Large Tubers Research Articles

ON THE ACCELERATING METHOD OF POTATO CULTIVATION

1. To accelerate the potato formation, we make tubers sprout out their buds in the fall of the previous year and they are allowed to elongate to the length of about 4 cm. in the diffused light. The buds must be stored under the condition of proper temperature and humidity. In winter time, temperature must be kept above O°, Calthough thus treated tubers are more resistant to freezing. Thus we can increase the yield of potatoes. On 5th June, we can get the yield of potatoes about twice as much as that of ordinary one which wag planted at the same time in March. On 15th June, it is about three times as much. 2. This procedure is very useful for the prevention of virus propagation in stems and leaves. 3. The number and weight of tubers increase in proportion to the length of buds. 4. The small buds shorter than 1 cm. of large tubers often gave abundant potatoes, this interesting fact being discussed in this paper. 5 This practice has been proved to be desirable in our district (Miyagi and Fukushima prefecture), and it may be generally recommended.

A histological study of hollow heart of potatoes

1. Hollow heart of potatoes was found to arise in a necrotic patch of cells after this had become surrounded by a cambium layer. 2. Though the largest hollows usually occurred in the largest tubers, early stages were found in tubers weighing as little as 1.8 gms. 3. The hollow heart condition was observed in the earliest harvest examined (July 24); the incidence in the first harvest was double that in the last; and treatments affected the incidence only when given early in the season. These three facts indicate that the disorder must have originated early in the season in all affected tubers. 4. Measurements revealed that the perimedulla cells adjacent to the edge of the hollow were larger than the pith cells adjacent to the face. This may indicate more rapid growth in the former tissue, a possible factor in hollow heart formation. 5. All six of the mineral elements investigated (K, Cu, Mg, Fe, Mn, Ca) occurred in higher quantities (on a dry weight basis) in the healthy than in the affected tubers. The excess in the pith compared with the perimedulla was also reduced.

The Susceptibility Of Certain Potato Varieties To Leaf‐Roll And Mosaic Infection

Summary.1. A trial planned to ascertain whether any differences in susceptibility to leaf‐roll and mosaic infection existed in seven varieties—two of which had been included in a revious trial—was laid down in 1929. It consisted of four replicated plots for each disease; the varieties being randomised in the plots to secure uniform chances of infection. Sources of infection were provided by drills of diseased plants alternating with varieties under test.2. Mosaic was generally transmitted but with such faint symptoms that percentage infection could not be determined. The apparent loss of vigour was very slight, but losses ascertained by weighing the crop, against that given by normal plants, ranged from 0·8 to 24·4 per cent.3. Leaf‐roll infection was very heavy; most varieties showing from 90 to 100 per cent. infection of the plants. Tuber infection on the infected plants was also heavier than in 1924, and ranged from 77·3 to 99·9 per cent. Both haulm (or plant) infection and tuber infection thus showed a marked dependence upon seasonal factors which affect the breeding of insect vectors.4. The loss in yield due to leaf‐roll was found to be the most reliable guide to the susceptibility of a variety. This loss cannot be estimated from the degree of stunting or the number of rolled leaves on a plant, but only by weighing and grading the crop. Some evidence is presented to show that loss in yield of an infected plant is less dependent upon seasonal factors than percentage haulm or tuber infection, and that, therefore, figures showing such losses have a more general applicability to other localities and seasons. On this assumption a table of susceptibility of fifteen varieties has been constructed.5. Although the variety Field Marshal suffered little from leaf‐roll infection, heavy losses occurred when mixed leaf‐roll and mosaic viruses entered the plant. In large tubers receiving mixed infection the effect was to produce neither leaf‐roll nor mosaic symptoms, but “crinkle.” The small tubers, however, gave apparently pure leaf‐roll.6. The value to be attached to field trials of this kind, and their applicability to other conditions, is discussed in detail. Suggestions are offered for improvement in the technique for such trials.

