1. In early February, young orange trees of Unshu (Citrus unshiu) and Natsumikan (C. natsu-daidai) were frozen by degrees from 0°C to -7°C in the refrigerator at night (9:30 p.m, to 9:00 a.m.). On the following day, they were taken out and each one third of them was treated in different ways. The first group was placed in the open air of 13.5°C under the direct ray of the sun, the second group was kept in the warm room of 13.5 °C, and the third group was warmed slowly up to 6-10°C by opening the door of the refrigerator. No apparent differences were found in the beginning among the treated and the non-treated plants. However, in early July the treated plants were very inferior in their growth to the non-treated plants in order of the first, second and third groups. 2. In early March, plants were treated with-5°C minimum temperature at night for 5 days successively. The longer the time of treatment, the higher was the freezing temperature, and the severer was the damage. Particularly, plants frozen at night for 4 or 5 days long sheded their leaves remarkably after melting. The tendency was more marked by Natsumikan than by Unshu oranges. 3. Plants frozen at night transpired more water in the daytime than plants not frozen, resulting in a decreased water content of leaves. On the fifth day of the freezing treatment, treated plants lost 1.3_??_1.4 times as much water as the non-treated plants, the water content of their leaves being 65% of the non-treated plants on fresh weight basis. On the other hand, plants suffered less cold injuries when watered before the treatment.
An important factor in the investigations of flowering in fruit trees has been a characteristic of many varieties and species known as alternate or biennial bearing. This characteristic probably exists in all fruit trees in varying degrees. It becomes so marked as to be of great economic importance with Unshû orange trees in Japan.
It has been recommended to thin fruits to one fruit per bearing shoot in early July for controlling biennial bearing in Japanese persimmon. But this common practice has not been able to control biennial bearing habit in our orchard. This study has been carried out to make clear the reason why the common practice failed to control biennial bearing, and to propose a proper standard for fruit thinning as a hypothesis. The orchard used for this study was composed of 33 trees including four varieties; Jirô and Hiratanenashi were biennial bearers and Mompei and Fuyû were annual bearers during the experiment from 1960 to 1962. Although fruits were thinned to one fruit per bearing shoot early in July, biennial bearing habit has still been hold in the following years in Jirô and Hiratanenashi. This method left too much fruits in on year and too few fruits in off year. To leave proper number of fruits after thinning seemed to be essential for controlling biennial bearing. A new standard for fruit thinning was searched to cover the weak point of the previous method. It was found that in spite of on and off years, about 85 percent of harvested fruits were borne on the shoots of 6_??_25cm in length Jirô and Hiratanenashi, and of 11_??_30cm in Mompei and Fuyû. The shoots of this length were tentatively called as the “yield composing shoots”. It was assumed to be reasonable to thin fruits to leave proper number of fruits per 100 yield composing shoots. Estimated desirable quantities of fruits per 100 yield composing shoots were 4.0_??_4.5kg for Jirô and Hiratanenashi, and 7_??_8kg for Mompei and Fuyu in our orchard, where yield of 2, 000kg per 10 ares is expected and leaf area index of trees is from one to two.
1. With grape vines grown in a glasshouse, experiments were carried out to break the dormancy of the vines by coating their surface with a solution of lime nitrogen, in two regions of different climatic conditions Niigata, and near Odawara. 2. The most effective time for such treatment was found to be from late December to the middle of January, that is, during a period of middle to late dormancy. The result was that sprouting and harvesting appeared approximately 10 to 15 days earlier respectively, and fruit growth was much promoted. No practical effects could be observed in the treatments which were given at a later time. 3. It is noticeable that the effect appeared only on the buds of treated twigs, and never on those of untreated twigs, in spite of their location being on the same trees; from which we assumed, the stimulus is limited to the treated parts of a tree. 4. When experiments were performed outdoors, no sufficient stimulating effect was gained in Niigata, with its severe and long, cold winter; while satisfactory results were obtained in Odawara, in a comparatively warm winter. The reasonn seemed to be that in Niigata, even though the inactivity was broken, the season was still too cold for grape vines to sprout immediately, and so the treatment had no significance.
