robert hooke stated that all plants are made of cells.
robert hooke stated that all plants are made of cells.
who stated that all plants are made of cells?
robert hooke
cells, which were once invisible to the naked eye, were first seen in 17th century europe with the invention of the compound microscope. robert hooke was the first person to term the building block of all living organisms as "cells" after looking at cork. the cell theory states that all living things are made up of cells. the theory also states that both plants and animals are composed of cells which was confirmed by plant scientist, matthias schleiden and animal scientist, theodor schwann in 1839. 19 years later, rudolf virchow contributed to the cell theory, arguing that all cells come from the division of preexisting cells. in recent years, there have been many studies which question the cell theory. scientists have struggled to decide whether viruses are alive or not. viruses lack common characteristics of a living cell, such as membranes, cell organelles, and the ability to reproduce by themselves. viruses range from 0.005 to 0.03 micrometers in size whereas bacteria range from 1-5 micrometers. modern day cell biology research looks at different ways to culture and manipulate cells outside of a living body to further research in human anatomy and physiology, to derive treatments and other medications, etc. the techniques by which cells are studied have evolved. advancement in microscopic techniques and technology such as fluorescence microscopy, phase-contrast microscopy, dark field microscopy, confocal microscopy, cytometry, transmission electron microscopy, etc. have allowed scientists to get a better idea of the structure of cells.
cell biology
sieve elements are specialized cells that are important for the function of phloem, which is highly organized tissue that transports organic compounds made during photosynthesis. sieve elements are the major conducting cells in phloem. conducting cells aid in transport of molecules especially for long-distance signaling. in plant anatomy, there are two main types of sieve elements which are sieve cells and sieve tube members. sieve cells are specialized cells in the phloem tissue of flowering plants. companion cells and sieve cells originate from meristems, which are tissues that actively divide throughout a plant's lifetime. they are similar to the development of xylem, a water conducting cells in plants whose main function is also transportation in the plant vascular system. sieve elements' major function includes transporting sugars over long distance through plants by acting as a channel. sieve elements elongate cells containing sieve areas on their walls. pores on sieve areas allow for cytoplasmic connections to neighboring cells, which allows for the movement of photosynthetic material and other organic molecules necessary for tissue function. structurally, they are elongated and parallel to the organ or tissue that they are located in. sieve elements typically lack a nucleus and contain none to a very small number of ribosomes. the two types of sieve elements, sieve tube members and sieve cells, have different structure. sieve tube members are shorter and wider with greater area for nutrient transport while sieve cells tend to be longer and narrower with smaller area for nutrient transport. although the function of both of these kinds of sieve elements is the same, sieve cells are found in gymnosperms, non-flowering vascular plants, while sieve tube members are found in angiosperms, flowering vascular plants.
sieve tube element