Partitioning of photosynthates originating from bent shoots in the arching and high-rack culture systems of cut rose production

The arching and high-rack culture systems were developed and patented by Japanese rose growers. Both culture systems have bent canopies (lower bent shoots). In the arching culture system, shoots sprouting from the crown are harvested as cut flowers. However, the high-rack culture system also has a bent canopy originating from the mother stem (upper bent shoots) and flower stems sprout and is harvested at the top of each mother stem. Partitioning of photosynthates originating from bent shoots in arching and high-rack culture systems of rose production was investigated to elucidate how carbohydrates are re-allocated from the bent shoots in different culture systems of roses. At the flowering stage in both culture systems, 50–70% of ¹³C-photosynthates originated from bent shoots were exported to other parts within 72 h after ¹³CO₂ feeding to the bent shoot. In the arching culture system, photosynthates from lower bent shoots were partitioned mainly to the roots and crown. Similarly, in the high-rack culture system, between 71 and 86% of the exported carbon from the bent shoots were allocated to below the point of bending (roots + crown + mother stems) and only 9–28% was allocated to flowering shoots above the point of bending. In both culture systems, photosynthate translocation from the lower bent shoot directly to flowers was low. Accordingly, bent shoots in rose plants acted as a source of photosynthates, independent of culture system. The height of the bent shoots determined for a great deal in the re-allocation of the photosynthates, and provides a partial explanation for difference in production of cut roses.     

Micropropagation of New and Old World Rose Species

Micropropagation comparisons were made between two Rosa hybrida cvs, Tropicana and Bridal Pink, and two old world spp. R. canina L. and R. damascena Mill. All species exhibited shoot-tip proliferation on a medium containing Murashige and Skoog (1962) (MS) basic salts plus nicotinic acid (0.5 mg 1^?1), pyridoxine HC1 (0.5 mg 1^?1), thiamin HC1 (0.5 mg 1^?1), glycine (2.0 mg 1^?1), myo-inositol (100 mg 1^?1), sucrose (30 g 1^?1), Bacto agar (8 g 1^?1) and supplemented with growth regulators. Species variation was observed for growth regulator requirement and rate of multiplication not only between the two R. hybrida cvs but also between the old world spp. It was concluded that 2.0 mg 1^?1 of BA was optimal for hybrid roses plus 0.05 and 0.10 mg 1^?1 of NAA for cvs Tropicana and Bridal Pink, respectively. Old world species required lower BA (1.0 mg 1^?1), and 0.15 mg 1^?1 NAA for R. canina and 0.10 mg 1^?1 NAA for R. damascena were optimal for maximum shoot proliferation. Both rooting ability and acclimation to the planting medium were lower in old world spp. compared with R. hybrida cvs.     

Vascular blockage in cut roses in a suspension of Pseudomonas fluorescens

Summary

To analyse quantitatively the relationships between cut rose (Rosa hybrida L. ‘Pascha’) vase-life, the onset of cavitation, plant water potential, and bacterial concentrations in the vase water, rose stems were placed in water containing different concentrations of Pseudomonas fluorescens 2892 tet^r rif ^r. There was a significant correlation (P = 0.0009) between cut rose vase-life and the concentration of bacteria in the vase water. As the number of bacteria in the vase water increased, the rate of senescence also increased. The water potential for roses in the bacterial suspension (at 8.50 log₁₀ CFU ml^–1) proceeded to drop constantly after 5.17 h in the vase solution, with the water potential falling to as low as -2.35 MPa by the end of the experiment (at 117 h). In contrast, the water potential of roses in deionised water dropped from -0.419 MPa at 5.17 h, to only –0.663 MPa after 117 h. When roses were stood in a bacterial suspension (at 8.5 log₁₀ CFU ml^–1) for 30 h, 63.8% of the total cumulative cavitation events were seen, while roses stood in deionised water exhibited only 26.8% of the total cavitation events. Uptake of acid fuchsin and the movement of tagged P. fluorescens 2892 in the xylem indicated that bacteria did not travel beyond the open-ended xylem vessels and were generally restricted to the first 50 mm from the cut end of the stem.     