Growth of Delaware grapes based on shoot length, and top and root weights decreased greatly with lowering soil oxygen concentration. In this case, the lower the soil oxygen concentration, the less was the content of K, P and Mg in leaves. Particularly, K content reached a deficient level when the oxygen concentration was depressed less than. 5% of the soil air.
The experiments were carried out to ascertain the effects of fertility of nursery bed soil, watering and spacing on the growth and flower formation of tomato seedlings. Seeds of “Fukuju No. 2” variety were sown in flat, and the seedlings were transplanted in clay pots (15cm in diameter) and were grown for 50 days after cotyledon expansion. 1. Effect of fertility of nursery bed soil on the vegetative and reproductive responses. Tomato seedlings were grown in the bed soils having three different levels of fertility The fertile bed soil induces vigorous growth, being followed with acceleration of flower differentiation with the decrease in number of leaves to the first inflorescence and the increased number of flowers with the acceleration of their development. 2. Effect of watering on the vegetative and reproductive responses. To set up the plots differing in water-regimes, irrigation water was supplied 50-100mc, 300mc and 500mc per pot every day. The more abundant the water supply, the more luxuriant the plant growth. The less water supply restricts the plant growth and retards the flower bud differentiation and its development, and decreases the number of flowers. 3. Effect of spacing on the vegetative and reproductive responses. The seedlings were transplanted 3×3cm, 6×6cm and 9×9cm apart in the nursery beds. The wider the spacing, the more vigorous the growth, being followed with earlier flower bud differentiation with less number of leaves to the first inflorescence, and increased number of flowers and acceleration of their development. 4. Relations between the flower formation and chemical constituents in tomato seedlings. The chemical constituents in the top of seedlings at 50 days stage grown under all the combinations of fertility levels of bed soil, watering and spacing vary significantly. They show high correlation with the total number of flowers up to the third inflorescence. The seedlings grown under the fertile bed soil, the favourable water supply and the wide spacing show higher level of carbohydrates, especially total sugars, and nitrogen compounds, especially protein, and differentiate many flowers. Carbohydrates, especially sugars and nitrogen, especially protein, are associated and needed for the better growth and reproductivity of the tomato plant.
In the previous paper, it was reported that tomato seedlings were severely injured in relatively short time when they were exposed to 50°C. It was also found that fruiting and germination of pollen were remarkably affected when seedlings were exposed to 45°C for three hours each in five days, though their vegetative parts were hardly affected. Expriments were conducted to determine the effect of different temperatures on tomato seedlings (Fukuju No. 2 variety) of various stages of growth. Seedlings were exposed to 30 (control), 35, 40 or 45°C for three hours daily lasting over five days. The stages of seedlings during high temperature treatment were cotyledon expanded, two to three leaves, five leaves, eight leaves, 11 leaves, and 14 to 15 leaves expanded. Temperature lower than 45°C generally induced no visible injuries on the plants, but in 14 to 15 leaves expanded stage, high temperature of 45°C induced necrosis in leaves and stem of some plants. Even the temperature as high as 45°C did not reduce yield when the seedlings were in the first three stages (till five leaves expanded). But the treatment of high temperature reduced both percentage of fruit setting and yield when plants were in the older three stages. In these three stages, the higher the temperature, the less the yield, also the older the seeding, the severer the effect. At eight leaves expanded stage yield was reduced only in the first cluster, while at 11 leaves expanded stage reduction in yield extended to the second cluster, and at 14 to 15 leaves expanded stage it was from first to third clusters. Considering the effect of high temperature on various stages of flower development, high temperature (40 to 45°C) resulted in overall reduction of fruit setting, when flower buds were treated in the stages 15 days prior to anthesis to nine days after anthesis. Reduction was especially severe in the flower buds five days before anthesis to one day after anthesis. It may, however, be mentioned that 40°C temperature treatment given one to two days before anthesis did not adversely affected fruit setting. A considerable number of small fruits of less than 50 grams in weight were obtained from the flower buds treated during and after anthesis, but no other types of abnormal fruits such as puffy or green gelatinous ones were obtained.
