Night interruption promotes vegetative growth and flowering of Cymbidium

The effects of night interruption (NI) were examined on the vegetative growth and flowering of Cymbidium ‘Red Fire’ and ‘Yokihi’. Plants were grown under 9/15 h ambient light/dark (control), 9 h ambient light plus night interruption (22:00–02:00 h) with low light intensity at 3–7 μmol m⁻² s⁻¹ (LNI) and 9 h ambient light plus NI with high light intensity at 120 μmol m⁻² s⁻¹ (HNI) conditions. The number of leaves, leaf length, number of pseudobulbs and pseudobulb diameter increased in both LNI and HNI compared to controls for both cultivars. While none of the control plants flowered within 2 years, 100% of the ‘Yokihi’ and 80% of the ‘Red Fire’ plants grown under HNI condition flowered. In the LNI group, 60% of the plants flowered in both cultivars. Plants in the HNI group showed a decreased time to visible inflorescence and flowering than those in the LNI group. The number of inflorescences and florets were greater in the plants grown under HNI than those in the LNI group. The tallest plants at flowering were in the HNI group in both cultivars. NI with low light intensity can be used effectively to promote flower induction with increased growth rate during the juvenile stage in Cymbidium. To obtain high quality plants, however, NI with high light intensity strategies should be considered.     

The response of plant growth and leaf gas exchange to the speed of lamp movement in a greenhouse

High-pressure sodium (HPS) light supplementation during the low-light months has become quite common for high-light requiring crops at latitudes above 45°. Most common systems have fixed installations, while movable systems have been tried with various results in greenhouses. The concept is that fewer lamps are used on a track system, and that light intensity varies over time. In two trials, we determined whether the speed of the HPS lamp movement had any effect on leaf CO₂ exchange rate, growth and developments of various plants species. Plants (chrysanthemum, petunia, rose and tomato) were grown in a greenhouse supplemented with HPS lamps which moved at various speeds (0, 2, 8 and 20 mm s⁻¹) between 06:00 and 24:00 h daily for about 6–7 weeks. One trial started at the end of November and one started at the end of January. The light sum from the lamps were 0.212 ± 0.004 mol m⁻² h⁻¹ at bench level, and the supplemental lighting represented 55 and 35% of the total light received by the plants for the two trial dates, respectively. The growth (dry matter) was reduced for tomato only when grown under moving lights compared to those grown under the stationary system, while plant height was not affected. Light saturated CO₂ exchange rate on the youngest fully developed leaves increased with lamp speed for petunia and tomato, but not for chrysanthemums, while apparent quantum yield was not affected by lamp speed for any species. In situ measurements of net CO₂ exchange rate (NCER) with supplemental lighting only, showed that NCER decreased exponentially when lamp speed increased from 0 to 20 mm s⁻¹.     

Establishment of in vitro tissue cultures from Echinacea angustifolia D.C. adult plants for the production of phytochemical compounds

The establishment of in vitro cultures of Echinacea angustifolia D.C. was obtained directly from sections of flower stalks of adult plants. The shoot formation was obtained from this plant material placed on a modified MS basal medium named CH supplemented with 0.5 mg L⁻¹ 6-benzylaminopurine (BA). The in vitro propagation procedure of E. angustifolia consisted of three distinct phases: an initial regeneration phase from stalk sections (IP shoots on basal medium with 0.25 mg L⁻¹ BA), an elongation phase on active charcoal and an axillary proliferation of the shoots (AP shoots on basal medium with 0.5 mg L⁻¹ BA).Regenerating calli were established from leaves of in vitro shoots cultured on CH medium supplemented with 3 mg L⁻¹ BA and 0.5 mg L⁻¹ indole-3-butyric acid (IBA). Developed shoots from the callus cultures were subcultured on the CH medium with 0.5 mg L⁻¹ BA (leaf regenerated shoots: LR shoots). The secondary metabolite content of the in vitro plant material was compared with that of the greenhouse growing plants. The quali-quantitative LC-DAD-ESI-MS analysis on the extracts from axillary proliferation shoots (AP shoots) showed significant production of caffeic acid derivatives while leaf callus and LR shoots, accumulated mainly alkamides. These results showed that the proper choice of the procedures for in vitro multiplication allowed us to obtain plant biomass able to produce the active compounds typical of E. angustifolia plants.     

