Effects of light quality on growth and development of protocorm-like bodies of <Emphasis Type="Italic">Dendrobium officinale</Emphasis> in vitro

The effect of light quality on protocorm-like bodies (PLBs) of Dendrobium officinale was investigated. PLBs of D. officinale were incubated under a number of different light conditions in vitro, namely: dark conditions; fluorescent white light (Fw); red light-emitting diodes (LEDs); blue LEDs; half red plus half blue [RB (1:1)] LEDs; 67% red plus 33% blue [RB (2:1)] LEDs; and 33% red plus 67% blue [RB (1:2)] LEDs. Growth parameters, number of shoots produced per PLB, chlorophyll concentration and carotenoid concentration were measured after 90 days culture. The percentage of PLBs producing shoots was 85% under blue LEDs. In contrast, the percentage of PLBs producing shoots was less than 60% under dark conditions, fluorescent white light and red LEDs. The number of shoots produced per PLB was more than 1.5 times greater under blue LEDs, RB (1:1) LEDs and RB (1:2) LEDs than those cultured under other light treatments [dark, Fw, red LEDs and RB (2:1)]. Chlorophyll and carotenoid concentrations were significantly higher under blue LEDs and different red plus blue LED ratios, compared to other light treatments (dark, Fw and red LEDs). Blue LEDs, Fw, and RB (1:2) LEDs produced higher dry matter accumulations of PLBs and shoots. This study suggests that blue LEDs or RB (1:2) LEDs could significantly promote the production of shoots by protocorm-like bodies of D. officinale and increase the dry matter of PLBs and the accumulation of shoot dry matter in vitro.     

Growth of Tsuru-rindo (Tripterospermum japonicum) culturedin vitro under various sources of light-emitting diode (LED) irradiation

We studied the effects of light generated by LEDs on the growth of Tsururindo (Tripterospermum japonicum) shoots. Apical shoots (2–3 cm long) were cultured on MS basal media supplemented with 3% sucrose, and were maintained for four weeks under five different light qualities: F (fluorescent lamp), red LED (R), 70% red + 30% blue LED (R7B3), 50% red + 50% blue (R5B5), or blue LED (B). Rooting was promoted by red light (100%) but was inhibited by blue light. Plant growth, as defined by root number, fresh weight, and chlorophyll content, was generally healthier for cultures irradiated with mixed LEDs, and was the best under R7B3. Ventilation resulted in more rapid apical shoot growth and rooting compared with control plants, when both were treated with the R7B3 system. We demonstrated here that plant growth can be controlled by using LEDs to adjust for the most effective irradiation conditions, compared with the performance observed when conventional fluorescent lamps are utilized.     

Modified light spectral conditions prior to cryopreservation alter growth characteristics and cryopreservation success of potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) shoot tips in vitro

Light is one of the most important factors affecting growth and morphogenesis of plants. Light intensity, photoperiod and spectral composition greatly affect morphogenetic responses of in vitro plants. Modification of light spectra during recovery after cryopreservation improves survival and regeneration, but the effect of modified light conditions prior to cryopreservation are not known. Therefore, the aim of the present study was to follow the photomorphogenetic response of potato plants (Solanum tuberosum L.) under different light qualities i.e. cool white fluorescent (CW) used as control, warm white (HQI), white LEDs (W), blue LEDs (B), red LEDs (R) and a combination of red with 10?% of blue LEDs (RB) prior to cryopreservation, affecting recovery of cultivars Agrie Dzeltenie, Bintje, Maret, Anti and Désirée in vitro. Light spectral quality had a significant effect on growth characteristics of potato plants in vitro. Red light (R) promoted elongation growth but biomass accumulation remained low under monochromatic light treatments. Some of the pre-cryopreservation light treatments significantly affected post-cryopreservation success. Under blue LEDs, high early recovery was observed for all cultivars tested, whereas under red (R) or (HQI), lowest survival percentages were obtained 2–4 weeks after thawing. Specifically, during early recovery, blue light increased survival from 26 to 66?%, 4 to 31?% and 16 to 48?% for cultivars Agrie Dzeltenie, Anti, and Désirée, compared to illumination by red LEDs. Therefore, light spectral quality prior to cryopreservation can significantly affect the cryopreservation success of potato shoot tips.     

