AGRICULTURAL SCIENCE

Timaru Herald, Volume LXXXIII, Issue 13016, 2 July 1906, Page 6

AGRICULTURAL SCIENCE

LECTURES TOr TEACHERS.

On Saturday at the Timaru Main school, Mr-Gray./F.CS., of the Lincoln College _rtaff,"gavejie second of a series of lactones on. .Agricultural Chemistry, to teachers of South Canterbury. \ Owing to the morning being wet "there* was not a •o good an attendance as at the* previous lecture*, about five-and-forty being present instead oFeighty. . : „ . . ~"<0 Mr brought with him a quan-\ tity-of apparatus and material'for experiments, ,and these were better seen by the class, the iiemonetraction table acd the lectarer being raised a> foot or (more. _ ' Tne-previons'lecture had dealt with, the constitution of, the atmosphere, 'the /respiration of plants and their assimilation of carbon extracted, from carbonic, .dioxide. The .planta a process distinct of carbon. In ' respiration-plantar take inoxygen and give ont/the dioxide r in. assimjlahon that* procesauis Reversed. .-- ' *"* . ~s\

TWcaxbbjS'taken in ia utilised~to form various substances one of. which. Js chloro-in-turn is the means of breaking v the absorbed carbon compounds and'inakmg others in., which carbon is united to~the elements .of water.. All, .vegetable' matter is built- up .of mmnte ■ceHtjLwbich.,when-young, are all nearly they grow older they may* take on different functions and>=m*y . then alter their appearance. J A cefl~is -usually: x cobfpa&iit'<6V "recognisable layers. .The outermost" layer is- a substance called cellulose. Within this, is a flayer of "protoplasm," generally containing small granular bodies • called nuclei, and within-tins layer the cell is filled with "cell sap."*' In young cells the protoplasm 'fifeithe-whole"of the'interior, but later on it attaches itself to the cell "wall. It is in the-protoplasm that the chemical activities of, the cell reside." ,f_ The .cejl. vail has mP opening, vet carbon, and other, substances ?pass through it by a process" called "osnfl&s,"" the lawfof which is that whenever two liquids of-different density are separated (fiom.each'other, by a mem-> brane, a liquid of less density to the mem-" . brane into the; '.other.v',%^^-iji---i J" , vMr Gr^^fflustratM^^ffi^ of osmosis feibyl.. any periment. <• a sheep's hver, : tilled witha solutiori of W&? /* and OTlouredred, wa*^^ *' tube. representing "a cell, was submerged m "a glaM vessel jfull^ot f water, and.the glass tubew«» fixed-p»-pendicularly iabbve^it.' ; Th%*bladder repfe-

- --'» seated a cell' containing 2 a" denser"'liqtrid than that surrounding it, and according > to the law of osmosis, the water without should pass into the"bladder. ' 'The* blad- . der was, not quite fall of the sugar solution, bjdt it presently' became fall, 'and the osmotic action still continuing, the ted fluid rose; in the tube nine or'ten aches aboyeJthe level of the water in. the vessel. TEnjgpf coarse, implied a pres- - sore per square inch, within the membraneouVcelL The stiffness of airports of a healthy -young Mr Gray, is due to the turgklity of its cells, and this ' is due to difference in osmotic pressures inside and'outaide of them. In a , hot suumerV day a plant will wilt or flag, because more .water is being taken out of it than, is being put in, the immediate result of *b«i being that the cells lose their ''turgidity or tightness. - xThe water lused by plants is mainly taken in through the roots, and the food mater--ials*" obtained from the soil are taken "up with'the water and distributed among the cells, of the leaves. Water is- not only necessary as-a transporting agent; it is absolutely necessary for the process of chemfeal change that go on within the plants. The. water stuffs from the k sojl to by channels 4 in the interior of the stem; the manufactured travel tf-own the stem chiefly in Tie st bass" layer, next the bark:7' To "ftigbark." a tiree does not directly'interfere with the "action of the leaves,; but it 'kills the tree through starvation of the roots. , The. simplest* compound formed by the chemistry of the leaves from the . plant food supplied to believed to be a rample combination of an atom of carbon with a molecule of water;. but this, supposed formative "element has not yet been * separated. Is |s assumed to be and it is spoken of as " formic aldehyde." Multiple compounds of this are "separable: Omitting fhe s "finlfc. substance prodnceq withm the vegetable cell by <the action of Jtigbt-npop. is a sextuple 'coSnpounH of carbon and This substance r <aimot"J)e' seenjjn. .the cell; because it exists there in* solution, bat it can be tested for. ' , The first visible substance is stareh, which is' glucose deprived of a molecule of water—sir. of carbon to five "of water ---C6 HlO 05;"7 Tor effect this 'change, i-e., to produce J March, the action of sunlight is absolutely/necessary. ' Leaves collected at daylight or on a dull day contain little or no starch; the same leaves collected in the evening cf a sunny day would contain much ftaTch. Tincture of iodine is tie test used for starch, which it turns blue, and Mr Gray showed some - leaves cohered at different times and soaked with iodine. Some, full of starch. were stained almost- black; others showed less. and fnme no stain at all. One large leaf the shadow of another, which had lain nn«n it, ar.d cut off the sunlight. Starch in the r.ischt, being cor-