Flavonol and phenolic acid composition of sweet cherries (cv. Lapins) produced on six different vegetative rootstocks

The effect of rootstock (‘MaxMa 14’, ‘Weiroot 13’, ‘PiKu 1’, ‘Weiroot 158’, ‘Gisela 5’ and ‘F12/1’) on phenolic acid and flavonol content of “Lapins” sweet cherry was investigated. Phenolic acids and flavonols were isolated from sweet cherries and analyzed by using reversed phase high-performance liquid chromatography (RP-HPLC). The major phenolic acids in sweet cherries were neochlorogenic acid (18–50 mg kg⁻¹), chlorogenic acid (19–62 mg kg⁻¹) and p-coumaric acid derivatives (15–125 mg kg⁻¹). The amount of flavonol quercetin-3-rutinoside (8–37 mg kg⁻¹) was significant as well. There are significant variations in the phenolic compound content among sweet cherry fruits grown on trees grafted on different vegetative rootstocks. The significantly higher chlorogenic acid, neochlorogenic acid, p-coumaric derivative and quercetin-3-rutinoside contents were found in sweet cherry fruits grown on trees grafted on ‘Weiroot 13’ and ‘PiKu 1’ rootstocks. Sweet cherries produced on trees grafted on other rootstocks had significantly lower phenolic compound content.     

Phosphorus toxicity in the Proteaceae: A problem in post-agricultural lands

South African Proteaceae are adapted to the low soil phosphorus (P) concentrations of the Cape Floristic Region. The efficient P uptake by Proteaceae means that these plants experience phosphorus (P) toxicity at lower rhizosphere [P] than crop plants. This is only problematic when cultivating Proteaceae (and many plants from this region) on previously agricultural land with high residual soil [P]. In this study we hypothesize that P toxicity will result in element imbalances in leaves of Proteaceae and information from this study aims to facilitate ameliorative treatments. Phosphorus toxicity was induced on-farm in Leucadendron ‘Safari Sunset’ (Proteaceae) with subsequent mapping of element distribution in non-necrotic leaf tissue using micro particle-induced X-ray emission spectrometry. Phosphate supply up to 0.01 mM in a fertigation solution resulted in increased stem length of Leucadendron ‘Safari Sunset’ while P concentrations in excess of this resulted in decreased stem length, increased leaf [P] up to 0.25% (w/w) and, between 1 mM and 5 mM P supply, typical P toxicity symptoms were observed. High P supply (5 mM P) resulted in increased leaf [P] in most leaf tissues including the epidermis, where calculations from an equilibrium speciation model indicated that there was 30% more dissolved PO₄³⁻ in the epidermis compared to leaves at low P supply (0 mM added P on soil with 34 mg P kg⁻¹). Concomitantly, bundle sheath and epidermal [Ca] were reduced and 10% more Ca was predicted to be adsorbed and precipitated as hydrapatite at high P supply. High P supply resulted in increased leaf [Cl] and [Mn] in all tissues studied; decreased total leaf [Fe], bundle sheath, xylem, phloem and epidermal [Fe] and decreased total leaf [Zn] and xylem and phloem [Zn]. The observed symptoms of P toxicity in Leucadendron ‘Safari Sunset’ (necrosis in some plants, chlorosis and leaf rosetting) co-occurred with (1) excess PO₄³⁻, which may bind Ca in the epidermis (leading eventually to necrosis); (2) reduced [Fe] and increased [Mn] (leading to chlorosis) and (3) reduced total and vascular [Zn] (leading to leaf rosetting).     

Methyl jasmonate plays a role in fruit ripening of ‘Pajaro’ strawberry through stimulation of ethylene biosynthesis

