Optimising the organic components of topsoil mixtures for urban grassland

In order to optimise the organic components of topsoil mixtures for urban grassland, we conducted two pot experiments, each with seven topsoil mixtures and perennial ryegrass (Lolium perenne) as the experimental crop. The mineral base material of the topsoil mixtures was a blend of crushed bedrock (0–2 mm), sand and agricultural topsoil. The organic components comprised three types of organic waste-based products (WBP), namely sewage sludge (SS), water sludge (WS) and garden-park compost (GPC), which were added in varying ratios to a total amount of 0.3 m³ WBP m^?3. In both experiments, mineral nitrogen (N) availability was the key limiting factor for plant growth. Plant growth increased with increasing amounts of the N-rich SS, whereas WS and/or GPC alone resulted in sparse biomass production. Topsoil mixtures with 0.1 m³ m^?3 each of SS, WS, GPC or with 0.1 m³ SS m^?3 and 0.2 m³ WS m^?3 resulted in favourable growth patterns and acceptable soil chemical properties. Topsoil mixtures containing ≤0.1 m³ SS m^?3 can therefore be recommended for the establishment of urban grassland. With >0.1 m³ SS m^?3, N and phosphorus (P) were applied in excess, causing intensive plant growth and strongly increased readily available phosphorus (P-AL) content in topsoil. We therefore suggest revision of the current Norwegian regulations, which permit inclusion of 0.3 m³ SS m^?3 in topsoil mixtures for urban greening.     

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.     

Bell pepper yield and soil properties during conversion from conventional to organic production in Indian Himalayas

A conversion period of at least two years is required for annual crops before produce may be certified as organically grown. There is a need for better understanding of the various management options for implementing from conventional to organic production. The purpose of this study was to evaluate the effects of three organic amendments on growth and yield of bell pepper (Capsicum annuum L.), the benefit:cost ratio, soil fertility and enzymatic activities during conversion to organic production. For that purpose six treatments were established: composted farmyard manure (FYMC, T₁); vermicompost (VC, T₂); poultry manure (PM, T₃) along with biofertilizers (BF) [Azotobacter + phosphorus solubilizing bacteria (Pseudomonas striata)] and mix of three amendments (FYMC + PM + VC + BF, T₄); integrated crop management (FYMC + NPK, T₅) and unamended control (T₆). The bell pepper yield under organic management was markedly lower (33–53% and 18–40% less in first and second year of conversion, respectively) than with the integrated crop management (FYMC 10 Mg ha⁻¹ + NPK – 100:22:41.5 kg ha⁻¹) treatment (T₅). Combined application of three organic amendments (FYMC 10 Mg ha⁻¹ + PM and VC each 1.5 Mg ha⁻¹ + BF, T₄) and T₁ produced similar but significantly higher bell pepper yield (27.9 and 26.1 Mg ha⁻¹, respectively) compared with other organic amendment treatments. Both T₄ and T₁ greatly lowered soil bulk density (1.15–1.17 Mg m⁻³), and enhanced soil pH (7.1) and oxidizable organic carbon (1.2–1.3%) compared with T₅ and unamended control (T₆) after a two-year transition period. However, the N, P and K levels were highest in the plots under integrated management. T₁ plots showed higher dehydrogenase activity values. However, acid phosphatase and β-glucosidase activities were higher in T₆ plots whereas urease activity was greater in T₅ plots compared with other treatments. Among the treatments involving organic amendments alone, T₁ gave a higher gross margin (US $ 8237.5 ha⁻¹) than other treatments. We conclude that T₁ was found more suitable for enhancing bell pepper growth and yield, through improved soil properties, during conversion to organic production.     

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 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.     

Sewage sludge and refuse composts as peat alternatives for conditioning impoverished soils: Effects on the growth response and mineral status of Petunia grandiflora

A glasshouse pot experiment is described comparing the growth reponse, nutritional , status and heavy metal content of Petunia grandiflora in an impoverished acid sandy soil amended with peat or composted sewage sludges and refuse. The composts consistently out-performed peat as soil améliorants because of greater nutrient availability. However, results indicated that rates of application of composts to soil should be adjusted according to the conductivity of the applied material and the salt tolerance characteristics of the plant species to be grown to avoid detrimental effects on plant growth. There were no phytotoxic effects on plant growth due to contamination of the composts with heavy metals irrespective of the level of incorporation into soil, indicating that proposed lower metal limits for composts compared with sewage sludge would be unnecessarily restrictive to compost use. Composted sewage sludges and refuse are shown to have considerable potential for use in the amenity and landscape industry for improving impoverished soils.     