A STUDY OF THE DEGENERATION OF CERTAIN POTATO STOCKS

Summary. Trials carried out at the University College Farm, near Bangor, N. Wales, have demonstrated the intimate relation of virus disease infection to the fall in yield experienced when potato “seed” is saved more than one year. These trials were laid down with seed tubers of three sizes corresponding to commercial “ware,”“seed” and “chats.” Two varieties were used, viz. Kerr's Pink and Great Scot, which had been grown for varying periods, up to seven years, without change of seed. Whatever size of seed tuber was used, the yield became progressively less from the youngest to the oldest stocks, except that grown for six years, which compared well with slightly younger stocks. Again, with the exception of the six‐year‐old stocks, the percentage of plants free from virus symptoms fell consistently from the youngest to the oldest stocks. The continued relative superiority of these six‐year‐old stocks of both varieties is considered to be due to (a) exceptional freedom from infection when received from Scotland, (b) the spread of disease more easily along the drills than across them, and (c) the relatively late infestation by aphides which occurs at the College Farm and results in a large number of tubers on primarily infected plants escaping infection—the effect of (b) and (c) being to maintain any original difference in infection between stocks. The possibility of a difference in the reaction of different strains of a variety to virus infection cannot be ignored but is regarded as unlikely in the present instance. The relationship between virus infection and loss in yield has been shown to be a linear correlation, and that it is of an extremely high order is evident from the fact that the correlation coefficient in the case of the Kerr's Pink is shown to be 0.83 ± 0.046, and with Great Scot 0.97 ± 0.008. “Misses” occurred to the extent of about 5 per cent, in the youngest stocks but increased progressively in the older ones, irrespective of the position they occupied in the chequerboard plots. There is, therefore, another source of loss, which has not hitherto been generally recognised, to be attributed to prolonged home‐saving of seed, and probably—though not certainly—to virus infection. The effect of virus diseases on the size of tubers produced has been studied. There is no clear evidence in either variety of any marked reduction in size attributable to virus infection, but definite evidence that the proportion of large tubers in the crop is affected by the size of set planted. No evidence was found that the rate of degeneration was affected by the size of tuber set planted, except possibly in the oldest stock of Kerr's Pink. In the variety Kerr's Pink there was no significant difference in virus infection in the three tuber classes, however long they had been grown without change. This was almost equally true of Great Scot so far as leaf‐roll was concerned, but the chats produced a higher percentage of mosaic and crinkle plants than did the ware. The effect of climatic, seasonal, and varietal factors on the rate of degeneration has been studied: A detailed comparison has been made of the vigour of the same stocks of two varieties maintained at the College Farm, near Bangor, and at Madryn Castle Farm Institute some thirty miles distant. Owing probably to climatic and topographical factors, aphides occurred only sparsely at the latter centre and practically no reduction in vigour in the six‐year‐old stocks occurred. Seasonal factors, by influencing the rate of breeding of insect vectors and the vigour of the potatoes, may considerably accelerate or retard the degeneration of a partially infected stock. It is shown that, owing to the difference in the response of healthy and diseased plants to unsuitable conditions, it may happen that a heavily diseased stock in an exceptionally good growing year will show less loss relative to the crop from a healthy stock than it did in a previous year in which less virus disease was present. The influence of variety on the rate of degeneration is shown to be the resultant of three separate forms of susceptibility, i.e. liability of haulm to infection, liability of tubers to contract infection from the diseased haulm, and the effect of infection on the yield. The variety Crusader showed all three forms of susceptibility in an extreme manner; Up‐to‐Date was very susceptible to infection both of haulm and tubers, but the virus infection had relatively little effect on the yield; on the other hand, the variety Great Scot exhibited considerably less susceptibility of haulm and tubers to infection, as compared with Up‐to‐Date, but appreciably more effect was produced on the yield. The value to be attached to field trials of susceptibility to virus diseases is discussed.

Five New Hypogaeous Fungi

Ascocarp light yellowish-gray, with wide white venae externae conspicuous on surface, 1.8-5.5 cm. in diameter, sub-globose, much convoluted; surface very minutely scabrous; gleba light chocolate colored at maturity, marbled with distinct shining white veins varying in width, older specimens containing several large fissures from breaking along venae externae; venae externae rarely converging at a distinct point; outer layer of cortex pseudoparenchymatous, changing to loose hyphal tissue which gradually merges into sub-cortical layer of more slender hyphae; thickness from the surface to the hymenium 220-260 ll; venae internae and hymenial tissue similar to structure of the subcortex; venae externae of loosely arranged hyphae, breaking away at maturity to form fissures; asci not stipitate, semi-globose, 52-70 x 74-80 ll, 1-4(rarely 5-) spored; spores dark yellowishbrown, ellipsoid or ovoid, 17-39 x 35-52 lx, alveolate, 5-9 x 7-10 alveoli across the diameters, these varying somewhat in size on a single spore; also apparently very minute alveoli on inner surface of epispore; sculpturing 2-3 ll in height. (Plate 26, Fig. 1.) Collected in clay soil under trees and shrubs, by John Sert, at Bandon, Oregon, May 2, 1921. This is, to my knowledge, the largest Tuber reported from the United States, several specimens of the collection reaching 5.5 cm. in diameter. Mr. Sert discovered the fruiting bodies from several inches to a foot deep in a clay hillside which was being graded for a road bed. The spores are long-ellipsoid like those of Tuber gibbosum Hark., but are rounded rather than pointed at the ends and are generally smaller. The ascocarp of T. gibbosum is cinnamon-brown rather than yellowish-gray; the surface is covered with knotty hairs which are absent in the above described species; and the inner surface of the epispore does not show the secondary sculpturing described above.