verted into glucose or grape sugar by absorption of -water, a necessary change, as starch being insoluble/ cannot pass through the cell wall. The' insoluble starch C 6 HlO 05' becomes the soluble glucose, C 6 H12;06. Starch is produced in the form of minute granules; > and the snaps of these differs in different kinds- of vegetables, so that it is, possibles.iri many cases'to tell what kind of plant a given specimen -of starch was derived;*, ; — r .-'* --> -*- -^'* Cellulose,, fibre (e.g*» cotton; wool),is-formed.in the same iway. Jsx£ other'change- water j:omv cane "There are"tyo'kinds.of. sugar,-similarvin^alU^^respe«^s.i«^pt;;?tn^'j one form,- thorns \tfie" right, and the other form, laevulose, /turns rim substance "can b* by heating r crust ■ j6f £a., glaze sold'as. ■ The substances mentioned, Y<the starches an<L glucoses,/ are icia^^f^^p^^"i»T-

Do-nyarates. xney axe cnaractenseo. ay containing oxygen and hydrogen an the proportions" necessary to form' water. The carbo-hydrates include: *-—■•-. I. The amyloids-* (amyl means'starch)/'all have the same chemical'formula as' starch, C 6 HKX'OS. They include'celluloee, thV ontaide layer of the vegetable cell, etarch," dextrin, iand'a special-form of starch ,'ciflled innlin. " *S - f! 1 ". ''i-'K «?&. ' H. The glucoses/ 'dextrose .and'laevuTose, C 6 Hl2 06. - m. The, sucroses,' cane sugar and maltose, 'CISJH2£ Oil.- -> ] «' ;(Ti> .- ' •> To prove that the wihte substances dealt with contain; xarbonj the element commonly "blown as a black substance, the lecturer "poured .some sulphuric acid into

a solution- of sugar, in the bottom of a glass jar. j In a few moments a quantity of -frothing black burned sugar swelled up of the bottle/and Mr Gray that the :acid 'had seized upon > t£«£water contained.Jn the structure of the *tttgar, separating- pub lite carbon. Another group ! of substances 'manufac; tared by plants, not "directly from plant food but throughXtransfonnation of .oils, the hydrates x always the hydro-carbons there 'carbon and hydrogen in e 2 sent. ' 'Cfcmsequently oils' andUfats are more serviceable'as food"for-animars. The ratis of food value js usually' given as 2£ to 1. The advantage 3eß'Jn.tiie fact? that* weight for weight,' the'fatsCarid more material capable\"of oxidation." 'f e < * pSdmitine (3) "oleine (liquid)." lAccording-these-"presentTwe have r a stolid fat, or a liquid oil,' shough'allr have the mical constitution. " Ordinary kidney faff of muttoxt, fdr •instance,') is almost wholly, stearine. ~ .•.. ' Simple fats are formed by the union of a fatty acid with -glycerine or glycerol. Stearine is made of stearicjacid united with, glycerine; olive oil is oleic acid and glycerine; and so on. . '

Another .class of the products ,of vegetable chemistry includes the albuminoids or porteids, which are formed by the union 'of carbo-hydrates with nitrogenous substances. , Albummoids as foods will support I life>by themselves, while the carbo-hydrates and!' will not. A specimen of .the gluten of wheat, an | was shown, and the presence i of nitrogen in it ?was' proved by heating some in a'test tube with an alkali, when ! ammonia was given off. Grinding an albuminoid in a- mortar with slaked lime, i the lecturer said, will bring out ammonia very' simply. * The tincture of iodine test wasapplied to wetted' starch, and the red tincture brought out a fine blue. lodjne was also applied 7 to the freshly cut' surfaces of tato,. carrot, parsnip, and the "starch _deposit shown to be .very differently arranged in these vegetables. The carrot has scarcely any starch in its composition, and' the/parsnip very little in its 'core.

A test for sugar was then shown. A rich blue.solution of copper sulphate (bluetone) waS'dianged to copper colour (by the formatioji of cjbgrper oxide) on being heated raisins' "(grape Cane rjqigar' does not' thus affect" the ;so-ljr^on^-unless it" is turned' into glucose. Copper 'sulphate >is the standard test for sugar, in analysing vegetable substances. Mr Gray concluded' bis lecture with showing the_ .results of experiments on germination of peas, under different conditions. A few peas of-the same sort, from the same parcel were put into small bottles at the same time, and the effect' of_ different conditions on their germination was visible on inspection. Some samples showed long sprouts, others none at all. v Three"-...pairs', and . one trio of bottles showing those results had been exposed to (1) heat and cold; (2) light and darkness; (3) plenty of air, deprived of oxygen; (4) enough of moisture, '(a> excess and (b) deficiencv. of moistvre.

The latter trio, said Mr" Gray, showed how excess of moisture in the ground was detrimental to germination; the drowned peas were swollen but had not sprouted at all, because the oxygen necessary to

** e growth of sprout had been .unable to_ them. ■«' The close of the lecture was the signal jior hearty;applause. ;:.■':-'■.'■.' :-'""