Cytokinin and gibberllin activity in apple seeds and fruit flesh was investigated in relation to early drop of fruit. The early drop of ‘McIntosh Red’ apple fruit was enhanced by high night temperatures (25°C) given for 30 days beginning on the 10th day after full bloom. The diameters of 1200 central fruits on two trees were measured at the same point every other day to determine the onset of reduced rate of fruit enlargement, which was used to identify the potential drop fruit. Persistent fruit and potential drop fruit were collected and extracted with ethanol. An acid ether fraction and a n-butanol fraction were obtained from the ethanol extract. Activities of plant growth regulators in each fraction were bioassayed. It was found that zeatin- and zeatinriboside-like substances existed in the seed as cytokinin and that these plus an undefined cytokinin-like substances were found in the fruit flesh. Cytokinin activity in the seed was high, 40 to 70 times that in the fruit flesh. It was presumed, therefore, that the biosynthesis of cytokinin occurred in the seeds. Cytokinin activity in the seeds of potential drop fruit showed a value 1/15 to 1/40 that of persistent fruit. This may indicate that a decline in cytokinin activity is closely related to the early drop of fruit. GA3 and GA4+7 existed as gibberellins in the seeds. Gibberellin activity in seeds of the potential drop fruit was lower than that of persistent fruit. A decline in gibberellin activity may also be related to the early drop of fruit.
The aim of this study was to determine the optimum leaf area index(LAI) for fruit production of grapes when using a structure of extending arms and horizontal canes on a complete overhead pergola, as is popular in Japan. From 21 days after full bloom to harvest time, net assimilation rate(NAR) was measured in 3-year-old ‘Delaware’ vines grown in pots, half of which were kept non-shaded and half under the pergola(foliage) of 5-year-old ‘Delaware’ vines. All vines used were grown in a plastic film house. Fruit quality, NAR and crop growth rate(CGR) were measured in 4-year-old ‘Delaware’ vines grown in pots in a glasshouse with different LAIs and fruit loads. 1. A close relation was found between the NAR(Y) of the shaded vines and the LAI(X) of the shading vines (Y=0.126X2-1.33X+3.10). Growth analysis showed that the optimum LAI of ‘Delaware’ was about 3, since the LAI of the shading vines was calculated to be 3.2 when the NAR of the shaded vines was 0. 2. Little difference was observed in NAR between the vines whose LAIs were 2.08 and 2.82 but CGR increased with an increase in LAI and crop load. Bunches of vines whose LAI was 2.08 did not color well when the crop load was higher than 2kg/m2. However, in the vines whose LAI was 2.82, nearly all bunches matured normally, even when the crop load was as high as 2.8kg/m2. 3. From these results, the optimum LAI for both quantitative and qualitative fruit production in ‘Delaware’ vines grown with a complete overhead pergola in a plastic house in thought to be at least 2, and preferably 3.
Bud breaking effects of a leaching solution containing 20% lime nitrogen (55% CaCN2) and cyanamide (H2CN2) applied to the surface of dormant buds of glasshouse grown vines and single-bud cuttings of ‘Kyoho’ grape were examined. Treatment of intact vines with CaCN2 in December, January and February advanced bud break in the following spring by 16, 9, and 5 days, respectively. Treatment during the period of deep dormancy was most effective, in agreement with previous results. The effect of 3% H2CN2 given at the corresponding times was very similar to that of CaCN2, with bud break being advanced by 15, 7 and 4 days, respectively. Treatment of the single-bud cuttings bedded in December with CaCN2 and 0.5 or 1% H2CN2 during the same month advanced the bud break by 2 to 4 days. The bud breaking effect on the cuttings was much smaller than on the intact vines. Furthermore, at concentrations of H2CN2 above 2%, buds of the cuttings died due to chemical injury. In cuttings, the effective concentration of H2CN2 was one-third to one-sixth of that in intact vines. This might be the result of shallower dormancy due to wound effects in the cuttings. In late February, when dormancy had been broken, chemical injury to the cuttings occurred even when treated with CaCN2 and 1% H2CN2. These results indicate that H2CN2 has the same effect as CaCN2 on bud break of ‘Kyoho’ grape, which suggests that the bud breaking effect of lime nitrogen is mainly due to the active form of the cyanide ion (CN-), H2NCN being produced by partial hydrolysis of CaCN2.