Interactions between hormonal and developmental signalling in the prevention of side-shoots in rose (Rosa hybrida L.)

Summary

This study investigated the effects of auxin sprays on the development of side-shoots in rose (Rosa hybrida L.). The rationale was to prevent or to minimise side-shoot development in a commercially acceptable rose cultivar. Equallyspaced doses (at 0, 15, 30, 45 or 60 mg l^–1) of -naphthaleneacetic acid (NAA) were applied at the equivalent of 100 l ha^–1 to roses grown on an inert substrate in a commercial greenhouse, via repeated foliar sprays at 2, 4, or 8 d intervals over 7 weeks. Unattended or hand-pinched plants were used as negative or positive controls, respectively.The interaction between auxin dose and spray interval had a significant (P ≤ 0.001) influence on the number and growth rate of side-shoots on a stem. All auxin doses tested completely prevented side-shoot development on rose stems at a 2 d spray interval. This high efficacy was attributed to prevention of the irreversible phase-change in the regulation of apical dominance. However, the interaction between auxin dose and spray interval significantly (P ≤ 0.001) influenced the occurrence of leaf epinasty, a physiological condition with a negative impact on cut-shoot quality. Bullheads, another undesirable physiological condition, was significantly (P ≤ 0.001) influenced by auxin dose. This novel technology is expected to lower rose production costs. The data obtained in this study demonstrate the interaction between hormonal and developmental signalling in apical dominance. Possible modes of action are discussed.     

Nitrogen and calcium nutrition of Petunia × hybrida ‘Coral Sea’

The effects of N and Ca nutrition on plant growth and shoot elemental content of Petunia × hybrida Hort. Vilm. - Andr. ‘Coral Sea’ were evaluated. Nitrogen and Ca were applied separately or in combination in three experiments: (1) N at 0, 100, 200 or 400 mg l^?1; (2) Ca at 0, 75, 150 or 300 mg l^?1; (3) N at 0 or 100 mg l^?1 and Ca at 0 or 150 mg l^?1 combined factorially. Shoot and root dry weights, branch length and flower number were highest when plants received 100 mg l^?1 N. Plants treated with 150 mg l^?1 Ca had the highest shoot and root dry weights. Branch length was maximal at 300 mg l^?1 Ca.Nitrogen and Ca interacted to increase shoot dry weights, branch number and length, leaf area and flower number. Increasing N concentrations increased N and decreased P, Mn and Zn shoot contents. Calcium content of shoots increased while N, P and Mg decreased in response to increasing applications of Ca to petunia plants. Minimal N and Ca tissue concentrations for optimal P. × hybrida growth were 3.3 and 0.67%, respectively.     

African spider flower (Cleome gynandra L./Gynandropsis gynandra (L.) Briq.) as a red spider mite (Tetranychus urticae Koch) repellent in cut-flower rose (Rosa hybrida L.) cultivation

Companion planting of Cleome gynandra, of Kenyan origin, in beds of cut-flower roses reduces significantly red spider mite (Tetranychus urticae Koch) infestation without any detrimental effect on productivity or flower quality. The level of reduction is dependent upon the density of the C. gynandra plants with 15 plants in a 1.8 m² bed (8.3 plants m²) being the most effective, planted either around the bed perimeter or within the rows of roses. The relatively high density of C. gynandra plants required may limit the direct application of this technology in export-focused, greenhouse rose production yet may be of significant value as a supplement to other mite-control strategies. The potential benefits of such companion planting for growers of field roses and those involved in some domestic markets are also evident. Research into the nature and extraction of the active, volatile mite-repellant components of C. gynandra is indicated.     

Gibberellic acid and flower bud development in loquat (Eriobotrya japonica Lindl.)