The role of methyl jasmonate (MJ) in strawberry (Fragaria × ananassa Duch. cv Pajaro) fruit ripening was investigated by monitoring its endogenous concentrations in fruit at various stages of development and the effects of exogenously applied MJ at these stages on ethylene biosynthesis. The concentration of endogenous trans-MJ was significantly higher in the white fruit (31.7–162.2 ng g⁻¹) and decreased sharply in half and fully ripe fruit. Higher concentrations of endogenous trans-MJ at the white stage of strawberry fruit development followed by a decline during fruit ripening indicate that MJ may play an important role in modulating fruit ripening. Significantly increased ethylene production was measured in the fruit when MJ was applied at white, half ripe and at fully ripe stage. The application of MJ (50 μM) resulted in significantly highest ethylene production and increased activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase as compared to all other treatments. The effect of exogenously applied MJ on ethylene production, ACC synthase and ACC oxidase activities was dependent on concentration of MJ applied and on fruit developmental stage. In conclusion, MJ in strawberry modulates fruit ripening, as its concentration is higher in white fruit and is declined with the progression of ripening and exogenous application of MJ increases ethylene production, activities of ACC oxidase and ACC synthase depending upon the concentration of MJ applied and fruit developmental stage.     

Effects of thermoperiodicity and plant population density on stem and flower elongation, leaf development, and specific fresh weight in single stemmed rose (Rosa hybrida L.) plants

Thermoperiodicity, i.e. growth in the alternating temperature regime with the same diurnal mean compared with growth at the constant temperature at which optimal growth occurs, was studied at three plant population densities in four cultivars of Rosa hybrida L. Single-node cuttings with five-leaflet leaves were excised and grown as single-stemmed rose plants at an average photosynthetic photon flux density of about 260 μmol m⁻² s⁻¹ and supplied with carbon dioxide at about 1000 μmol mol⁻¹. The optimal constant temperature regime was 22 °C day (20 h)/22 °C night (4 h); alternating temperatures were 23 °C day (20 h)/18 °C night (4 h). The plant population densities were 100, 131 and 178 plants m⁻² of bench area. Thermoperiodicity was absent, or could not be detected, in the parameters related to the growth period, the formation of fresh biomass, the bloom quality, and most parameters related to shoot elongation. However, classic thermoperiodic effects of alternating regime were significant in the cultivars Red Velvet and Sonia, with shoot elongation promoted (7.1 and 10.5%, respectively) in the growth phase from onset of axillary bud growth until the flower bud became visible. Compared with the other two cultivars, plants of Red Velvet and Sonia tended to develop longer internodes. The results, obtained concurrently at three different plant population densities, suggest that thermoperiodicity can affect (single-stemmed) plant growth and development in R. hybrida. Increased plant population density also increased plant height at visible flower bud, but the bloom quality, expressed as specific fresh weight, and the flower height at anthesis was decreased at the highest density. Increased plant population density increased the number of five-leaflet leaves developed in Red Velvet, but had no effect on leaf number in Texas and Sonia, while, in Lambada the leaf number was decreased at the highest density.     

Effect of the culture environment on stomatal features, epidermal cells and water loss of micropropagated Annona glabra L. plants

Shoots of Annona glabra L. were rooted in vitro under three levels of irradiance and two closure systems (conventional and natural ventilation) of the culture vessels. Once the shoots had been rooted, we studied how the manipulation of the culture environment affects the stomata features and water loss through leaf tissues after the plants are removed from the vessel. The stomata frequency increased significantly in the leaves of plants grown under high (300 μmol m⁻² s⁻¹) compared to low (50 μmol m⁻² s⁻¹) or intermediate (150 μmol m⁻² s⁻¹) irradiance, with higher effect under natural ventilation. Irrespective of the culture environment, leaves developed in vitro attained a higher stomata frequency than those grown in vivo. Under high irradiance and natural ventilation, the leaves presented functional stomata of characteristically elliptical shape and the epidermal cells were smaller and had slightly sinuous anticlinal walls. Besides, water loss through leaves of plants grown under high irradiance and natural ventilation was drastically reduced if these plants were exposed to an environment with low relative humidity thereafter. Our results indicate that an increased light availability and the use of natural ventilation improve the regulatory capacity of water loss in micropropagated A. glabra L. plants and can favor the plants’ survival and growth after transference to the natural environment.     

