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Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
The wheel and axle is a simple machine, consisting of a wheel attached to a smaller axle so that these two parts rotate together, in which a force is transferred from one to the other. The wheel and axle can be viewed as a version of the Lever , with a drive force applied tangentially to the perimeter of the wheel, and a load force applied to ...
This tissue system is present between the dermal tissue and forms the main bulk of the plant body. Parenchyma cells have thin primary walls and usually remain alive after they become mature. Parenchyma forms the "filler" tissue in the soft parts of plants, and is usually present in cortex , pericycle , pith , and medullary rays in primary stem ...
A simple machine is a mechanical device that changes the direction or magnitude of a force. [1] In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. [2] Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: [3] [4 ...
Wheel and axle motion (e.g. screwdrivers, doorknobs): A wheel is essentially a lever with one arm the distance between the axle and the outer point of the wheel, and the other the radius of the axle. Typically this is a fairly large difference, leading to a proportionately large mechanical advantage.
It seems the basic definition of a wheel and axle as a simple machine comes from its use in lifting machines to provide leverage to wind up ropes. While this is technically the source of the term, many also refer to gears as wheels and axle simple machines, while at the same time not calling wheels alone simple machines.
From the time of Archimedes to the Renaissance, mechanisms were viewed as constructed from simple machines, such as the lever, pulley, screw, wheel and axle, wedge, and inclined plane. Reuleaux focused on bodies, called links , and the connections between these bodies, called kinematic pairs , or joints.
Lepidodendron is an extinct genus of primitive lycopodian vascular plants belonging the order Lepidodendrales.It is well preserved and common in the fossil record. Like other Lepidodendrales, species of Lepidodendron grew as large-tree-like plants in wetland coal forest environments.