Mammalian <Emphasis Type="Italic">CYP2E1</Emphasis> gene triggered changes of relative ions fluxes,CaM content and genes expression profiles in <Emphasis Type="Italic">Petunia hybrida</Emphasis> cells to enhance resistance to formaldehyde

The influence of light quality and cytokinin content in media on growth, development, photosynthetic pigments and secondary metabolite content of Myrtus communis L. was evaluated in an in vitro culture. Various treatments with light emitting diodes (LEDs): 100% blue (B), a mix of 70% red and 30% blue (RB) and 100% red were applied and compared with a traditional fluorescent lamp as control. Axillary shoots were incubated on Murashige and Skoog medium with 30 g dm^?3 sucrose, 0.5% BioAgar, 0.5 μM 1-naphthaleneacetic acid and different concentrations of 6-benzyladenine (BA): 1, 2.5 and 5 µM. Cultures were maintained for 6 weeks in 23/21?±?1 °C (day/night), 80% relative humidity and 16/8 h photoperiod; photosynthetic photon flux density (PPFD) was 35 µmol m^?2 s^?1 in all treatments. Light spectra and BA content in media affected biometrical and phytochemical M. communis properties. Red LEDs and 5 µM BA resulted in the highest multiplication rate. The highest shoots were obtained under red LEDs, but with the lowest concentration of cytokinin in media. Fresh weight was greatest on LEDs containing blue light in the spectrum (B and RB); moreover, 5 µM BA increased dry weight. Photosynthetic pigment levels were lower under LED light compared to control lamps. Phenolic acids and flavonoids were identified in M. communis leaf extracts. Myricetin was the major constituent with highest concentration under red LEDs and highest BA level.     

Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting

Red light-emitting diodes (LEDs) are a potential light source for growing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attractive features, red LEDs must satisfy requirements for plant photosynthesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LEDs on wheat photomorphogenesis, photosynthesis, and seed yield, wheat (Triticum aestivum L., cv. 'USU-Super Dwarf') plants were grown under red LEDs and compared to plants grown under daylight fluorescent (white) lamps and red LEDs supplemented with either 1% or 10% blue light from blue fluorescent (BF) lamps. Compared to white light-grown plants, wheat grown under red LEDs alone demonstrated less main culm development during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lower seed yield compared to plants grown under white light. Wheat grown under red LEDs+10% BF light had comparable shoot dry matter accumulation and seed yield relative to wheat grown under white light. These results indicate that wheat can complete its life cycle under red LEDs alone, but larger plants and greater amounts of seed are produced in the presence of red LEDs supplemented with a quantity of blue light.     

Effect of light and natural ventilation systems on the growth parameters and carvacrol content in the in vitro cultures of <Emphasis Type="Italic">Plectranthus amboinicus</Emphasis> (Lour.) Spreng

The aim of the current study is to investigate the influence of light intensity, quality of light and alternative membrane sytems on the growth and headspace-GC/MS chemical analysis of Plectranthus amboinicus cultivated in vitro. Nodal segments were grown under light intensities (26, 51, 69, 94 and 130 µmol m^?2 s^?1) provided by cool-white fluorescent lamps. Apical segments were grown under light-emitting diodes blue; red; 1 blue/2.5 red; 2.5 blue/1 red; 1 blue/1 red and white fluorescent lamps. Apical and nodal segments were grown under alternative membrane and membrane-free systems. One, two or four PTFE membranes were used on the lid of the culture vessel. The membranes provided natural ventilation and worked as filters. The results have shown significant differences in the growth and carvacrol content, as well as in the content of carvacrol precursors (γ-terpinene and p-cymene) in different treatments. Among all tested light intensities, the significant increase in the dry weight and in the carvacrol content of plantlets derived from the nodal segments was recorded at 69 µmol m^?2 s^?1. The monochromatic red led to greater shoot length and higher dry weight in plantlets derived from the apical segments, as well as to carvacrol accumulation greater than that provided by the fluorescent lamps. The culture vessel enclosure by one and two membranes led to higher dry weight in plantlets derived from the apical and nodal segments, respectively. They also showed higher carvacrol content. Thus, it is possible optimizing the growth and carvacrol content in P. amboinicus cultivated in vitro by adjusting these environmental parameters.     

Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting

Red light-emitting diodes (LEDs) are a potential light sourcefor growing plants in spaceflight systems because of their safety,small mass and volume, wavelength specificity, and longevity.Despite these attractive features, red LEDs must satisfy requirementsfor plant photosynthesis and photomorphogenesis for successfulgrowth and seed yield. To determine the influence of galliumaluminium arsenide (GaAIAs) red LEDs on wheat photomorphogenesis,photosynthesis, and seed yield, wheat (Triticum aestivum L.,cv. ‘USU-Super Dwarf’) plants were grown under redLEDs and compared to plants grown under daylight fluorescent(white) lamps and red LEDs supplemented with either 1% or 10%blue light from blue fluorescent (BF) lamps. Compared to whitelight-grown plants, wheat grown under red LEDs alone demonstratedless main culm development during vegetative growth throughpreanthesis, while showing a longer flag leaf at 40 DAP andgreater main culm length at final harvest (70 DAP). As supplementalBF light was increased with red LEDs, shoot dry matter and netleaf photosynthesis rate increased. At final harvest, wheatgrown under red LEDs alone displayed fewer subtillers and alower seed yield compared to plants grown under white light.Wheat grown under red LEDs+10% BF light had comparable shootdry matter accumulation and seed yield relative to wheat grownunder white light. These results indicate that wheat can completeits life cycle under red LEDs alone, but larger plants and greateramounts of seed are produced in the presence of red LEDs supplementedwith a quantity of blue light. Key words: Triticum aestivum L., red light, blue light, subtillering, bioregenerative advanced life support     

The effect of light quality on the growth and development of in vitro cultured Doritaenopsis plants

The influence of light quality on growth and development of in vitro grown Doritaenopsis hort. (Orchidaceae) plants was investigated. Growth parameters like leaf and root fresh/dry mass and leaf area were highest with plants grown under red plus blue light emitting diodes (LEDs). Leaf length was greater with the plants grown under red LED. Carbohydrate (starch, sucrose, glucose and fructose) and leaf pigment (chlorophylls and carotenoids) biosynthesis of the plants was significantly increased in plants grown under red plus blue LEDs compared to red or blue LED and fluorescent light treatments. This study suggests that the production of quality Doritaenopsis plants is possible by culturing the plants in vitro under a mixture of blue plus red light sources.     

LED光质对乌饭树组培苗茎段增殖和生根的影响

采用发光二极管（LED）调制光质,以荧光灯为对照,研究LED不同红蓝光质比对乌饭树茎段增殖及生根的影响,为利用光质调控技术提高乌饭树组培效率和品质提供科学依据。结果表明,红光有利于新梢伸长及叶面积增加,但显著抑制叶绿素合成;蓝光抑制茎段新梢的诱导,但能促进组培苗不定根形成。红蓝复合光最有利于乌饭树组培苗茎段增殖、生物量积累以及根系发育,其中,在70% R（红光）+30% B（蓝光）处理下,带芽茎段的新梢诱导率、新梢数、叶片数、鲜重和干重均达到最大;而在生根阶段,组培苗的生根率、根数和根长在50% R+50% B处理下达到最大。此外,在单色蓝光处理下叶绿素a/b比值最大,是红光处理下的1.46倍;红蓝复合光促进乌饭树组培苗类胡萝卜素的合成。与荧光灯相比,适宜的LED光质能显著促进乌饭树茎段增殖和生根,是替代荧光灯的理想光源。     

