Plant maize is a staple crop and member of the grass family. A new study shows how the grass leaf evolved. Credit: Annis Richardson.
Grass is cut by our mowers and grazed on by cows and sheep. The shape of its leaves is one of the secrets to its amazing regeneration powers.
The debate is relevant to our crops because they are members of the grass family with the same type of leaf.
The John Innes Centre team has been working with other universities to understand the mystery of grass leaf formation.
The grass leaf has been a problem according to Professor Coen. By testing different models for its evolution and development, we have shown that current theories are likely incorrect and that a discarded idea proposed in the 19th century is much closer to the mark.
There are two types of flowers: monocots and Eudicots. The grass family of monocots have leaves that encircle the stem at their base and veins throughout. Eudicot, which include brassicas, legumes and most common garden shrubs and trees, have leaves that are held away from the stem by stalks, and typically have broad laminas with net-like veins.
The sheath is a tube-like structure in grasses. The sheath protects the plant from the blades of lawnmowers and incisors of herbivores by increasing the plant's height and keeping its growing tip close to the ground.
The grass sheath was thought to be the same as the eudicot leaves. The view was challenged in the 20th century when plant anatomists found that the grass leaf was derived from the petiole.
The team used recent advances in modeling and genetics to revisit the problem of grass development. They tested the predictions of the different models against the experimental results. The model based on the 19th century idea of sheath-petiole equivalence was more supported than the current view.
This is in line with findings in animal development where a discarded theory about thebelly side of insects was vindicated in the light of new genetic research.
The grass study shows how simple changes in growth rules can create a remarkable diversity of leaf shapes, without the need for our gardens and dining tables to be poorer.
The journal Science has a paper titled "Evolution of the grass leaf by primordium extension and petiole-lamina remodeling."
Annis Richardson and her team have information on the evolution of the grass leaf. www.science.org/doi/10.1126/science.abf9407
Science journal information.
The grass leaf dilemma was solved by scientists on 9 December 2021.
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