Optimization of saline water level for sustainable Barnea olive and oil production in desert conditions

The main aim of the present study is to evaluate the effects of long-term irrigation with water at three different levels of salinity on Barnea olive trees with a view to optimize vegetative growth, productivity and oil quality. The study was carried out on trees growing in the Negev desert of Israel. The intermediate salinity (4.2 dS m⁻¹ EC) inhibited growth significantly only in the first year after planting, while from the second year onward retardation of vegetative growth as compared with the control treatment (1.2 dS m⁻¹ EC) was slight and non-significant. However, the high salinity (7.5 dS m⁻¹ EC) retarded tree growth significantly. Furthermore, the intermediate treatment led to significant increase in tree productivity relative to the other treatments, and also to an increase in olive oil yield. In conformity with the greater number of fruits produced, the olives of the 4.2 dS m⁻¹ EC treatment tended to be smaller.No significant differences were found between saline- and control-water irrigated trees in terms of olive oil basic quality parameters, such as free fatty acids, peroxide value, and fatty acid profile. The saline treatments increased the levels of certain antioxidant components (polyphenols and Vitamin E) in the oil extracted from the olives as compared with the control. The data obtained clearly show that, of the three water salinities tried, the moderate level of 4.2 dS m⁻¹ EC is best suited for production of olives and olive oil under the conditions prevailing in the central Negev, at least during the first 9 years from planting. The sustainability of Barnea cultivation under moderately saline water is discussed.     

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.     

Effects of nutrient solution electrical conductivity and sulfur, magnesium, and phosphorus concentration on sesquiterpene lactones in hydroponically grown lettuce (Lactuca sativa L.)

The effect of nutrient solution electrical conductivity (EC) and sulfur (S), magnesium (Mg), and phosphorus (P) levels on the content of the primary sesquiterpene lactones (SLs), lactucin, 8-deoxylactucin, and lactucopicrin, in hydroponically grown lettuce was assessed. Lettuce grown at 4 EC levels (0.5, 1.0, 2.0, and 3.0 dS m⁻¹) displayed significant differences in leaf area index, number of leaves, plant height, fresh weight per plant, and chlorophyll content that were highest at EC 2.0 dS m⁻¹. Lactucin (5.5 μg g⁻¹ dry weight), 8-deoxylactucin (7.5), lactucopicrin (35.8), and total SLs (48.7) concentraions were highest at EC 0.5 dS m⁻¹. Four S (8, 16, 48, and 80 mg L⁻¹) and Mg (6, 12, 36, and 60 mg L⁻¹) levels and 3 P (8, 16, and 48 mg L⁻¹) levels were assessed for their effect on individual and total SLs. S and P had the greatest effect on SL levels. Plants in the lowest S level had significantly higher lactucin, lactucopicrin and total SLs. Each of the SLs was higher in the highest P level while Mg influenced only the lactucopicrin level in a quadratic manner. The results indicate that solution culture conditions can strongly influence the SL concentration and therefore bitterness and acceptability of lettuce.     

Use of a cyclic high-pressure sodium lamp to inhibit flowering of chrysanthemum and velvet sage

Photoperiod is commonly controlled in the commercial production of ornamental crops to induce or prevent flowering. Flower induction in short-day (SD) plants can be prevented or delayed when the natural daylength is short by providing low-intensity lighting during the dark period. A stationary high-pressure sodium (HPS) lamp with an oscillating aluminum parabolic reflector (cyclic HPS) has been developed to provide intermittent lighting to greenhouse crops. We determined the efficacy of a cyclic HPS lamp at preventing flowering in SD plants garden chrysanthemum [Chrysanthemum × grandiflorum (Ramat.) Kitam.] ‘Bianca’, pot chrysanthemum ‘Auburn’, and velvet sage (Salvia leucantha L.) relative to traditional night interruption (NI) lighting strategies. Plants were grown in a glass-glazed greenhouse at a mean daily temperature of 19.5–20.7 °C with natural SD photoperiods. NI lighting was delivered during the middle of the night (2230–0230 h) from a 600 W cyclic HPS lamp mounted at one gable end of the greenhouse or from incandescent (INC) lamps that were illuminated for the entire 4 h (CONT INC) or for 6 min every 30 min for 4 h. Plants under cyclic HPS were grown at lateral distances of 1, 4, 7, 10, or 13 m from under the lamp. Control plants were grown under an uninterrupted 15 h skotoperiod. As the distance from the cyclic HPS lamp increased from 1 to 13 m, the maximum irradiance measured during the NI decreased from 25.4 to 0.3 μmol m⁻² s⁻¹ and time to visible inflorescence (VI) and the number of nodes at VI decreased. All species had a VI within 54 d, but ≤10% of plants flowered when grown at a lateral distance of 1 or 4 m from the cyclic HPS lamp or under CONT INC. Plants grown without NI had a VI 2 to 15 d earlier and flowered 7 to 24 d earlier than plants grown at 10 or 13 m from the cyclic HPS. All garden chrysanthemums flowered under cyclic INC, whereas velvet sage and pot chrysanthemum had 15% and 35% flowering, respectively. These results indicate that a cyclic HPS lamp can be used effectively to delay flower induction and prevent flowering in these species when NI is delivered at ≥2.4 μmol m⁻² s⁻¹.     

