JP2006067948A - Method for accelerating growth of short day plant and neutral plant by utilizing light supplement for short time at night - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accelerating the growth of short day plants and neutral plants by utilizing a light supplement in short time at nights. <P>SOLUTION: This method for accelerating growth is provided by irradiating far-infrared light at the beginning of the nights for the short day plants and neutral plants. Here, as for the supplement of light by the light, it is sufficient to secure a light energy amount (irradiance × time length) in an extent of inducing the growth acceleration reaction, and even with a weak light for a short time, it is possible to cause the induction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for promoting plant growth by using supplementary light. More specifically, the present invention relates to an improvement in a method for promoting the growth of short-day plants and neutral plants using short-time supplementary light at night.

  In the case of greenhouse cultivation under poor daylight conditions, the introduction of supplementary lighting is being considered to improve poor plant growth due to lack of light. For example, according to research so far, it is known that spinach, which is the main institutional vegetable, promotes growth even when using low-light night lighting. Extending the morning and evening day length by night lighting for several hours shows the same level of growth promotion under various illuminance conditions. Therefore, the growth promotion of spinach by night lighting is not due to an increase in the amount of photosynthesis, but with the extension of the day length. Has been considered an effect. For this reason, in order to obtain the growth promotion effect, it is thought that it is necessary to carry out night illumination for a longer time, which involves a problem that it involves much power consumption. For this reason, in order to spread the growth promotion method by introducing supplementary illumination as a practical technology, it is desired to develop a supplementary technology that consumes less power and has a large effect.

  In order to respond to such demands, the present inventors have repeatedly conducted various experiments on the effects of nighttime supplementary light quality and irradiation time, as well as the irradiation time zone, on spinach, which is the main facility vegetable. It was confirmed that even if spinach was grown under short-day conditions where no flowering was induced, growth was promoted by short-time light supplementation at night, and the effect was not due to prolonged daylength. Therefore, we focused on the physiological functions of plants, and in order to find ways to use light as a stimulus, which can improve the yield and quality of crops even with low light intensity, we used spinach, a major institutional vegetable, to supplement light at night. The effects of light quality and irradiation time on growth have been investigated by artificial light chamber experiments. As a result, it was found that when blue light was irradiated at the end of the night or red light was irradiated at the start of the night, growth was promoted even with supplementary light for 30 minutes (Non-patent Document 1). ). Further, both blue and red short-time supplementary light are effective for the purpose of improving poor growth under low illumination conditions, and it has been confirmed that the growth promotion effect can be enhanced by using both supplementary light supplements. Moreover, it has been confirmed that these short-time light irradiations are effective as a light supplementing method that compensates for poor growth under low illumination conditions (Non-Patent Document 2).

  Therefore, it was considered that this growth promotion technology using short-time supplementary illumination can be expected to be applied to the production of various leaf vegetables other than spinach.

Japan Society for Agricultural Meteorology, Japan Society for Bioenvironmental Regulation, Japan Society of Plant Factory, CELSS Society 2002 Annual Conference Proceedings, page 357 2002.8.6 Japan Society for Agricultural Meteorology, Japan Society for Bioenvironmental Regulation, Japan Society of Plant Factory, Ecological Engineering Society, Agricultural Information Society 2003 Annual Conference Proceedings, page 173 2003.9.8

However, in radish, which is the same long-day plant as spinach, it was possible to induce growth promotion by irradiating red light at the beginning of the night like spinach, but short-day plants such as perilla, ensai, sunny lettuce, etc. The plants did not promote growth when irradiated with red light at the beginning of the night or with blue light at the end of the night.
That is, the growth promotion reaction to short-time supplementation of red light and blue light, which was effective in spinach, does not occur in short-day plants or neutral plants such as perilla, ensai and sunny lettuce, and is effective in promoting growth. It has been clarified by research by the present inventors that there is no such thing.

  Therefore, an object of the present invention is to provide a growth promotion method using short-time supplementary light that is effective for short-day plants and neutral plants.

  In order to achieve such an object, the present inventors explored the possibility of using leaf vegetables other than spinach for the production of perilla, ensai, sunny lettuce, radish for short-time irradiation of blue, red, and far red at night. The growth response was examined.