Relative salt tolerance of selected herbaceous perennials and groundcovers

In order to use reclaimed water to irrigate landscape plants and minimize damage and loss, salinity tolerance of commonly used landscape plants needs to be determined and characterized. Eight herbaceous perennials and groundcovers were obtained from a local nursery, transplanted to 2.6-L plastic containers and grown in the greenhouse for 2 weeks before saline irrigation at electrical conductivity (EC) of 0.8 (tap water), 3.2, 6.4, or 12 dS m⁻¹ were initiated. Plants were irrigated with measured amount of saline solutions to obtain 30% leaching when approximately 50% water had been depleted. After 12 weeks, four plants in each treatment were destructively harvested and dry weights of shoots and roots were determined. Three Penstemon species (P. eatonii A. Gray, P. pseudospectabilis M.E. Jones, and P. strictus Benth.) and Lavandula angustifolia Mill. at 6.4 and 12 dS m⁻¹ and most at 3.2 dS m⁻¹ did not survive. Shoot dry weight of Delosperma cooperi (Hook.f.) L. Bolus decreased by 25% at 12 dS m⁻¹, but there were no significant differences among the rest of the treatments. All plants of Teucrium chamaedrys L. survived but growth was reduced significantly with lower visual scores as salinity of irrigation water increased. Although growth was reduced in Gazania rigens (L.) Gaertn. as salinity increased, no other signs of stress or injury were observed. Ceratostigma plumbaginoides Bunge had reduced growth at 3.2 dS m⁻¹ and higher EC levels compared to the control, older leaves showed reddish pigmentation at 6.4 dS m⁻¹, whereas those at 12 dS m⁻¹ did not survive. Ion concentrations of shoot and root tissue at the end of the experiment on surviving plants were also affected by salinity levels and varied among species. Among the tested species, D. cooperi and G. rigen indicated a relatively high tolerance to salinity, T. chamaedrys and C. plumbaginoides were moderately tolerant, and the rest were less tolerant.     

Effects of explant type, culture media and growth regulators on callus induction and plant regeneration of Chinese jiaotou (Allium chinense)

To establish an efficient protocol of shoot regeneration from callus, effects of explant type, culture media and plant growth regulators on callus induction and shoot regeneration of Chinese jiaotou (Allium chinense) were evaluated. The results showed that basal plate was the best explant for callus induction (47.5%) when cultured on B5 medium supplemented with 0.1 mg l⁻¹ 6-benzylaminopurine (BA) and 1.0 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D), and B5 was the best medium to induce callus formation with 49.3% of the explants forming callus. The highest callus induction (65.2%) was achieved culturing basal plate on B5 medium supplemented with 0.1 mg l⁻¹ BA and 1.0 mg l⁻¹ 2,4-D after 8 weeks of culture. The best callus proliferation was observed on B5 medium with 1.5 mg l⁻¹ 2,4-D. Shoots regenerated at the highest frequency of 58.8% with 4.5 shoots when calli were cultured on B5 medium with 0.1 mg l⁻¹ BA and 1.0 mg l⁻¹ a-naphthaleneacetic acid (NAA). This protocol provides a basis for future studies on genetic improvement and could be applied to large-scale multiplication systems for commercial nurseries of Allium chinense.     

The effect of nitrogen fertilization on plant growth and the nitrate content of leaves and roots of parsley in the Mediterranean region

Curly-leafed and turnip-rooted parsley have recently been introduced to Greece as alternative herbs within the programme for crop diversification. Because the response of these subspecies to nitrogen (N) application under the warm climatic conditions of the Mediterranean region is unknown, both were cultivated over three consecutive years in order to evaluate their yield potential and quality (in terms of nitrate content) in relation to nitrogen application in comparison with the traditionally cultivated plain-leafed subspecies. Nitrogen was applied as ammonium nitrate in the form of liquid feeds at rates of 30–450 mg kg⁻¹. Foliage and root yield increased with N application up to a level of 150 mg kg⁻¹ and the nitrate content of the tissues was low. Increasing N application rates to 300 or 450 mg kg⁻¹ did not cause a further increase in yield, but the nitrate content of the tissues increased. In view of health concerns with respect to human nitrate intake and environmental threats posed by excessive N application, it is concluded that the optimum level of ammonium nitrate application under local conditions should be 150 mg kg⁻¹. Overall, all three subspecies responded to N in a similar way in terms of yield and nitrate content.     

