Sap - Revision history

WikiWorks at 19:12, 7 May 2009

2009-05-07T19:12:38Z

← Older revision		Revision as of 19:12, 7 May 2009
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	~~{{Inc~~\|		[[Image:Plant sap.jpg\|thumb\|Sap]]
	Sap, a term ~~applied to the juices of living plants~~.		[[Image:Sap on pine tree bark.jpg\|thumb\|Sap]]
			The watery contents of a plant; an indefinite and undescriptive term little used by botanists.{{SCH}}

	Sap ~~is composed of water containing mineral salts absorbed from the soil~~, ~~and organic substances chiefly constructed within living cells. The water taken from~~ the soil by the roots or other absorbing organs may contain potassium, sodium, magnesium, calcium, iron, and nitrates, phosphates, sulfates, and chlorides. The different processes and the different reactions that take place in separate tracts of ~~tissue are responsible for the fact that the sap is not alike in composition throughout the body of the plant~~.		Sap, a term applied to the juices of living plants.{{SCH}}

	~~The~~ mineral ~~elements and their~~ salts ~~may be found in nearly all saps. The limits of this note do not permit~~ the ~~enumeration of the large number of~~ organic substances ~~which may be found in the sap of various species~~. The ~~more important of such compounds~~ may ~~be grouped under the acids~~, ~~sugars~~, ~~or carbohydrates~~ and ~~proteins~~. ~~Many plants are of economic importance because of~~ the ~~materials dissolved~~ in ~~the sap. The sap~~ of the ~~sugar maple, for example, contains over 3 1/2 per cent of sugar, while~~ the ~~sugar-beet and sugar-cane have a~~ sap in ~~which~~ the ~~proportion is very much higher~~.		Sap is composed of water containing mineral salts absorbed from the soil, and organic substances chiefly constructed within living cells. The water taken from the soil by the roots or other absorbing organs may contain potassium, sodium, magnesium, calcium, iron, and nitrates, phosphates, sulfates, and chlorides. The different processes and the different reactions that take place in separate tracts of tissue are responsible for the fact that the sap is not alike in composition throughout the body of the plant.{{SCH}}

	The ~~popular expression~~ of ~~"ascent~~ of ~~sap" refers to the fact that water entering~~ the ~~living cells~~ of ~~the roots is forced into the woody tissues or non-living elements through~~ which ~~it passes upward to~~ the ~~leaves at a rate which may vary from a few inches to over a yard an hour~~. ~~(See Transpiration.)~~ The ~~forces operative and the mechanism~~ of the ~~flow~~ are ~~not perfectly understood. Among other facts~~ of ~~interest it may be mentioned that~~ the sap~~-current may pass through dead sections~~ of ~~stem~~, ~~although it is equally certain that the activities~~ of the ~~living cells furnish at least~~ a ~~part of~~ the ~~motive power~~.		The mineral elements and their salts may be found in nearly all saps. The limits of this note do not permit the enumeration of the large number of organic substances which may be found in the sap of various species. The more important of such compounds may be grouped under the acids, sugars, or carbohydrates and proteins. Many plants are of economic importance because of the materials dissolved in the sap. The sap of the sugar maple, for example, contains over 3 1/2 per cent of sugar, while the sugar-beet and sugar-cane have a sap in which the proportion is very much higher.{{SCH}}

	The ~~flow~~ of sap ~~from~~ the ~~sugar maple and other trees in~~ the ~~early spring, before~~ the ~~soil has thawed and while it~~ is ~~yet too cold for~~ the living ~~matter of the plant to show any great activity, is not due~~ to the ~~bleeding pressure, but~~ to ~~the expansion of the gases~~ and ~~liquids in~~ the ~~trunk and branches~~ of the ~~tree due to the direct warming action of the sun's rays~~. ~~During the daytime the bubbles~~ of ~~air in~~ the ~~wood~~-~~cells become heated and expand~~, ~~driving~~ the ~~sap from~~ the ~~wood-~~cells ~~into the auger-hole which has been bored into the tree. At night the trunk~~ of the ~~tree cools slowly and the flow ceases, to be begun again next day~~.		The popular expression of "ascent of sap" refers to the fact that water entering the living cells of the roots is forced into the woody tissues or non-living elements through which it passes upward to the leaves at a rate which may vary from a few inches to over a yard an hour. (See Transpiration.) The forces operative and the mechanism of the flow are not perfectly understood. Among other facts of interest it may be mentioned that the sap-current may pass through dead sections of stem, although it is equally certain that the activities of the living cells furnish at least a part of the motive power.{{SCH}}