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.     

Effects of artificial amendments in potting media on Orthosiphon aristatus growth and development

Artificial polyacrylamide gel (PAG) and urea-formaldehyde resin foam (UFRF) amendments are used for putative enhancement of soil physical properties, including increasing their water holding capacity (WHC). Effects were investigated of these two amendments alone and combined on growth and development of Orthosiphon aristatus (Cats’ Whiskers) grown in either composted pine bark or washed river sand, including under transient water deficit stress. UFRF and PAG were incorporated into these potting media substrates at recommended rates of 30% (v/v) and 0.1% (w/w), respectively. UFRF incorporation reduced bulk density and increased air-filled porosity of composted pine bark from 0.24 g cm⁻³ and 43.3% to 0.18 g cm⁻³ and 50.2%, respectively. UFRF also reduced bulk density of sand from 1.43 g cm⁻³ to 1.17 g cm⁻³ and increased its air-filled porosity from 18.5% to 25.3%. PAG slightly decreased bulk density of composted pine bark to 0.23 g cm⁻³ and also reduced sand bulk density to 1.32 g cm⁻³. Water content of composted pine bark and sand was increased by PAG addition from 47.6% and 27.7% to 51.0% and 34.2%, respectively. However, UFRF and/or PAG did not increase plant available water (PAW) in either composted pine bark or sand. PAW was 23.8% and 14.4%, 23.6% and 15.8%, 22.8% and 14.8%, and 25.2% and 17.8% for composted pine bark and sand controls, these two substrates amended with UFRF, these substrates amended with PAG, and these substrates with UFRF plus PAG, respectively. Neither shoot length nor number was increased by adding UFRF and/or PAG. Similarly, neither shoot fresh nor dry weight was increased by UFRF and/or PAG amendments. UFRF and, moreso, UFRF plus PAG slightly delayed the onset of wilting by 4–15 h in water deficit stressed O. aristatus compared to control and PAG alone in composted pine bark (experiment 1), but PAG did not. However, in experiment 2, UFRF and/or PAG did not delay wilting in either composted pine bark or sand. Thus, when incorporated at suppliers recommended rates, neither UFRF nor PAG conferred appreciable benefits for O. aristatus plant growth in either composted pine bark or sand potting media.     

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.     

Reducing oxidative browning during in vitro establishment of Protea cynaroides

Oxidative browning is one of the reasons why Protea cynaroides is not being extensively propagated via tissue culture techniques. The reduction of oxidative browning was best achieved by stirring the explants for 1 h in an antioxidant solution mixture containing 100 mg l⁻¹ ascorbic acid and 1500 mg l⁻¹ citric acid before inserting them into the medium. In combination with this antioxidant solution, in vitro establishment was highly successful where 100% bud growth was achieved by explants growing under 16 h photoperiod.     

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.     

Growth, photosynthesis and antioxidant metabolism in mustard (Brassica juncea L.) cultivars differing in ATP-sulfurylase activity under salinity stress

Salinity is one of the major environmental factors limiting crop productivity. The effect of increasing salinity levels (0, 50, 100 mM NaCl) on growth, photosynthetic traits, leaf water potential, oxidative stress, enzymatic and non-enzymatic antioxidants was studied in Pusa Jai Kisan and SS2 cultivars of mustard (Brassica juncea L. Czern & Coss.) differing in ATP-sulfurylase activity at 30 days after sowing (DAS). The cultivar SS2 (low ATP-sulfurylase activity) accumulated higher content of Na⁺ and Cl⁻ in leaf than root. SS2 also showed greater content of thiobarbituric acid reactive substances (TBARS) and H₂O₂ and higher decrease in growth, photosynthetic traits and leaf water potential than Pusa Jai Kisan with increasing salinity levels. Contrarily, Pusa Jai Kisan (high ATP-sulfurylase activity) exhibited higher Na⁺ and Cl⁻ content in root than leaf, lower TBARS and H₂O₂ content and higher activity of catalase, ascorbate peroxidase and glutathione reductase. However, the activity of superoxide dismutase was greater in SS2 than Pusa Jai Kisan. Higher activity of ATP-sulfurylase in Pusa Jai Kisan resulted in increased content of glutathione, a reduced form of inorganic sulfur and an essential component of cellular antioxidant defense system. The lesser decrease in growth and photosynthesis in Pusa Jai Kisan was the result of lesser Na⁺ and Cl⁻ in leaf, higher turgidity and increased activity of antioxidant enzymes and glutathione content.     

