Current status of commercial Calibrachoa cultivars as assessed by morphology and other traits

To study the morphological diversity of the popular ornamental crop Calibrachoa, traded since the 1990s, floral and vegetative characters of 91 commercial cultivars were compared to those of natural species. Floral colours were classified according to the ISCC-NBS system and the CIE LAB system. The numerical data obtained by measuring 19 floral and vegetative characters was tested with principal component (PC) analysis. Floral colour classes of commercial cultivars were divided into 37 groups according the ISCC-NBS system, whereas those of natural species were divided into 9 groups. These tendencies were readily observable in the scatter diagrams of the a* vs. b* values and the C* vs. L* values. As the result of PC analysis, six PCs were obtained. For PC4, which negatively correlated with the degree of nocturnal corolla limb closure, the majority of natural species showed negative scores whereas the majority of cultivars had positive PC4 scores. In terms of PC2 (flower size), PC3 (growth form), PC5 (floral shape) and PC6 (leaf shape), natural species were dispersed in a range wider than the cultivars. These results suggest that Calibrachoa cultivars possess more highly variable floral colour than natural species, and breeding programmes to diversify the floral colour seem to have progressed rapidly. The tendency of natural species to close the corolla limb toward evening has been removed almost completely from the cultivars. The floral size, growth form, floral shape and leaf shape of the cultivars were rather uniform compared to those of natural species.     

Characterization of interspecific hybrids of Petunia and Calibrachoa by multiplex PCR,DNA content,and chromosome number

Petunia and Calibrachoa are ornamental plants of worldwide economic importance. Commercially, it is useful to combine desirable characteristics of Calibrachoa, including the large diversity of flower colors, with the pH tolerance and vigorous growth of Petunia. For investigation of interspecific hybrids between Petunia and Calibrachoa we used four different introns with flanking exon areas, each from a different gene and with a different sequence for Petunia and Calibrachoa, as genus-specific markers for chromosomes in interspecific hybrids. PCR primers specific for Petunia and Calabrachoa were made from the determined sequences and tested on a range of presumed hybrids using multiplex PCR, which confirmed that the hybrids were derived from these two species. Flow cytometry demonstrated that the hybrids were triploid, and determination of chromosome numbers showed that two of the chromosome sets were from Calibrachoa, i.e. that the other parent, Petunia, was diploid. Similar methods can be used for molecular characterization of other new hybrids made between closely related species or cultivars.     

Effect of temperature on flowering in Primula vulgaris

When grown in a glasshouse, flowering in Primula vulgaris ‘Aalsmeer Giant’ (yellow) and ‘Ducat’ (blue) was delayed with increasing temperature from approximately 12°C to 18°C. In addition, size of the first open flower and the number of flowering axillary shoots decreased, whereas the number of leaves and leaf area increased with the temperature increase. All temperature responses were greater in ‘Aalsmeer’ than in ‘Ducat’.When grown in growth rooms at 9°C, flowering in P. vulgaris ‘Aalsmeer Giant’ (yellow) was inhibited compared with 15°C. However, when 9 weeks of 15°C was applied to plants grown for 9 weeks at 9°C, the inhibition was overcome; longer periods of 15°C being no more effective. This indicates than an early stage of flower formation, probably the initiation, in Primula vulgaris is inhibited by 9°C, and not the further development of the buds towards open flowers.     

Initiation and development of microspore embryogenesis in recalcitrant purple flowering stalk (Brassica campestris ssp. chinensis var. purpurea Hort.) genotypes

Purple flowering stalk (Brassica campestris ssp. chinensis var.purpurea Hort.) was generally regarded as a recalcitrant species for microspore culture in Brassica crops. Conditions for reliable induction of microspore embryogenesis were studied in 12 genotypes of purple flowering stalk. A treatment of short heat shock to microspore by incubating at 32 °C for 18 h was suitable for the survival of microspores, sustained cell divisions, and further induced embryogenesis. Subsequently, the reduced concentration of macro salts (1/2 NLN) provided an optimal condition for the development of embryoids. Under the optimized conditions for microspore embryoid development, 10 genotypes responded to microspore culture with the frequencies ranging from 2.7 to 70.5 embryoids per dish. However, regenerated plants were obtained from 9 genotypes, and more than 75% these regenerated plants were double haploid. This report establishes an efficient protocol for microspore culture and offers great potential for DH breeding in purple flowering stalk.     