Een onderzoek naar de faktoren, die ontijdige knolvorming bij vroege aardappels bepalen

Premature formation of tubers ('submarines') is a disturbance in the normal growth of a planted seed potato, resulting in the formation of some small daughter tubers without any aerial growth. In certain years losses may be heavy. The main cause is the formation of sprouts during storage which have to be removed. All factors preventing or reducing such sprout formation favour normal development: especially low temperature (above freezing-point) and light during storage, also late lifting of the seed tubers, large tubers, planting at higher temperature and in moist soil. The underlying process of premature tuber formation was assumed to be loss of water by removal of sprouts during storage, resulting in an increase in the concentration of solutes. Essentially the same occurs with normal tuber formation but there by an increase in assimilates. This concept was supported by plasmolysis studies in the hairs of the sprouts.

On an apocynaceous plant yielding large edible tubers

On an apocynaceous plant yielding large edible tubers

Societies and Academies

LONDON Linnean Society, November 7.—Prof. Allman, F.R.S., president, in the chair. —Sir Joseph D. Hooker, C.B., presented to the Society, in the name of a committee of gentlemen, a portrait of the Rev. M. J. Berkeley. A great matted mass in sheet of a Chara (Nitella sp.?) was exhibited by Dr. Thos. Boycott. It had been got from a dried-up pond in St. Leonard's Forest, Sussex, June, 1877; within its-meshes many interesting microscopic forms were obtained.—Mr. Thos. Christy next called attention to living specimens of West African indian-rabber trees, the Urostigma Vogelii, and another undetermined species recently arrived. He likewise showed the fruit, flower, and leaf in spirit, with a dried ball of the gum of the commercially valuable Landolphia florida.—Dr. Maxwell Masters read an extract from a letter of Dr. Beccari describing a gigantic Aroid found by him in Sumatra, side by side with the Rafflesia arnolii. The species has a large tuber 5 feet round, from which is pushed up a single leaf, with a long, stout petiole, the divided blade covering an area of 45 feet, or 15 metres. —Dr. R. C. A. Prior showed a specimen of Colletia cruciata in blossom, grown out of doors in Somersetsbire by the Rev. W. Sotheby.—“Notes on Euphorbiaceæ,”by Mr. G. Bentham, read in title, was a paper treating of the history, nomenclature, systematic arrangement, and the origin and geographical distribution of this remarkable order of plants. Among Dicotyledons, Euphorbiaceæ stands fourth in point of numbers, having above 3000 species and 200 genera. In investigating the origin of the order the geological record, unfortunately, is of no assistance. Their evident, generally tropical nature, is a striking feature, and, judging from various data, it is conjectured that their most ancient home was in the old world. Their affinities have repeatedly been discussed by botanists, but though there are individual genera which may exhibit some one character supposed to ally to other orders, yet no real connection has hitherto been pointed out. Their isolation is produced, not so much by any one special character, as by a special combination of several. As to position in the linear series, unless the order be broken up, practically it must remain among the Monochlamydese, in spite of occasional presence of corolla in some forms. The author has a most interesting chapter on nomenclature and synonymy, well worthy the study and serious attention of biologists generally. —Mr. Lewis A. Bernays, in a letter to the secretary, records the undoubted existence of Carpesium cernuum, in Queensland, and suggests its being indigenous there.—In a paper given in abstract, “Descriptions of New Hemiptera,” by Dr. F. Buchanan White, the diagnosis of 2 new genera (Helenus and Neovelia) and 17 new species are entered. These mainly are the results of Prof. Trail's late exploration of the regions bordering the River Amazon. —Mr. Alfred W. Bennett read a communication, “Notes on Cleistogamic Flowers; chiefly of Viola, Oxalis, and Impatiens.” According to him there are two kinds: —(I) Those which hardly differ from the perfect open flowers, other than the partial or entire suppression of the corolla, and the closing of the calyx (= homocleistogamic); and (2) those with a distinct modification in the flower to aid self-fertilization (= heterocleistogamic). He was at first disposed to regard those two kinds as having arisen, one by degradation, the other by a rudimentary form of the organ: but subsequent examination convinced him that both kinds owe their origin to degradation. In the extreme cleistogamic flowers a large number of organs have been correlatively modified. Most interesting phenomena occur in the mode of emission of the pollen tubes, these travelling through the air in a straight line from the anther vertically upwards in Oxalis, horizontally in others, and creep along the surface and even back of ovary in Viola canina. An unseen agency directs, for none wander with uncertainty; and this is all the more remarkable because, when not in proximity to the stigma, the pollen grains protrude their tubes in all possible directions.—The Rev. G. Henslow orally delivered the gist of a pape e On the Absorption of Dew and Rain by the Green Parts of Plants” (vide Science Notes).The Rev. W. W. Fowler and Messrs. Wilfred Huddlestone and T. M. Shuttleworth were elected Fellows of the Society.