Since 1953, laboratory studies on the pathogens causing the rot disease of lotus rhizome and field survey on the prevalence of the disease in relation to the environmental conditions were carried out, and control measures have been established basing on the field experiments. The results obtained are summarized as follows. 1. The rot disease of lotus rhizome was classified into three types basing on the prevailing pathogens. Type 1. Brown rot disease caused by Fusarium spp. Type 2. Light-dark purple rot disease caused by Pythium sp. Type 3. Complex rot disease caused by mixed infection of Fusarium and Pythium. 2. It was found that the disease was transmitted through seed rhizome, water, and diseased leaves and rhizomes ploughed into the soil. The pathogens invaded into the rhizome mainely through the ab-sorbing roots or directly through the diseased por-tions of the seed rhizome, and sometimes through the wounds on the rhizome or soft tissues of the growing point. 3. The pathogenetic Fusaria could not survive 20cm or deeper in the soil under the drained condition, and 25cm or deeper under the waterlodged condition. Pythium was never perished under the above men-tioned conditions, though it could not survive on the soil or water surface. The brown rot disease caused by Fusaria is pre-valent mainely in the paddy-fields irrigated with shallow depth of water and with shallow ploughed layer of soil. On the contrary, the light-dark purple disease caused by Pythium is mainely prevalent in the lotusmoats filled with deep water or in the low and constantly wet paddy fields. 4. The temperature and pH ranges for the grow-th of the pathogens were as follows. Temperature Range Optimum Lethal Fusarium spp. 1033°C 27_??_30°C 54°C(lOmin.) Pythium sp. 10_??_45 30 50 (5min.) pH Range Optimum Fusarium spp. 2.2_??_11.7 7.2 Pythium sp. 3.2_??_9.4 6.2 The rot disease was more prevalent and proleptic when soil or water temperature was high. There-fore, deep irrigation or waterfilling for long period was more effective for the control of the rot disease. 5. Keeping the field filled with water during winter was an effective control measure of the brown rot disease. Draining or cultivating the field in winter made the field favorable for the prevalence of the brown rot disease. For the light-dark purple rot disease, those measures had an entirely contrary effect. 6. Soil disinfection by applying calcium cyana-mide at soil preparation was found to be an effective measure for controlling the disease. Application of lime sulfur in the period from soil preparation to early May was also effective. Application of wettable Captan to the soil in the period from soil preparation to early May was prov-ed to be surprisingly effective for the disinfection of soil. 7. Resistance of the lotus varieties to the diseases was tested by inoculating cultivated pathogens to the cross sections of lotus rhizomes. The results showed that Shina-shu was most resistant, Kobasu and Tenno were most susceptible, and Bitchu, Ka-zusa and Chukan-shu were intermediate to Fusaria. Field experiments showed the same results on the varietal difference in resistance to the brown rot. Significant differences were hardly found in the susceptibility to Pythium among lotus varieties.
1. Since 1954 the authers have carried out seed treatment investigations for principal vegetable crops with the view of examining the physiological and pathological effects of seed-soaking on seed germi-nation and growth of young seedlings, and the effects of seed protectant treatment on improving vegetable stands. The present report includes the results of experiments on carrot seed dressing per-formed during the period from 1955 to 1958. 2. In the field trials, carrot stands were improv-ed by dressing seeds with fugicidal dusts, especi-ally with thiuram (Arasan, Pomasol Forte, and Kawasen), dichlone (Phygon), and chloranile (Sp-ergon). 3. In the greenhouse experiments, carrot seeds naturally infected with Alternaria radicina were sown on steamed soil. This fungus proved to be responsible for carrot damping-off, especially in the pre-emergence phase. The dressing treatment was effective in improving the stands by control-ling damping-off. 4. In the germination tests on Petri dishes, most fungicides used more or less inhibited seed germination and also the growth of radicles. Practically, however, the inhibiting effect seemed to be negligible when seeds were sown in soil. 5. The effectiveness of the dressing treatment appeared to vary with the following factors: den-sity of fungal infection of seeds, temperature of seed beds, and depth of seeding. 6. Recommendation based on the trials is the dressing carrot seeds with Arasan, Pomasol Forte, Kawasen, Phygon, or Spergon at the dosage of 0.75 percent of dehaired seeds by weight.