Quantitative long-day flowering response in the perpetual-flowering F1 strawberry cultivar Elan

Summary

Perpetual-flowering strawberry cultivars are commonly classified as photoperiodically day-neutral, even though early investigations demonstrated long-day (LD) regulation. An important reason for this inconsistency is that these freely flowering plants are difficult to establish in a true vegetative state, and experiments have therefore often been started using runner plants with pre-formed inflorescences. In order to circumvent this problem, we have used the perpetual-flowering F₁-hybrid ‘Elan’ that is propagated by seed, and is thus not pre-conditioned by its earlier life history. The results demonstrated a marked quantitative LD response across a range of temperatures from 9° – 27°C. Seedlings were responsive to the LD stimulus at an early stage, and early flowering required LD exposure almost from germination. The critical daylength for the early flowering response was about 15 h at 18°C. Because of this threshold LD response, it is concluded that regulation of flowering is truly photoperiodic in nature, and not merely an effect of additional light. Flower development was also slightly advanced by LD conditions. Stolon formation was strongly enhanced by short-day conditions in combination with high temperature. Thus, not only flowering, but also runnering, was oppositely affected by photoperiod in ‘Elan’ compared with mono-flowering cultivars. The results are discussed in relation to the photoperiodic classification of strawberries.     

Gibberellin-mediated suppression of floral initiation in the long-day plant Rhododendron cv. Hatsugiri

In a number of woody perennial species a decrease in gibberellins concentrations in the apical meristems is required for floral initiation to occur. In Rhododendron, applied gibberellins inhibit flowering and gibberellin biosynthesis inhibitors promote flowering. However, unlike previous reports on other Rhododendron cultivars, Rhododendron cv. Hatsugiri is a faculatitive LDP. It was therefore unknown how gibberellins regulate flowering in this cultivar and if non-inductive short daylengths stimulate the productions of endogenous gibberellins to suppress flowering. By inhibiting floral initiation while not stimulating vegetative growth we found applications of GA₅ to best match the natural response of Rhododendron cv. Hatsugiri under short-day regimes. GA₅-mediated effects on flowering have previously been reported to be due to conversion to GA₆, however, GA₅ was found to be present in tissue samples at up to 0.57 ng g⁻¹ FW, while GA₆ was never found. In addition, foliar applications of [¹⁴C] GA₅ were not found to have metabolised to GA₆. In line with the hypothesis that gibberellins inhibit floral initiation in short days in Rhododendron cv. Hatsugiri, the concentration of GA₂₀, a precursor to many bioactive gibberellins, was higher in leaf tissues from plants in short days, compared to those in permissive long days when analysed using GC–MS.     

Environmental and chemical control of growth and flowering of Chamelaucium uncinatum Schauer

The main factor affecting floral initiation of Geraldton Wax-Flower (Chamelaucium uncinatum) is the photoperiod, while temperature is the major factor affecting flower development. Four weeks of short days (SD) are generally required for obtaining full flowering. The number of flowers produced per plant increases with increasing the number of SD. Under mild temperatures of $\text{20}\text{14°}\text{C}$ (day/night), plants initiated flowers even in long days (LD). However, fewer flowers were produced and on higher nodes as compared to SD plants. Chlormequat promoted flowering under prevailing summer conditions of high temperatures and LD. Under prevailing autumn conditions favourable for flower initiation, LD treatment or weekly sprays with gibberellic acid (GA) reduced the number of flowers per plant. Combined treatment of LD and GA reduced both the flowering percentage and the number of flowers per plant. Discontinuing the LD or the GA treatments caused a resumption of full flower initiation.     

