Vegetative traits can predict flowering quality in Phalaenopsis orchids despite large genotypic variation in response to light and temperature.

Phalaenopsis is an economically important horticultural ornamental, but its growth is slow and costly. The vegetative cultivation phase is long and required to ensure sufficient plant size. This is needed to develop high quality flowering plants. We studied the effects of temperature (27 or 31 °C) and light intensity (60 or 140 µmol m-2 s-1) on plant growth and development during the vegetative cultivation phase in two experiments, with respectively 19 and 14 genotypes. Furthermore, the after-effects of treatments applied during vegetative growth on flowering traits were determined. Increasing light intensity in the vegetative phase accelerated both vegetative plant growth and development. Increasing temperature accelerated vegetative leaf appearance rate, but strongly reduced plant and root biomass accumulation when temperatures were too high. Flowering was greatly affected by treatments applied during vegetative growth, and increased light and temperature increased number of flower spikes, and number of flowers and buds. Genotypic variation was large in Phalaenopsis, especially in traits related to flowering, thus care is needed when generalising results based on a limited number of cultivars. Plant biomass and number of leaves during vegetative growth were positively correlated with flowering quality. These traits can be used as an early predictor for flowering capacity and quality of the final product. Additionally, this knowledge can be used to improve selection of new cultivars.

CAM-physiology and carbon gain of the orchid Phalaenopsis in response to light intensity, light integral and CO2.

The regulation of photosynthesis and carbon gain of crassulacean acid metabolism (CAM) plants has not yet been disclosed to the extent of C3-plants. In this study, the tropical epiphyte Phalaenopsis cv. "Sacramento" was subjected to different lighting regimes. Photosynthesis and biochemical measuring techniques were used to address four specific questions: (1) the response of malate decarboxylation to light intensity, (2) the malate carboxylation pathway in phase IV, (3) the response of diel carbon gain to the light integral and (4) the response of diel carbon gain to CO2 . The four CAM-phases were clearly discernable. The length of phase III and the malate decarboxylation rate responded directly to light intensity. In phase IV, CO2 was initially mainly carboxylated via Rubisco. However, at daylength of 16 h, specifically beyond ±12 h, it was mainly phosphoenolpyruvate carboxylase (PEP-C) carboxylating CO2 . Diel carbon gain appeared to be controlled by the light integral during phase III rather than the total daily light integral. Elevated CO2 further enhanced carbon gain both in phase IV and phase I. This establishes that neither malate storage capacity, nor availability of PEP as substrate for nocturnal CO2 carboxylation were limiting factors for carbon gain enhancement. These results advance our understanding of CAM-plants and are also of practical importance for growers.

Blue Light Acclimation Reduces the Photoinhibition of Phalaenopsis aphrodite (Moth Orchid).

The moth orchid is an important ornamental crop. It is very sensitive to high light irradiation due to photoinhibition. In this study, young orchid tissue culture seedlings and 2.5" potted plants pretreated under blue light (BL, λmax = 450 nm) at 100 µmol m-2 s-1 for 12 days (BL acclimation) were found to have an increased tolerance to high light irradiation. After BL acclimation, orchids had an increased anthocyanin accumulation, enhanced chloroplast avoidance, and increased chlorophyll fluorescence capacity whenever they were exposed to high light of 1000 µmol m-2 s-1 for two weeks (HL). They had higher Fv/Fm, electron transport rate (ETR), chlorophyll content, catalase activity and sucrose content when compared to the control without BL acclimation. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that transcript levels of phototropins, D1, RbcS, PEPCK, Catalase and SUT2 were upregulated in the BL-acclimated orchids. Consequently, BL acclimation orchids had better growth when compared to the control under long-term high light stress. In summary, this study provides a solution, i.e., BL acclimation, to reduce moth orchid photoinhibition and enhance growth before transplantation of the young tissue culture seedlings and potted plants into greenhouses, where they usually suffer from a high light fluctuation problem.