The application of gibberellic acid (GA₃) to the whole loquat tree from mid-May to early June and from early August to the onset of flowering, significantly reduced the number of premature flowering shoots per current shoot and per m³ of canopy, and so reduced the total number of panicles per m³ of canopy. The number of vegetative shoots per m³ of canopy was also significantly reduced by applying GA₃. The response depended on the concentration applied and produced optimal results at 50 mg l⁻¹. Differences in the number of flowers per panicle and leaves per shoot were not significantly modified by the treatment. Nevertheless, GA₃ applied directly to the developing apex near to flower differentiation reduced the number of flowers per panicle by 25–35% and without modifying the morphological characteristics of the panicle. Results suggest that less sprouting of lateral buds was largely responsible for the reduction in flowering intensity caused by GA₃. Best treatments reduced thinning costs (60%, approximately) of premature flowering shoots, slightly increased fruit diameter and significantly improved fruit colour and juice quality, thus advancing harvest date.     

Propagation temperature,PPFD, auxin treatment,cutting size and cutting position affect root formation,axillary bud growth and shoot development in miniature rose (Rosa hybrida L.) plants and alter homogeneity

Summary

Rooting and growth responses of miniature rose cuttings were investigated in an experiment in which four propagation temperatures, two photosynthetic photon flux densities (PPFDs) with five auxin (IBA) concentrations, cutting sizes and cutting positions, were combined factorially in a response-surface design. Most prominently, temperature, cutting size and auxin and their interactions, influenced root and shoot growth. A propagation temperature of 24.6°C, and IBA concentrations between 10^–3 and 10^–1M, depending on temperature, were optimal for root formation. Root formation in extra short cuttings was delayed at low IBA concentrations. Regarding root formation, IBA could substitute for increased temperature as well as for increased cutting size. Onset of axillary bud growth was fastest at 24.6°C, and delayed in extra short cuttings. Application of IBA at 10^–4 to 10^–3M was optimal for axillary bud growth. By increasing the IBA concentration both time to flowering and plant height increased at 24.6°C. In cuttings from higher positions on stock plants, axillary shoots enhanced their growth to flowering, became shorter, and weighed less, suggesting occurrence of positional effects (topophysis). The growth rate increased with increasing IBA concentration, as well as from medial to low positioned cuttings. Increasing propagation PPFD from 46 to 72 µmol m^–2s^–1 did not affect the parameters. Time to axillary bud growth and time to first flower were related to time-to-visible root. Fast formation of roots apparently resulted in fast axillary bud growth. In time-to-visible root and axillary bud growth, the smallest variation between plants was found at optimal ranges for temperature, IBA concentration and cutting size, and further factors optimal for root formation and axillary bud growth provided the most synchronized plant development.     

Rose productivity and physiological responses to different substrates for soil-less culture

Cultivation of roses in various soil-less media was studied with the aim to identify the optimum soil condition for rose production. Madelon roses grafted on rootstock of Rosa indica var. major were transplanted to polyethylene bags containing zeolite and perlite (at ratios of 25z:75p, 50z:50p, 75z:25p and 100z:0p, v/v) in a climate-controlled greenhouse. Net photosynthesis (A_net), stomatal conductance (g_s) and water use efficiency (WUE) of roses were followed for 5 months. Flower production and quality were recorded in three flowering flushes during a 5-month period. Analysis of variance of repeated measurements showed that even though the overall A_net did not differ among treatments (average 18.7 μmol m⁻² s⁻¹), trends in A_net seasonality for roses in 25z:75p substrate differed significantly from those in 50z:50p, 75z:25p or 100z:0p. Stomatal conductance did not show any significant seasonality or trends in response to substrate mixtures, averaging 0.89 mol m⁻² s⁻¹. Water use efficiency was significantly lower for roses in 25z:75p than in 100z:0p mixtures (1.8 ± 0.15 and 2.0 ± 0.13 μmol m⁻² s⁻¹ CO₂/mmol m⁻² s⁻¹ H₂O, respectively). Cumulative production of rose plants did not differ among substrate mixtures. Productivity significantly differed among flower stem classes. Stem class I (>70 cm) and class V (≤30 cm) exhibited the least production, contributing to only 7.6 and 3.7% of the total production, respectively. The highest productivity was observed in classes III (51–60 cm) and IV (31–50 cm), contributing to the bulk of productivity (68.4%). Class II contributed a 20.3% of the production. Results showed that zeolite and perlite acted as inert materials. Zeolite did not exert any positive effect on productivity, in contrast to what has been reported in literature recently. Use of perlite resulted in a little improvement in photosynthesis, however this improvement was not reflected by a significant increase in production.     