A greenhouse method for screening lettuce for resistance to Sclerotinia sclerotiorum

Agar blocks colonized by Sclerotinia sclerotiorum, causal agent of lettuce drop, were used as inoculum in screening for resistance to this pathogen in the greenhouse.Since the degree of resistance to the pathogen among cultivars varied with the time observed after inoculation, resistance was assessed by the number of days for 50% of the plants of each cultivar to die, as well as the number of plants that died. The cultivars ‘PI (Plant Introduction) 250427’, ‘Taiwan’, ‘PI 251790’, ‘PI 255568’, ‘MSU 73-44’ and ‘Bibb’ were found to have a higher level of resistance to S. sclerotiorum than the cultivar ‘Grand Rapids’ at 12 or 15 days following inoculation.     

Identification of Petunia hybrida cultivars that diurnally emit floral fragrances

In order to identify genetic resources for breeding fragrant petunias for use as bedding plants, volatile compounds released by day from the flowers of 40 commercial Petunia hybrida cultivars were analyzed using a solid-phase micro-extraction technique coupled with GC–MS. The three cultivars with solid deep-blue flowers that accumulate malvidin in corollas with high tissue pH were found to emit abundant iso-eugenol as the principal floral fragrance. Several other cultivars that emitted considerable amounts of methylbenzoate and/or benzylbenzoate from the flower were also identified. Association between the floral fragrance and the other floral traits such as floral anthocyanin composition and corolla-tissue pH was discussed.     

Growth and flower quality of four Rosa hybrida L. cultivars in response to propagation by stenting or cutting in soilless culture

Performance of four Rosa hybrida L. cultivars (‘African Dawn’, ‘Ilios’, ‘Maroussia’ and ‘Soprano’) was evaluated. They were grown either on their own roots or grafted (stenting) onto Rosa canina L. ‘Inermis’ rootstock in a polyethylene greenhouse with hydroponics system. Parameters of plant growth and flower quality were investigated for two successive harvesting years (2005 and 2006). Results indicated that, all the cultivars were superior for most of the parameters studied when grafted onto rootstock compared to being on their own roots. Flowering stem fresh weight and diameters, flower fresh and dry weight, flower diameter and length, petal number, leaf chlorophyll content and quality index were higher in grafted plants compared to those propagated by cuttings. However, highest flowering stem length and number were observed in plants propagated by cutting, although not significant as compared with stenting method.     

Diversity in environmental controls of flowering in Australian plants

In adapting their flowering to a particular season of the year, plants utilize a number of environmental inputs. Knowledge of these environmental controls of flowering is important for production in commercial horticulture. Such information is also relevant for assessing whether or not a species is threatened by global warming. Here, for five Australian plant species, we document ways in which the environment regulates their flowering. Spring flowering of Croweaexalata ‘Bindelong Compact’ reflects a response to increased daily light integral, these plants showing no hint of a true long day photoperiodic response. Higher temperatures not only cause earlier flowering of this Crowea cultivar but also depress flower production (5% loss per 1 °C increase). By contrast, another Crowea, ‘White Star’, flowers only if exposed to cool temperatures (15 °C) at the time of the increase in daily light integral. Thus, in commercial horticulture, synchronous and rapid flowering of Crowea will be possible by shifting plants from shade to high light conditions. In nature, light intensity will also have a major impact on flowering. By contrast, best flowering of Lechenaultia formosa in spring is a response to short photoperiods at high temperature while L. biloba prefers long days and has potentially spring to summer flowering. Whereas rising summer temperatures could have a deleterious effect on flowering of C.exalata, global warming may have little impact on L. formosa and L. biloba which flower more profusely in warmer conditions. Another spring flowering species, Verticordia chrysantha, responds both to short days and to exposure to cool temperatures so its survival could be threatened by global warming. For Calytrix fraseri its late summer flowering in nature is explained by its requirement for an exposure to long days. When combined with information previously published for Australian plants, it is clear that there are no simple generalizations to explain why a plant species flowers when it does.     