Transcriptome analysis to identify candidate genes associated with the yellow-leaf phenotype of a Cymbidium mutant generated by γ-irradiation.

Leaf color is an important agronomic trait in flowering plants, including orchids. However, factors underlying leaf phenotypes in plants remain largely unclear. A mutant displaying yellow leaves was obtained by the γ-ray-based mutagenesis of a Cymbidium orchid and characterized using RNA sequencing. A total of 144,918 unigenes obtained from over 25 million reads were assigned to 22 metabolic pathways in the Kyoto Encyclopedia of Genes and Genomes database. In addition, gene ontology was used to classify the predicted functions of transcripts into 73 functional groups. The RNA sequencing analysis identified 2,267 differentially expressed genes between wild-type and mutant Cymbidium sp. Genes involved in the chlorophyll biosynthesis and degradation, as well as ion transport, were identified and assayed for their expression levels in wild-type and mutant plants using quantitative real-time profiling. No critical expression changes were detected in genes involved in chlorophyll biosynthesis. In contrast, seven genes involved in ion transport, including two metal ion transporters, were down-regulated, and chlorophyllase 2, associated with chlorophyll degradation, was up-regulated. Together, these results suggest that alterations in chlorophyll metabolism and/or ion transport might contribute to leaf color in Cymbidium orchids.

Effects of the total dose and duration of γ-irradiation on the growth responses and induced SNPs of a Cymbidium hybrid.

Purpose: Ionizing radiation has been used for developing new cultivars of diverse plant species, including Cymbidium orchid species. The effects of the total dose on mutation induction have been investigated; however, there is relatively little research on the influence of the dose rate or irradiation duration.Materials and methods: Thus, we analyzed the effects of the total dose and irradiation duration on the growth of Cymbidium hybrid RB001 protocorm-like bodies (PLBs). We completed a genotyping-by-sequencing analysis to compare the induced SNPs among five γ-irradiated populations with similar growth responses (LD50) to γ-rays.Results: The optimal time to assess the effects of the γ-irradiation was at 6 months after the treatment. On the basis of the survival rate of γ-irradiated PLBs, the optimal doses (LD50) for each irradiation duration were estimated: 1 h, 16.1 Gy; 4 h, 23.6 Gy; 8 h, 37.9 Gy; 16 h, 37.9 Gy; and 24 h, 40.0 Gy. The estimated optimal doses were duration-dependent at irradiation durations shorter than 8 h, but not at irradiation durations exceeding 8 h. A SNP comparison revealed a lack of significant differences among the mutations induced by γ-irradiations.Conclusions: These results indicate the irradiation duration affects PLB growth in response to γ-rays. Moreover, the mutations induced by a short-term treatment may be similar to those induced by a treatment over a longer period.

Stimulation of cyclic electron flow around photosystem I upon a sudden transition from low to high light in two angiosperms Arabidopsis thaliana and Bletilla striata.

In angiosperms, cyclic electron flow (CEF) around photosystem I (PSI) is more important for photoprotection under fluctuating light than under constant light. However, the underlying mechanism is not well known. In the present study, we measured the CEF activity, P700 redox state and electrochromic shift signal upon a sudden transition from low to high light in wild-type plants of Arabidopsis thaliana and Bletilla striata (Orchidaceae). Within the first 20 s after transition from low to high light, P700 was highly reduced in both species, which was accompanied with a sufficient proton gradient (ΔpH) across the thylakoid membranes. Meanwhile, the level of CEF activation was elevated. After transition from low to high light for 60 s, the plants generated an optimal ΔpH. Under such condition, PSI was highly oxidized and the level of CEF activation decreased to the steady state. Furthermore, the CEF activation was positively correlated to the P700 reduction ratio. These results indicated that upon a sudden transition from low to high light, the insufficient ΔpH led to the over-reduction of PSI electron carriers, which in turn stimulated the CEF around PSI. This transient stimulation of CEF not only favored the rapid ΔpH formation but also accepted electrons from PSI, thus protecting PSI at donor and acceptor sides. These findings provide new insights into the important role of CEF in regulation of photosynthesis under fluctuating light.