  As a result, the present inventors, such as short-day perilla and ensai, conditional long-day Sunny lettuce (neutral plant) that is not easily affected by daylength, show growth promotion when irradiated with far-red light, On the other hand, it was found that long-day radish, like spinach, produced growth promotion when irradiated with red light, but stopped growth promotion when irradiated with far-red light. In this way, vegetables show growth promotion when irradiated with either red light or far red light for a short time, and are classified into two opposite photoreaction types, in other words, different growth responses to far red light. It came to discover that there are two types of plants. In addition, vegetables other than spinach have little growth-promoting effect even when irradiated with blue light at the end of the night, and any vegetable containing spinach grows while maintaining nutrients such as β-carotene and ascorbic acid. It came to know that the effect of promotion is acquired.

The present invention is based on this finding, and irradiates short-day plants or neutral plants with far-red light at the start of the night. Here, the far red light is light having a wavelength of 700 to 800 nm. In addition, it is sufficient for the supplementary light by far-red light to secure a light energy amount (irradiance × time length) that is a light stimulus for inducing a growth promoting reaction, and even in the case of weak light in a short time. Even if there is, it can cause induction. On the other hand, since far-red light does not contribute to photosynthesis, even if it is irradiated for a long time, there is no direct influence on the growth and increase in the amount of dry matter, and input electric energy is wasted. Moreover, the growth-promoting reaction of short-day plants and neutral plants functions as a switch in which the photoreceptors of these plants sense far-red light and send some signal to detect periodic changes between day and night. Estimated. From this, it is considered that the supplemental light of far-red light can induce the growth promotion even for 1 minute when the amount of light energy sufficient to cause light stimulation is secured, and 50 μmol m ⁻ used in the experiment. Even in the case of weak light with a low irradiance of about ² s ⁻¹ , induction is caused. In this case as well, a short time of at least 5 minutes, preferably about 30 minutes is sufficient. According to the experiments by the present inventors, supplementation was performed for about 30 minutes at an irradiance of about 50 μmol m ⁻² s ⁻¹ , but the effect was obtained even if it was shorter or longer than that. However, since the effect on the input energy (amount of electricity) is reduced, about 30 minutes is the most effective and sufficient. Further, since it is induced by weak light, that is, light stimulation, an irradiance level of 50 μmol m ⁻² s ⁻¹ is sufficient. However, from experimental experience, it can grow even at a fraction of a fraction. Promotion is thought to be induced.

  Thus, when short-day plants or neutral plants are irradiated with far-red light at the start of the night, the average total dry matter weight is about 30% (29% for perilla, 27% for ensai, 35% for sunny lettuce) ) Increased. Moreover, even when growth was promoted by short-time supplementary light at night, it was confirmed that the decrease in the concentrations of β-carotene and ascorbic acid (vitamin C), which are the main nutritional components of leafy vegetables, was small. In other words, short-time supplementary light at the beginning of night of far-red light reduces the decrease of major nutrients such as vitamins against various short-day and neutral plant leafy vegetables grown under low-light conditions. It is an effective method to suppress and improve growth defects. Of course, further growth promoting effects can be obtained even under sufficient sunshine conditions.

The growth promotion method for short-day plants and neutral plants according to the present invention irradiates short-day plants and neutral plants with far-red light at the start of the night. Here, the far red light is light having a wavelength of 700 to 800 nm, and a far red light lamp (FR lamp) can be used. Far-red light supplementation is sufficient if the amount of light energy (irradiance x time length) is sufficient to be a light stimulus that induces a growth promoting reaction, and even in the case of weak light, Can also induce induction. According to experiments by the present inventors, it was confirmed that the amount of light energy of supplementary light is sufficient as a light stimulus when a level of about 10 ⁻³ mol m ⁻² or more is secured. Accordingly, when a level of light energy ^sufficient to cause this light stimulation, for example, a level of about 10 ⁻³ mol m ⁻² or more is secured, it is considered that the light can be induced even for 1 minute, and 50 μmol m ⁻ used in the experiment. Even in the case of weak light with a low irradiance of about ² s ⁻¹ , induction is caused. In this case as well, a short time of at least 5 minutes, preferably about 30 minutes is sufficient. That is, according to the experiments by the present inventors, supplementation was performed for about 30 minutes at an irradiance of about 50 μmol m ⁻² s ⁻¹ , but the effect was obtained even if it was shorter or longer. However, about 30 minutes is the most effective and sufficient because the effect on the input energy (amount of electricity) is reduced. Further, since it is induced by weak light, that is, light stimulation, an irradiance level of 50 μmol m ⁻² s ⁻¹ is sufficient. However, from experimental experience, it can grow even at a fraction of a fraction. Promotion is thought to be induced. It should be noted that the amount of light energy required for inducing growth induction by short-time supplementation of far-red light may vary depending on the plant species even in the same short-day plant or neutral plant, and in some cases, 10 ⁻³ mol m ^It may occur at a light energy level of about ⁻² or less. However, strictly specifying the criticality of the amount of light energy required for supplementary light is not important for the establishment of the present invention. What is important in the present invention is to irradiate far-red light having a sufficient amount of light energy at the start of the night as a light stimulus for inducing growth induction, and preferably an amount of light energy more than necessary from the viewpoint of energy saving. That is not to give.