Light acclimation in rose (Rosa hybrida cv. Grand Gala) leaves after pruning: Effects on chlorophyll a fluorescence,nitrate reductase,ammonium and carbohydrates

Changes in light intensity have a particular effect on the photosynthetic apparatus. Most of the studies on light acclimation in higher plants have focused on the effects of fixed light intensity. Few works deal on sudden changes in light intensity due to pruning for long periods of time. Pruning the bent shoots in roses (cv. Grand Gala) can modify the light interception in internal leaves and change their photosynthetic reactions. Before pruning, internal leaves were acclimated to low light intensity and after pruning, internal and external leaves received the same light intensity. The aim of this work was to find out how the photosynthetic light reaction, measured by chlorophyll (Chl) a fluorescence in internal and external leaves of arched shoot could be modulated by light changes. Other parameters described as light dependent were also measured: nitrate reductase (NR) activity, NH₄⁺, sucrose and starch levels. Internal and external leaves in rose have shown a high plasticity, rapid and dynamical acclimation, in response to changes in incident sunlight produced by pruning, that can be explained by Chl a fluorescence parameters. The modified NR activity, NH₄⁺, sucrose and starch levels were difficult to associated with light intensity changes, and their modulation could be the response to long-time light acclimation.     

The influence of constant and diurnally changing CO2 concentrations on plant growth and development

Plants of Ficus benjamina and miniature rose (Rosa hybrida cv. Red Minimo) were grown under four CO₂ treatments. Two had constant CO₂ levels (600 and 900 ppm) and the other two had diurnal changes in CO₂ levels, one increasing from 600 to 1500 ppm and one decreasing from 1500 to 600 ppm, each in four steps of 300 ppm during the day-time. In all treatments 900 ppm CO₂ was maintained during the night when supplementary light was used, except in the treatment with constant 600 ppm where 600 ppm was also continued throughout the night. Plant growth was monitored under both decreasing and increasing natural daylength and irradiance. The tallest plants and greatest increment in height for Ficus occurred with plants grown under constant CO₂ concentration at 600 ppm and also with increasing CO₂ concentration. In both experiments the dry weight per pot was lowest when plants were grown under a constant CO₂ concentration at 900 ppm. In both experiments with miniature roses the number of flower buds was significantly increased under diurnally changing CO₂ concentration or when the CO₂ level was constant at 600 ppm compared with a constant 900 ppm. Time to flowering was decreased by constant CO₂ at 900 ppm as compared with the other treatments.     

In vitro propagation of garlic by shoot proliferation

Shoot buds (5–8 mm long), excised from dormant cloves of the New Zealand commercial garlic (Allium sativum L.) and a virus-free French cultivar ‘Rose-de-Kakylis’, proliferated both axillary and adventitious shoots on B-5 basal medium supplemented with 0.5 mg l^?1 isopentenyladenine (2-ip) and 0.1 mg l^?1 naphthaleneacetic acid (NAA). An 8-fold increase in shoot number occurred every 6 weeks. Shoots were readily rooted in B-5 + 0.01 mg l^?1 2-ip + 0.2 mg l^?1 NAA and transferred to pots, where about 70% of the shoots formed established plants. The plants raised by this shoot-proliferation method retained the diploid condition of the parents.     