Phototropins Mediate Chloroplast Movement in Phalaenopsis aphrodite (Moth Orchid).

Chloroplast movement is important for plants to avoid photodamage and to perform efficient photosynthesis. Phototropins are blue light receptors in plants that function in chloroplast movement, phototropism, stomatal opening, and they also affect plant growth and development. In this study, full-length cDNAs of two PHOTOTROPIN genes, PaPHOT1 and PaPHOT2, were cloned from a moth orchid Phalaenopsis aphrodite, and their functions in chloroplast movement were investigated. Phylogenetic analysis showed that PaPHOT1 and PaPHOT2 orthologs were highly similar to PHOT1 and PHOT2 of the close relative Phalaenopsis equestris, respectively, and clustered with monocots PHOT1 and PHOT2 orthologs, respectively. Phalaenopsis aphrodite expressed a moderate level of PaPHOT1 under low blue light of 5 µmol�m-2�s-1 (BL5) and a high levels of PaPHOT1 at >BL100. However, PaPHOT2 was expressed at low levels at BL100. Analysis of light-induced chloroplast movements using the SPAD method indicated that orchid accumulated chloroplasts at BL25 and significant chloroplast avoidance movement was observed at >BL100. Virus-induced gene silencing of PaPHOTs in orchids showed decreased gene expression of PaPHOTs and reduced both chloroplast accumulation and avoidance responses. Heterologous expression of PaPHOT1 in Arabidopsis phot1phot2 double mutant recovered chloroplast accumulation response at BL5, but neither PaPHOT1 nor PaPHOT2 was able to restore mutant chloroplast avoidance at BL100. Overall, this study showed that phototropins mediate chloroplast movement in Phalaenopsis orchid is blue light-dependent but their function is slightly different from Arabidopsis which might be due to gene evolution.

Light quality affects light harvesting and carbon sequestration during the diel cycle of crassulacean acid metabolism in Phalaenopsis.

Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway present in a variety of genera including many epiphytic orchids. CAM is under circadian control and can be subdivided into four discrete phases during a diel cycle. Inherent to this specific mode of metabolism, carbohydrate availability is a limiting factor for nocturnal CO2 uptake and biomass production. To evaluate the effects of light quality on the photosynthetic performance and diel changes in carbohydrates during the CAM cycle. Phalaenopsis plants were grown under four different light qualities (red, blue, red + blue and full spectrum white light) at a fluence of 100 µmol m-2 s-1 and a photoperiod of 12 h for 8 weeks. In contrast to monochromatic blue light, plants grown under monochromatic red light showed already a significant decline of the quantum efficiency (ΦPSII) after 5 days and of the maximum quantum yield (Fv/Fm) after 10 days under this treatment. This was also reflected in a compromised chlorophyll and carotenoid content and total diel CO2 uptake under red light in comparison with monochromatic blue and full spectrum white light. In particular, CO2 uptake during nocturnal phase I was affected under red illumination resulting in a reduced amount of vacuolar malate. In addition, red light caused the rate of decarboxylation of malate during the day to be consistently lower and malic acid breakdown persisted until 4 h after dusk. Because the intrinsic activity of PEPC was not affected, the restricted availability of storage carbohydrates such as starch was likely to cause these adverse effects under red light. Addition of blue to the red light spectrum restored the diel fluxes of carbohydrates and malate and resulted in a significant enhancement of the daily CO2 uptake, pigment concentration and biomass formation.

Exposure of Catasetum fimbriatum aerial roots to light coordinates carbon partitioning between source and sink organs in an auxin dependent manner.