  In addition, the start of the night is from when the daytime lighting (PPFD) is turned off in the case of facility cultivation by artificial light, but it changes depending on the speed at which the day falls under natural light cultivation conditions. And includes an error of 1 to 2 hours. However, supplementing far-red light at midnight had no effect, so if it is supplemented at the end of the light period (dusk), growth is induced. Here, the present invention is for improving poor plant growth due to lack of light in an environment with poor daylight conditions, so daylighting (PPFD) in the case of facility cultivation by artificial light is Needless to say, it is more effective when it is under low illuminance or under bad natural light conditions such as Japan, but it is also effective in cultivation under good sunshine conditions or high illuminance. .

  The followings are spinach, which is a major institutional vegetable and a long-day plant, and a chrysanthemum plant that is a short-day plant, a perillaceae of the family Lamiaceae, an ensai of the convolvulaceae family, and a conditional long-day plant (it is difficult to show long-day characteristics at suitable cultivation temperatures). Sunny lettuce of the family, and radish of the Brassicaceae family as a long-day plant like spinach was grown by the following method, and the effect on growth by short-time supplementary light was tested.

(Plant material and cultivation method)
(A) Spinach seeds were soaked in running water overnight, then sown on moistened paper towels in a plastic case and germinated at 25 ° C. in the dark. Two days later, the cover was removed, and the seeds with young roots extended to 1 to 2 cm were transplanted to urethane cube medium in a plastic tray, and white fluorescent lamp (FLR110HW / A / 100; Mitsubishi Electric) in a constant temperature room maintained at 25 ° C. Grown for 7 days under.
(B) Perilla seeds were sown on a damp paper towel in a plastic case and germinated in the dark at 28 ° C. Two days later, seeds with larvae extended to 1 to 2 cm were transplanted to a urethane cube medium in a plastic tray and grown under a white fluorescent lamp (same as above) in a temperature-controlled room maintained at 25 ° C. for 14 days.
(C) Ensai seeds were soaked in running water for 4 hours, then sown in plastic bats filled with vermiculite and germinated at 25 ° C. in the dark. After 2 days, remove the cover and grow for 7 days under a white fluorescent lamp (same as above) in a constant temperature room maintained at 25 ° C. Transplant the seedlings whose radicles have grown to 2 to 3 cm onto a urethane cube medium in a plastic tray. Cultivated for another 5 days.
(D) Sunny lettuce seeds were directly sown on a urethane cube medium in a plastic tray and germinated at 25 ° C. in the dark. After 3 days, the cover was removed and the plants were grown for 4 days under a white fluorescent lamp (same as above) in a constant temperature room maintained at 25 ° C.
(E) The radish seeds were soaked in running water for 1 hour, then directly sown on a urethane cube medium in a plastic tray and germinated at 25 ° C. in the dark. After 2 days, the cover was removed, and the plants were grown for 7 days under a white fluorescent lamp (same as above) in a constant temperature room maintained at 25 ° C.

The temperature-controlled room used for raising the test plants was set to light and dark periods of 12 hours each and the photosynthesis effective photon flux density (PPFD) was set to 110 μmol m ⁻² s ⁻¹ . In each experiment, the seedlings with the first two leaves having the same size were selected and transplanted to the cultivation bed installed in the growth chamber below. Grown by tillage. Culture solution contains NH ₄ 23, NO ₃ 223, P ₂ O ₅ 120, K ₂ O ₃ 60, CaO ₂ 30, MgO75, MnO1.5, B ₂ O1.5, Fe2.7 (mg L ^-1 ) Otsuka House Fertilizer A formulation (Otsuka Chemical) was used, and the electrical conductivity was adjusted to 1.2 dSm ⁻¹ at the time of planting, 2.4 dSm ⁻¹ on the fifth day of planting, and the pH was maintained at about 5-6.