不同品种菜薹可溶性固形物含量比较

分别以四九菜心、佰顺812、东莞80天3个广东菜心品种和十月红二号、十月红一号、大股子3个红菜薹品种为材料,比较了不同品种不同薹位的可溶性固形物含量。结果显示,不同品种间菜薹可溶性固形物含量存在一定差异,其中东莞80天广东菜心和大股子红菜薹含量最高;各品种均表现为自薹基部向上,可溶性固形物含量逐渐上升,花穗顶部可溶性固形物远高于其他薹位;叶片部位可溶性固形物含量最高,薹部居中。     

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.     

Determination of pineapple (Ananas comosus, MD-2 hybrid cultivar) plant maturity,the efficiency of flowering induction agents and the use of activated carbon

Natural flowering is one of the major agronomic problems in pineapple (Ananas comosus) cultivation. It causes heterogeneous flowering and fruit development with multiple harvest passes of the same field as an inevitable consequence. To avoid natural flowering, pineapple plants are induced to synchronize flowering by external ethylene treatments. In this research it is shown that pineapple plants (MD-2 hybrid cultivar) are already sensitive to external ethylene treatments at an early developmental stage, i.e. 3 months after planting, although no natural flowering occurs during this early stage of plant development. These results indicate that young pineapple plants already posses all the necessary factors to induce flowering in response to ethylene treatments. Additionally the efficiencies of flowering induction of different external ethylene treatments, including a novel agent developed at our lab, called ‘zeothene’, were evaluated. Zeothene (=zeolite containing ethylene gas) and ethylene dissolved in water (both applied in the central cup of the plant) were proved to be very efficient flowering induction agents. The commercial cultivation practice, in which ethylene gas is sprayed with water over whole plants, was found less efficient confirming that central cup applications are more efficient than whole plant spraying. Cup applications allow the active ingredient (ethylene or ethephon) to be taken up immediately by the apical meristem resulting in an efficient flowering induction signal. The addition of activated carbon to enhance the flowering induction treatment was found to be useful only with a very high dose of activated carbon (5%) and a long interaction time (at least 5–30 min) between the activated carbon and the flowering induction solution.     

Response to water stress of some oleander cultivars suitable for pot plant production

Oleander (Nerium oleander L.) is an evergreen shrub of great ornamental interest which, in recent times, has been increasingly used as a flowering pot plant. Plants grown in pots undergo more frequent water stress conditions than those grown in the soil, due to the limited volume of substrate available for the roots. Oleander is a species adaptable to dry conditions and able to survive long periods of drought. It is well known that under water stress conditions all plants reduce photosynthetic activity, resulting in reduced plant growth. In case of severe water stress, leaves undergo strong wilting and senescence resulting in the loss of ornamental value. In the present work, a study was conducted to evaluate the ecophysiological response to water stress in four oleander cultivars previously recognised (on the basis of traits such as size, habit, earliness, abundance and duration of flowering, aptitude for cutting propagation and rapidity of growth) as suitable for pot plant production. Our data confirm the high drought tolerance of oleander. In the studied cultivars, plants submitted to water stress showed only minor variations in leaf gas exchange parameters [transpiration (E), stomatal conductance (g_s) and CO₂ net assimilation (A)] for at least 10 days without a change in leaf water content [assessed as relative water content (RWC)] for 22 days from the beginning of the stress treatment. During this period, non-irrigated plants maintained the same water status as control plants and were visually undistinguishable from them. Moreover, plants survived without water supply for one month. Following the supply of water again, they were able to restore RWC, gas exchange parameters and instantaneous water use efficiency [A/E ratio (WUE_inst)] to the values of control plants. Furthermore, if at the end of the stress period plants appeared withered and were pale green in colour, they regained their normal appearance after they were irrigated again. Although the four studied cultivars showed some minor differences in leaf gas exchange parameters and in the manner in which the latter parameters changed after irrigation was stopped, the response to water stress was essentially the same. Therefore, as far as drought tolerance is concerned, all these cultivars have a good aptitude for use as flowering pot plants.     

