august weismann discovered all cells come from other cells.
august weismann discovered all cells come from other cells.
who discovered all cells come from other cells?
august weismann
in biology, cell theory is the historic scientific theory, now universally accepted, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells. cells are the basic unit of structure in all organisms and also the basic unit of reproduction. with continual improvements made to microscopes over time, magnification technology advanced enough to discover cells in the 17th century. this discovery is largely attributed to robert hooke, and began the scientific study of cells, also known as cell biology. over a century later, many debates about cells began amongst scientists. most of these debates involved the nature of cellular regeneration, and the idea of cells as a fundamental unit of life. cell theory was eventually formulated in 1839. this is usually credited to matthias schleiden and theodor schwann. however, many other scientists like rudolf virchow contributed to the theory. it was an important step in the movement away from spontaneous generation.
cell theory
collenchyma cells – collenchyma cells are alive at maturity and have thickened cellulosic cell walls. these cells mature from meristem derivatives that initially resemble parenchyma, but differences quickly become apparent. plastids do not develop, and the secretory apparatus (er and golgi) proliferates to secrete additional primary wall. the wall is most commonly thickest at the corners, where three or more cells come in contact, and thinnest where only two cells come in contact, though other arrangements of the wall thickening are possible. pectin and hemicellulose are the dominant constituents of collenchyma cell walls of dicotyledon angiosperms, which may contain as little as 20% of cellulose in "petasites". collenchyma cells are typically quite elongated, and may divide transversely to give a septate appearance. the role of this cell type is to support the plant in axes still growing in length, and to confer flexibility and tensile strength on tissues. the primary wall lacks lignin that would make it tough and rigid, so this cell type provides what could be called plastic support – support that can hold a young stem or petiole into the air, but in cells that can be stretched as the cells around them elongate. stretchable support (without elastic snap-back) is a good way to describe what collenchyma does. parts of the strings in celery are collenchyma.
plant cell