(Experimental device)
A hydroponic bed (90 x 60 x 10 cm, vertically circulating fluid type) is installed in four growth chambers (VB1514-internal dimensions 200 x 75 x 140 cm; Votsch) that can control the number and height of the main light sources. Immediately after transplanting, spinach was cultivated under supplementary lighting for 26 days, perilla for 19 days, ensai for 17 days, sunny lettuce for 16 days, and radish for 19 days. The growth chamber maintained an air temperature of 25 ° C and a relative humidity of 60% with a built-in air conditioner.
The main light source equipped with a 30-w daylight fluorescent lamp (W lamp, Lumilux plus L30w / 31-830, Osram) was used for daytime lighting. For nighttime supplementary lighting, the 32-w blue, red and far-red fluorescent lamps (B lamp (λmax 454 nm), R lamp (λmax 659 nm) and FR lamp (λmax 749 nm), FLR900T6 type, Nippon Electric) It was used by placing it on the upper side of the side wall so as not to hinder it. The output of the supplementary lamp was adjusted by a power unit (FDP-2001, Nippon Electric).
The spectral photon distribution of each fluorescent lamp was measured with a spectroradiometer (MSR7000, Opt Research). PPFD was measured with a photon sensor (LI-190SB, Li-Cor Inc.) and obtained as an average value of 9 points on the cultivation panel.

(Light processing)
In all growth chamber experiments, daytime PPFD was set constant at 200 μmol m ⁻² s ⁻¹ under low illumination conditions. For blue, red, and far-red nighttime supplements, the irradiance was 50 μmol m ^-2 s ^-1 and the irradiation time was 30 minutes, and the effects on growth and nutritional components were compared with those of no supplementary light.
(A) Short-time supplementation to spinach: Comparative Example 1
In the experiment, the daytime is 10 hours (6: 00-16: 00) and the nighttime is 14 hours (16: 00-6: 00). Irradiate with blue light for 30 minutes before the hour (5:30 to 6:00) or with red light or far red light for 30 minutes (16:00 to 16:30) from the beginning of the night. Experiments 1 and 2 were performed for 26 days under different light treatment conditions.
(Experiment 1): At the beginning of the night (16: 00-), irradiate red light (R zone) or far red light (FR zone) for 30 minutes, or alternately irradiate red light and far red light for 30 minutes each. (R + FR).
(Experiment 2): Red light and far-red light were alternately irradiated for 30 minutes at the beginning of the night (16: 00-) (R + FR, R + FR + R, R + FR + R + FR) Ward).
(B) Short-time supplementation to perilla: Example 1
The daytime was 14 hours (6: 00-20: 00) and the night was 10 hours (20: 00-6: 00). For supplementary lighting at night, use non-complementary light as a control zone and irradiate with blue light at the end of the night (5:30 to 6:00) or at the start of the night (20:00 to 20:30) Irradiated with red or far red light and treated for 19 days.
(C) Short-time supplement to ensai: Example 2
The daytime was 14 hours (6: 00-20: 00) and the night was 10 hours (20: 00-6: 00). For supplementary lighting at night, use non-complementary light as a control zone and irradiate with blue light at the end of the night (5:30 to 6:00) or at the start of the night (20:00 to 20:30) Irradiated with red or far red light and treated for 17 days.
(D) Short-time supplementation to sunny lettuce: Example 3
Since day length sensitivity was not high, the daytime was set to 14 hours (6: 00-20: 00) and the night was set to 10 hours (20: 00-6: 00). For supplementary lighting at night, use non-complementary light as a control zone and irradiate with blue light at the end of the night (5:30 to 6:00) or at the start of the night (20:00 to 20:30) Irradiated with red or far red light and treated for 16 days.
(E) Short-time supplementation to Japanese radish: Comparative Example 2
Daytime was 10 hours (6: 00-16: 00) and nighttime was 14 hours (16: 00-6: 00). For supplementary illumination at night, use non-complementary light as a control zone and irradiate with blue light at the end of the night (5:30 to 6:00) or at the start of the night (16:00 to 16:30) Irradiated with red or far red light and treated for 19 days.

(Plant growth measurement and analysis)
The test plants were harvested 10 strains on each day of the light treatment, spinach, perilla, ensai and Japanese radish were divided into leaves, petioles, stems and roots, and sunny lettuce was divided into leaves, stems and roots. In addition, the number of leaves, the number of nodes, and the stem length were investigated, and the maximum petiole length (petiole length) was measured for spinach and Japanese radish with short stems. For leaves, the total leaf area (leaf area) was measured using an image processing device (minimum detection area 0.03 cm ² ), and the ratio of leaf area / number of leaves (individual leaf area) was compared with the difference in morphology. Leaf area (SLA; leaf area / leaf dry weight) was calculated. In addition, the leaf length and leaf width of the largest leaf were measured, and the leaf length: leaf width ratio (L: W ratio) was determined. The separated material was dried at 60 ° C. for 7 days using an air dryer, and the dry weight was measured separately for leaves, petiole and stem (hereinafter referred to as petiole / stem) or stem and root to determine the total dry matter weight.
All growth parameters were analyzed by Tukey's multiple comparison test (n = 10, p <0.05), and the presence or absence of a significant difference between the mean values was compared.