In 1962-1963, a study was carried out to examine effects of temperature on the branching in pea (Pisum sativum L. subsp. arvense, cv. GW). In one of the experiments, seeds were planted in outdoor rows five times at 15-day intervals from September 15 to November 15, and throughout the growing period the fluctuating natural daylengths were prolonged uniformly to 16 hours by daily artificial illumination so as to exclude possible effects of daylength on the branching (Experiment I). In the other experiments, seeds were sown in pots in the greenhouse where they were given various temperature regimes with electric bottom heating setup or by covering with transparent plastic sheets under 16-hour long days or 8-hour short days (Experiment II), or the pots were installed in the phytotrone in which they were grown at a constant temperature 20 or 30°C on long or short photoperiod (Experiment III). In the last experiment, potted plants received two different night temperatures 10° or 20°C for 25 days immediately after sowing (Experiment IV). When the first flower began to open, the plants were harvested and examined for the number of total branches, mean and maximum lengths of primary branches and their distribution on the main shoot. The results gave the following general trend: 1. Emergence and elongation of branches on lower nodes of the main shoot are encouraged by relatively cool temperatures, while warmer temperatures favour the branching on upper nodes (Tables 4 and 6). So far as the present experiments are concerned, the former lie around 10°C and the latter range from 15 to 20°C. 2. The emergence of lower branches is decisively determined by the environmental conditions at the very early stage of growth. In Experiment IV, the plants receiving a night temperature of 10°C for 25 days immediately after sowing gave lower branches almost twice as many as in the plants kept at 20°C at night (Table 8). 3. Under short-day conditions, branches develop on lower nodes at relatively high temperatures, while on long photoperiod, cool temperatures have little effect in arresting the branching on upper nodes (Table 4). 4. Further, the upper branches are produced more on short days than on long days when the plants are grown at 30°C, but the situation is reversed at 20°C (Table 6). Thus here an interaction between temperature and photoperiod is said to be working on the branching in pea.
In order to investigate the mechanism of salt injury of vegetable crops, spinach, turnip, celery, welsh onion, kidney bean, and chard were grown in sand culture under glass. HOAGLAND'S solution (about 0.6 atmosphere osmotic concentration) was used as the base nutrient solution, to which the mixture of NaCl, MgCl2, Na2SO4, CaCl2, and KCl at the same ratio in sea water, or each of NaCl, Na2SO4, CaCl2, or MgCl2, was added at 2 and 4 atmospheres osmotic concentration (4 and 8 atm. only for chard). Further, the osmotic concentration of HOAGLAND's solution was raised as high as that of these solutions containing excess salts. 1. In most cases, growth reduction was almost linear with the increasing osmotic concentration of the substrate, and the reduction was independent of the kind of salts on an equal osmotic basis. Therefore, the inhibitory effect of excess salts on the plant growth is considered to be primarily due to the osmotic effects in general. However, MgCl2, was generally more toxic than the other salts, and chloride salts were definitely toxic for chard. Sodium salts had favourable effects on the fresh weight yield of spinach and celery, but in the latter crop severe blackheart, a calcium deficiency symptom, developed. 2. Effects of excess salts on the calcium absorption by plants were recognized as follows: The increase of the osmotic concentration of nutrient solution markedly inhibited the calcium absorption in celery which easily developed calcium deficiency symptom. In most of the other crops, however, such osmotic inhibition of calcium absorption was not or only slightly observed. In NaCl, Na2SO"4 or MgCl2, treatments, antagonistic relation was observed between Ca and any other cations added; and on an equal osmotic basis, MgCl2, had most marked inhibitory effect on the calcium absorption. The inhibitory effect of excess NaCl on the Ca absorption by plants was recognized to be due to the interaction between Na and Ca in most crops except for celery. In general, sea water salts resulted in slightly lower Ca content in leaves than NaCl, which fact seems to be due to the effect of Mg++ ion in sea water salts. 3. Direct toxic effects of Na or Cl were not observed in most crops except for the chloride toxicity in chard. 4. On an equal osmotic basis, sea water salts and NaCl produced similar results as to the plant growth, visual symptoms and inorganic composition of leaves except for the Mg content. This fact shows that the ion effects of sea water salts are principally due to N+ and Cl- ions. This point was discussed further on the basis of the composition of real sea water.