Efficient in vitro regeneration systems for Vaccinium species

Efficient protocols for shoot regeneration from leaf explants suitable for micropropagation as well as for the development of transgenic plants were developed for blueberry (Vaccinium corymbosum) and lingonberry (Vaccinium vitis-idaea) cultivars. Nodal segments were used to initiate in vitro shoot cultures of lingonberry cultivar ‘Red Pearl’ and southern highbush blueberry cultivar ‘Ozarkblue’. In order to develop an optimized regeneration procedure, different types and concentrations of plant growth regulators were tested to induce adventitious shoot regeneration on excised leaves from micropropagated shoots of both cultivars. The effect on percentage regeneration and number of shoots per explant was investigated. Results indicated that zeatin was superior to TDZ and meta-topolin in promoting adventitious shoot formation. A concentration of 20 μM zeatin was most effective in promoting shoot regeneration in both cultivars, in case of ‘Red Pearl’ along with 1 μM NAA. Shoots were either allowed to root in vitro on medium containing IBA or NAA or ex vitro in a fog tunnel. IBA was superior to NAA for induction of root development in vitro in both Vaccinium cultivars. Ex vitro rooting under high humidity was tested with cuttings from mature field-grown plants, from acclimatized tissue culture derived plants and with unrooted in vitro proliferated shoots planted directly. It was found that in vitro shoots rooted better under fog than cuttings from the other plant sources and rooting was equivalent to that achieved in vitro.     

Influence of light quality and photoperiod on flowering of Cyclamen persicum Mill. cv. ‘Dixie White’

The effect of light quality (spectral quality) and photoperiod (day length) were studied on flowering of Cyclamen persicum cv. Dixie White. Light generated from light emitting diodes (LED) i.e. monochromatic blue (10 or 12 h per day), monochromatic red (10 or 12 h per day), blue plus red (10 or 12 h per day) and fluorescent lights were used in these studies. It was found that blue plus red LEDs improved flower induction in cyclamen, the number flower buds and open flowers being highest in the plants grown under blue plus red LED (10 h per day). Blue and red LEDs alone reduced the flowering response. Peduncle length (flower stalk length) and blooming period of flowers were also influenced by light qualities and photoperiod treatments. Peduncle length was 23.8 cm on plants grown under red LED (12 h per day) treatment but 14 cm on plants grown under fluorescent light. Blooming period of flowers grown under fluorescent light was 20 d, whereas it was 40 d with the plants grown under red LEDs (10 h per day). The results indicate that flowering and subsequent growth of cyclamen can be controlled by manipulating light quality and lighting period.     

Effects of different spectral lights on <Emphasis Type="Italic">Oncidium</Emphasis> PLBs induction,proliferation, and plant regeneration

The effects of different spectral light distribution on in vitro induction and proliferation of Oncidium protocorm-like bodies (PLBs) and subsequent growth of plantlets were investigated. Shoot tips (5 mm in length) of proliferating shoots of Oncidium “Gower Ramsey” were vertically incubated on 1/2 Murashige and Skoog (MS) medium supplemented with 1.0 mg l⁻¹ 6-benzyladenine (BA), and grown under either monochromatic red light-emitting diodes (LEDs) (RR), blue LEDs (BB), yellow LEDs (YY) or green LEDs (GG). Cultures grown under fluorescent lamps (FL) were used as control. Selected FL-induced PLBs were cut into 3- to 4-mm sections and incubated on MS medium supplemented with 1.0 mg l⁻¹ BA and 0.5 mg l⁻¹ α-naphthaleneacetic acid (NAA), and grown under RR, BB, YY, GG, or FL. Moreover, FL-differented shoots (15 mm in length with two leaves) were incubated on 1/2 MS medium with 0.5 mg l⁻¹ NAA, and grown under either FL, RR, 10% blue + 90% red LEDs (1BR), 20% blue + 80% red LEDs (2BR), 30% blue + 70% red LEDs (3BR), BB, 80% red + 10% blue + 10% far-red LEDs (RBFr), or 80% red + 10% blue + 10% green LEDs (RBG). Overall, the red light spectrum enhanced induction, proliferation, and the carbohydrate contents of PLBs, as well as subsequent plantlet lengths, while the blue spectrum promoted differentiation, protein accumulation, and enzyme activities in PLBs, as well as pigment content accumulation in PLBs and developing plantlets. The combination of red and blue LEDs resulted in higher energy efficiency as well as dry weight and enzyme activities in these plantlets.     