Light energy is essential for carbon metabolism in plants, as well as controlling the transport of metabolites between the organs. While terrestrial plants have a distinct structural and functional separation between the light exposed aerial parts and the non-exposed roots, epiphytic plants, such as orchids, have shoots and roots simultaneously fully exposed to light. The roots of orchids differ mainly from non-orchidaceous plants in their ability to photosynthesize. Since the roots of Catasetum fimbriatum can synthesize auxin which is acropetally transported to the shoot region, we decided to investigate whether: (1) light treatment of C. fimbriatum roots raises the auxin levels in the plant; and (2) distinct auxin concentrations can change the source-sink relationships, altering the amounts of sugars and organic acids in leaves, pseudobulbs and roots. Among the organs studied, the roots accumulated the highest concentrations of indole-3-acetic-acid (IAA); and when roots were exposed to light, IAA accumulated in the leaves. However, when polar auxin transport (PAT) was blocked with N-(1-Naphthyl)phthalamic acid (NPA) treatment, a significant accumulation of sugars and organic acids occurred in the pseudobulbs and leaves, respectively, suggesting that auxin flux from roots to shoots was involved in carbon partitioning of the aerial organs. Considering that C. fimbriatum plants lose all their leaves seasonally, it is possible the roots are a substituting influence on the growth and development of this orchid during its leafless period.

Photoprotection related to xanthophyll cycle pigments in epiphytic orchids acclimated at different light microenvironments in two tropical dry forests of the Yucatan Peninsula, Mexico.

MAIN CONCLUSION: Epiphytic orchids from dry forests of Yucatán show considerable photoprotective plasticity during the dry season, which depends on leaf morphology and host tree deciduousness. Nocturnal retention of antheraxanthin and zeaxanthin was detected for the first time in epiphytic orchids. In tropical dry forests, epiphytes experience dramatic changes in light intensity: photosynthetic photon flux density may be up to an order of magnitude higher in the dry season compared to the wet season. To address the seasonal changes of xanthophyll cycle (XC) pigments and photosynthesis that occur throughout the year, leaves of five epiphytic orchid species were studied during the early dry, dry and wet seasons in a deciduous and a semi-deciduous tropical forests at two vertical strata on the host trees (3.5 and 1.5 m height). Differences in XC pigment concentrations and photosynthesis (maximum quantum efficiency of photosystem II; F v/F m) were larger among seasons than between vertical strata in both forests. Antheraxanthin and zeaxanthin retention reflected the stressful conditions of the epiphytic microhabitat, and it is described here in epiphytes for the first time. During the dry season, both XC pigment concentrations and photosystem II heat dissipation of absorbed energy increased in orchids in the deciduous forest, while F v/F m and nocturnal acidification (ΔH(+)) decreased, clearly as a response to excessive light and drought. Concentrations of XC pigments were higher than those in orchids with similar leaf shape in semi-deciduous forest. There, only Encyclia nematocaulon and Lophiaris oerstedii showed somewhat reduced F v/F m. No changes in ΔH(+) and F v/F m were detected in Cohniella ascendens throughout the year. This species, which commonly grows in forests with less open canopies, showed leaf tilting that diminished light interception. Light conditions in the uppermost parts of the canopy probably limit the distribution of epiphytic orchids and the retention of zeaxanthin can help to cope with light and drought stress in these forests during the dry season.

DhEFL2, 3 and 4, the three EARLY FLOWERING4-like genes in a Doritaenopsis hybrid regulate floral transition.

