Trees Are So Weird

Plants evolved from ocean-dwelling ancestors to conquer land approximately 470 million years ago. A key evolutionary innovation was lignin, a rigid and tough macromolecule that allowed plants to grow taller, leading to the development of wood around 385 million years ago. This enabled the first trees to emerge, becoming the largest living beings and initiating a competition for sunlight.

Trees grow through the cambium, a thin layer of stem cells. Inward-growing cells become xylem, which are a 'conveyor belt of death'. These cells produce lignin, hollow out, and then die, forming hard, empty tubes. These dead cells stack to create wood, a giant network of pipes extending the tree's length. This system efficiently transports water using the adhesive properties of water molecules and the process of transpiration in the leaves, creating an immense pulling force capable of lifting water over 100 meters.

The cambium's outward-growing cells form the phloem, which transports sugar (produced in the leaves) and information throughout the tree. Phloem consists of sieve cells, which self-destruct their organelles to become living transport tubes, and companion cells, which maintain the sieve cells. Parenchyma cells in the phloem store nutrients, repair damage, and produce defensive compounds. Another layer of stem cells outside the phloem produces bark, which is also made of dead cells and protects the tree's vital living layers.

The living part of a tree is an extremely thin layer, supported by vast amounts of dead cells (wood and bark). This unique structure means trees don't age in the same way as other organisms and can be potentially immortal, with some living for thousands of years, limited mainly by external factors like disease or human interference. Trees are a highly successful life strategy, having taken over the planet and currently numbering three trillion globally. The video emphasizes the need to protect these vital ecosystems and promotes Planet Wild's conservation efforts.

The video partnered with Planet Wild, a community-based nature protection organization that funds conservation projects worldwide. Viewers are encouraged to join Planet Wild to help restore nature, with the first 100 people using code KURZGESAGT11 getting their first month paid. Additionally, the video promotes Kurzgesagt's 10-year anniversary Human Era Calendar and their first artbook, along with a video poster, which support the channel's creation of human-made art.