SUPPOSED DEGENERACY OF THE POTATO.

Dominion, Volume 1, Issue 228, 19 June 1908, Page 3

SUPPOSED DEGENERACY OF THE POTATO.

SOME INTERESTING NOTES. Sir W. T. Tliistletou-Dyer, K.C.M.G., F.R.S., contributed to the April number of tho "Journal of the Board of Agriculture" somo interesting notes on this subjcct. He says:— , "Tho undoubted difficulties which now/ occur in the cultivation of at • any rate somo kinds of potatoes present a problem which is obviously of great practical importance as well as of scientific interest. It is not, however, satisfactorily disposed of when attributed to degeneracy. The potato plant has not been run out, but too much has been demanded of it, and it has broken' down in the attempt to rospond. I think a little further light may be thrown on tho' subject by examining rather more closoly what happens in a potato under natural and healthy conditions. . The Work of Olastass. "A potato tuber is an underground branch, which, towards the end of the growing season, becomes swollen out laterally and filled with accumulated nutriment for the purpose of giving its buds' a vigorous start in the following, year. This nutriment is stored up for tho most part in the form of starch. Now this is insolublo, and is not availablo to support growth till it has been converted into something—a sugar—which is soluble. This conversion is alfccted by a ferment or enzyme called diastase. It can bo extractod from the potato tuber, and it will do its work quite as effectively outside as inside; it has been found, however, that if an extract bo made from an ordinary healthy potato it has, at first, no action on starch;' but, after standing' for a few days, attacks it energetically. "The explanation is, that diastase is not present as such in a potato tuber,. but is the result of tho decomposition of another substance called a zymogen, a word which merely means 'ferment producer.' Before the starch in a potato tuber can bo made availablo to support growth two things have to take placo: (1) Decomposition of tho zymogen to produce diastase; (2) conversion of the starch into sugar by its action. Until they do take place there will be no growth from tho tuber. Tubers that do not Sprout. "When, therefore, a tuber fails to grow it is not _ a sufficient explanation ,of the failure to' say thai the plant is degenerate, or that dia6taso is wanting. Both explanations aro conclusively disproved by the interesting experiment of the Curator of Kew in' exposing the sluggish tubers to a higher tomperature. They. then sprouted vigorously and, after planting, produced a normal crop. It is clear that what was really amis 3 ■ was that tho'diasta'se remained locked up in the zymogen and was available'to do , its work. It is known that tho production of diastase requires tho access of oxygen ■ from tho air; it also needs somo amount of warmth' and is probably stimulated by light. A Remedy. : _ "When a sluggish tuber is planted, it either remains. completely dormant or sends up a feeble growth which utilises little of the accumulated starch. On tho other hand, the shoot manufactures more, and this is transferred to tho tuber which' actually increases in size. What is now complained of seems to bo only an extreme form of a state of things which has long been known to cultivators. In Gloucestershire tho N remedy recommended is 'greening. 1 the tubers. The method is described in Leaflet No. 173, pp. i, o, issued by the board. The tubers 'are placed in the autumn in shallow boxes containing no soil or other, material,- and stared throughout .the winter ...in., tiers .in r,a,-.cool, well-ventilated and well-lighted shed.' Under tho inlluonco of light tho dormant surfaco of the tuber becomes active arid grooii.. This means that chemical action takes placo; diastase, will be set free, starch will bo made available for. growth, and sprouting follows. It was "found in'Yorkshire-in 1903 that with Up-to-Dato, 'an' advantage of two tons per aero followed tho use of boxed seed.' Havo we Reachod a Limit. "Aa ( 'far as auy general conclusions' can bo drawn from the facts as stated it can hardly bo said that tho potato is in any intelligible sense degenerate/ but ; it' appears to have , become sluggish in starting into growth,'and to require the stimulus of a higher temperature than formerly. It must he remembered that tho modern potato is a highly artificial ' produet. It has been induced .by continual selection to load itself with starch to ;a point far in excess of any natural requirements of tho plant. It may bo that,, as ajready suggested, too much is demanded of it and that tho-machinery foi tho processes, of growth- has reached its breaking.point. The tuber desirable for food may,not bo quo whioh is prompt to start, into growth without increased stimulus from heat and light. We can control nature in altering tho constitution of a plant; but eventually a barrier is reached beyond which it is impossible to go. Tho caso of tho sugarbeet is instructive. Beginning with 8° to 10 per cent, of its weight-of sugar, it has been brought up by selection to 16 to 18 per cent.. But H. L. de Vilmorin informed' me this was the limit. 'Beet-roots containing more than 18 per cent, sugar cease to vegetate'properly and die.' ('Kew Bulletin,' 131)7, p. 317.) If a similar limit ha 3 been reached in the potato,' growers must be content with sturdier but perhaps from a-cul-inary point of viow less desirable kinds."

HUSK LESS OATS. " A Press Association cablegram from London states that experiments show that huskless oats from China can bo successfully grown in Norfolk on a substantial scale. ABORTION AND TUBERCULOSIS. Dr. David Roberts, the Wisconsin State Vetorinarian, states that 90 per cent, of all tuberculous _ cows he ,had killed were affected also with abortion. 1 1 SHIPPING FREIGHTS DOWN. Tho reduction in the shipping freights on frozen mutton, to what are known as tho winter freights, commenced on June 1,1 and will continue to September. OUR DIARY. SHOWS. Juno 23 to 26.—National Dairy Show, Palmerston North. . . July 8, il.—Waikato Winter Show (Hamilton). Oct. 21, 22.—Hawke's Bay A. and P. (Hast* iugs). Octobor 28, 29.—Wairarapa A. and P. (Car- 1 terton). Nov. —Manawatu. Nov. 11,12. 13.—ChriBtehurch. Feb. 26.—Bush Districts (Woodville). Nov. 11, 12—Wanganui. Sept. 2.-rßulb Show, Masterton. Nov. 17, 18.—Marlborough (Blenheim). Nov. 18, 19.—Egmont (Hawora). . - LONDON WOOL SALES. 4th series begin j u ] y 14 sth „ a ... ... Sopt. 29 6th „ „ Nov. 2-i