Influence of mixed LED radiation on the growth of annual plants

We investigated the effect of mixed radiation from light-emitting diodes (LEDs) on the growth and flowering of ageratum, marigold, and salvia bedding plants. Blue, red, and far-red lights were applied under controlled environmental conditions for 28 d. Both the combination of blue-plus-red radiation as well as fluorescent lighting treatment (control) caused increases in dry weights, but shoot lengths were shortest when plants were exposed to blue plus red light compared with either red or blue plus far-red treatments. The number of floral buds as well as the occurrence of flower opening for ageratum and salvia plants was also enhanced under the blue plus red mixture. Likewise, carbohydrate accumulation was stimulated by that combination compared with the other radiation treatments.     

Influence of light spectra and elicitors on growth and ascaridole content using in vitro cultures of Dysphania ambrosioides L.

Dysphania ambrosioides L. is a medicinal plant with anti-helmintic potential. The aim of this study was to evaluate separately the effect of light spectra and elicitors on Dysphania ambrosioides growth and volatile constituents in vitro. Thus, plantlets were first cultured under blue (B), red (R), white, combinations of B:R (1:1, 2:1, 1:2) from LEDs and fluorescent lamps. Secondly, nodal segments were inoculated in the medium supplemented with chitosan (0, 50, 100, 150, and 200 mg L^??1) and salicylic acid (0, 3, 6, 9, and 12 mg L^??1). After 40 days of cultivation, the growth parameters and chemical composition of volatile constituents were evaluated. The light spectra significantly influenced in vitro growth of D. ambrosioides. The best growth occured using white LED or a blue:red combination of 2:1. It was also observed that the blue LEDs inhibited the synthesis of Z-ascaridole, while fluorescent light promoted a greater conversion of α-terpinene into ascaridole. The elicitors, chitosan and salicylic acid had a negative effect on the growth of nodal segments. However, the highest Z-ascaridole content was obtained at 50 to 100 mg L^??1 of chitosan and with 6 to 9 mg L^??1 of salicylic acid. The present study demonstrates that shoots regenerated from nodal segments exposed to different light spectra or on MS medium containing chitosan and salicylic acid can exhibit an altered growth and increased volatile constituents of interest.

     

Effect of irradiance on shoot development in vitro

The growth of Disanthus cercidifolius and Rhododendron cultivars, and to a lesser extent Crataegus oxyacantha cv. Paul's Scarlet, was modified by altering either the spectral quality or the level of irradiance received by shoot cultures; which were otherwise maintained under uniform medium and plant growth regulator (PGR) conditions in vitro. When the spectrum of Philips colour 84 (white) fluorescent lamps was modified by coloured cellulose acetate filters, red light promoted shoot extension and axillary branching, whereas blue light inhibited shoot growth and reduced leaf chlorophyll content in the sensitive cultivar R. cv. Dopey. By using single or multiple layers of neutral density filters, or moving cultures nearer to the light source, irradiance from white light was varied. All cultures grew well at low levels of irradiance (c. 11 µmol m^–2 s^–1), but the growth and leaf chlorophyll content of cultures of Disanthus and Rhododendron cultivars were suppressed by increasing irradiance. In three related Rhododendron cultivars, increased irradiance promoted the development of adventitious shoots. Crataegus shoots were tolerant of a wide range of irradiances and only shoot extension was inhibited at the highest level tested; leaf chlorophyll content was unaffected. These results are discussed in terms of the differential perception of light relative to the natural habitats of these plants, and of the possible direct effect of irradiance upon PGRs in the culture system.     