This experiment was carried out to clarify the effect of spring weeds on the uptake of fertilizer nitrogen which had been applied on March 5. The citrus orchard was located on a site with a gentle slope and where 8-year-old satsuma trees were grown. The soil had originated from granite. In the bare ground plot, all of the weeds were wiped out with herbicide in the early spring. In the weed plot, most of the weed roots were found in the surface soil 0 to 5cm deep, while most of the satsuma roots were below 5cm. The soil temperature was consistently higher in the bare ground plot than in the weed plot, and was higher at the soil surface than in the subsoil. At a depth of 10cm, it reached 12°C in the middle of March to early April. In the bare ground plot, this temperature was reached 20 days earlier. The spring weeds, when cut and weighed on May 12, amounted to 3.23 tons per 10a. Total nitrogen content of the weeds was 10.5kg per 10a, and 38.6% of 15N applied in the early spring was absorbed by the weeds. After the cut weeds were mulched, about 75% of 15N had disappeared by September. This nitrogen was probably transferred into the soil and was partly reabsorbed by the satsuma trees. Thus, in the weed plot, 15N content in the leaves and fruit of the tree increased after September, while in the bare ground plot, the 15N content in the flowers and leaves was higher in early summer. In the bare ground plot, soil carbon and nitrogen contents were very low on May 12. 15N content in the subsoil of the bare ground plot was high in inorganic matter on May 12, but decreased markedly by July 21. In contrast, the 15N content in the surface to subsoil of the weed plot did not decrease as drastically during this period. The total amount of 15N absorbed by the trees over 13 months was very small compared with the 15N remaining in the soil. Nearly 90% of the 15N in the soil was found in the surface soil. The percentages of 15N remaining in the soil in the bare ground and weed plots were 29.7% and 63.6%, respectively. In conclusion, the pathway of nitrogen applied in early spring to citrus orchards differs considerably from spring to early summer depending on whether or not the ground is weed coverd.
Characteristics of photosynthesis and transpiration of a single leaf or seedlings of Citrus species were compared to clarify the responses to climatic conditions of Citrus species. The light compensation point of a single leaf was 1.5 to 3.5klx, which was similar in all species tested. There were remarkable difference, on the other hand, in the light saturation point among the species tested. That is, it was 10 to 20klx in ‘Morita’ Navel orange, 30 to 40klx in other several species and seemed to be 50klx or more in ‘Iyo’. The optimum temperature for photosynthesis of a single leaf was about 25°C, though there was little difference depending on temperature at 20 to 35°C, in Wase and Common Satsuma mandarin. It was, however, a little higher, i.e. about 30 °C, in ‘Ohta’ Ponkan and ‘Kawano’ Natsudaidai. The photosynthetic characteristics of the seedlings were similar to those of a single leaf, except that the light compensation point was slightly lower and light saturation point was higher than those of a single leaf. The transpiration rate increased as temperature rose up to 30°C, decreasing at 35°C to a certain extent depending on the species. The transpiration rate of a single leaf of ‘Morita’ Navel orange was hardly dependent on the temperature. It was suggested, therefore, ‘Morita’ Navel orange had a typical characteristic as to the temperature response of transpiration rate.
Proline was continuously fed in uniformly labelled 14C-form to the leaf of 4-year-old trees for 30hrs in late fall, and the 14C was analyzed in the petiole of 14C-fed leaf, other leaves, stems and roots. In the petiole, the recovered 14C as proline was accounted for 90% of the soluble 14C at the end of feeding. This demonstrates that proline exported from leaves to woody tissues in mostly unmetabolized form. The 14C was translocated partially into other leaves, but more into the stem bark and wood, and further a little into the roots. In the stem and root tissues, a part of the 14C was found in the anionic and neutral components and insoluble components. However, large parts of it remained in proline.
Growth characteristics of ‘Ohkubo’ peach trees grafted on P. persica (wild form, vigorous), P. japonica (dwarfing) and P. tomentosa (dwarfing) rootstocks were investigated for 4 years after grafting. All trees were trained to a slender spindle type. Tree height, trunk diameter and annual shoot growth were smaller in the trees on P. japonica and P. tomentosa than P. persica rootstocks. Many flower budswere formed in the first three years in the dwarfing rootstocks, compared with P. persica rootstocks. This indicates precosity of the trees on the dwarfing rootstocks. Fruit maturation was accelerated and soluble solids content in the fruit was high in the dwarfing rootstocks. Fruit size at harvest was largest in P. persica, followed by P. tomentosa and P. japonica rootstocks. This is mainly due to over-loaded fruit of the trees on the dwarfing rootstocks. Practices such as thinning, picking and pruning could be accomplished from the ground and the amount of shoots pruned per tree was small in the plots of dwarfing rootstocks. Root distribution of the dwarfing rootstocks was confined to small rhizospheres, where P. tomentosa roots were more likely to extend shallow than P. japonica roots. Many suckers were formed from P. japonica rootstocks.
Potassium fertilizer experiments of spinach were carried out to clarify the effects of growing season and plant age on the critical K concentration expressed as dry weight or % tissue water. The relationships between the dry weight of tops and K concentration of the youngest leaf were usually delineated by the second or the third degree polynomials. At the sixth leaf stage, the critical K concentration of the youngest leaf ranged from 4.3 to 6.7% when expressed on a dry weight basis. When expressed on a tissue water basis, it was not variable with about 0.7%, except after plants had been chilled. In early summer, the critical K concentration of the youngest leaf was kept constant at about 0.7% on a tissue water basis, but that on a dry weight basis decreased from the fifth to the seventh leaf stage.
Morphological feature of the shoot tip of the Japanese radish during transition into flowering was investigated by using the scanning electron microscope (SEM). The radish was vernalized by a low temperature (5°C) for 30 days in order to induce flowering. The radish was then transplanted into a water culture during the month of September. The induced plants bolted and flowered with an average of 12 and 29 days after transplanting, respectively, while the non-induced plants failed to bolt within the designated period (72 days after transplanting). At the anthesis stage, the number of leaves on main flower stalk was 12.4 per plant. This included 3.2 deformed leaves (small size, no or less than two lobes and pointed leaf apex) which developed near the top of the plant. The characteristics of these deformed leaves are discussed. The periodical sampling of shoot tips observed by SEM showed that the development of meristem from the vegetative stage to the flower bud initiation stage should consist of four stages. They are: (a) vegetative stage (flattened, <250μm in diameter), (b) dome shaped stage (>300μm in diameter), (c) initiation of lateral meristem at the young leaf axils, and, (d) individual flower bud initiation of apical meristem. Flower initiation should be indicated at lateral meristem initiation stage, especially flowering occurring under unfavorable conditions. The growth and development of lateral meristem were of the same pattern as those found in apical meristem.
The levels of endogenous hormones and nutrients in shoot apices of tomato plant were compared between the seedlings exposed to high and low temperature conditions in relation with occurrence of fruit malformation. The amounts of total sugar, total nitrogen, proteinous nitrogen in the seedlings grown at low temperaturecondition were greater than those in the seedlings grown at high temperature condition. The low level of auxin and high level of gibberellin were noticed in the seedlings grown under low temperature condition. Nutritional restrictions reduced occurrence of fruit malformation by decreasing ovary split rather than oblate and triangular shaped fruits. The treatment combined with auxin spray and nutritional restrictions reduced the occurrence of both ovary split and oblate/triangular shaped fruits.
Cucumber ovaries began to show curvature when they reached a length of 4.5 mm, and at about 12 days before flowering. Ovary curvature seemed to occur subsequent to a temporary suppression of ovary growth. Thus, on a node with 2female flowers were developing, removing the tendril, 2nd female flower and lateral shoot of the node and the main stem above the node (hereafter described as neighboring organs), either alone or in combination, promoted ovary growth and consequently decreased ovary curvature of the 1st female flower. The earlier the removal, the greater its effects. Fruit curvature also occurred after the suppression of early fruit growth. Thus, removing the neighboring organs alone or in combination late after flowering had no effect on fruit growth and curvature. As far as fruit curvature is concerned, fruit growth could be divided into 3 stages: (1) increasing, (2) maximizing, and (3) decreasing stage. The decrease in curvature occurred when fruit were left to grow on after the usual harvest time for fresh fruit. Curved fruit almost recovered their normal shape when they reached their final size. The maximum curvature angle of fruit was found to occur just before harvest time, when fruit were 10-15cm in length, and 5-6 days after flowering. There was little correlation between the curvature angle and length of ovary at flowering, but there was a close correlation between the increase in curvature after flowering and the number of days from flowering to harvest. These results suggest that curvature of ovaries and fruit is the result of a temporary suppression of growth during their rapid growth periods.
Germination tests of seeds were carried out at 5 different temperatures, i.e., 5, 15, 25, 35, and 45°C, using 11 different crops of Brassica. Germination was examined every two hours and, afterwards, every 12 or 24 hours. In every crop, seeds began to germinate earliest at 35°C and latest at 5°C. The start of germination became later in the decreasing order of temperature from 35 to 5°C. Seeds at 45°C began to germinate as early as those at 35°C in many crops, but in some crops the start of germination was much delayed. Mean germination period was shortest at 35°C, and shorter at 25°C in every crop. These temperatures were followed by either 15 or 45°C with respect to mean length of period. The longest period was needed for germination at 5°C. As for germination percentage, seeds at 35, 25 and 15°C showed more than 85% in all of the crops examined. At 45 or 5°C, low percentages of germination were frequently observed. Differences among crops were observed at these temperatures: some crops showed bad germination at 45°C, and some at 5°C, and others at both 45 and 5°C. The response of non-dormant seeds was different from that of dormant seeds in terms of germination temperature. Optimum temperatures for germination of non-dormant seeds were higher than those of partially dormant seeds.
In comparison of 9 leaves embryologically below the first flower of eggplant (Solanummelongena L., cv. Senryo No. 2), external and internal anatomy and photosynthetic capacity varying with the time after transplanting at the 2-leaf stage were investigated. 1. The increase in laminar dry weight per unit laminar length during leaf expansion was highest in leaf 5 (abbreviated as L5. L1 is the basal) and lower in leaves below and above it. While, the increase in laminar area per unit laminar length was higher in upper leaves. 2. Specific laminar dry weight (SLW) was higher in upper leaves at unfolding. Then, it decreased in upper leaves and slightly increased in lower leaves until it became almost constant and differed little with leaf position 35 days after transplanting. This trend was especially true for the values of SLW/laminar thickness, which, however, was slightly higher in upper leaves after becoming constant. 3. The numbers of palisade parenchyma and mesophyll cells per unit laminar area were higher at unfolding regardless of leaf position, and then decreased until becoming almost constant. Within a leaf, they were always higher at the basal, middle and distal parts in this order, but differed little after taking constant values. Palisade cells enlarged with leaf growth, but were always greater in upper leaves. 4. The number of chloroplasts per palisade cell was slightly greater at the distal, middle and basal parts in this order. It increased with leaf growth and the increase stopped in L3, L5 and L8 at the 7-, 8- and 11-leaf stages, respectively. 5. The chlorophyll content per unit laminar area increased with leaf growth. It reached the maxima at the 8- and 10-leaf stages in L3 and L5, and in L8, respectively, and then decreased. The maximal values were higher in upper leaves. The total nitrogen content per unit laminar area decreased with leaf growth, and the decrease was greater in upper leaves. 6. The photosynthetic rate increased from unfolding and reached the maxima of 21.2 (mgCO2 dm-2 h-1) for L3, 23.3 for L5 and 23.7 for L8 at the 8-, 10- and 11-leaf stages, respectively. The chlorophyll content was only parameter that showed a high correlation with the photosynthetic rate throughout the period up to the 14-leaf stage. 7. The stomatal density on the adaxial side of laminar was about a half of that of the abaxial side. Stomatal density was higher at the basal, middle and distal parts in this order on both sides and decreased with leaf growth. In upper leaves, it was higher at unfolding and the decreasing rate thereafter was also higher than in lower leaves.
Internodal sections at upper parts of flower stalks were used for clonal propagation of Phalaenopsis tissue culture. Around 100 days after explanting, 50 to 80% of these explants produced PLBs (protocorm like bodies) at their basal end. During several times of subculturing, these PLBs proliferated and grew into plantlets. Supplement of 10% coconut milk, 5mg/l α-naphtaleneacetic acid and 20mg/l 6-benzylaminopurine to the basal medium consisting of macro elements of Thomale GD (1954), minor elements and organic addenda of Ringe and Nitsch (1968), increased formation rate of PLBs. The primordia of PLB seem to initiate in the inner part of cortex. In this method, at least 400 PLBs and shoots will be obtained from one stalk in the first year.
Freesia corms freshly harvested late in spring are known to be in a state of deep dormancy and can be released from dormancy after exposure to high summer temperatures. This study was carried out to determine when dormancy starts duringthe growth period and when it ends during storage. New corms gradually entered dormancy as they increased in size. They reached a state of true dormancy at flowering time of the mother plants in mid-April. At this stage, differentiation of leaves on the uppermost axillary buds stopped and sprouting percentage of these excised buds cultured in vitro was very low. Similarly, intact corms cultured in vitro also sprouted poorly. The state of true dormancy continued till harvest time at the end of May. The dormancy disappeared at the end of August, when corms showed a high rate of sprouting and resumption of leaf differentiation on their uppermost buds. At the same time, the total sugar content of the corms increased greatly.
The relationship between anthocyanin and carbohydrate concentrations was examined in benitade (Polygonum hydropiper L.) seedlings grown in sand supplied only with water under different treatments of light or temperature. Shading was provided by covering field grown seedlings with cheesecloth for 7 days after the unfolding of cotyledons. The lower the degree of shading, the higher the concentration of anthocyanin, reducing sugar and starch. When seedlings were kept in a chamber and irradiated with blue, green or red light from fluorescent tubes (10.8-11.9J/m2 sec, 12 hours per day) for 5 days after emergence, anthocyanin, reducing sugar and starch concentrations were highest in the seedlings irradiated with red light. Seedlings were also grown for 9-10 days after the unfolding of cotyledons under outdoor plastic chambers at a constant temperature of 5, 15 or 25°C. Anthocyanin and reducing sugar concentrations were highest in seedlings grown at 15°C, but starch concentration was highest in seedlings grown at 25°C. When the day temperature was controlled to 15, 20, 25 or 30°C, with a night temperature of 5°C, concentrations of anthocyanin, reducing sugar and starch increased as the day temperature decreased. When seedlings were grown under night temperatures of 5, 10, 15 or 20°C, with a day temperature of 15°C, concentrations of anthocyanin and reducing sugar were higher at lower night temperature, although starch concentration was higher at 5-15°C than at 20°C. In the above experiments, without added nitrogen, the concentration of nitrogen in seedlings was relatively low, and no relationship to anthocyanin concentration was found. Combining the data from all the treatments described, and including results from previous nitrogen treatments (12), anthocyanin concentration was highly positively correlated with the concentration of reducing sugar or starch. However, reducing sugar concentration was negatively correlated with seedling fresh weight. Spraying with glucose, fructose or sucrose solution (0.1M) increased the anthocyanin concentration of seedlings. Promotion of anthocyanin synthesis in Polygonum seedlings seems to be closely correlated with a growth restriction, accompanied by the accumulation of carbohydrates such as sugar and starch.