SUMMARY / RELATED TOPICS

Root

In vascular plants, the roots are the organs of a plant that lie below the surface of the soil. Roots can be aerial or aerating, that is, growing up above the ground or above water. Furthermore, a stem occurring below ground is not exceptional either. Therefore, the root is best defined as the non-nodes bearing parts of the plant's body. There are important internal structural differences between roots; the fossil record of roots—or rather, infilled voids where roots rotted after death—spans back to the late Silurian, about 430 million years ago. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows, they can be discriminated using a range of features. The first root that comes from a plant is called the radicle. A root's four major functions are: absorption of inorganic nutrients. In response to the concentration of nutrients, roots synthesise cytokinin, which acts as a signal as to how fast the shoots can grow. Roots function in storage of food and nutrients.

The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizae, a large range of other organisms including bacteria closely associate with roots. When dissected, the arrangement of the cells in a root is root hair, epiblem, endodermis, pericycle and, the vascular tissue in the centre of a root to transport the water absorbed by the root to other places of the plant; the most striking characteristic of roots that distinguishes them from other plant organs such as stem-branches and leaves is that roots have an endogenous origin, i.e. they originate and develop from an inner layer of the mother axis, such as pericycle. In contrast, stem-branches and leaves are exogenous, i.e. they start to develop from the cortex, an outer layer. In its simplest form, the term root architecture refers to the spatial configuration of a plant's root system; this system can be complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients.

The configuration of root systems serves to structurally support the plant, compete with other plants and for uptake of nutrients from the soil. Roots grow to specific conditions. For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as seasonal changes. Root architecture plays the important role of providing a secure supply of nutrients and water as well as anchorage and support; the main terms used to classify the architecture of a root system are: Branch magnitude: the number of links. Topology: the pattern of branching, including:Herringbone: alternate lateral branching off a parent root Dichotomous: opposite, forked branches Radial: whorl of branches around a rootLink length: the distance between branches. Root angle: the radial angle of a lateral root's base around the parent root's circumference, the angle of a lateral root from its parent root, the angle an entire system spreads.

Link radius: the diameter of a root. All components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli; these developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the environmental influences and are interpreted by signal transduction pathways. The extrinsic factors that affect root architecture include gravity, light exposure and oxygen, as well as the availability or lack of nitrogen, sulphur and sodium chloride; the main hormones and respective pathways responsible for root architecture development include: Auxin – Auxin promotes root initiation, root emergence and primary root elongation. Cytokinins – Cytokinins regulate root apical meristem size and promote lateral root elongation. Gibberellins -- Together with ethylene they promote elongation. Together with auxin they promote root elongation. Gibberellins inhibit lateral root primordia initiation. Ethylene – Ethylene promotes crown root formation.

Early root growth is one of the functions of the apical meristem located near the tip of the root. The meristem cells more or less continuously divide, producing more meristem, root cap cells, undifferentiated root cells; the latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. These cells differentiate and mature into specialized cells of the root tissues. Growth from apical meristems is known as primary growth. Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants. For example, storage roots of sweet potato are not woody. Secondary growth occurs at the lateral meristems, namely the vascular cork cambium; the former forms secondary phloem, while the latter forms the periderm. In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a cylinder of tissue along the stem and root; the vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, those on the outside forming secondary phloem cells.

As secondary xylem accumulates

Chess (Northwestern University)

Chess was a pioneering chess program from the 1970s, written by Larry Atkin and David Slate at Northwestern University. Chess ran on Control Data Corporation's line of supercomputers. Work on the program began in 1968, it dominated the first computer chess tournaments, such as the World Computer Chess Championship and ACM's North American Computer Chess Championship. Chess was the first published use of the bitboard data structure applied to the game of chess. In 1976, Chess 4.5 won the Class B section of the Paul Masson American Chess Championship, the first time a computer was successful in a human tournament. The performance rating was 1950. In February 1977 Chess 4.6, the only computer entry, surprised observers by winning the 84th Minnesota Open against competitors just under Master level. It achieved a USCF rating close to or at Expert, higher than previous programs' Class C or D, by winning five games and losing none. Stenberg became the second Class A player to lose to a computer in a tournament game, the first being Jola.

Because of its Minnesota victory, grandmaster Walter Browne invited Chess 4.6 on a CDC Cyber 176 to his simultaneous chess exhibition. In 1977, Chess 4.6 won the second World Computer Chess Championship in Toronto, ahead of 15 other programs including KAISSA. The favorite to win the tournament, like all but one other entry Chess 4.6 ran on a computer located away from the tournament. Chess 4.6 was capable of defeating 99.5% of United States Chess Federation-rated players under tournament conditions, was stronger in blitz chess. In 1978 and 1979 Atkin and Peter W. Frey published in BYTE a series on computer chess programming, including the Pascal source for Chess 0.5, a chess engine suitable for microcomputers. That year the improved Chess 4.7—which had by now achieved a 2030 rating after 31 tournament games—played against David Levy who, in 1968 had wagered that he would not be beaten by a computer within ten years. Whereas Chess 4.7 had beaten Levy under blitz conditions, the bet involved forty moves over a two-hour period, the computer's choices being relayed by telephone from Minnesota to the board.

Levy won the bet, defeating the Chess 4.7 in a six-game match by a score of 4.5-1.5, The computer scored a draw in game two after getting a winning position but being outplayed by Levy in the endgame, a win in game four—the first computer victory against a human master—when Levy essayed the sharp, dubious Latvian Gambit. Levy wrote, "I had proved that my 1968 assessment had been correct, but on the other hand my opponent in this match was very much stronger than I had thought possible when I started the bet." He observed that, "Now nothing would surprise me." International Master Edward Lasker stated in 1978, "My contention that computers cannot play like a master, I retract. They play alarmingly. I know, because I have lost games to 4.7."Atkin and Frey wrote microcomputer chess and Reversi programs for Odesta. Advertisements cited their Northwestern affiliation and authorship of Chess 4.7, "World Computer Chess Champion, 1977-1980". Notes"Computer Chess Compendium", L. Atkin & D. Slate, Springer-Verlag, 1988, pp. 80–103 "Chess Skill in Man and Machine" Peter W. Frey, 1977, pp. 82–118 - devotes a chapter to the internals of Chess 4.5 Source code for Chess 4.6 available at

Bonde

House of Bonde is an ancient Swedish noble family. Today, two branches of the family lives on. Prominent members and others bearing the name include: Tord Bonde, medieval Swedish magnate Karl Knutsson Bonde, King Charles VIII of Sweden, Charles I of Norway, Magdalena of Sweden Gustaf Bonde, Swedish statesman Wilhelmina Bonde, Swedish courtier Jens-Peter Bonde, Danish politician Carl Bonde, Swedish Army officer, equerry Carl C:son Bonde, Swedish Army officer Thord Bonde, Swedish Army officer Gustaf Bonde, Swedish diplomat Oskar Bonde, Swedish drummer Line Bonde, Danish fighter pilotBonde was a member one of the four houses of the Swedish Riksdag of the Estates