Volume 27 (2015): Issue 2 (December 2015)

Parks in urbanised areas fulfil an important function as they create a positive climate in cities and contribute to the good health of their inhabitants. The study gives an answer to the question of which of the species under investigation is the most suitable for planting in urbanised areas. The aim of the research conducted from 2013 to 2014 at selected sites in Poznan (Poland) was to determine the state of health of Tilia cordata Mill., Acer platanoides L. and Quercus robur L. trees and to compare their state of health depending on the location of the research sites. The aim of the research was also to determine the environmental variables that may have an influence on the state of health of the tree species under analysis. The research included statistical analyses and models based on discriminant analysis. The research revealed that the state of health of the tree species under investigation growing in the city is determined by anthropogenic factors. The closeness of the city centre, main thoroughfares and estates heated with fossil fuels are the factors that have the most negative influence on the state of health of oak, maple and lime trees. Acer platanoides L. was the species in the best state of health in parks, whereas in forests it was Tilia cordata Mill.

Two hyperspectral remote sensing techniques, spectral reflectance and chlorophyll fluorescence, were used for the identification of biotic stress (sharka disease) in plum trees at an early stage without visible symptoms on the leaves. The research was focused on cultivars that are widely spread in Bulgaria: ‘Angelina’, ‘Black Diamond’ and ‘Mirabelle’. Hyperspectral reflectance and fluorescence data were collected by means of a portable multichannel fibre-optics spectrometer in the visible and near infrared spectral ranges (400-1000 nm). Statistical and deterministic analyses were applied for assessing the significance of the differences between the spectral data of healthy (control) and infected plum leaves. Comparative analyses were performed with complementary serological test DAS-ELISA, broadly implemented in plant virology. The strong relationship that was found between the results from the two remote sensing techniques and serological analysis indicates the applicability of hyperspectral reflectance and fluorescence techniques for conducting health condition assessments of vegetation easily and without damage before the appearance of visible symptoms.

Studies conducted during 2009-2013 at the Experimental Orchard located in the central region of Poland showed that the highest number of V. inaequalis pseudothecia occurred on ‘McIntosh’ and ‘Cortland’ leaves. A smaller number of pseudothecia was found on the leaves of the Alwa and Jonagold cultivars, but there were no statistical differences. The first discharges of ascospores were noted at a similar time on the leaves of all of the apple cultivars, usually at the end of March or in early April. For the forecasting of ascospore discharges and dates of critical periods, a simulation model by RIMpro was used. The number of critical periods and apple scab severity differed in each season. The most critical periods (above 20) were recorded in 2010 and 2013, which also corresponded with a high severity of apple scab. The number of infected leaves and fruits on the untreated trees of the very susceptible cultivar McIntosh reached nearly 100% during these seasons. In other years, the severity of the disease on the same apple trees was lower and amounted to 30-54% of infected leaves and 23-80% of infected fruits.

Flower development and senescence was studied in Narcissus tazetta ‘Kashmir Local’. Flower development was divided into six stages (I-VI), from the tight bud stage to the senescent stage. Flower fresh and dry weight increased as the flowers progressed from bud to bloom and then declined during senescence. Membrane permeability of tepal tissues increased as the flower progressed through various stages. The content of sugars (reducing and total) increased during flower development and declined thereafter during senescence. The α-amino acid content registered an increase during flower development with a concomitant decrease in soluble protein content. The SDS-PAGE of protein extracts from tepal tissues revealed a general decrease in the expression of some high molecular weight proteins and an increase in low molecular weight proteins during flower development and senescence. It may be suggested that the flower senescence of N. tazetta may be linked to the protein turnover and sugar status of the perianth tissues and that these newly synthesized proteins may be involved in proteolysis. At this stage, it is not known whether these polypeptides play an important role in senescence but revealing the nature of these proteins can provide new insights into the pathways executing senescence in this flower system.

