不同LEDs光質下普通白菜開花以及花期生理特性的動態變化

李慧敏，陸曉民

(安徽科技學院 生命科學學院，安徽鳳陽 233100)

不同LEDs光質下普通白菜開花以及花期生理特性的動態變化

李慧敏，陸曉民

(安徽科技學院 生命科學學院，安徽鳳陽 233100)

摘要:以普通白菜品種‘蘇州青’為試材，采用單因素隨機區組設計的盆栽試驗，將基質育苗后長至子葉展平時的幼苗轉入熒光燈(FL,對照)、藍光(B)發光二極管(LEDs)、藍紅復合光(BR)和紅光(R)下進行照射處理至開花，考察不同光質對普通白菜開花以及花期光合色素含量、品質和碳代謝等的光效應，為利用人工光源調節普通白菜的育種周期提供理論指導。結果顯示：(1)隨著開花時間延長，普通白菜的開花數目均以R和BR處理顯著高于FL；花蕾數目在處理100 d時R和BR處理顯著多于FL，但是在110和120 d時B處理下明顯多于FL。(2)隨著花期延長，白菜葉片中的光合色素含量呈降低趨勢，其在處理100 d時表現為BR處理顯著高于FL，而在110 d時B處理最高，在120 d時BR處理最高。(3)隨著花期延長，葉片中可溶性蛋白和抗壞血酸含量也呈逐漸降低的趨勢；可溶性蛋白含量均在B處理下較大，而抗壞血酸含量在100 d時在B處理下最高，但是在110和120 d時B和BR處理下較高。(4)隨著花期延長，葉片中碳水化合物含量也逐漸降低，其中可溶性糖、蔗糖和淀粉含量均以R處理下最高。研究表明，與熒光對照相比，LEDs光源對普通白菜幼苗的營養生長和生殖生長更有效，其中藍光有利于普通白菜的營養生長，而紅光和藍紅復合光則有利于其生殖生長；可采用紅光和藍紅復合光作為普通白菜育種的人工光源，有效促進其工廠化生產進程。

關鍵詞:普通白菜；開花；光合色素；品質；碳代謝

Brassicacampestrisssp.chinensisMakino var.communisis a typical biennial vegetables, the advantages of crossbreeding often need eight to nine generations of breeding, so as to accelerate the breeding process, shrinking the short breeding period, breeders often use the greenhouse artificially created to promote green vegetables transition from vegetative growth to reproductive growth, plus generation of breeding[1]. The timing of flowering is primarily influenced by environmental factors, which serve to communicate the time of year and/or growth conditions favorable for sexual reproduction and seed maturation, including light quality, photoperiod, light quantity, and verbalization[2]. The sun emits the most of its radiation in the visible range, it covers the range of wavelength from 400-700nm[3]. The integration, quality, duration and intensity of red, far-red, blue, UV-A and UV-B light have a profound influence on plants by triggering physiological reactions to control their growth and development[4-6]. The quality and quantity of light affect plant development mainly through two types of photoreceptors-the red/far red light receptors phytochromes and blue/UV-A light receptors cryptochromes[7]. LEDs are solid-state, long-lasting and durable sources of narrow-band light that can be implemented in dynamic lighting strategies to control plant growth, development, physiological responses and production, it is important to learn more about the influence of light quality on these processes[8-11].

Various studies have shown that LEDs have been successfully used for cultivation in several horticultural plant species such as lettuce, tomato, cucumber, Chinese cabbage, pepper, rapeseedetc[8-10,12-20]. Although previous studies have identified various physiological and morphological effects of light quality in many plant species, few reports have addressed the effect of LED light sources and fluorescent lamps on flowering, the sugar metabolism and quality of pakchoi (BrassicacampestrisL. ssp.chinensis(L) Makino var.communisTsen et Lee) during the budding and flowering stages. The objective of the present study was to examine the effects of blue LEDs, red LEDs, blue plus red LEDs (BR)[18]and fluorescent lampson flowering, sugar metabolism and quality in leaves of pakchoi seedlings during the budding and flowering stages and to select the best lights for the cultivation of pakchoi seedlings under a controlled environment.