A nectar oasis for urban Glossophaginae bats: Temporal resource dynamics of the chiropterophilous Crescentia cujete (Bignoniaceae)

Pollinator-friendly plants are often a necessary component of the management of urban ecosystem that aim to reduce the impact of the artificial urban matrix on natural pollinator populations. Nectarivorous bats are neglected components of the urban pollinator community and there is a paucity of assessments on pollinator-friendly plants that may provide urban bats with reliable, year-long resources. Crescentia cujete is a bat-pollinated Bignoniaceae with very distinctive chiropterophilous features that is often used as an ornamental species in tropical urban areas worldwide. Its flowers are large and produce copious amounts of nectar, which accumulates in the flower’s storage-shaped flowers. Thus, the species is a potential bat-friendly urban plant. We assessed the species’ year-round flower emission and nightly nectar production dynamics in a green area in northeastern Brazil, and described the behavior of its floral visitors. C. cujete showed a steady, year-round flowering pattern, with no significant seasonality. Its flowers secreted copious amounts of diluted nectar and were visited exclusively by the Pallas long-tongued bat Glossophaga soricina throughout the night at high visiting frequencies, delivering successive visits to individual flowers spaced by short intervals. Our results suggest overexploitation of floral resources from C. cujete by urban bats. Moreover, its continuous flowering and copious nectar production may become a reliable resource in an artificial environment generally lacking bat-pollinated plants, thus mitigating the effects of food shortage for urban nectar bats.     

观赏海棠品种群的花期物候特征研究

 以82个观赏海棠品种为研究对象,进行了始花期（S₁）—盛花期（S₂）—末花期（S₃）3个阶段的花期物候观测,系统地研究了品种群的花期物候特征,旨在为海棠专类园建设及海棠花期物候性状特异种质挖掘与定向育种提供参考。结果表明：根据始花期的候区分布,可将82个品种划分为最早（VE）、早（E）、中（M）、晚（L）和极晚（EL）5大花期时序品种群;最早与最晚开花品种的始花期间隔22 d。根据S₁ ~ S₃花期持续时间长短,以3 d为级差,可将82个品种划分为超短（VS）、短（S）、中等（M）、长（L）和超长（VL）5大花期长短类群;82个品种平均花期长度为（11.4 ± 2.8）d。基于花期物候频率统计,构建了始花期（S₁）、盛花期（S₂）和末花期（S₃）的品种频度指数动态分布函数（CFI）,其动态函数的直线斜率存在显著差异（k₁ = 6.312 < k₂ = 6.821 < k₃ = 9.1557）,反应了3个花期阶段物候节奏由慢而快的变化趋势。还构建了观赏多度指数函数（CDI）,为品种群花期整体观赏性评价提供了新的参考依据;基于CDI,将品种群的群体观赏期划分为6个阶段,即启动期（P₀）、指数快速上升期（P₁）、指数高位稳定期（P₂）、指数快速下降期（P₃）、窗口期（P₄）和指数低位持续期（P₅）;P₁ ~ P₃期间CDI值 ≥ 13.6%,时间长达21 d;P₂时段的CDI值高达75.3% ~ 80.3%,时间达3 d。基于82个观赏海棠品种S₁ ~ S₃的花期长度（L）和开花期间每日最高气温均值（T）的二维源数据,以T = 23 ℃和T = 27 ℃为分界点,拟合了L与T之间的分段耦合函数,不同温度区间耦合度（R²）差异显著：52个品种分布于A区（T = 19.2 ~ 22.9 ℃）,21个品种分布于B区（T = 23.0 ~ 26.9 ℃）,9个品种分布于C区（T = 27.0 ~ 32.0 ℃）;这反应了花期长短的相对性,当T ≤ 23 ℃时,花期长短的主导因子为遗传因素,T ≥ 27 ℃时,花期长短的主导因子为日最高气温,T = 23.0 ~ 26.9 ℃时,花期长短由遗传因素和日最高气温共同主导。     

