Leaf development




According to Agnes Arber's partial-shoot theory of the leaf, leaves are partial shoots, being derived from leaf primordia of the shoot apex. Early in development they are dorsiventrally flattened with both dorsal and ventral surfaces. Compound leaves are closer to shoots than simple leaves. Developmental studies have shown that compound leaves, like shoots, may branch in three dimensions. On the basis of molecular genetics, Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties."

Comments

Post a Comment

Popular posts from this blog

Evolutionary adaptation

Image
In the course of evolution, leaves have adapted to different environments in the following ways: citation needed Waxy micro- and nanostructures on the surface reduce wetting by rain and adhesion of contamination ( See Lotus effect ). Divided and compound leaves reduce wind resistance and promote cooling. Hairs on the leaf surface trap humidity in dry climates and create a boundary layer reducing water loss. Waxy plant cuticles reduce water loss. Large surface area provides a large area for capture of sunlight. In harmful levels of sunlight, specialized leaves, opaque or partly buried, admit light through a translucent leaf window for photosynthesis at inner leaf surfaces (e.g. Fenestraria ). Kranz leaf anatomy in plants who perform C4 carbon fixation Succulent leaves store water and organic acids for use in CAM photosynthesis. Aromatic oils, poisons or pheromones produced by leaf borne glands deter herbivores (e.g. eucalypts). Inclusions of crystalline minerals deter herbivor
Read more

24) Republic Day 2020 Parade FEATURES: Colourful tableaux, daredevilry, navy might on display

India Republic Day -- The indian subcontinent Republic Day 2020 Parade, Flag Hosting HIGHLIGHTS: Primary Minister Narendra Modi paid out his tributes to martyrs by laying a wreath at the National War Memorial in the presence of Support Minister Rajnath Singh, the three service chiefs and Primary of Defence Staff Bipin Rawat. India Republic Morning Parade 2020, Flag Web host HIGHLIGHTS: India is drinking its 70th Republic Morning Today. The celebration with Rajpath started with Primary Minister Narendra Modi paying out homage to the fallen military at the newly-built National War Memorial on the Republic Morning for the first time instead of the Amar Jawan Jyoti beneath the India Gate arch. This was followed by Chief executive Ram Nath Kovind unfurling the tricolour. The special occasion marks the day when India’s Constitution came into effect, and also the country became a republic. Heavylift helicopter Chinook and also attack helicopter Apache, the two recently inducted in the Nat
Read more

Ecology

Image
Biomechanics edit Plants respond and adapt to environmental factors, such as light and mechanical stress from wind. Leaves need to support their own mass and align themselves in such a way as to optimize their exposure to the sun, generally more or less horizontally. However, horizontal alignment maximizes exposure to bending forces and failure from stresses such as wind, snow, hail, falling debris, animals, and abrasion from surrounding foliage and plant structures. Overall leaves are relatively flimsy with regard to other plant structures such as stems, branches and roots. Both leaf blade and petiole structure influence the leaf's response to forces such as wind, allowing a degree of repositioning to minimize drag and damage, as opposed to resistance. Leaf movement like this may also increase turbulence of the air close to the surface of the leaf, which thins the boundary layer of air immediately adjacent to the surface, increasing the capacity for gas and heat exchange, as well
Read more