1Materials and methods

1.1Plant materials

The experiments were conducted in RXZ-1 Phytotron (Ningbo Jiangnan Instrument Factory CO., Ningbo, China) at Anhui Science and Technology University. Pakchoi cultivar ‘Suzhouqing’ seeds with a similar size were selected for sowing. Seeds were sown in cells filled with vermiculite and peat (1∶1 by volume) for cultivation, with one seed per cell. After seven days, seedlings with two expanded cotyledons were transferred to the different lights.

1.2Light treatments

Seedlings were grown under a mixture of blue plus red light-emitting diodes (LEDs) (BR, B∶R=2∶7) , blue LEDs, red LEDs (OPTORUN LTD. CO., Shanghai, China) at a photosynthetic photo flux density (PPFD) of 140 μmol·m-2·s-1and fluorescent lamps (FL, the control, T5-28 W, PHILIPS CO., Yangzhou, China) PPFD of 85 μmol·m-2·s-1(Fig. 1). The growth temperature was set at 24-26 ℃, and the relative humidity fluctuated between 55% and 60%. The photoperiod was 12 hours. Seedlings were randomly assigned to each light treatment, and LEDs arrays were randomly assigned positions in the greenhouse. Seedlings were cultured under the four lights for samples at the budding stage (100thdays), at the 10th(110thdays) and 20th(120thdays) of flowering stages.

1.3Flower buds and open flowers measurements

When seedlings were cultured under the four lights for samples at the budding stage (100thdays), at the 10th(110thdays) and 20th(120thdays) of flowering stages, and recorded the number of flowering and the number of buds on that day.

1.4Pigment measurements

Leaves were weighed to 0.1 g (fresh weight, W), and 10 mL (V) of 80% acetone was added to 0.1 g of leaf samples placed into a mortar with quartz sand. The chlorophyll was extracted until the leaf turned white. The optical density (OD) was measured with a UV-1200 spectrophotometer (Jinpeng, Shanghai, China) at 470 nm for carotenoid (OD470), at 663 nm for chlorophyll a (OD663), and at 645 nm for chlorophyll b (OD645)[21].

FL. Fluorescent lamp(control); B: Blue light emitting diodes; R: Red light emitting diodesFig.1　The light energy distribution of different lights

1.5Soluble protein measurements

Leaves (1.0 g of fresh weight, W) were ground in a mortar with liquid nitrogen, to which 5 mL (V1) of 0.067 mol·L-1potassium phosphate buffer (PBS) was added, and were then filtered through filter paper. The extract was centrifuged at 12000 g for 10 min, and the supernatant was removed. The extract (1 mL,V2) and Coomassie brilliant blue G-250 (5 mL) was thoroughly mixed. The optical density was measured using a UV-1200 spectrophotometer at 595 nm. To determine a standard curve, 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of 100 μg·L-1bovine serum albumin was added to 6 volumetric flasks, and distilled water was added to reach a volume of 1 mL. The optical density was measured by a UV-1200 spectrophotometer at 595 nm (ρ). The concentration of soluble protein was determined using the following equation: soluble protein (mg·g-1) =ρV1/WV2[22]. Where ρ is optical density,V1is total volume of extract,V2is volume of reactions, andWis fresh weight (g) of the samples.

1.6Ascorbic acid measurements

Leaves (1.0 g, fresh weight, W) were ground in a mortar with liquid nitrogen. Next, 5 mL (V1) of 5% trichloroacetic acid (TCA) was added and the mixture was filtered through filter paper. The extract was centrifuged at 10000 g for 10 min, and the supernatant was removed. The extract (1.0 mL,V2) and 1.0 mL of ethanol were thoroughly mixed. Next, 0.5 mL of 0.4% phosphoric acid-ethanol, 1 mL of 0.5% 1, 10- phenanthroline-ethanol and 0.5 mL of 0.03 g·L-1ferric chloride were added for a total volume of 5 mL. The optical density was measured using a UV-1200 spectrophotometer (Jinpeng, Shanghai, China) at 534 nm. To obtain a standard curve, 0, 0.2, 0.4, 0.6, 0.8, or 1.0 mL of 100 mg·L-1bovine serum albumin was added to 6 volumetric flasks, and distilled water was added to reach a volume of 1 mL. The optical density was measured by a UV-1200 spectrophotometer at 534 nm (ρ). The concentration of ascorbic acid was determined using the following equation: ascorbic acid concentration (mg·g-1) =ρV1/WV2[22]. Where ρ is optical density,V1is total volume of extract,V2is volume of reactions, andWis fresh weight (g) of the samples.