The use of CPPU for efficient propagation of pineapple

The use of forchlorfenuron (N-(2-chloro-4-pyridyl)-N′-phenylurea) (CPPU) for efficient propagation of pineapples was investigated. About 85% of axillary buds can be forced to sprout by soaking defoliated stem pieces (12 cm in length) in a 2.5 or 5.0 mg l⁻¹ CPPU solution for more than 3 h. The use of old stems taken from the third or fourth ratoon plants had the advantage of less liability to fungal decay, as compared to young stems from the first crop plants. The CPPU treatment combined with the removal of shoots from stems at monthly intervals significantly increased the number of shoots per stem piece (about 15 shoots per piece at 5.0 mg l⁻¹ CPPU), and resulted in a more uniform shoot size (the percentage of shoots within a range of 5–15 cm in length was about 90% at 5.0 mg l⁻¹ CPPU). The rooting of shoots was easily promoted within 1 month by treating the basal portion of shoots with 20 mg l⁻¹ indole-3-butyric acid (IBA) for 15 min. The CPPU method required about 5 months for plantlet propagation. From these results, we found that pineapple plantlets could be efficiently propagated by the following method: (1) soaking defoliated stems in a 2.5–5.0 mg l⁻¹ CPPU solution for more than 3 h; (2) harvest of developed shoots from the stems at regular intervals; and (3) promotion of rooting on the shoots at 20 mg l⁻¹ IBA for 15 min.     

Effects of NH4:NO3:urea ratio on cut roses yield, leaf nutrients content and proton efflux by roots in closed hydroponic system

The effects of the NH₄:NO₃ ratio in replenishment solution on Rosa L. flower yield and the impact of NH₄ substitution by urea on plant performance and on solution EC and pH have not been studied previously in closed (no leaching) hydroponic systems. A greenhouse experiment with six NH₄:NO₃:urea ratios (0:100:0, 12:88:0, 25:75:0, 50:50:0, 100:0:0 and 0:50:50) and two harvest cycles (winter and spring) was carried out to investigate these relationships. In winter, total and >40 cm cut flower yields were maximal in treatment 25:75:0. At lower NH₄ percentages (12.5:87.5:0 and 0:100:0), growth container solution pH varied between 7.8 and 8.5, reducing P, Ca and Mn concentration in leaves and increasing dry matter allocated to them. At higher NH₄ percentages, Ca uptake was inhibited, solution pH reached 3, and %P in leaves increased. Consequently, reducing sugars concentration in leaves increased and sucrose and starch concentrations decreased. A stepwise regression analysis indicated that the optimal NH₄:NO₃ ratio in feed solution is 40:60, with resulting solution pH of 5.9 in the growth container. In spring the maximum yield was obtained in treatment 0:50:50 and it exceeded the winter yield despite a higher solution EC (4.3 dS m⁻¹ vs. 3.5 dS m⁻¹ at harvest). The beneficial effect of urea (0:50:50 vs. 50:50:0) stemmed from the relatively lower NH₄ concentration in solution, that alleviated the NH₄–Ca uptake competition, and higher pH. The slope of the straight line relating [H⁺ efflux rate] to [NH₄⁺ uptake rate] in treatments 25:75:0, 50:50:0 and 100:0:0 was 0.44 mol H⁺/mol NH₄. In all other treatments the proton efflux was negligible.     

Effects of flurprimidol and daminozide on growth and flowering of oriental lily ‘Mona Lisa’

Two separate experiments were conducted to evaluate the effectiveness of growth retardants in controlling height of oriental lily ‘Mona Lisa’. In first experiment flurprimidol was applied as a single foliar spray (0, 10, 20, 30 and 40 mg l⁻¹) or a soil drench (0, 0.1125, 0.225, 0.3375 and 0.45 mg/pot) at two plant growth stages (7 and 15 cm). In second experiment flurprimidol (0, 10, 20, 30 and 40 mg l⁻¹) and daminozide (0, 2500, 3500 and 4500 mg l⁻¹) were applied once or twice as a foliar spray. Daminozide applied once or twice at concentrations of 2500–4500 mg l⁻¹ was ineffective in ‘Mona Lisa’ growth retardation. Flurprimidol was effective growth retardant in reducing stem extension without adverse side-effects. The maximum reduction in plant height obtained was 45% compared to controls. Flowering time was not affected by lower rates of flurprimidol, but it was slightly delayed when retardant was applied at higher doses. The tepal size, leaf size and pedicel length were smaller than those of the control plants. Intensified leaf colour was observed on flurprimidol treated ‘Mona Lisa’. The effect of flurprimidol persisted in the year after treatment.     

Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada

Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local -scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clay-rich luvisols than on brunisols, and areas burned 1–15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition.