Present study was performed to promote flower-bud differentiation of strawberry grown in the NFT (Nutrient Film Technique) system where the nutrient solution was cooled at night.
During raising period of strawberry (‘Terunoka’and‘U7-13’: ‘Pajaro’seedlingבTerunoka’), nutrient solution was kept at 10°C from 16: 00 in the evening to 8: 00 next morning, and nitrogen element was removed from the solution.
The treatment resulted in earlier flowering and harvesting, and in increase in fruit yield from the first harvesting through February.
During the treatment, rhizosphere temperature was 11-12°C and about 1°C higher than the solution temperature. Temperature in the crown was 13-15°C. Seemingly the solution temperature affected strongly at both root and crown, but not so significantly at leaf and petiole.
From the results, it was concluded that running cold nutrient solution through the channel of NFT cooled the roots and the shoot apex of strawberry and promoted flower-bud differentiation.

抄録全体を表示

Tomato, cv.‘Fukuzyu No. 2’, eggplant, cv.‘Hayabusa’and sweet pepper, cv.‘Shinsakigakemidori’were grown in sand culture under glasshouse conditions in order to clarify the differences in the effects of various concentration ratios of NO₃-N to NH₄-N (10: 0, 7: 3, 5: 5, 3: 7, and 0: 10) on growth, fruit development and chemical constituent.
1. The highest dry weight of plants and fruit yield were found in each crop under the concentration ratio of 7 NO₃-N: 3 NH₄-N, but higher concentration ratio of NH₄-N severely inhibited growth and fruit development. The decrease in dry weight and yield at higher concentration ratio of NH₄-N was greatest in tomato followed by sweet pepper and then eggplant.
2. When the plants were supplied with higher concentration ratio of NH₄-N, the incidence of fruits with blossom-end rot was observed in tomato and sweet pepper in contrast with very few incidence in eggplant.
3. The higher concentration ratio of NH₄-N markedly enhanced NH₄-N and soluble organic N in all plant tissues, and conversely reduced insoluble N and ratio of insoluble N to total N in the following descending order; tomato, sweet pepper, and eggplant.
4. The higher concentration ratio of NH₄-N reduced not only starch content in all plant tissues, especially in the root, but also soluble sugar content in the stem and root. Eggplant showed higher soluble sugar and starch contents in the leaf, stem and root than those of other crops.
5. P content in all plant tissues was increased as the concentration ratio of NH₄-N increased, whereas the cations such as K, Ca, Mg, Fe, Mn, Cu and Zn were decreased, particularly K, Ca and Mg. The mineral uptake of tomato was more remarkably impaired compared to that of eggplant and sweet pepper.

抄録全体を表示

Effects of the number of air changes per hour of the closed vessel (1.5 and 2.7 h^-1) and the photosynthetic photon flux (PPF, 34.3 and 133 μmol m^-2s^-1) on the CO₂concentration inside the vessel (C_in) and the growth of strawberry plantlets in vitro were investigated.
Cin during the photoperiod was lower than CO₂outside the vessel (Cout, inside the culture room) on 5 days after the start of experiments in all treatments. On 20 days after the start of experiments, C_inwas lower than C_out (350-400 ppm) by 100-300 ppm. The difference in CO₂concentration between inside and outside was relatively larger in the higher PPF treatment and in the larger number of air changes per hour treatment.
On 20 days after the start of experiments, the dry weight of the plantlet was larger in the higher PPF treatment than in the lower PPF treatment. However, the difference in the dry weight was not so large among the treatments, comparing with the large differences in C_inamong the treatments.
Relative growth rate, chlorophyll content, net photosynthetic rate, dark respiration rate etc. were estimated to explain the relatively small difference in the dry weight among the treatments. Furthermore, suggestions were made to improve the environment in the vessel further for promoting the plantlet growth.

抄録全体を表示

In our previous study, we identified the effect of the pulsed light illumination on the photosynthesis of Okayama Saradana with an one input-output system model and showed the possibility of saving electrical power by the application of the new artificial light source in the plant factory.
Photosynthesis of plant is also affected by CO₂concentration besides the pulsed light. So, the dynamic characteristics of the photosynthesis to CO₂concentration is also important to the analysis of the cultivating processes in the plant factory.
In this paper, we used a multivariable system model to estimate the effect of the pulsed light illumination on the photosynthesis of Okayama Saradana. Pulsed light illumination and CO₂concentration were taken as two input signals and the net CO₂uptake as the output signal. Impulse responses of net CO₂uptake to the two inputs were estimated. From the simulation, we got the same result to that of the one input-output system model discussed in our previous study that the net CO₂uptake of the plant under the illumination of low duty ratio of the pulsed light could be increased if CO₂concentration of the environment is increased.
Furthermore, we discussed the differences between the result from the one input-output system model and the multivariable system model. It seems that the one input-output system model could not give a reasonable result when CO₂concentration had great change as to ±50 ppm, but the multivariable system identification could do.
Plant and environments make up a very complicated system, in which many factors are included. We think that the multivariable system identification is a powerful method to analyse this system.

抄録全体を表示

The growth of the seeds of plants (Cucurnis statinusL., Triticum aestivumL. andRap hanus sativusL.) in the soil set up with magnetic field within 30 days are different from the growth of the seeds in the normal soil without magnetic field. In this experiment 1400±50G (G=Gauss) magnetic field and 700±50G magnetic field are used.
As a result, it is found that the length of the taproot in 1400±50G magnetic field becomes from 40% to 60% longer than that of the taproot in the normal soil, but the diameter of taproot becomes 50% shorter. The length of the taproot in 700±50G magnetic field becomes from 15% to 30% longer than that of taproot in the normal soil, but the diameter of taproot becomes 33% shorter.
But after 40 days it is found that the growth of the seeds of plants in the magnetic field and in the normal soil becomes nearly same.
As for the bloom and fructication in case of a cucumbers, it is found that the condition of the bloom and the fructication in the magnetic field becomes worse than that of the bloom and fructication in the normal soil after 90 days from planting seeds. As for the condition of a seed, it is found that a seed in the magnetic field becomes 50% smaller and softer than a seed in the normal soil.

抄録全体を表示

It is important to measure water content for analyzing plant physiology and controlling plant growth. There are some reports about measurement of it. They are the capacitance method that detects change of capacitance between two electrodes on a stem in proportion to the change of amount of water in a stem.
It is tried to measure the capacitance between the two electrodes on a stem by the easy electric circuit using the phase sensitive detector with analog switches and IC operational amplifier. The output voltage of this electric circuit is in good proportion to the change of the known capacitance and shows the response of water content in the stem of the poinsettia with vibration to sudden switching on and off of light like step-function.

抄録全体を表示