(Quantification of plant components)
For each plant type, harvest 5 plants in each ward on the day after the end of light treatment (growth survey date), and chop the edible part such as leaves into 1-2 cm ² for each strain and sample 3 samples of 2.0 g each. Was immediately immersed in an extraction solvent (20 ml each) for quantification of ascorbic acid (vitamin C) and β-carotene (vitamin A).

(Quantitative determination of ascorbic acid)
2.0 g of the chopped sample was immersed in an extraction solvent (5% metaphosphoric acid aqueous solution) and pulverized in ice using a homogenizer (POLYTRON, KINEMATICA AG., Switzerland). A 1.5 ml aliquot is taken from the solution, centrifuged at 10,000 rpm for 1 minute, and then the ascorbic acid test paper (Merck, KGaA, Darmstadt, Germany) is immersed in the supernatant extract, and the small reflective photometer RQflex Quantification was performed using plus (Merck, KGaA, Darmstadt, Germany).

(Quantification of β-carotene)
A 2.0 g chopped sample was immersed in 20 ml of acetone containing 0.4 g of pyrogallol and immediately ground in ice in the dark. The solution was suction filtered through a filter paper (GF / A, Whatman) to obtain an extract. After making up to 100 ml with acetone, 50 μl was taken and quantitatively analyzed by HPLC.
Inertsil ODS-3 (4.6φ, 150 mm, GL Science) was used for the HPLC column, and methanol and chloroform were mixed at a ratio of 4: 1 (v / v) as the mobile phase, and then a degassed solution was used. The pump (L-7100, Hitachi) flow rate is 1.5 ml min ^-1 , the temperature of the column oven (L-7300, Hitachi) is 30 ° C, and the detection wavelength of the UV absorption detector (SPD-6AV, Shimadzu) is set to 450 nm did.

(Quantitative determination of anthocyanins)
According to the method of Hayashi (1988), 2.0 g of shredded sample was added to 1% hydrochloric acid / methanol solution (v / v) and left in a refrigerator (4 ° C.) for 24 hours to extract the pigment. 200 ml of the extract was dispensed into a 96-well microplate (Costar 3370 Assay Plate), and the absorbance at 530 nm was measured using a microplate reader (Benchmark, Bio • Rad).

(Experimental result)
1. Effects of short-time supplementary light on vegetable growth

a. Spinach Alternating irradiation with red light and far-red light and promoting growth of spinach (see Fig. 1, Fig. 2 and Table 1)
In Experiment 1, irradiation with red light increased the total dry matter weight, leaf area, individual leaf area, leaf length, petiole length, and dry matter distribution to the aerial part compared to the case without supplemental light, and SLA also increased. In contrast, when far-red light is irradiated instead of red light, the total dry matter weight, leaf area, individual leaf area, leaf length, and increase in dry matter distribution to the aerial part are not observed (the leaf area decreases) Only the petiole length increased. In addition, irradiation with red light followed by far red light showed no increase in total dry matter weight, leaf area, individual leaf area, leaf length, and dry matter distribution to the aerial part, but petiole length increased, The growth change was the same as when red light was irradiated.
In Experiment 2, when red and far-red light were alternately irradiated, the petiole length increased under all irradiation conditions, but total dry weight, leaf area, individual leaf area, leaf length, SLA and above-ground part There is no increase in dry matter distribution to "red light + far red light" and "red light + far red light + red light + far red light", but "red light + far red light + red light". In the case of, an increase was observed.
From the results of Experiment 1 and Experiment 2, growth is promoted when irradiated with red light, and the petiole expands when irradiated with far red light, but growth promotion does not occur, and when red light and far red light are irradiated alternately, red The effects of light and far-red light on the growth were reversible, and it became clear that growth promotion occurred such as the total dry matter weight increased when red light was the last. Moreover, when the red light was irradiated, the leaf was thinly expanded, but no significant effect on the L: W ratio was observed. Although detailed explanation is omitted, when the blue light is irradiated for a short time at the end of the night, the growth of leaves and petiole is promoted, and the distribution of dry matter to the above-ground part (especially petiole / stem) is increased to promote growth. It was confirmed that it would happen.

