28 July 2009
The invention: Method for propagating plants in artificial media that has revolutionized agriculture. The people behind the invention: Georges Michel Morel (1916-1973), a French physiologist Philip Cleaver White (1913- ), an American chemist Plant Tissue Grows “In Glass” In the mid-1800’s, biologists began pondering whether a cell isolated from a multicellular organism could live separately if it were provided with the proper environment. In 1902, with this question in mind, the German plant physiologist Gottlieb Haberlandt attempted to culture (grow) isolated plant cells under sterile conditions on an artificial growth medium. Although his cultured cells never underwent cell division under these “in vitro” (in glass) conditions, Haberlandt is credited with originating the concept of cell culture. Subsequently, scientists attempted to culture plant tissues and organs rather than individual cells and tried to determine the medium components necessary for the growth of plant tissue in vitro. In 1934, Philip White grew the first organ culture, using tomato roots. The discovery of plant hormones, which are compounds that regulate growth and development, was crucial to the successful culture of plant tissues; in 1939, Roger Gautheret, P. Nobécourt, and White independently reported the successful culture of plant callus tissue. “Callus” is an irregular mass of dividing cells that often results from the wounding of plant tissue. Plant scientists were fascinated by the perpetual growth of such tissue in culture and spent years establishing optimal growth conditions and exploring the nutritional and hormonal requirements of plant tissue. Plants by the Millions A lull in botanical research occurred during World War II, but immediately afterward there was a resurgence of interest in applying tissue culture techniques to plant research. Georges Morel, a plant physiologist at the National Institute for Agronomic Research in France, was one of many scientists during this time who had become interested in the formation of tumors in plants as well as in studying various pathogens such as fungi and viruses that cause plant disease. To further these studies, Morel adapted existing techniques in order to grow tissue from a wider variety of plant types in culture, and he continued to try to identify factors that affected the normal growth and development of plants. Morel was successful in culturing tissue from ferns and was the first to culture monocot plants. Monocots have certain features that distinguish them fromthe other classes of seed-bearing plants, especially with respect to seed structure. More important, the monocots include the economically important species of grasses (the major plants of range and pasture) and cereals. For these cultures, Morel utilized a small piece of the growing tip of a plant shoot (the shoot apex) as the starting tissue material. This tissue was placed in a glass tube, supplied with a medium containing specific nutrients, vitamins, and plant hormones, and allowed to grow in the light. Under these conditions, the apex tissue grew roots and buds and eventually developed into a complete plant. Morel was able to generate whole plants from pieces of the shoot apex that were only 100 to 250 micrometers in length. Morel also investigated the growth of parasites such as fungi and viruses in dual culture with host-plant tissue. Using results from these studies and culture techniques that he had mastered, Morel and his colleague Claude Martin regenerated virus-free plants from tissue that had been taken from virally infected plants. Tissues from certain tropical species, dahlias, and potato plants were used for the original experiments, but after Morel adapted the methods for the generation of virus-free orchids, plants that had previously been difficult to propagate by any means, the true significance of his work was recognized. Morel was the first to recognize the potential of the in vitro culture methods for the mass propagation of plants. He estimated that several million plants could be obtained in one year from a single small piece of shoot-apex tissue. Plants generated in this manner were clonal (genetically identical organisms prepared from a single plant).With other methods of plant propagation, there is often a great variation in the traits of the plants produced, but as a result of Morel’s ideas, breeders could select for some desirable trait in a particular plant and then produce multiple clonal plants, all of which expressed the desired trait. The methodology also allowed for the production of virus-free plant material, which minimized both the spread of potential pathogens during shipping and losses caused by disease. Consequences Variations on Morel’s methods are used to propagate plants used for human food consumption; plants that are sources of fiber, oil, and livestock feed; forest trees; and plants used in landscaping and in the floral industry. In vitro stocks are preserved under deepfreeze conditions, and disease-free plants can be proliferated quickly at any time of the year after shipping or storage. The in vitro multiplication of plants has been especially useful for species such as coconut and certain palms that cannot be propagated by other methods, such as by sowing seeds or grafting, and has also become important in the preservation and propagation of rare plant species that might otherwise have become extinct. Many of these plants are sources of pharmaceuticals, oils, fragrances, and other valuable products. The capability of regenerating plants from tissue culture has also been crucial in basic scientific research. Plant cells grown in culture can be studied more easily than can intact plants, and scientists have gained an in-depth understanding of plant physiology and biochemistry by using this method. This information and the methods of Morel and others have made possible the genetic engineering and propagation of crop plants that are resistant to disease or disastrous environmental conditions such as drought and freezing. In vitro techniques have truly revolutionized agriculture.