The effects of sodium chloride on ornamental shrubs

The use of saline waters is an option for the irrigation of salt tolerant ornamentals as competition for high quality water increases. However, despite the importance of ornamental shrubs in Mediterranean areas, salt tolerance of such species has received little attention. The aims of our investigation were to quantify the growth response and any injury symptom of 12 widely cultivated ornamental shrubs to irrigation with saline water and to investigate any possible relation with the concentration of Na⁺ and Cl⁻ in the plants. Species were irrigated with different salinities (10, 40, and 70 mM NaCl) for a 120-day period. At the end of salt treatment, plants were sampled and dry biomass recorded; the relative growth rate (RGR) was also calculated. Root and leaf samples from each species were used to evaluate Na⁺, K⁺ and Cl⁻ concentrations. Growth rates were significantly reduced in Cotoneaster lacteus, Grevillea juniperina and Pyracantha ‘Harlequin’, which also showed the highest percentage of necrotic leaves. The increasing external NaCl lead to an increase of Na⁺ and Cl⁻ in roots and leaves of the different species, although less Na⁺ was accumulated than Cl⁻: growth reduction well correlated with the concentration of Cl⁻ and/or Na⁺ in the leaves. The most sensitive species (i.e. C. lacteus, G. juniperina and Pyracantha ‘Harlequin’) had high concentrations of Na⁺ and/or Cl⁻ in their leaves and also showed a decrease in their leaf K⁺/Na⁺ ratios. Even though other species (i.e. Bougainvillea glabra, Ceanothus thyrsiflorus, Leptospermum scoparium, Leucophyllum frutescens and Ruttya fruticosa) demonstrated a high ion concentration in their leaves, they could be considered relatively salt tolerant as there was little growth reduction and few symptoms of injury in the leaves. In some other cases (i.e. Cestrum fasciculatum, Escallonia rubra and Viburnum lucidum) the observed tolerance was related to higher ion concentration in the roots compared to the leaves, probably indicative of a limited transport to the shoots. Only in Eugenia myrtifolia was the absence of symptoms associated with a limited Na⁺ and Cl⁻ uptake from the rhizosphere.     

Chill unit models for blackcurrant (Ribes nigrum L.) cultivars ‘Ben Gairn’, ‘Ben Hope’ and ‘Ben Tirran’

Temperate-zone crops require a period of winter chilling to terminate dormancy and ensure adequate bud break the following spring. The exact chilling requirement of blackcurrant (Ribes nigrum), a commercially important crop in northern Europe, is relatively unknown. Chill unit models have been successfully utilized to determine the optimum chilling temperature of a range of crops, with one chill unit equating to 1 h exposure to the optimum temperature for chill satisfaction. Two-year-old R. nigrum plants of the cultivars ‘Ben Gairn’, ‘Ben Hope’ and ‘Ben Tirran’ were exposed to temperatures of −10.1 °C, −3.4 °C, 0.1 °C, 1.5 °C, 2.1 °C, 3.4 °C or 8.9 °C (±0.7 °C) for durations of 0, 2, 4, 6, 8 or 10 weeks and multiple regression analyses used to determine the optimum temperature for chill satisfaction.     

Cold treatment modifies the photoperiodic flowering response of Lobelia×speciosa

Lobelia×speciosa Sweet ‘Compliment Scarlet' was grown under a range of photoperiods and low temperature treatments to determine their effects on flowering. In the first experiment, plants were held at 5°C for 0 or 15 weeks, then grown at 20°C under the following photoperiods: 10, 12, 14, 16, or 24 h of continual light or 9 h with a 4 h night interruption (NI). Non-cooled ‘Compliment Scarlet' flowered as a qualitative long-day plant (LDP) with a minimum flowering photoperiod of 14 h. Following cold, flowering was quantitative with respect to photoperiod, until ≈14.2 h, when the calculated rate of progress toward flowering reached a plateau. In cooled plants, node number below the inflorescence decreased from 27 to 16 as the photoperiod increased from 10 to 24 h. Cooled plants developed 61–149% more flowers and were ≥17% taller than non-cooled ones under the same photoperiod. To determine the cold duration required for flowering under short days (SD), plants were held at 0, 3, 6, 9, 12, or 15 weeks at 5°C then grown at 20°C under SD (9 h photoperiod) or long days (9 h photoperiod with a 4 h NI). Under SD, few plants flowered after ≤6 weeks of cold. As cold treatment increased from 9 to 15 weeks, flowering percentage increased, time to flower decreased from 93 to 64 days, and node count decreased from 24 to 13. Cold treatment did not affect flowering percentage or time under NI, but plants always had more flowers and were taller than reproductive ones under 9 h day lengths. Thus, ‘Compliment Scarlet', is a qualitative LDP, but an extended cold treatment can partially substitute for the long day (LD) photoperiodic requirement.     

