of growing even outside aquatic environments. The real colonization of the emerged lands therefore took place around 450 million years ago and the evolutionary link between the multicellular green algae and the plants that still today cover the entire earth's surface is recognized.
This is demonstrated by numerous facts: the photosynthetic pigments of algae and plants are the same (chlorophylls and carotenoids), the presence of cellulose in the cell walls, similarities between some steps in biological cycles and more.
About 430 million years ago, the first plants with a vascular system (tracheophytes) detached from a group of bryophytes (to which mosses belong) direct descendants of the ancestral algae. Some tissues specialized in these to give rise to the various organs that performed the task of anchoring the plant to the substrate (roots) and making the most of the energy deriving from sunlight (stems).
Among these, xylem is a specialized tissue that arises from the need to transport water and mineral ions dissolved in it through the plant. The phloem, another specialized tissue, obviated the other transport need, the one linked to the products of photosynthesis.