Effect of green tea extract powder on the vase-life of fresh-cut rose (Rosa hybrida L.) ‘Carola’ stems

To develop an innocuous, easy-to-use, and inexpensive preservative for the cut flower industry, green tea extract (GTE) powder was applied in the fresh-cut rose stem preservation process to exploit its high anti-oxidative and anti-microbial properties. The effects of 2.0 g l^?1 GTE powder in the vase solution on the vase-life and flowering profile of cut rose (Rosa hybrida ‘Carola’) stems were investigated. The effectiveness of GTE powder was also compared with other preservatives such as 2% (w/v) sucrose, 200 mg l^?1 8-hydroxyquinoline citrate plus 2% (w/v) sucrose, or 0.2 mM silver thiosulphate in the vase solution, with distilled water as a control. The results showed that, compared to the control, the 2.0 g l^?1 GTE powder treatment extended the vase-life and reduced the loss in fresh weight in cut rose stems in the vase solution. GTE at 2.0 g l^?1 provided the highest anti-bacterial activity (4.2 log₁₀ CFU ml^?1 on day-6) and prevented the decline in anthocyanin concentrations compared to that seen in the control stems, suggesting that GTE powder could be used as a preservative to extend the vase-life of fresh-cut rose flowers.     

Responses of glasshouse roses to light conditions

Effects of light intensity and duration on the vegetative and reproductive characters of the rose cultivar ‘Baccara’ were studied for a year. Production of unlighted ‘Baccara’ in S.W. England reflected the solar energy curve; the highest flower yield followed the vegetative phase receiving the most natural light. Lighting improved flower yield, decreased blind shoots and hastened flowering, in proportion to the quantity of light received, especially during periods of limited natural light. Intensity was more effective than duration. Bottom breaks and axillary shoot development were stimulated by lighting, the latter being associated with higher yields. Lighting the plants in the morning and evening increased yield more than giving the same quantity of light during the day.High pressure sodium lamps (SON/T) were effective as supplementary light to glasshouse roses, especially when higher intensities were required. Lighting with sodium lamps significantly increased flower yield and decreased the number of blind shoots. Some characteristics studied were highly correlated in all experiments.     

Influence of planting geometry on growth,yield and quality of rainfed garlic (Allium sativum L.) cultivated under Mediterranean conditions

Summary

The establishment of the optimum plant population has been shown to be one of the most crucial determinants of the marketable yield of bulbous crops. This study was conducted to determine the best plant arrangements for maximum yields and maximum bulb quality in rainfed garlic (Allium sativum L.) grown under Mediterranean conditions. The effects of row width and plant spacing on the yield and quality of the two cvs. Morado de Pedroneras and Germidour, were investigated on Córdoba, Spain, in Vertisol Chromoxerert soil. In 1987–1988, a wet growing season, higher yields and higher bulb quality were obtained than in 1988–1989; cv. Germidour yielded more per unit of land area of higher quality bulbs during both seasons. Narrow row width and/or narrow plant spacing resulted in higher values of dry matter, LAI, LAD, CGR and yield, whereas wide row spacing and/or wide plant spacing resulted in higher ware-sized bulb yield. LAD was closely related to yield (r² = 0.96**) and total dry matter (r² = 0.90**). Mean leaf surface was affected by plant density and climatic conditions and showed a high positive relationship (r² = 0.90**) with the percentage of Extra grade of bulbs (>50 mm). As a result of this study, a row width of 45–60 cm with plant spacing of 12–16 cm is recommended for cv. Germidour and 45 × 16 cm for cv. Morado, to maximize the proportion of high-quality yield under Mediterranean rainfed cropping systems.     

The effect of water availability and quality on photosynthesis and productivity of soilless-grown cut roses

Low matric and to a lesser extent osmotic potential reduce significantly leaf area and rose yield. Net assimilation rate and transpiration are also negatively affected although less dramatically. Low water potential causes an increase in the water use efficiency of greenhouse roses when tested in closed, no-discharge systems. When a stable osmotic potential is maintained in open systems, using increased leaching fraction (LF), low osmotic potential results in lower water use efficiency. Osmotic potential in porous media serving for greenhouse cut-rose production is usually lower than the matric potential. However, low matric potential in porous media is usually accompanied by very low unsaturated hydraulic conductivity, causing localized zones of very low matric potential adjacent to the root–medium interface. This phenomenon, that cannot be measured using tensiometers, is the main limiting factor to water uptake by plant roots. Restricted water uptake results in low leaf water potential and cessation of leaf and shoot expansive growth.Combined effects of drought and salinity on photosynthesis have been studied for a number of agronomic crops but studies on roses have been limited. In most greenhouse crops a close relationship between total water potential in the root zone (Ψ_t^soil) and in the shoot (Ψ_t^shoot) is found and there are good indications about the plant’s ability to make osmotic adjustments in order to lower Ψ_t^shoot and prevent excessive water losses from the leaves thus maintaining the plant’s turgidity. Future studies conducted with roses can provide a better insight into the adaptive processes within the plants when exposed to salt or water stresses.     