Growth and photosynthesis of Chinese cabbage plants grown under light-emitting diode-based light source

We compared growth and the content of sugar, protein, and photosynthetic pigments, as well as chlorophyll fluorescence parameters in 15- and 27-day-old Chinese cabbage (Brassica chinensis L.) plants grown under a high-pressure sodium (HPS) lamps or a light source built on the basis of red (650 nm) and blue (470 nm) light-emitting diodes (LEDs) with a red to blue photon ratio of 7: 1. One group of plants was grown at a photosynthetic photon flux (PPF) level of 391 ± 24 μ mol/(m² s) (normal level); the other, at a PPF level of 107 ± 9 μ mol/(m² s) (low light). Plants of the third group were firstly grown at the low light and then (on the 12th day) transferred to the normal level. When grown at the normal PPF level, the plants grown under LEDs didn’t differ from plants grown under HPS lamps in shoot fresh weight, but they showed a lower root fresh and dry weights and the lower content of total sugar and sugar reserves in the leaves. No differences in the pigment content and photosystem II quantum yield were found; however, a higher Chl a/b ratio in plants grown under LEDs indicates a different proportion of functional complexes in thylakoid membranes. The response to low light conditions was mostly the same in plants grown under HPS lamps and LEDs; however, LED plants showed a lower growth rate and a higher nonphotochemical fluorescence quenching. In the case of the altered PPF level during growth, the plant photosynthetic apparatus adapted to new conditions of illumination within three days. Plants grown under HPS lamps at a constant normal PPF level and those transferred to the normal PPF level on the 12th day, on the 27th day didn’t differ in shoot fresh weight, but in plants grown under LEDs, the differences were considerable. Our results show that LED-based light sources can be used for plant growing. At the same time, some specific properties of plant photosynthesis and growth under these conditions of illumination were found.     

Differences in response to drought stress among highbush blueberry plants propagated conventionally and by tissue culture

Abstract

The effects of drought stress on the morphological and physiological features of highbush blueberry Brigitta Blue plants were investigated. The plants were propagated conventionally by stem cutting (SC) and tissue culture (TC). Micropropagated plants originating from axillary (TC-Ax) and adventitious (TC-Ad) shoots were separated. An additional group consisted of plants propagated several times by stem cuttings, derived from TC mother plants (TC/SC). Different concentrations of polyethylene glycol (PEG) (3% and 7%) were applied to induce drought stress. Parameters such as dry and fresh weight, water content, shoot elongation as well as chlorophyll fluorescence and content were measured. The effect of PEG treatment varied in plants of different origin. Shoot elongation was mainly inhibited in SC plants, whereas TC/SC plants exhibited a stronger reduction of photosystem II efficiency. Fm and Fv differences between TC plants propagated by axillary or adventitious shoots were also observed under control conditions. These epigenotypes also differed in shoot elongation under 7% PEG treatment. The obtained results confirmed the influence of the propagation method of highbush blueberry plants not only on morphological traits, but also on the physiological status.     