	The ~~exudation pressure by which water or~~ sap ~~is forced~~ from the ~~living cells is exhibited~~ in the ~~bleeding which ensues when stems~~ and ~~branches are cut away. The pressure which produces bleeding is often called root-pressure; although~~ it is ~~exerted by any part~~ of the plant~~. Bleeding~~ is ~~exhibited by a large number~~ of ~~trees at~~ the ~~beginning~~ of the ~~growing season, and is also especially noticeable~~ in the ~~vine~~, ~~dahlia, castor~~-~~oil plant, calla, nicotiana~~, ~~and corn~~.		The flow of sap from the sugar maple and other trees in the early spring, before the soil has thawed and while it is yet too cold for the living matter of the plant to show any great activity, is not due to the bleeding pressure, but to the expansion of the gases and liquids in the trunk and branches of the tree due to the direct warming action of the sun's rays. During the daytime the bubbles of air in the wood-cells become heated and expand, driving the sap from the wood-cells into the auger-hole which has been bored into the tree. At night the trunk of the tree cools slowly and the flow ceases, to be begun again next day.{{SCH}}

	The ~~amount of~~ bleeding ~~exhibited~~ by any plant ~~may be found if~~ the ~~stem~~ is ~~cut and bent over~~ in ~~such manner that~~ the ~~end is thrust into a tumbler or small vessel~~, ~~which will serve to collect the escaping sap~~.		The exudation pressure by which water or sap is forced from the living cells is exhibited in the bleeding which ensues when stems and branches are cut away. The pressure which produces bleeding is often called root-pressure; although it is exerted by any part of the plant. Bleeding is exhibited by a large number of trees at the beginning of the growing season, and is also especially noticeable in the vine, dahlia, castor-oil plant, calla, nicotiana, and corn.{{SCH}}

	~~Interesting records of measurement of the~~ amount of bleeding ~~are available. A specimen of Betula papyracea gave off~~ over ~~sixty-three pounds of water~~ in ~~twenty-four hours; an Agave americana yielded twelve and one-half pounds in twenty-four hours. The pulque of Mexico~~ is the ~~preparation of~~ sap ~~which collects in the center of the mature rosette of agave when a cavity is cut into it~~.		The amount of bleeding exhibited by any plant may be found if the stem is cut and bent over in such manner that the end is thrust into a tumbler or small vessel, which will serve to collect the escaping sap.{{SCH}}

	~~The range~~ of ~~concentration~~ of ~~sap as denoted by its osmotic properties varies widely~~. ~~Cacti and other succulents have a sap which would set up a pressure~~ of ~~only~~ three ~~to twelve atmospheres. Spinose desert shrubs may have a sap which would set up a pressure~~ of ~~over a hundred atmospheres. The concentration is greatest~~ in ~~mature leaves,~~ and in ~~the lilac this may be from twelve to~~ twenty-~~five atmospheres, while~~ the ~~roots~~ of the ~~same plant may not show more than four or six atmospheres~~.		Interesting records of measurement of the amount of bleeding are available. A specimen of Betula papyracea gave off over sixty-three pounds of water in twenty-four hours; an Agave americana yielded twelve and one-half pounds in twenty-four hours. The pulque of Mexico is the preparation of sap which collects in the center of the mature rosette of agave when a cavity is cut into it.{{SCH}}
	}}

	~~[[Image:Upload~~.~~png\|thumb\|[[Special:Upload\|Upload image!]]]]~~		The range of concentration of sap as denoted by its osmotic properties varies widely. Cacti and other succulents have a sap which would set up a pressure of only three to twelve atmospheres. Spinose desert shrubs may have a sap which would set up a pressure of over a hundred atmospheres. The concentration is greatest in mature leaves, and in the lilac this may be from twelve to twenty-five atmospheres, while the roots of the same plant may not show more than four or six atmospheres.{{SCH}}
	The ~~watery contents~~ of a plant~~; an indefinite and undescriptive term little used by botanists~~.{{SCH}}

	{{glossary}}		{{glossary}}

Murali.lalitha at 17:31, 7 May 2009

2009-05-07T17:31:21Z

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 [[Image:Upload.png|thumb|[[Special:Upload|Upload image!]]]]
 The watery contents of a plant; an indefinite and undescriptive term little used by botanists.{{SCH}}
 {{glossary}}

WikiWorks: SCH

2009-04-16T21:05:26Z

SCH

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[[Image:Upload.png|thumb|[[Special:Upload|Upload image!]]]]
The watery contents of a plant; an indefinite and undescriptive term little used by botanists.{{SCH}}

{{glossary}}