An investigation was conducted to study the effects of explant sources, plant growth regulators, carbohydrates and light conditions on indirect cormlet regeneration and the induction of embryogenic callus of freesia (Freesia × hybrida Bailey ‘Argenta’). Sections of two different types of explants, corms and pupae (cold storage-produced corms), were placed on Murashige and Skoog (MS) media containing different concentrations of plant growth regulators. The results showed that the highest percentage of callus induction (100%), the highest callus growth (15 mm diameter) and the best type of calli were achieved for pupa explants grown on the medium that contained 4 mg L⁻¹ 1-naphthaleneacetic acid (NAA) and 2 mg L⁻¹ 6-benzylaminopurine (BAP) in the dark. Increasing BAP up to 3 to 4.5 mg L⁻¹ resulted in the maximum number of regenerated cormlets from 1 cm² calli (2 cormlets) under light conditions. Overall, the best rooting of regenerated cormlets was achieved on MS media supplemented with 1 mg L⁻¹ indole-3-butyric acid (IBA). In the next stage, high quality calli were subcultured on MS media containing sorbitol, sucrose, maltose and mannitol (0, 5, 10 and 15 g L⁻¹). The results indicated that 15 g L⁻¹ maltose was able to induce the highest percentage of embryogenic callus, with an average of 88.9% on media containing 2 mg L⁻¹ BAP and 1 mg L⁻¹ NAA.

White rot fungi (WRF) are known to have the ability to degrade organic pollutants with a structure similar to lignin. Because of this, the degradation of polychlorinated biphenyls (PCBs) congeners no. 28, 52, 101, 138, 153 and 180 by substrate before fruiting (substrate) and/or after fruiting (SMS) from cultivated mushrooms Pleurotus ostreatus, Lentinula edodes and Agaricus bisporus was examined. The experiment was carried out in four replications for each treatment using a mixture of substrate/SMS and sandy soil with PCBs at a concentration of each congener at 50 and 100 μg kg⁻¹ soil DW. The results indicate that degradation was dependent on substrate/SMS addition, the concentration of PCBs and time of incubation. The efficiency of PCB degradation was generally reduced with the number of chlorine atoms in the structure of congeners: 28, 52, 101, 138, 153 or 180. In all combinations, degradation increased with incubation time. Degradation by SMS was lower in comparison to degradation by a substrate of the same mushroom. The degree of degradation of a single PCB after 12 weeks of incubation for A. bisporus ranged from 31.32 ± 1.52 to 83.91 ± 1.07%, while for P. ostreatus it was between 37.88 ± 2.54 and 78.29 ± 1.41%; for L. edodes it ranged from 17.38 ± 1.06 to 75.30 ± 1.46%. The best average degradation was confirmed for 20% SMS of A. bisporus at 50 μg kg⁻¹ PCB.

A growing demand for blueberry fruit has necessitated the development of an efficient propagation method of this species that would provide large quantities of planting material. The aim of this study was to evaluate the effects of auxin indole-3-butyric acid (IBA 50 mg dm⁻³), the commercial rooting powder Rhizopon containing 1% IBA, and salicylic acid (50 mg dm⁻³) on the in vivo rooting of microcuttings of Vaccinium corymbosum ‘Bluecrop’ and ‘Duke’. The contents of chlorophyll a + b, soluble proteins, free amino acids, as well as total soluble and reducing sugars were determined in rooted cuttings. All of the treatments increased the degree and percentage of rooting in the cuttings of both cultivars. While improving rhizogenesis in blueberry, salicylic acid did not perform as a cofactor of the auxin IBA. Foliar applications of IBA or salicylic acid (SA) increased the contents of soluble proteins, free amino acids and sugars, but no effects on chlorophyll levels were observed.

Borage is a valuable medicinal plant with various constituents in leaves, flowers and seeds. Hence, it is important to improve the performance of this medicinal plant under different environmental conditions. Thus, two field experiments were arranged as split-plots based on a RCB design with three replications in 2012 and 2013, to evaluate the effects of seed priming and different irrigation intervals on selected physiological properties of borage leaves. Irrigation intervals (irrigation after 60, 90, 120, 150 mm evaporation from Class A pans, respectively) and priming treatments (control, water, KNO₃ and KH₂PO₄) were allocated to the main and sub plots, respectively. The chlorophyll content index was enhanced under limited irrigation treatments, mainly due to a decrease in leaf area index and intercepting more radiation. However, the membrane stability index was stable under different irrigation intervals. Decreased relative water content and leaf area index and increased leaf temperature under lower water availability led to some reductions in the grain yield of borage. All of the priming techniques, particularly hydro-priming, enhanced the seedling emergence rate, leaf area index and consequently grain yield per unit area. Therefore, seed hydro-priming can be used to improve the field performance of borage, particularly when sufficient water is available.