Moving lamps increase leaf photosynthetic capacity but not the growth of potted gerbera

To investigate the responses of leaf photosynthesis and plant growth to a moving lighting system, potted gerberas (Gerbera jamesonii H. Bolus ex J.D. Hook “Festival”) were grown under supplemental lighting in a greenhouse with either a stationary or a moving lighting system positioned above the benches. The stationary system consisted of a fixed high pressure sodium (HPS) lighting system, while the moving lighting system consisted of a moving HPS fixture attached to a cable system to move the light fixture back and forth over the crop. In both cases, the supplemental lighting was applied from 6:00 to 24:00 h with the same supplemental daily light integral (4.9 mol m⁻² day⁻¹). Moving lamps significantly increased leaf photosynthetic capacity as represented by light saturated net CO₂ exchange rate (NCER) (A_sat), light- and CO₂-saturated rate of NCER (A_max), maximum rate of Rubisco carboxylation (V_cmax), maximum rate of electron transport (J_max) and rate of triose phosphate utilization. However, in situ leaf NCER and stomatal conductance, leaf chlorophyll content index, leaf area, leaf thickness, fresh weight of plants were significantly lower under moving lighting than under stationary lighting. It is suggested that the reduced growth of plants under moving lighting might be due to (1) the overall lower light use efficiency of leaves under moving lighting than those under stationary lighting; (2) the slower response time of the photosynthetic system compared to the rate of change in light intensity under moving lighting.     

Influence of medium composition and vessel ventilation on in vitro propagation of Phillyrea latifolia L.

Micropropagation of Phillyrea latifolia L. a wild species present in Mediterranean coastal areas having drought and salt tolerance was performed using explants from adult plants. Shoots were induced from nodal explants on the Rugini’s initial medium (IM). Then these were proliferated on either Rugini olive medium (OM) or Linsmaier and Skoog (LS) medium, each supplemented with 2.22 μM 6-benzylaminopurine (BA) or 4.56 μM zeatin (Z). Rooting (66.1±11%) was induced on shoots grown in perlite soaked with half-strength Rugini olive proliferation medium (OMr) containing 2.69 μM α-naphthaleneacetic acid (NAA) and 160 mg l⁻¹ putrescine. Both shoot multiplication and rooting were performed using Magenta^® GA-7 (Sigma) vessels either non-permeable or permeable to gas exchanges. Contamination (about 40%) was observed during the first five passages notwithstanding the addition of cefotaxime to the culture medium, but a high proliferation rate (90%) of explants provided enough healthy plant material. The highest shoot proliferation was observed on LS medium and zeatin whereas the presence of the ventilated filters reduced fresh weight of explants growing on LS media and did not affect shoot growth on OM media. During rooting, the use of ventilated vessels in comparison with the closed ones enhanced development of roots, and doubled the dry weight of plantlets. The vessel ventilation combined with the artificial substrate (perlite) was beneficial for in vitro acclimatization of rooted Phillyrea plantlets.     

Variation among Kalanchoe species in their flowering responses to photoperiod and short-day cycle number

Summary

Our objectives were to identify the critical daylength and number of short-day (SD) cycles necessary for flowering in Kalanchoe glaucescens, K. manginii, and K. uniflora. In Experiment I, plants were grown for 20 weeks under 9, 10, 11, 12, 13, 14, or 15 h photoperiods at 300 µmol m^–2 s^–1 for 8 h 55 min (9 h photoperiod), or 9 h and extended with dayextension (3 µmol m^–2 s^–1) lighting (10 – 15 h photoperiods). All species flowered when grown under photoperiods ranging from 9 – 12 h. The percentage of flowering plants decreased for all species as the photoperiod increased from 12 h to 14 h. No flowering occurred on plants grown under a 15 h photoperiod. Node numbers below the terminal inflorescence increased from 18 nodes to 28 nodes on K. glaucescens, from 12 nodes to 14 nodes on K. manginii, and from 12 nodes to 16 nodes on K. uniflora as the photoperiod increased from 12 h to 14 h, from 10 h to 12 h, and from