1.7Sugar and starch measurements

Leaves (0.5 g, dry weight) were ground in a mortar with liquid nitrogen. Then 1 mL of 80% ethanol was added, and the mixture was filtered through filter paper. The filtrates were recovered, and the residues were washed again with 70% ethanol and filtered. Both filtrates were mixed, and 3 mL of distilled water was added. The extract was centrifuged at 12 000 g for 15 min, and 1 mL of supernatant was collected. Soluble sugar concentration was determined by the sulfuric acid-anthrone method and measured at 620 nm. Sucrose concentration was determined using the phloroglucinol method and measured at 480 nm[21]. Takahashi’s method was used for starch extraction[23]. The residue obtained after ethanol extraction was re-suspended with 0.1 mol·L-1sodium acetate buffer (pH 4.8) and boiled for 20 min. The gelatinized starch was digested with amyloglucosidase for 4 h at 37 ℃ and boiled again to stop the enzymatic reaction. After cooling, the mixture was centrifuged, and the amount of soluble sugar in the supernatant was determined by anthrone colorimetry[22]. The starch concentration was estimated by converting glucose to starch equivalents using a factor of 0.9.

1.8Statistical analysis

Statistical analyses were conducted with Statistical Product and Service Solutions (SPSS) for Windows, Version 16.0 (SPSS Inc. 2007). Data were analyzed using analysis of variance (ANOVA), and the differences between means were tested using Tukey’s Test (P<0.05).

2Results

2.1The number of flower buds and open flowers

Different light sources had variable effects on the development of flowers in pakchoi seedlings from 100 to 120 days (Table 1). The numbers of open flowers were significantly higher in seedlings under R and BR than in those under FL during the flowering stage. The number of flower buds was significantly higher at the 100thday under R and BR than FL and B. However, The number of flower buds was significantly higher at the 110thday and 120thday under B than under FL. The present results showed that R and BR LEDs promoted the flowering process.

2.2The concentrations of pigments

The leaf pigments of pakchoi seedlings varied in response to the different lights. The photosynthetic pigment content of leaves was gradually decreased with the extension of flowering period. The concentrations of chlorophyll a, b and total chlorophyll were greatest in seedlings under BR at 100thday, followed by B, which were significantly higher than FL and lowest under FL (Fig. 2, A-C). The concentrations of carotenoid was highest under BR and B, which were significantly higher than FL, and lowest under FL (Fig. 2, D). The concentrations of pigments were greatest in seedlings under B at 110thday, which were significantly higher than BR, R and FL (Fig. 2). The concentrations of pigments were greatest in seedlings under BR at 120thday, followed by B and FL and lowest under R (Fig. 2). The present results demonstrated that BR and B LEDs were beneficial to pigments accumulation of pakchoi seedlings.

2.3Soluble protein concentration

The soluble protein content in leaves decreased gradually as the flowering time was prolonged. The concentration of soluble protein was highest in pakchoi seedlings under B LEDs at 100thday, followed by BR and lowest under FL (Fig. 3).The concentration of soluble protein was greatest in seedlings under B LEDs at 110thday, and the other light treatments showed no significant differences. The concentration of soluble protein was highest in seedlings under B and FL at 120thday and lowest under R. The present results showed that B LEDs was responsible for the accumulation of soluble protein in pakchoi seedlings.

Table 1　The number of flower buds and open flowers per plant in pakchoi grew under different

Note: BR. Blue plus red light-emitting diodes; B: Blue light-emitting diodes; R. Red light-emitting diodes; FL. Fluorescent lamp. Values are the mean ± standard deviation. Different letters within the column indicate significant differences among light treatments at 0.05 level according to Tukey’s test (n=3). The same as below.