KEY MESSAGE: DhEFL2, 3 and 4 regulate the flowering of Doritaenopsis . These genes could rescue elf4-1 phenotype in Arabidopsis while its overexpression delayed flowering. Phalaenopsis are popular floral plants, and studies on orchid flowering genes could help develop off-season cultivars. Early flowering 4 (ELF4) of A. thaliana has been shown to be involved in photoperiod perception and circadian regulation. We isolated two members of the ELF4 family from Doritaenopsis hybrid (Doritaenopsis 'Tinny Tender' (Doritaenopsis Happy Smile × Happy Valentine)), namely, DhEFL2 and DhEFL3 (DhEFL4 has been previously cloned). Multiple alignment analysis of the deduced amino acid sequences of the three DhEFL homologs showed that DhEFL4 and DhEFL2 are similar with 72% identical amino acids, whereas DhEFL3 is divergent with 72% similarity with DhEFL2 and 68% similarity with DhEFL4. DhEFL3 forms a separate phylogenetic subgroup and is far away from DhEFL2 and DhEFL4. The diurnal expression patterns of DhEFL2, 3, and 4 are similar in the long-day photoperiod conditions; however, in the short-day conditions, DhEFL3 is different from DhEFL2 and 4. For the DhEFL2, 3, and 4 genes, the strongest audience expression organs are the stem, petal and bud, respectively. The ectopic expression of DhEFL2, 3, or 4 in transgenic A. thaliana plants (Ws-2 ecotype) showed novel phenotypes by late flowering and more rosette leaves. The ectopic expression of DhEFL2, 3, or 4 could complement the elf4-1 flowering time and hypocotyl length defects in transgenic A. thaliana elf4-1 mutant plants. These results strongly suggest that DhEFL2, 3, and 4 may be involved in regulation of flower formation and floral induction in Doritaenopsis.

UV-B light contributes directly to the synthesis of chiloglottone floral volatiles.

BACKGROUND AND AIMS: Australian sexually deceptive Chiloglottis orchids attract their specific male wasp pollinators by means of 2,5-dialkylcyclohexane-1,3-diones or 'chiloglottones', representing a newly discovered class of volatiles with unique structures. This study investigated the hypothesis that UV-B light at low intensities is directly required for chiloglottone biosynthesis in Chiloglottis trapeziformis. METHODS: Chiloglottone production occurs only in specific tissue (the callus) of the labellum. Cut buds and flowers, and whole plants with buds and flowers, sourced from the field, were kept in a growth chamber and interactions between growth stage of the flowers and duration and intensity of UV-B exposure on chiloglottone production were studied. The effects of the protein synthesis inhibitor cycloheximide were also examined. KEY RESULTS: Chiloglottone was not present in buds, but was detected in buds that were manually opened and then exposed to sunlight, or artificial UV-B light for ≥5 min. Spectrophotometry revealed that the sepals and petals blocked UV-B light from reaching the labellum inside the bud. Rates of chiloglottone production increased with developmental stage, increasing exposure time and increasing UV-B irradiance intensity. Cycloheximide did not inhibit the initial production of chiloglottone within 5 min of UV-B exposure. However, inhibition of chiloglottone production by cycloheximide occurred over 2 h of UV-B exposure, indicating a requirement for de novo protein synthesis to sustain chiloglottone production under UV-B. CONCLUSIONS: The sepals and petals of Chiloglottis orchids strongly block UV-B wavelengths of light, preventing chiloglottone production inside the bud. While initiation of chiloglottone biosynthesis requires only UV-B light, sustained chiloglottone biosynthesis requires both UV-B and de novo protein biosynthesis. The internal amounts of chiloglottone in a flower reflect the interplay between developmental stage, duration and intensity of UV-B exposure, de novo protein synthesis, and feedback loops linked to the starting amount of chiloglottone. It is concluded that UV-B light contributes directly to chiloglottone biosynthesis. These findings suggest an entirely new and unexpected biochemical reaction that might also occur in taxa other than these orchids.

Spectral effects of LEDs on chlorophyll fluorescence and pigmentation in Phalaenopsis 'Vivien' and 'Purple Star'.