12 h to 13 h, respectively. Total flower numbers on K. uniflora decreased from 45 flowers to 13 flowers as the photoperiod increased from 9 h to 13 h. In Experiment II, plants were exposed to 0, 1, 2, 3, 4, 5, 6, 7, or 8 weeks of SD (8 h photoperiod) before being placed under night-interruption lighting (2 µmol m^–2 s^–1; between 22.00 – 0.200 h). One-hundred percent of K. glaucescens, K. manginii, and K. uniflora plants flowered when they received more than 1, 3, or 6 weeks of SD, respectively. The node number below the terminal inflorescence in each species was not affected by SD cycle-number. Total flower numbers per plant, and days to first open flower, were unaffected as the number of SD cycles exceeded the number required to induce flowering for all species.     

Varietal differences in phenolic content and astringency in skin and flesh of hardy kiwifruit resources in Japan

Varietal differences in the total phenolic content and astringency in the skin and flesh were determined among the cultivars and local collections of hardy kiwifruit with a ploidy variance found in Japan. The average values of the total phenolic content in the skin and flesh were 2.66 and 0.18 g 100 g⁻¹ FW, respectively. There were large varietal differences in the total phenolic content in the skin in the range of 1.3–5.0 g 100 g⁻¹ FW. Kochi (tetraploid), while Gassan and ‘Mitsuko’ (hexaploid) contained a larger amount of total phenolics. High astringency was found in Gassan, ‘Mitsuko’ and ‘Hoko’ (hexaploids) and Kochi. HPLC analysis showed that the major components of phenolics in the flesh were (+)-catechin, chlorogenic acid, rutin, (−)-epicatechin and quercetin.     

Flowering induction of Guzmania by ethylene

Ethylene exposure time required to induce flowering of Guzmania lingulata Mez. ‘Anita’ was investigated by exposing plants to ethylene at 100 μl l⁻¹ for 4, 6, 8, 10, 12, 16, or 24 h. Plants were also exposed to ethylene-free air for the same lengths of time. Plants exposed to ethylene for 4 h did not flower, but exposure for 6 h or longer resulted in 100% flowering. Suppression of endogenous ethylene synthesis by aminoethoxyvinylglycine (AVG) resulted in a longer exposure time of 20 h being required to obtain 100% flowering. This result suggests that endogenous ethylene production contributes substantially to floral induction. Ethylene treatment on a single young leaf induced flowering as well. Application of a protein synthesis inhibitor, cycloheximide, prevented flowering induced by ethylene, indicating that activation of ethylene responsive genes is followed by synthesis of new proteins involved in flowering.     

Light quality of continuous illuminating at night to induce floral initiation of Fragaria chiloensis L. CHI-24-1

A wild strawberry strain, Fragaria chiloensis CHI-24-1, produced inflorescences from both parent and asexually propagated daughter plants linked with runners when grown at 23 °C/20 °C (day/night) under a 24 h day-length (DL) of daylight plus nightly lighting by an incandescent lamp, but not under 8 or 16 h DLs. In the present study, the effect of light quality for continuous illuminating at night on floral initiation of CHI-24-1 plants grown under a 24 h DL was examined. The CHI-24-1 plants were grown under a 24 h DL consisting of natural daylight and continuous lighting at night by an incandescent, a blue fluorescent, a red fluorescent or a far-red fluorescent lamp for 40 days in summer and autumn. Also, the CHI-24-1 plants were grown for 40 days in a growth chamber at 25 °C/20 °C (day/night) with natural daylight and continuous lighting at night by red- and four types of far-red light-emitting-diodes (LEDs with peak wavelengths of 660, 700, 735, 780 and 830 nm). In both experiments, floral initiation of the parent and daughter plants was observed under a stereomicroscope. Although more than 50% of the parent and daughter plants initiated flower buds under the incandescent and far-red fluorescent lamps, about 15% and 0% of those initiated flower buds under blue and red fluorescent lamps, respectively. Floral initiation of the parent and daughter plants occurred under the far-red LED light source whose peak wavelength was 735 nm, but not under the red or the other far-red LEDs. From these results, it can be concluded that the effective light wavelength range of nightly continuous illuminating for floral induction in the CHI-24-1 plants is 735 nm in the far-red light region. Hence, the induction of floral initiation by nightly continuous far-red light (735 nm) appeared to be a response mediated by phytochrome.