Different letters within the same stage indicate significant differences among light treatments at 0.05 level according to Tukey’s test (n=3). The bars represent the standard error. The same as below.Fig. 2　The pigment concentrations of pakchoi seedlings under different light qualities for 100th, 110th and 120th day

2.4Ascorbic acid concentration

The ascorbic acid content in leaves decreased gradually as the flowering time was prolonged. The The concentration of ascorbic acid was highest in pakchoi seedlings under B LEDs at 100thday, followed by R LEDs and lowest under FL (Fig. 4). The concentration of ascorbic acid was significantly higher under B and BR in seedlings than under FL at 110thday and 120thday (Fig. 4). The results showed that B and BR LEDs was responsible for the accumulation of ascorbic acid in pakchoi seedlings.

2.5Sugar and starch concentrations

The sugar and starch concentrations of pakchoi seedlings varied in response to different lights treatments. As the extended flowering, leaf carbo hydrate content is also gradually reduced. The concentrations of sucrose, soluble sugar and starch were greatest in seedlings under R LEDs, which showed significant higher than the other lights, followed by BR and B LEDs, which showed significant higher than FL and lowest in seedlings under FL (Fig.5, A-C). These results revealed that R LEDs are the best lights for accumulation of sucrose, starch and soluble sugar in pakchoi seedlings.

Fig. 3　The soluble protein concentration of pakchoi seedlings under different lights treatments for 100th, 110th and 120th day.

Fig. 4　The ascorbic acid concentration of pakchoi seedlings under different light treatments for 100th, 110th and 120th day

Fig. 5　The photosynthesis production of pakchoi seedlings under different light treatments for 100th, 110th and 120th day

3Discussion

3.1Blue plus red LEDs and red LEDs may profit for the flowering of plants

Flowering is one of the morphogenic events in plants, which is affected by light irradiance and / or wavelength[24]. The number of flowers was highest in non-heading Chinese cabbage seedlings grown under R LEDs and B plus R LEDs (1∶8)[18]. The numbers ofCyclamenflower buds and open flowers were highest in plants grown under a mixture of B plus R LEDs (B∶R=10∶1) compared with FL and other light sources[25]. However, the development of visible flower buds in marigolds was about five times greater in FL than in B or R LEDs[26]. Monochromatic B light delayed flowering inArabidopsispossibly by influencing cryptochromes[7]. The present study showed that the number of flowers was highest in pakchoi seedlings grown under R LEDs and B plus R LEDs (2∶7), and the number of flower buds was higher in seedlings grown under LEDs than FL. The findings from the present study are consistent with those of Lietal.[18], Heoetal.[25]and Mockleretal.[7], but inconsistent with a report from Heo[26]. The shift in plants from vegetative growth to floral development is regulated by red-far-red light receptors (phytochromes) and blue-ultraviolet A light receptors (cryptochromes)[27]. The number of flower buds and open flowers and the duration of flowering may correlate with the different plant species, which reactions to the light receptors were variable[18]. Spectral quality has a major influence on induction rate of flower budding and subsequent development. The present study showed that R LEDs and BR LEDs were benefit for the flowering process.

3.2Blue LEDs benefited the leaf quality of plants

The present results indicated that B LEDs benefits ascorbic acid and soluble protein accumulation of pakchoi seedlings, which are consistent with reports by Lietal.[18], Yangetal.[28]and Zhangetal.[29]. However, the concentrations of soluble protein in lettuce leaves showed no significant differences among treatments[10]. B LEDs might benefit the accumulation of nutritional substances, and these effects may correlate with plant species or cultivars[18]. The present study also showed that the flowering was delayed under B LEDs, this might relate with the high nutritional substances, which the substances was accumulated in leaves offered the material security to vegetative growth of green vegetables. In summary, for the purpose of improving the nutritional quality of vegetables, B LEDs could be chosen as the preferred lights in artificial cultivation of pakchoi.