Quality and intensity of light affect <Emphasis Type="Italic">Lippia gracilis</Emphasis> Schauer plant growth and volatile compounds in vitro

The aim of this study was to evaluate the effects of different intensities and quality of light and explant type on the growth of and volatile compounds in Lippia gracilis in vitro. The treatments were as follows: light intensities of 26, 51, 69, 94, or 130 µmol m^?2 s^?1 from fluorescent lamps and light-emitting diode (LED) lamps at different wavelengths, namely, white, red, blue, and combinations of red and blue light at ratios of 2.5:1 and 1:2.5, respectively, and two explant types, namely, nodal and apical segments. On the 30th day of culture on half-strength Murashige and Skoog (Physiol Plant 15(3):473–497, 1962) medium, growth, production of photosynthetic pigments, chlorophyll a and b, total chlorophyll, carotenoids, and volatile constituents (using headspace gas chromatography-mass spectrometry) were analyzed. The light quality and intensity significantly influenced the in vitro growth of L. gracilis. The apical segments were superior in all parameters evaluated compared to nodal segments. The number of segments plantlet^?1, root length, and leaf, shoot, root, and total weight were higher with increasing light intensity, especially under the 94 µmol m^?2 s^?1 treatment, for both explant types. The red light showed the highest leaf (32.28 mg plantlet^?1) and total (58.33 mg plantlet^?1) dry weight of all the light qualities. Major constituents, namely, ρ-cymene, γ-terpinene, thymol, carvacrol, and E-caryophyllene, were identified, regardless of light conditions. The amount and composition of volatile compounds varied according to light intensity and quality. Low intensity (26 µmol m^?2 s^?1) increased γ-terpinene content (12.42%) and concomitantly decreased carvacrol (38.52%). Blue LED light showed higher production of carvacrol (48.11%).     

Blue and red light-emitting diodes with or without sucrose and ventilation affect in vitro Growth ofRehmannia glutinosa plantlets

Single-node, in vitro cuttings ofRehmannia glutinosa were transplanted to MS basal media and grown for 30 d. Plantlets were grown under various culture conditions: four different light qualities (red LEDs, blue LEDs, mixed LEDs, and fluorescent); with sucrose (30 mg.L^-1) or without (0 mg.L^-1); with air exchanges (3.5 h.^-1) or without (0.1 h.L^-1). Highest dry weights were obtained from plantlets under blue LEDs with 3.5h.L^-1 air exchanges. Light source did not affect shoot elongation in ventilated conditions, but without ventilation, the shoots of plantlets under red LEDs were twice as long as for plantlets growing under other types of lighting. Plantlets grown without sucrose showed little difference in photosynthesis under any of the tested light qualities. In contrast, the photosynthetic rate of those in the sucrose-containing media varied according to light source.     

Optimization of in vitro and ex vitro regeneration and micromorphological studies in <Emphasis Type="Italic">Basella alba</Emphasis> L.

The optimum concentrations of the plant hormones for in vitro regeneration and subsequent effect of auxins on rooting (in vitro and ex vitro) of shoots of Basella alba L. have been investigated in present study. Nodal shoot segments were used as explants to initiate the cultures. The bud breaking from explants was observed within 1 week of incubation on agar gelled Murashige and Skoog’s (MS) medium. Multiple axillary shoots (7.30 ± 0.56 shoots per explant) were induced on MS medium supplemented with 2.0 mg/L 6-benzylaminopurine (BAP). The shoots were multiplied (maximum 17.10 ± 0.44 shoots per explant) on the same medium fortified with 0.5 mg/L each of BAP and Kin (Kinetin) +0.1 mg/L IAA. These shoots were excised and rooted in vitro (10.73 ± 0.92 roots per shoot) on half-strength MS medium augmented with 2.0 mg/L indole-3 butyric acid (IBA). Hundred percentage success rates have been achieved by ex vitro rooting of the in vitro regenerated shoots with IBA at 300 mg/L. The in vitro and ex vitro rooted shoots were acclimatized in greenhouse and subsequently transferred to the natural field conditions where 100 % survival rate was reported. The ex vitro rooting method was found more advantageous than in vitro rooting in terms of time, energy and survival percentage of B. alba. A comparative foliar micromorphological study of B. alba was conducted to understand the micromorphological changes in plants while shifting from in vitro to the in vivo conditions in terms of variations in stomatal index, venation pattern and vein density, and the arrangement of crystals. The study could help in understanding the response of in vitro raised plants towards in vivo environment.