b. Perilla Figure 4 shows the effect of short-time supplementary light on perilla growth. Irradiation with far-red light increased the total dry weight, leaf area, leaf area / number of leaves, and stem length compared to non-complementary light, and showed the effect of promoting growth. On the other hand, when blue light or red light was irradiated, no significant increase was observed for any item.
As for the leaf morphology, it became clear that irradiation with far-red light did not change the L: W ratio but increased the SLA and the leaf expanded thinly. In addition, no significant change in SLA is observed when red light is irradiated, but the L: W ratio decreases and leaves are rounded, and blue light irradiation shows no change in SLA and L: W ratio. I knew it was n’t there.
Irradiation with far-red light, as shown in Fig. 5, shows a change in dry matter distribution compared to non-complementary light, distribution to leaves and roots decreases, distribution to stem and petiole increases, edible part It became clear that the distribution to the above-ground part also increased somewhat.

c. Ensai Figure 6 shows the effect of short-time supplementary light on nightlife growth. Irradiation with far-red light increased the total dry weight, leaf area / number of leaves, and stem length compared to non-complementary light (the leaf area also showed an increasing tendency), and the effect of promoting growth was observed. On the other hand, when blue light or red light was irradiated, no significant increase was observed for any item.
Regarding the leaf morphology, it became clear that irradiation with far-red light increased the SLA and decreased the L: W ratio, expanding thinly and widely. Also, neither SLA nor L: W ratio changed when red light or blue light was irradiated.
When far-red light was irradiated, as shown in FIG. 7, changes in dry matter distribution were observed compared to non-complementary light, distribution to leaves and roots decreased, and distribution to stems and petioles increased by 10%. Along with this, distribution to the above-ground part, which is an edible part, also increased.

d. Sunny lettuce Figure 8 shows the effect of short-time supplementary light at night on the growth of sunny lettuce. Irradiation with far-red light increased total dry weight, leaf area, leaf area / number of leaves, and stem length compared to non-complementary light. On the other hand, when blue light or red light was irradiated, no significant increase was observed for any item.
With regard to leaf morphology, it was found that when irradiated with far-red light, the SLA did not change and the L: W ratio increased, and the leaf expanded elongated while maintaining its thickness. On the other hand, no change was observed in the L: W ratio when irradiated with red or blue light, but when irradiated with red light, the SLA decreased and the leaves increased in thickness.
Since lettuce has no petiole, we compared the dry matter distribution of the ground part (leaves and stems) and roots, but as shown in Fig. 9, when irradiated with far-red light, to the ground part which is an edible part compared to non-complementary light The distribution to the root increased and the distribution to the root decreased.

e. Japanese radish Figure 10 shows the effect of short-time light supplements at night on radish growth. Irradiation with far-red light increased the petiole length by 76% compared to non-complementary light, but the leaf area and leaf area / number of leaves decreased (total dry weight also showed a tendency), and growth was suppressed. In contrast, when the red light was irradiated, the total dry matter weight and the leaf area increased, and when the blue light was irradiated, the leaf area decreased.
Regarding the leaf morphology, it became clear that irradiation with far-red light decreased SLA and increased the L: W ratio, suppressing leaf expansion and becoming thick and elongated. On the other hand, no change was observed in the L: W ratio when irradiated with red or blue light, but when irradiated with blue light, the SLA decreased and the leaf thickness increased.
When far-red light was irradiated, as shown in FIG. 11, the distribution of dry matter to the stem and petiole increased by 5% compared to non-complementary light, and the distribution to the above-ground part tended to increase. Even when irradiated with blue or red light, the change in dry matter distribution was small.

2. Effect of short-time supplementation on nutrient concentration Perilla, ensai cultivated under short-term supplementation at night (blue light at the end of the night, red light at the start of the night, far red light at the start of the night), In Sunny lettuce, Table 2 shows the results of concentration analysis of β-carotene and ascorbic acid contained in edible parts such as leaves, and anthocyanin contained as a coloring component in perilla and sunny lettuce.
The concentration of β-carotene contained in perilla and sunny lettuce was not significantly different from non-complementary light when irradiated with blue light, red light, or far-red light. Then, the concentration decreased by 22% compared to non-complementary light.
Ascorbic acid is irradiated with blue light, red light, and far-red light in Shiso and Sunny lettuce, and the concentration difference between individuals is large in Ensai. No effects were observed.
In this way, in perilla, ensai, and sunny lettuce, irradiation with far-red light promoted growth, but no significant decrease in the concentrations of β-carotene and ascorbic acid, which are nutrients, was observed. .
In addition, the anthocyanin concentration contained in perilla and sunny lettuce was not significantly different from non-complementary light even when irradiated with blue light or red light, but perilla decreased 22% when irradiated with far red light, Coloring was suppressed.