Rapid micropropagation of Psoralea corylifolia L. using nodal explants cultured in organic additive-supplemented medium

Summary

The influence of different growth regulators and additives on shoot multiplication from nodal explants of Psoralea corylifolia was investigated. Prolific shoot multiplication was achieved within 4 weeks of culture on Murashige and Skoog (MS) medium supplemented with 5 μM benzyladenine (BA), 5 μM ascorbic acid (AA), 100 mg l^–1 casein hydrolysate (CH) and 5% (v/v) coconut water (CW). Shoots elongated on half-strength MS basal medium devoid of inositol, but containing 5 μM 2-isopentenyladenine (2iP), 10 g l^–1 sucrose and 8 g l^–1 agar. Elongated shoots rooted on half-strength MS basal medium supplemented with 3 μM indole-3-butyric acid (IBA), 10 g l^–1 sucrose and 7 g l^–1 agar within 5 d of culture. The in vitro-raised plants were established successfully in 2:1:1 (v/v/v) garden soil:farmyard soil:sand, and maintained in a growth chamber with 100% survival. Acclimatised plants were transferred to a glasshouse and established successfully in the field. Flowers and fruits appeared after 4 months and resembled those on source plants. This system could be used for rapid commercial propagation of P. corylifolia for conservation strategies and to produce phytomedicines.     

Shoot production from cultured Allium porrum tissues

Large numbers of shoots have been obtained from the excised basal regions of leek plants, cultured on BDS medium. Shoots could be induced optimally upon media within the range of 6.0–8.0 mg 1^?1 6-(3-methyl-2-buten-1-ylamino)-purine (2iP) and 1.0–2.0 mg 1^?1 napthaleneacetic acid (NAA). Sub-culture of induced shoots onto fresh media, from the above hormone ranges, resulted in further multiplication. Sub-culture, onto fresh medium from the above hormone ranges, of the callus-like region around the bases of induced shoots and adjacent tissue, could also result in shoot production. Internally developing shoot primordia occurred in close proximity to meristematic regions, whereas superficially developing primordia did not show distinct affinities, although there was evidence of localised pockets of meristematic cells amidst senescing explant material at the surface of the culture. Such regions may represent early stages in the formation of the superficial primordia. The production of large numbers of leek shoots in vitro is mentioned in relation to present techniques of micro-propagation and cryopreservation.     

In vitro high frequency direct plant regeneration from whole leaves of blackberry

High frequency and direct (without callus) plant regeneration was achieved from whole leaf explants of thornless blackberry (Rubus hybrid) cv. Black Satin (EC No. 381258; PI No. 553272) in vitro. Leaf blade explants from 1-, 3- and 5-month-old mother cultures were cultured on Murashige and Skoog (MS) medium with thidiazuron (TDZ), N⁶-benzylaminopurine (BAP), indol-3-butyric acid (IBA) and α-naphthalene acetic acid (NAA), alone or in combination. Three-month explants cultured on 0.02 mg l⁻¹ TDZ produced a high regeneration frequency (91.7%) and the most shoots/leaf explant (17.3). The shoot primordia developed within 3 weeks from the point of detachment of the petiole from the leaf blade. The age of the explant source significantly affected the shoot regeneration potential of the leaf explants. Leaves excised from 3-month-old in vitro-cultured shoots performed better than those from 1- and 5-month-old shoots. Shoots rooted best on half-strength MS basal medium with 0.5 mg l⁻¹ IBA and 90% of the plantlets survived acclimatization. The regenerated plantlets were morphologically similar to the mother plants.