Cut lily flowers are very popular but their longevity is not satisfactory. The quality of cut lily flowers is determined by two factors: the longevity of the flowers and the general appearance of the entire cut stem during its vase life. The aim of this work was to evaluate the effects of gibberellic acid (GA₃), standard preservative (8HQC and 2% sucrose) and commercial preservatives Chrysal Professional 2 and Chrysal sachet as well as Floralife 200 and Floralife 300 on the quality of ‘Rialto’ cut oriental lily, a white blooming cultivar very popular on the Polish market. The contents of reducing sugars, soluble proteins, free amino acids and free proline were also determined in the senescing flowers. As a major problem in the postharvest handling of lilies is leaf yellowing, the effects of postharvest treatments on the quality of leaves and their chlorophyll contents were also studied. Conditioning (24 h) with GA₃ (500 mg d.m.⁻³) immediately after harvest delayed chlorophyll loss in leaves. When combined with the standard preservative and commercial preparations Chrysal Professional 2 and Chrysal sachet as well as Floralife 200 and Floralife 300, GA₃ prolonged flower vase life. The most effective method was using GA₃ and Floralife products, which prolonged the vase life of flowers to 23 days, 43% longer relative to the untreated flowers, and maintained the decorative value of the leaves (53 days). During the senescence of flowers held in water, the contents of reducing sugars, free amino acids and proline increased. However, the holding solutions modified changes in these parameters relative to the control.

Rhodohypoxis baurii is an ornamental plant recommended for pot and garden cultivation. The aim of this study was to determine the relationships between rhizome weight and the growth, flowering and rhizome yield in two cultivars (‘Dusky’ and ‘Ruth’) of R. baurii grown as pot plants. The rhizomes were sorted into three groups by weight: 0.10-0.20 g, 0.21-0.30 g and 0.31-0.40 g. The study revealed that the plants developed from the largest rhizomes were the highest, the widest, produced the most leaves, inflorescences per rhizome, flowers per inflorescence and were the first to flower. The plants developed from rhizomes of 0.21-0.30 g and 0.31-0.40 g did not differ in their flowering rate, flower diameter or the weight of rhizomes at the end of the growing season. Flowers developed in all of the plants grown from rhizomes weighing at least 0.2 g. A comparison of cultivars showed that 'Dusky' plants were higher, wider, had more leaves, inflorescences and flowers per inflorescence, flowered earlier and produced rhizomes of greater weight than 'Ruth' plants, which had a higher greenness index and larger flowers. Both cultivars did not differ in their flowering rate. Rhizome weight gain after the cultivation period depended rather on the cultivar than on the size of the planted rhizomes.

The leaves of Zantedeschia and Hosta are used as florist greens in different floral arrangements. The most efficient postharvest treatment for cut foliage is the use of growth regulators, which prolong their vase life by delaying degradative changes occurring in leaves, especially proteolysis. Cycloheximide (CHI) is one of the protein synthesis inhibitors, blocking the enzymes responsible for decreasing membrane integrity, a phenomenon hastening senescence. The aim of this experiment was to evaluate the effects of CHI and benzyladenine (BA) or gibberellic acid (GA₃) on the longevity of cut foliage in hosta (Hosta sp.) cultivars and Ethiopian calla (Zantedeschia aethiopica) and to follow the changes in certain proteolytic processes occurring during senescence. Generally, 24 h conditioning with cycloheximide shortened the longevity of cut calla leaves while having no effect on hosta vase life. In ageing leaves of ‘Minima Glauca’ hosta and calla, the total proteolytic activity increased, including that of cysteine protease. Due to the application of BA or GA₃ in hosta and calla, respectively, this activity was limited. On the contrary, the use of CHI either did not affect the activity of cysteine protease or increased it several-fold relative to the control, in hosta and calla, respectively. Leaves treated with growth regulators had many more soluble proteins and fewer free amino acids, including free proline, than leaves from other treatments. The highest free proline level was determined in calla leaves conditioned with CHI, where it increased 18-fold relative to the initial level.

Thin cell layers (TCLs) are small and versatile explants for the in vitro culture of plants. At face value, their morphogenic productivity may appear to be less than conventional explants, but once the plant growth correction factor and geometric factor have been applied, the true (potential) productivity exceeds that of a conventional explant. It is for this reason that for almost 45 years, TCLs have been applied to the in vitro culture of almost 90 species or hybrids, mainly ornamentals and orchids, but also to field and vegetable crops and medicinal plants. Focusing on 12 new studies that have emerged in the recent past (2013-2015), this paper brings promise to other horticultural species that could benefit from the use of TCLs.