This research was carried out to study the influence of the date of harvest and the curing of harvested bulb on bulb formation and the date of sprouting. Variety Imai-wase was used for this research and plants were harvested at seven times from May 25 to July 25 every ten days. 1. Even after falling of the top, thickening of the bulb continued for 20-30 days and the process of bulb formation finished when the death of the leaf blade occurred. The bulbs dug out in early stage had less storage leaves than that of late harvest, while there was no effect of harvest time on other parts in bulb. 2. In bulbs planted on late August, the date of sprouting was influenced by the date of their digging: the earlier the date of digging, the earlier sprouting. Accordingly it is considered that the bulbs dug out in its bulbing period enters dormancy, and after a certain period dormancy of bulb is broken; the earlier the date of digging, the earlier the breaking of dormancy. 3. In bulbs stored in room, however, harvesting at an early stage in the bulbing period, except the extremely early harvesting, caused late sprouting because of inhibition of leaf growth after the breaking of dormancy. 4. The curing of harvested bulbs delayed the time of sprouting, while the withering of leaf blade by a desiccant promoted the sprouting of onion bulb.
This paper reports the results obtained from the observations on the maturing process of plant grown under natural condition and on the effect of external factors on some characteristic phenomena which are found in relation to the bulbing of onion plant as a part of experiments carried out from 1959 to obtain the fundamental data of onion cultivation. 1. The process of bulb development was observed with Senshuki onion plants grown in the field under long day condition from April to July in 1959 and 1961. The increases in height and rooting occurred rapidly from April and reached their maximum at the beginning of May, being followed by the remarkable thickening of bulbs. As the bulb developed, the number of new roots decreased and their root activities declined. As a result the ratio of top weight to root weight increased gradually. The top prostration was observed at the later stage of bulbing, and was significantly correlated with the increase in the ratio of top weight to root weight. 2. Onion plants were grown under short or long day condition to clarify the effect of external factors on the following phenomena concering bulbing. (1) The increase in height was very slow under short photoperiod, wheareas the rapid increase occurred under long photoperiod, being followed by a remarkable bulb thickening. Accordingly it is clear that a rapid increase in height indicates the initiation of bulbing, and that the two growth periods are noticed in the bulbing, that is, the rapid leaf growth period and the bulb thickening period. (2) The morphological characteristics of bulb in onion plant were the scale leaf formation and the thickening of basal part of leaf sheath. The former was induced by the long photoperiod at first, and then the latter by the aid of photosynthesis. Measurement of transversal diameter at the base of leaf sheath is not proper for determining the time of scale leaf formation. The time of scale leaf formation may be determined by the following two ways: (1) To know the time to reach the maximum in height and (2) to examine the curve of the ratio of leaf blade to leaf sheath from outer leaf to inner one. (3) Development and activity of roots were affected not only by day length and temperature, but also by the bulb thickening. Namely, both long photoperiod and high temperature arrested rooting and curtailed root activity. The thickened bulbs had little ability to develop their roots. (4) The neck of bulb is the weak point where top falls down owing to the weakness of solid core of growing leaf blade which gives the neck rigidity before bulbing. It appeared that the top prostration may be affected by water supply from the roots too. (5) It was observed that the tillering of the first order was formed even under short photoperiod, while the bulb division up to the third order was found under long photoperiod with the thickening of bulbs. It seemed that the tillering is not directly affected by the photoperiod but by the thickening of bulbs.
There are root forming substances which are extracted by ether or water from leaves and stems of Portulaca, while inhibiting substances for rooting extracted by alcohole or water are detected simultaneously in leaves and stems of green color stem. The substances extracted by ether from Portulaca decrease the root forming power of IAA, while the substances extracted by water do not. It seems that the activity of root forming substances vary depending on the change of growing stage and environment. Particularly, flowering, cool temperature of short day act as negative factors. The root forming power of the substances extracted from Portulaca are weaker than that of IAA of 10ppm under the room condition. The root forming power of the ether extract is stronger than that of the water extract. The fact and other features show the extracted substances might contain the natural auxin. But, the presence of other substances besides natural auxin is doubtful within the series of this experiments.