The invention: A relatively small, simple, and inexpensive computer that is often credited with having launched the personal computer age. The people behind the invention: Howard H. Aiken (1900-1973), an American mathematician Charles Babbage (1792-1871), an English mathematician and inventor Herman Hollerith (1860-1929), an American inventor Computers: From the Beginning Computers evolved into their modern form over a period of thousands of years as a result of humanity’s efforts to simplify the process of counting. Two counting devices that are considered to be very simple, early computers are the abacus and the slide rule. These calculating devices are representative of digital and analog computers, respectively, because an abacus counts numbers of things, while the slide rule calculates length measurements. The first modern computer, which was planned by Charles Babbage in 1833, was never built. It was intended to perform complex calculations with a data processing/memory unit that was controlled by punched cards. In 1944, Harvard University’s Howard H. Aiken and the International Business Machines (IBM) Corporation built such a computer—the huge, punched-tape-controlled Automatic Sequence Controlled Calculator, or Mark I ASCC, which could perform complex mathematical operations in seconds. During the next fifteen years, computer advances produced digital computers that used binary arithmetic for calculation, incorporated simplified components that decreased the sizes of computers, had much faster calculating speeds, and were transistorized. Although practical computers had become much faster than they had been only a few years earlier, they were still huge and extremely expensive. In 1959, however, IBM introduced the Model 1401 computer. Smaller, simpler, and much cheaper than the multimillion-dollar computers that were available, the IBM Model 1401 computer was also relatively easy to program and use. Its low cost, simplicity of operation, and very wide use have led many experts to view the IBM Model 1401 computer as beginning the age of the personal computer. Computer Operation and IBM’s Model 1401 Modern computers are essentially very fast calculating machines that are capable of sorting, comparing, analyzing, and outputting information, as well as storing it for future use. Many sources credit Aiken’s Mark I ASCC as being the first modern computer to be built. This huge, five-ton machine used thousands of relays to perform complex mathematical calculations in seconds. Soon after its introduction, other companies produced computers that were faster and more versatile than the Mark I. The computer development race was on. All these early computers utilized the decimal system for calculations until it was found that binary arithmetic, whose numbers are combinations of the binary digits 1 and 0, was much more suitable for the purpose. The advantage of the binary system is that the electronic switches that make up a computer (tubes, transistors, or chips) can be either on or off; in the binary system, the on state can be represented by the digit 1, the off state by the digit 0. Strung together correctly, binary numbers, or digits, can be inputted rapidly and used for high-speed computations. In fact, the computer term bit is a contraction of the phrase “binary digit.” A computer consists of input and output devices, a storage device (memory), arithmetic and logic units, and a control unit. In most cases, a central processing unit (CPU) combines the logic, arithmetic, memory, and control aspects. Instructions are loaded into the memory via an input device, processed, and stored. Then, the CPU issues commands to the other parts of the system to carry out computations or other functions and output the data as needed. Most output is printed as hard copy or displayed on cathode-ray tube monitors, or screens. The early modern computers—such as the Mark I ASCC—were huge because their information circuits were large relays or tubes. Computers became smaller and smaller as the tubes were replaced first with transistors, then with simple integrated circuits, and then with silicon chips. Each technological changeover also produced more powerful, more cost-effective computers. In the 1950’s, with reliable transistors available, IBM began the development of two types of computers that were completed by about 1959. The larger version was the Stretch computer, which was advertised as the most powerful computer of its day. Customized for each individual purchaser (for example, the Atomic Energy Commission), a Stretch computer cost $10 million or more. Some innovations in Stretch computers included semiconductor circuits, new switching systems that quickly converted various kinds of data into one language that was understood by the CPU, rapid data readers, and devices that seemed to anticipate future operations. Consequences The IBM Model 1401 was the first computer sold in very large numbers. It led IBM and other companies to seek to develop less expensive, more versatile, smaller computers that would be sold to small businesses and to individuals. Six years after the development of the Model 1401, other IBM models—and those made by other companies—became available that were more compact and had larger memories. The search for compactness and versatility continued. A major development was the invention of integrated circuits by Jack S. Kilby of Texas Instruments; these integrated circuits became available by the mid-1960’s. They were followed by even smaller “microprocessors” (computer chips) that became available in the 1970’s. Computers continued to become smaller and more powerful. Input and storage devices also decreased rapidly in size. At first, the punched cards invented by Herman Hollerith, founder of the Tabulation Machine Company (which later became IBM), were read by bulky readers. In time, less bulky magnetic tapes and more compact readers were developed, after which magnetic disks and compact disc drives were introduced. Many other advances have been made. Modern computers can talk, create art and graphics, compose music, play games, and operate robots. Further advancement is expected as societal needs change. Many experts believe that it was the sale of large numbers of IBM Model 1401 computers that began the trend.