We examined the effect of light emitting diode (LED) lighting in greenhouse facilities on growth, chlorophyll fluorescence and pigmentation in Phalaenopsis 'Vivien' and 'Purple Star' under purpose-built LED arrays yielding c. 200 µmol m(-2) s(-1) at plant height for 14 h per day and 24/18°C day/night temperature, respectively, from January to April 2013. The light treatments were (1) 40% blue in 60% red (40% B/R), (2) 0% blue in 100% red (0% B/R) and (3) white LEDs with 32% blue in white (32% B/W, control), with background daylight under shade screens. The plants were harvested twice for leaf growth and pigmentation. There was no clear pattern in the spectral effect on growth since the order of leaf size differed between harvests in March and April. Fv /Fm was in the range of 0.52-0.72, but overall slightly higher in the control, which indicated a permanent downregulation of PSII in the colored treatments. The fluorescence quenching showed no acclimation to color in 'Purple Star', while 'Vivien' had lower ETR and higher NPQ in the 40% B/R, resembling low light acclimation. The pigmentation showed corresponding spectral response with increasing concentration of lutein while increasing the fraction of blue light, which increased the light absorption in the green/yellow part of the spectrum. The permanent downregulation of PSII moved a substantial part of the thermal dissipation from the light regulated NPQ to non-regulated energy losses estimated by ΦNPQ and ΦNO and the difference found in the balance between ΦPSII and ΦNPQ in 'Vivien' disappeared when ΦNO was included in the thermal dissipation.

The velamen protects photosynthetic orchid roots against UV-B damage, and a large dated phylogeny implies multiple gains and losses of this function during the Cenozoic.

UV-B radiation damage in leaves is prevented by epidermal UV-screening compounds that can be modulated throughout ontogeny. In epiphytic orchids, roots need to be protected against UV-B because they photosynthesize, sometimes even replacing the leaves. How orchid roots, which are covered by a dead tissue called velamen, avoid UV-B radiation is currently unknown. We tested for a UV-B protective function of the velamen using gene expression analyses, mass spectrometry, histochemistry, and chlorophyll fluorescence in Phalaenopsis × hybrida roots. We also investigated its evolution using comparative phylogenetic methods. Our data show that two paralogues of the chalcone synthase (CHS) gene family are UV-B-induced in orchid root tips, triggering the accumulation of two UV-B-absorbing flavonoids and resulting in effective protection of the photosynthetic root cortex. Phylogenetic and dating analyses imply that the two CHS lineages duplicated c. 100 million yr before the rise of epiphytic orchids. These findings indicate an additional role for the epiphytic orchid velamen previously thought to function solely in absorbing water and nutrients. This new function, which fundamentally differs from the mechanism of UV-B avoidance in leaves, arose following an ancient duplication of CHS, and has probably contributed to the family's expansion into the canopy during the Cenozoic.

Are carbon and nitrogen exchange between fungi and the orchid Goodyera repens affected by irradiance?

BACKGROUND AND AIMS: The green orchid Goodyera repens has been shown to transfer carbon to its mycorrhizal partner, and this flux may therefore be affected by light availability. This study aimed to test whether the C and N exchange between plant and fungus is dependent on light availability, and in addition addressed the question of whether flowering and/or fruiting individuals of G. repens compensate for changes in leaf chlorophyll concentration with changes in C and N flows from fungus to plant. METHODS: The natural abundances of stable isotopes of plant C and N were used to infer changes in fluxes between orchid and fungus across natural gradients of irradiance at five sites. Mycorrhizal fungi in the roots of G. repens were identified by molecular analyses. Chlorophyll concentrations in the leaves of the orchid and of reference plants were measured directly in the field. KEY RESULTS: Leaf δ(13)C values of G. repens responded to changes in light availability in a similar manner to autotrophic reference plants, and different mycorrhizal fungal associations also did not affect the isotope abundance patterns of the orchid. Flowering/fruiting individuals had lower leaf total N and chlorophyll concentrations, which is most probably explained by N investments to form flowers, seeds and shoot. CONCLUSIONS: The results indicate that mycorrhizal physiology is relatively fixed in G. repens, and changes in the amount and direction of C flow between plant and fungus were not observed to depend on light availability. The orchid may instead react to low-light sites through increased clonal growth. The orchid does not compensate for low leaf total N and chlorophyll concentrations by using a (13)C- and (15)N-enriched fungal source.

Effects of plant size, temperature, and light intensity on flowering of Phalaenopsis hybrids in Mediterranean greenhouses.