In the previous papers, we described the results of experiments concerning the inferior growth of onion planted following cabbage, a phenomenon pe-culiar in Fuji district known for its production of early spring cabbage. Now, in recent years, the production of early spring cabbage itself decreased rapidly; for exam-ple, annual acreage, production and yield value in 1959 were 110 ha, 1700 tons and ¥17, 787, 000 res-pectively as compared with 250 ha, 5600 tons and ¥86, 196, 000 in 1955. This acute drop of cabbage production is remark-able especially in the central area of this district where cabbage has been grown successively year after year, while in the surrounding area where cabbage is a new crop or has been grown in rota-tion with barley, the normal growth and early har-vesting are possible as it was once so in the central area. One of the causes of this decline is the occurrence of nutritional disorder which appeared as the so called “heart rot” for the first time in the spring of 1957 and successively in 1958, and another is the severe infection of Botrytis. The nutritional disorder seems to be due to the calcium deficiency or rather the failure of calcium absorption and its characteristics, which are strik-ingly similar to some of the calcium deficiency symptoms observed in sand and water cultures, are as follows: when appear before heading; the darkening of leaf color and the splitting and brown-ing of the margins of green leaves: when appear after heading; the hooking and the development of water-soaked areas around the margins of head leaves which turn light brown, in both cases second-ary invasions of soft rot bacteria can be often recognized. The severe occurrence of this disorder has been seen, as above-mentioned, especially in the central area where cabbage had been grown successively and consequently supplied with a great deal of in-organic fertilizers, and moreover it has been seen exclusively following dry winter as in 1957 and 1958, while no occurrence following wet winter as in 1959. In addition it is noteworthy that even in the central area the disorder has been mild in the fields with high water table and also that even in the year in which no disorder occurred in the fields, typical calcium deficiency symptoms appeared in all of the cabbage plants grown under glass cover for seed growing, perhaps due to drying of the soil under glass. Now, we investigated the relation of the occur-rence of calcium deficiency in cabbage to the com-position of culture solution, as its occurrence in celery and tomato had been elucidated to be due to the high salt concentration or the unbalance of the nutrients. The results were as follows. Among seven treatments (culture solutions) includ-ing the standard (Ca 7m. e./l), -Ca (Cal m. e./l), (-Ca)×3, -Ca+NH4, -Ca+K, -Ca+Mg and-Ca+Na (in the latter four treatments, 6(=7-1) m. e./l of Ca was substituted by each of NH4, K, Mg and Na), the growth was superior in the standard, -Ca+K and -Ca+Na while inferior in(-Ca)×3 and -Ca+Mg. Visual deficiency symptoms on the green leaves before heading appeared only in (-Ca)×3, while those on the head leaves, which were often com-plicated with and difficult to distinguish from the decay due to bacteria, developed severely in all of the treatments except the standard and there was little difference in its severity. In addition, it was very interesting that the sudden infection of soft rot bacteria occurred on the outer head leaves immediately before harvest, and it was most severe in -Ca+Mg, followed by -Ca+K, while almost no infection occurred in the standard. Prior to this infection the marginal wilting of the outer head leaves was seen in some plants but the relation of this wilting to the bacterial infection was not clear
1. Studies on the effect of some growth regula-tors on the floral initiation in spinach plants were carried out for the purposes of making easy the breeding procedure, and of obtaining a good product of seeds in certain slow bolting strains, such as the variety “King of Denmark”. The results obtained are as follows. 2. The application of MH (50 or 100 ppm in conc.) to the young seedlings resulted in the accele-ration of floral initiation, bolting and flowering, and also in raising a large amount of seeds. The plants treated with NAA (10 ppm in conc.) were more or less retarded, in turn, in their reproductive development compared with non-treated controls. 3. The application of Gibberellin (1_??_40 ppm in conc.) to the young seedlings during summer days showed a striking elongation of flower-stalks, but the floral initiation itself could not be induced at all. While the plants treated during autumn or winter months showed a remarkable acceleration of their floral induction. From these results with spi-nach plants, it might' be deduced that gibberellin can exert an effect equal to the so-called “vernalin”. 4. Different responses to the so-called chemical vernalization were detected with several chemicals. Gibberellin was the most effective one. One ppm of NAA was also quite effective to flower promotion, while 10 ppm of NAA had no definite effect. Maleic-hydrazide (50 ppm in conc.) used on the chemical vernalization showed a slight inhibitory effect on flowering.
KROH (1956) has recently reported the following interesting experimental results with the self-incom-patible Raphanus raphanistrum: four different self-pollination methods after removing the stigma pro-duce some fruits respectively. The fertility of cross-pollination after removing the stigma is almost as low as that of self-pollination after removing the stigma. This fact leads to the conclusion that the relatively low fertility of self-pollination after re-moving the stigma is due to the mechanical injury caused by the experimental treatment. The intro-duction of pollen grains into the stigmatic tissues produces an eighty percent of selfed fruits. Conse-quently it seems probable that the inhibiting reaction is limited to the surface stigmatic tissues. The present author paid attention to these results and attempted experiments similar to these with the self-incompatible Japanese radish. The results ob-tained were fully in accord with those of KROH (See Fig. 1, Table 1, 2, 3 and 4).