3.3Which light was the best light for accumulation of photosynthates in plants

Variations in light conditions will affect the metabolic processes[30]. Light quality regulates the carbohydrate metabolism of higher plants, and carbohydrate content is increased under red light[31]. Red light may inhibit the translocation process of photosynthates[32]. Red light enhances starch accumulation in glycine and sorghum species[33]. The present study revealed that the starch concentration was greatest in seedlings grown under R LEDs, and this light was advantageous to accumulation of starch in pakchoi which was consistent with the previous studies. R LEDs may promote the accumulation of the photosynthetic products but inhibit the translocation of photosynthetic products out of leaves. Thus, the starch ultimately accumulated in leaves[18]. The present study also showed that the concentrations of sucrose and soluble sugar were greatest in seedlings under R LEDs during the budding and flowering stages and the R LEDs and B plus R LEDs promoted the flowering process. The flowering might relate with the high sugar and starch concentrations, which advanced the transition from vegetative growth to reproductive growth and early flowering. R LEDs may be used as the main lights for reproductive growth of pakchoi seedlings.

In conclusion, R LEDs and B plus R (2∶7) LEDs should be selected as the preferred lights in the artificial cultivation of pakchoi seedlings to get more flowers and early flowering. By contrast, B LEDs should be used as the preferred lights for higher nutritional quality to improve the growth and development of pakchoi seedlings.

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(編輯:裴阿衛)

Effects of Light Quality on Flowering, Dynamic Variation in Physiological Characteristics of Pakchoi during Budding and Flowering Stage

LI Huimin, LU Xiaomin

(College of Life Science, Anhui Science and Technology University, Fengyang, Anhui, 233100, China)

Abstract:With the purpose of examining the effects of light quality on flowering, the pigment content, quality and carbon metabolism of pakchoi (Brassica campestris L.ssp.chinensis (L) Makino var. communis Tsen et Lee) seedlings on the budding and flowering-age-types, the present study were carried out to use the cultivar ‘Suzhouqing’ as plant material, which were grown under four different light treatments including blue plus red light-emitting diodes (LEDs, B∶R=2∶7), blue LEDs (B), red LEDs (R) and fluorescent lamps (FL) for 120 days. Some indices such as flower buds, open flowers, pigments and ascorbic acid, soluble protein, sucrose, soluble sugar, and starch concentrations were determined. The results showed that. (1) with the extension of flowering time, the numbers of open flowers were significantly larger in seedlings under R and BR than that under FL. The number of flower buds was significantly larger under R and BR than that under FL at the 100thd. However, the number of flower buds was significantly larger under B than that under FL at the 110thd and 120thd; (2) the photosynthetic pigment content of leaves was gradually decreased with the extension of flowering period. The concentrations of pigments were significantly higher in seedlings under BR than that under FL at 100thd. However, the concentrations of pigments were significantly higher in seedlings under B than that under FL at 110thd. The concentrations of pigments were the highest in seedlings under BR at 120thd; (3) the soluble protein and ascorbic acid content in leaves decreased gradually as the flowering time was prolonged. The concentration of soluble protein was higher in seedlings under B than that under FL during the flowering periond. However, the concentration of ascorbic acid was higher in seedlings under B than that under FL at 100thd. The concentration of ascorbic acid was higher under B and BR in seedlings than that under FL at 110thd and 120thd; (4) as the extended flowering, leaf carbohydrate content also gradually reduced, which soluble sugar, sucrose and starch contents were significantly higher under R than that under the other lights. Obviously, compared with the FL, LEDs is more effective for the vegetative growth and reproductive growth of pakchoi seedlings, B is conducive to the vegetative growth of pakchoi, while R and BR are beneficial to their reproductive growth. The R LEDs and BR LEDs lights can be used as the artificial light source for the pakchoi breeding, and it might promote the factory production process of pakchoi.

Key words:pakchoi; flowering; pigments; quality; carbon metablism

文章編號:1000-4025(2016)04-0730-08

doi:10.7606/j.issn.1000-4025.2016.04.0730

收稿日期:2015-12-30;修改稿收到日期:2016-03-17

基金項目:安徽省高校省級自然科學研究重點項目(KJ2014A053);安徽省現代農業產業技術體系專項(AHCYTX-13); 安徽科技學院重點學科(AKZDXK2015C05)

作者簡介:李慧敏(1981-)，女(漢族)，博士，講師，主要從事作物栽培生理與設施環境調控的相關研究工作。E-mail:hmli0621@163.com

中圖分類號:Q945.6;S626.9

文獻標志碼:A