Mediterranean greenhouses for cultivation of Phalaenopsis orchids reproduce the warm, humid, and shaded environment of tropical underbrush. Heating represents the highest production cost, due to the high thermal requirements and the long unproductive phase of juvenility, in which plants attain the critical size for flowering. Our researches aimed to investigate the effect of plant size, temperature, and light intensity, during the phase of flower induction, on flowering of modern genotypes selected for Mediterranean greenhouses. Three experiments were carried out to compare (i) plant size: reduced size versus size considered optimal for flowering (hybrids "Sogo Yukidian," "Chain Xen Diamond," and "Pinlong"); (ii) temperature: moderate reduction of temperature versus standard thermal regime (hybrid "Premium"); (iii) light intensity: supplemental lighting versus reference light intensity (hybrid "Premium"). The premature exposure of plants to the inductive treatment delayed the beginning of flowering and reduced the flower stem quality, in all the tested hybrids. In "Premium," the lower temperature did not affect flowering earliness and commercial quality of flower stems compared to the standard regime, whereas it promoted stem branching. In the same hybrid, supplemental lighting anticipated flowering and promoted the emission of the second stem and the stem branching, compared to the reference light regime.

[Effects of different culture conditions on main chemical compositions of Anoectochilus roxburghii].

OBJECTIVE: To investigate the effects of different culture conditions on the main chemical compositions of Anoectochilus roxburghii, so as to determine the optimum culture conditions and provide theoretical support for large-scale production of Anoectochilus roxburghii. METHODS: The light qualities, photoperiods and induction periods were changed to regulate the main chemical compositions of Anoectochilus roxburghii. RESULTS: The contents of total flavonoids, quercetin, isorhamnetin and kaempferol in blue light were higher than that in yellow light, the worst was under red light. There was the highest total flavonoids, kaempferol and isorhamnetin content in photoperiod of 14 h/d. After one month inoculation, the total flavonoids, quercetin, isorhamnetin and kaempferol contents were the highest. CONCLUSION: The results show that the optimum culture condition is: inducted 15 days with blue light inoculated one month later at the photoperiod of 14 h/d.

Evaluación de diferentes medios de cultivo in vitro en el desarrollo de híbridos de Phalaenopsis (Orchidaceae) / Evaluation of different in vitro culture media in the development of Phalaenopsis hybrid (Orchidaceae)

Los híbridos de Phalaenopsis tienen una gran importancia económica a nivel mundial, como flor cortada y planta ornamental, debido a sus flores vistosas y a la capacidad de adaptación a diferentes condiciones ambientales. Las técnicas de cultivo in vitro resultan indispensables para mejorar la eficacia germinativa, el crecimiento y desarrollo de orquídeas con fines comerciales e investigativos. En esta investigación se determinó el medio de cultivo más apropiado para la germinación in vitro de un híbrido de Phalaenopsis. Inicialmente se evaluó la viabilidad de las semillas utilizando la prueba de tetrazolio (TZ). Las semillas se desinfectaron y se cultivaron aplicando el método de la jeringuilla. El porcentaje de viabilidad en promedio fue de 92,2 % (P≤ 0,05: Tukey HSD), con un porcentaje de germinación entre todos los medios de 95,1 % (P≤ 0,05: Tukey HSD). El medio de cultivo más eficiente para la germinación de híbridos de Phalaenopsis a las 18 semanas de cultivo fue el Murashige & Skoog (MS) suplementado con agua de coco, y jugo de piña con diferencias estadísticamente significativas (P≤ 0,05: Tukey HSD), con respecto a los demás medios de cultivo, contribuyendo de esta manera al uso de componentes orgánicos con el fin de mejorar la germinación y desarrollo de Phalaenopsis.