Quantifying the thermal flowering rates of eighteen species of annual bedding plants

The effect of mean daily air temperature (MDT) on flowering rate (the reciprocal of days to flower) was quantified for 18 species of annual bedding plants. Plants were grown in environmental growth chambers at constant air temperature set points of 5, 7.5, 10, 15, 25, or 30 °C and under an irradiance of 160–180 μmol m^–2 s^–1, with a 16-h photoperiod. Nonlinear mathematical equations were developed to predict the effect of MDT on flowering rate and to estimate the base, optimum, and maximum temperatures (T_min, T_opt, and T_max), which are the temperatures at which flowering rates are zero (low temperature), maximal, and zero once again (high temperature), respectively. The estimated T_min varied among species and ranged from 1.1 °C in French marigold (Tagetes patula L.) to 9.9 °C in angelonia (Angelonia angustifolia Benth.). T_opt and T_max were only observed for 8–10 species with the temperature range tested. T_opt ranged from 19.1 °C in dahlia (Dahlia × hybrida Cav.) to 28.0 °C in blue salvia (Salvia farinacea Benth.), whereas T_max ranged from 30.3 °C in snapdragon (Antirrhinum majus L.) to 31.7 °C in moss rose (Portulaca grandiflora Hook.). Angelonia, browallia (Browallia speciosa Hook.), cosmos (Cosmos sulphureus Cav.), dahlia, and snapdragon grown at 25 or 30 °C developed a mean of two to seven more nodes before flowering compared with plants grown at ≤15 °C. The results indicate that in many species, flowering rate in response to MDT is asymmetrical around T_opt and the temperature range between T_min and T_opt is wider than that between T_opt and T_max. This information could be used to improve the predictability of flowering time of these ornamental crops and to assist growers in determining energy-efficient production temperatures.     

Gibberellin substitution for the high night temperatures required for the long-day promotion of flowering in Gypsophila paniculata L.

Gibberellic acid (GA) promoted flowering of Gypsophila paniculata plants grown under long-day (LD) conditions at low night temperatures, which otherwise prevented the realization of the LD induction. GA did not induce flower formation of plants grown in short-days (SD), either under low winter temperatures or at the relatively high night temperatures of spring and summer, which allow flowering under LD. GA had only a marginal promotive influence under fully inductive conditions of LD and high temperatures. Thus, in gypsophila, GA substitutes for the high night temperature which is required as a background for the photoperiodic induction, but not for the long photoperiod itself.     

Promotion of flowering by photoperiodic lighting in winter-grown gladiolus planted at high densities

Gladiolus plants were grown in winter and early spring at several densities, under natural day, or long day (LD) regimes, with low intensity light at night. LD treatment promoted flowering-percentage (by reducing “blindness”), and enhanced flower quality features, (length of stem and spike, and number of florets per spike). The effect was observed even at planting-densities of 2–3 times the normal winter density. Lighting for 1 hour at mid-night was effective, but the greatest effect was observed by lighting throughout the night. Most of the promotive effects were obtained by lighting for 4 hours as day extension or as night break, and this treatment was recommended for commercial use. Cyclic lighting of 5 minutes of light and 10 minutes of dark was as effective as continuous light for 4 hours, and light intensity of 35 lux was as effective as 130 lux.All cultivars of gladiolus grandiflorus tested responded to the LD treatment, but the miniature cultivar ‘Charm’ did not. The LD effect was especially pronounced under conditions when the normal flowering was defective, such as with high-density plantings, low temperatures and with summer cultivars.