  From the above experimental results, in the case of spinach, which is a long-day plant, growth promotion was observed when irradiated with red light for a short time at the start of the night, whereas when exposed to far red light, the petiole grew. No increase in total dry weight or leaf area was observed. Further, when red light and far red light were alternately applied, the growth promotion by red light was canceled by the far red light. From this, in spinach, the effect on the growth of red light and far-red light is reversible, red light functions as a switch that induces growth, and far-red light functions as a switch that stops induction. did.

  On the other hand, Sunny lettuce (neutral plant), which is not easily affected by perilla, ensai and day length of short-day plants, did not promote growth even when irradiated with blue or red light at the start of the night, Irradiation with far-red light at the start showed an effect of promoting growth. In contrast, radish grew petiole but growth was rather suppressed (Figs. 4, 6, 8 and 10). In this way, regarding the growth response to far-red light, Japanese radish coincided with spinach, and perilla, ensai and sunny lettuce showed contrasting characteristics with spinach, but five types of vegetables were based on the growth response to far-red light. The spinach and radish are long-day plants, perilla and ensai are short-day plants, and Sunny lettuce is a conditional long-day plant that is not susceptible to daylength (Wareing and Phillips, 1983). ), It may reflect the photoperiodic reaction type.

  Comparison of changes in dry matter distribution in perilla, ensai and sunny lettuce, where growth was recognized by irradiation with far-red light (Figs. 5, 7, and 9). The distribution to the roots decreased and the distribution to the roots decreased. In perilla and ensai, the distribution to the leaves and roots decreased and the distribution to the stem and petiole increased. However, when the dry matter distribution is divided into the above-ground part and the root, these three kinds of leafy vegetables have a common point that the assimilation product is redistributed from the root to the above-ground part.

  On the other hand, regarding the results that radish and spinach do not show growth promotion even when irradiated with far-red light at the beginning of the night, in radish and spinach, the growth of petiole and stem is promoted by irradiation with far-red light. Considering that the leaf area does not increase, it is considered essential to promote the elongation of leaves in order to promote growth.

  In addition, when far-red light was irradiated at the start of the night, the leaf area increased (decrease in radish), and the shape varied depending on the type of vegetable (FIGS. 4, 6, 8, and 10). There is no finding that suggests the cause of the difference in length between the leaf length and leaf width due to the irradiation of far-red light, but contrary to perilla, ensai and radish, The result that the elongation in the direction of the leaf length is larger than the width is presumed that the increase in the leaf length substitutes for the promotion of the elongation of the petiole because the sunny lettuce has no petiole.

  As mentioned above, when irradiating far-red light at the beginning of the night, petiole elongation shows different reactions between species, but growth promotion is not affected by perilla, ensai and day length of short-day plants. In neutral plants), the effect of promoting growth was observed. Specifically, the total dry matter weight increased by 29% for perilla, 27% for ensai, and 35% for sunny lettuce, and the effect of promoting growth was obtained while maintaining the nutritional components β-carotene and ascorbic acid. It was revealed. On the other hand, growth promotion by far-red light was not recognized in the radish of the same long-day plant as spinach and spinach. Furthermore, when blue light was irradiated at the end of the night, growth promotion was observed only in spinach, and was not confirmed even in long-day radish. This revealed that there are two types of plants with different growth responses to far-red light (see FIG. 3, Table 2 and FIG. 12).

This growth induction phenomenon is caused by light stimulation (light signal), and can be expected to be used as energy-saving supplementary illumination. For example, even if a small amount of supplementary light (50 μmol m ⁻² s ⁻¹ × 1 hour) is used, if PPFD is 200 μmol m ⁻² s ⁻¹ , it is possible to promote growth equivalent to 300 μmol m ⁻² s ^−1. Therefore, it was judged as an effective way to enhance the growth promotion effect under low light conditions.
Moreover, the concentrations of β-carotene (vitamin A) and ascorbic acid (vitamin C), which are the main nutritional components of leafy vegetables, have an effect on the concentrations of both components during the growth-promoting reaction by far-red light irradiation at the beginning of the night. (Table 2). Cultivation environment and growth stage may affect β-carotene and ascorbic acid concentrations in leafy vegetables. However, in this experiment using perilla, ensai, and sunny lettuce, it was confirmed that the effect of short-time supplementary light at night was small. In perilla, the concentration of anthocyanins has decreased, so coloring components may be reduced, but short-time supplementary light at night is the main nutritional component such as vitamins for various leaf vegetables grown under low-light conditions. This is considered to be an effective method of suppressing the decrease in growth and improving growth defects.
From this, short-time supplementary light at night is an effective method for improving poor growth without reducing the main nutrients such as vitamins for various leaf vegetables grown under low-light conditions. Conceivable.