The Phalaenopsis hybrids have a significant economic importance throughout the world, as ornamental flower or plant. It is because of its attractive flowers and its adaptation capacity into different environments. The different culture media in vitro are vital to improve the efficacy of germination, growing and development of the Orchids for commercial and research purposes. In this research, the most appropriated medium for in vitro propagation of Phalaenopsis hybrid was determined. At first, the seeds viability was evaluated by using tetrazolium test (TZ). The seeds were disinfected and cultivated by means of the syringe method. The viability percentage average was 92.2 % (P≤ 0.05: Tukey HSD), with a percentage of germination of 95.1 % (P≤ 0.05: Tukey HSD) in all the environments. The most efficient culture Medium for Phalaenopsis hybrid phenological development, at 16 weeks, was Murashige & Skoog (MS). Coconut water and pineapple juice were used as supplement showing statistically significant differences (P≤ 0,05: Tukey HSD), in comparison with the other culture media, contributing this way to the usage of organic components, which will be employed to improve the germination and development of the Phalaenopsis.

The production of a key floral volatile is dependent on UV light in a sexually deceptive orchid.

BACKGROUND AND AIMS: Plants use a diverse range of visual and olfactory cues to advertize to pollinators. Australian Chiloglottis orchids employ one to three related chemical variants, all 2,5-dialkylcyclohexane-1,3-diones or 'chiloglottones' to sexually attract their specific male pollinators. Here an investigation was made of the physiological aspects of chiloglottone synthesis and storage that have not previously been examined. METHODS: The location of chiloglottone production was determined and developmental and diurnal changes by GC-MS analysis of floral tissue extracts was monitored in two distantly related Chiloglottis species. Light treatment experiments were also performed using depleted flowers to evaluate if sunlight is required for chiloglottone production; which specific wavelengths of light are required was also determined. KEY RESULTS: Chiloglottone production only occurs in specific floral tissues (the labellum calli and sepals) of open flowers. Upon flower opening chiloglottone production is rapid and levels remain more or less stable both day and night, and over the 2- to 3-week lifetime of the flower. Furthermore, it was determined that chiloglottone production requires continuous sunlight, and determined the optimal wavelengths of sunlight in the UV-B range (with peak of 300 nm). CONCLUSIONS: UV-B light is required for the synthesis of chiloglottones - the semiochemicals used by Chiloglottis orchids to sexually lure their male pollinators. This discovery appears to be the first case to our knowledge where plant floral odour production depends on UV-B radiation at normal levels of sunlight. In the future, identification of the genes and enzymes involved, will allow us to understand better the role of UV-B light in the biosynthesis of chiloglottones.

Slow photosynthetic induction and low photosynthesis in Paphiopedilum armeniacum are related to its lack of guard cell chloroplast and peculiar stomatal anatomy.

Paphiopedilum and Cypripedium are close relatives in the subfamily Cypripedioideae. Cypripedium leaves contain guard cell chloroplasts, whereas Paphiopedilum do not. It is unclear whether the lack of guard cell chloroplasts affects photosynthetic induction, which is important for understory plants to utilize sunflecks. To understand the role of guard cell chloroplasts in photosynthetic induction of Paphiopedilum and Cypripedium, the stomatal anatomy and photosynthetic induction of Paphiopedilum armeniacum and Cypripedium flavum were investigated at different ratios of red to blue light. The highest stomatal opening and photosynthesis of intact leaves in P. armeniacum were induced by irradiance enriched with blue light. Its stomatal opening could be induced by red light 250 µmol m⁻² s⁻¹, but the magnitude of stomatal opening was lower than those at the other light qualities. However, the stomatal opening and photosynthesis of C. flavum were highly induced by mixed blue and red light rather than pure blue or red light. The two orchid species did not differ in stomatal density, but P. armeniacum had smaller stomatal size than C. flavum. The stomata of P. armeniacum were slightly sunken into the leaf epidermis, while C. flavum protruded above the leaf surface. The slower photosynthetic induction and lower photosynthetic rate of P. armeniacum than C. flavum were linked to the lack of guard cell chloroplasts and specific stomatal structure, which reflected an adaptation of Paphiopedilum to periodic water deficiency in limestone habitats. These results provide evidence for the morphological and physiological evolution of stomata relation for water conservation under natural selection.