The progress of citrus taxonomy has been greatly delayed from various reasons, primarily due to the misapplication of specific names to classify obvious unit species. From the time of LINNAEUS, a num-ber of definite unit species of Citrus have been passes into two major groups symbolized by Citrus Medica and C. Aurantium, under which good unit species are placed in either one of them with the status of lower categories such as their subspecies, subvarieties and so on. HOOKER, and later ENGLER, followed the same erraneous scheme in using these specific names to group existing units which are quite independent from each other having definite characteristics with type materials, geographic dis-tribution and historical careers together with au-thentic descriptions and valid names worthy of bo-tanical species. C. Medica, for instance, is an unit species, representing the Turunj type of citron, known in India from the Sanskrit time under the name Matulunga, and in China from CHI-Han's period (A. D. 290_??_307) under Kou yuan. By simple resembrance, it cannot involve C. Limon (the lemon), C. Limonia (Canton lemon) and the lime (C. aurantifolia) of different taxonomic status and geographical independence. All of them are equally separate species of different origin and C. Medica cannot stand at an upper taxon to group them all. From this principle, every one of citrus units is to be handled equally to hold species rank so far as it represents valid specific status with definite geo-graphical background and historical bearing to prove its concrete existence. Higher taxa, such as sub-genus, section, subsection, etc., are to be created to systematize these unit species, which should not be in the shape of specific taxon, as these great authors unjustly misapplied against the present day type-concept. Minor difficulties blocking so far the smooth pathway of the taxonomic development of citrus fruits, are misidentification based upon graphical and historical absurdity, repeated abues of non-valid specific names, too frequent negligence of valid species by the lack of critical investi-gations, and the random use of obscure non-specific botanical units without proper justification. Citrus taxonomy, therefore, must proceed with the secure mapping of independent specific units authorized by taxonomic-geographical proof with historical endorsement if possible, then followed by their sys-tematic arrangement properly classified keeping the evolutionary sequence in sight.
The effects of green wood pruning on the development of flowers and shoots were observed from 1936 to 1938, and again in 1953 and 1955. The results obtained can be summarized as follows: 1. Cutting back of branches of one, two or three years old decreased not only the number of flowers and shoots, but also the vigour of shoot growth in the following spring. The more severely the branches shoots were cut back, the stronger the effects appeared. Thus, cutting back of green wood was of no value in growing the bearing shoots for the next year. 2. When the cutting back of green wood was so severe as to decrease the number of flowers by one-third, it promoted the growth of shoots. But such heavy pruning is too laborious to be applied on large trees. 3. Pruning off of all branches of one-year-old without cutting back two-year-old branches induced more vigorus growth of shoots than that with cutting back of two-year-old branches. 4. The seasonal effect of pruning on the number of flowers and the shoot growth was not remarkable for a period of five months from November to March next. 5. When the previous summer's shoots were cut back in early spring, vigorous shoots grew in late spring. When all the summer shoots, saving the portion of spring shoot, were pruned off, the shoots grew more vigorously.
1. Further experiment was conducted to clarify the reason of the growth promoting effect of slag applied to young apple trees on the volcanic-ash soil on which the author's previous paper reported. 2. When supplied separately with slag and its three main, components viz, lime, silica and magne-sia, the growth of one-year-old apple trees planted in the pots with volcanic-ash soil, was remarkably promoted, with a result that the trees given with slag or magnesia were much superior to those with lime or silica. 3. And, according to the leaf analysis for N, P, K, Ca, Mg and SiO2, it was common that leaves of the trees fertilized with slag or magnesia con-tained more Mg than those with lime or silica, which appearently showed the magnesium deficiency. This fact might suggest that the effect of slag application exists in Mg element it contains. 4. However, considerable differences in the tree form were observed between the trees given with slag and with magnesia, that is, the former was inferior to the latter in the top-growth, while regard-ing the root-growth, the relation was reverse, thus top-root ratio (T/R) of the former being much lower than that of the latter.
1. With the deceleration of the process of grow-th, the cane of rose becomes frost-hardy to some degree without being subjected to low temperature and then can be hardened further when they are subjected to low temperature. On the other hand, the growing cane is neither frost-hardy nor able to increase its frost-hardiness, even if it is subjected for ten days to 0°C. It is, therefore, very likely that in canes of the rose, the frost-hardiness as well as the abilty to be effectively hardened by ar-tificial chilling is closely associated with their stage of development. A variety that increase earlier its frost-hardiness in early fall has greater winter frost-hardiness than others. 2. The minimum temperature at which the canes of rose varieties are able to survive after 24 hours of freezing in winter are as follows: R. laevigata: -10°_??_-12°C, H. T., Floribunda, R. kordesii: -14°_??_16°C, H. P., Sub. Zero: -17_??_-18°C, Dorothy Perkins (Rambler): -20°C, R. multiflora, R. wichuraiana, R. setigera: -22°_??_-24°C and R. rugosa, R. pendulina: -27°_??_-28°C (Table 1). 3. In both natural and artificial frost-hardening of the parenchyma cells in the cortex of the rose, the increase in frost-hardiness of parenchyma cells is intimately proportional to that in their osmotic concentration (Table 2, Fig.2). 4. The canes of R. pendulina, and R. rugosa were immersed in liquid oxygen for 24 hours after pre-freezing for 16 hours at -30°C in order to draw from the cell interior almost all of the easily freez-able water by sufficient extracellular freezing. After having been thawed, they were planted in moist sand to test the capacity for development in green-house. The canes so treated put forth buds (Fig. 3); the parenchyma cells of their cortex were normally stained by neutral red solution and retain-ed their plasmolysis capacity (Fig. 4), but gradual-ly th canes withered because their inner cortex, pith-ray and pith periclinal tissue are less resistant to pre-freezing at -30°C than the parenchyma cells of cortex and buds.