The results of Experiments 1 and 2 comparing the effects of red light and far-red light irradiated on spinach growth at the start of the night on spinach growth with no supplementary light are shown for total dry weight, leaf area, and leaf area / number of leaves. It is a graph, data is an average value of 10 strains (error bars are standard errors), and different alphabets in the graph indicate significant differences by Tukey's multiple comparison test (p <0.05). It is a graph showing the results of Experiments 1 and 2 for comparing the effects of red light and far-red light irradiated on spinach growth at the start of the night on spinach growth with no supplementary light for petiole length, SLA and leaf length. Is an average value of 10 strains (error bars are standard errors), and different alphabets in the graph indicate significant differences by Tukey's multiple comparison test (p <0.05). It is a graph which shows the influence which the short-time supplementary light of the night has on the growth of various vegetables by total dry weight, and data are the average values of 10 stocks (error bars are standard errors). The results of an experiment comparing the effect of short-time supplemental light at the start of the night on perilla growth compared to non-complemented light were compared with the total dry weight, leaf area, stem length, SLA, leaf area / number of leaves and leaf L: It is a graph each shown about W ratio, and data are the average values of 10 stocks (error bars are standard errors), and different alphabets in the graph indicate significant differences by Tukey's multiple comparison test (p <0.05). It is a graph showing the results of experiments comparing the effect of short-time supplementary light at the start of the night on the dry matter distribution of perilla with non-complementary light for roots, stems, petiole and leaves, respectively. (Error bars are standard errors), and different alphabets in the graph indicate significant differences according to Tukey's multiple comparison test (p <0.05). The results of an experiment comparing the effect of short-time supplementary light on the growth of ensai with the non-complementary light at the start of the night are compared with the total dry weight, leaf area, stem length, SLA, leaf area / number of leaves and leaf L: It is a graph each shown about W ratio, The different alphabet in a graph shows the significant difference by Tukey's multiple comparison test (p <0.05). The graph shows the results of experiments comparing the effects of short-time supplementary light on the dry matter distribution of ensai with non-complementary light for roots, stems, petioles, and leaves, respectively, and the data is the average of 10 strains (Error bars are standard errors), and different alphabets in the graph indicate significant differences according to Tukey's multiple comparison test (p <0.05). The results of experiments comparing the effect of short-time supplementary light at the start of the night on the growth of sunny lettuce compared to the case of non-complemented light were compared with total dry weight, leaf area, stem length, SLA, leaf area / number of leaves, and leaf L : W graphs showing W ratio, data are average values of 10 strains (error bars are standard errors), and different alphabets in the graph indicate significant differences by Tukey's multiple comparison test (p <0.05). It is a graph showing the results of experiments comparing the effect of short-time supplementary light at the start of the night on dry matter distribution of sunny lettuce and the case of non-complementary light for the root and the ground part, respectively, and the data is the average value of 10 strains (error Bars are standard errors), and different alphabets in the graph indicate significant differences according to Tukey's multiple comparison test (p <0.05). The results of experiments comparing the effect of short-time light supplementation at the start of the night on the growth of radish were compared with the case of non-complementary light supplementation. Total dry weight, leaf area, petiole length, SLA, leaf area / number of leaves and leaf L: It is a graph each shown about W ratio, and data are the average values of 10 stocks (error bars are standard errors), and different alphabets in the graph indicate significant differences by Tukey's multiple comparison test (p <0.05). It is a graph showing the results of experiments comparing the effect of short-time supplementary light at the start of the night on dry matter distribution of radish compared with the case of non-complementary light for roots, stems, petiole and leaves, respectively. (Error bars are standard errors), and different alphabets in the graph indicate significant differences according to Tukey's multiple comparison test (p <0.05). It is a photograph which shows the influence which nighttime supplementary light has on growth of various vegetables.

Claims (2)

A method for promoting the growth of a short-day plant or a neutral plant, which induces growth promotion by irradiating a short-day plant or a neutral plant with far-red light at the beginning of the night. 2. The short irradiation according to claim 1, wherein the irradiation with the far-red light is performed for a short period of time sufficient to secure a light energy amount sufficient to provide a light stimulus that induces a plant growth promotion reaction. A method for promoting the growth of Japanese plants and neutral plants.