Nada Parađiković

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees. II. Functional and molecular adjustment of PSII

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees. II. Functional and molecular adjustment of PSII In the present study we aimed to investigate physiological and molecular mechanisms of photosynthetic performance decline in prematurely aged bleached leaves of silver maple (Acer saccharinum L.) trees. We used in vivo chlorophyll a fluorescence measurement to analyze changes in PSII photochemistry, relative abundance of photosynthetic proteins (D1, LHCII, Cytf and Rubisco LSU), relations between chlorophylls and their precursor protochlorophyllide as well as elemental composition of the leaves. Decreases in Al, Cr, Cu, Fe, K, Zn and an increase in S concentrations were found in bleached leaves in comparison to healthy green ones. The bleached leaves were visually expressing symptoms characteristic of Fe deficiency. Further, they had considerably decreased chlorophyll contents and protochlorophyllide contents, overall photosynthetic activity and relative abundance of major photosynthetic proteins. All the results indicate that modifications in the molecular organization of photosynthetic electron-transport chain components in bleached leaves led to functional adaptation of the PSII achieved by modifications of some reaction centres (RCs), turning them from active to dissipative. This provided efficient adaptation of bleached leaves to high-light induced oxidative damage during summer.

Cytokinin response in pepper plants (Capsicum annuum L.) exposed to silver nanoparticles

ABSTRACT The increasing development of different nanomaterials, such as silver nanoparticles (AgNPs), and their practical use in agriculture and biotechnology has created a strong need for elucidations of biological effects and risk assessments of AgNPs in plants. This study was aimed to investigate AgNPs effects on metal uptake and their biodistribution in pepper plants as well as on morphological parameters and hormonal responses of the isoprenoid cytokinin (CK) family. In addition, the comparison of effects silver form, nanoparticles vs. ionic, has also been examined. To the best of our knowledge, this is the first study describing CK responses in plants exposed to metallic NPs. The obtained results indicate that both AgNPs and Ag+ ions significantly increased total content of Ag+ in pepper tissues in a dose‐dependent manner and affected on plant development by decreasing both plant height and biomass in a similar way. This study evidenced for the first time the role of CKs in abiotic stress in plants caused by AgNPs. The hormonal analysis, conducted by an ultra‐high performance liquid chromatography‐electrospray tandem mass spectrometry, revealed a significant increase in total CKs in the leaves and also highlighted the importance of cis‐zeatin type CKs in plants treated with AgNPs. Our observations suggest potential risks of AgNPs on plant ecosystems upon their release into the environment. Graphical abstract Figure. No Caption available. HighlightsCitrate‐coated silver nanoparticles significantly affected development of pepper.Nano and ionic form of Ag showed similar phytotoxicity effects in pepper plants.Both Ag forms increased total Ag in pepper tissues in a dose‐dependent manner.This is first study establishing the role of cytokinins in abiotic stress in plants.Results indicate possible importance of cZ cytokinins in nanostressed plants.

Influence of biostimulant and substrate volume on root growth and development of scarlet sage (Salvia splendens L.) transplants.

The influence of biostimulant and substrate volume on scarlet sage transplants growth and development was examined in this investigation. There was one cultivar of scarlet sage used in trial which was transplanted in pots of two different volumes. Plants were treated with biostimulant (Radifarm) in concentration of 0.25% or left untreated (control). During the trial, root and aboveground fresh and dry mass were recorded. Treatment with biostimulant and bigger substrate volume showed good results by increasing investigated parameters. Investigation shows how biostimulant application to scarlet sage transplants production improves growth and development of root and aboveground mass which is important for faster plant adaptation to stress during transplanting.

Maize and soybean seed vigour under influence of seed age, seed treatment and temperature in cold stress test

Maize and soybean seed (maize hybrid OS 499 and soybean cultivar Ika originated from Agricultural Institute in Osijek, Croatia) harvested in year 2006 as well as one year old seed (harvested in 2005 and aged in storehouse conditions) were used for the evaluation of seed vigour in germination chamber. Seeds were pretreated with fungicide. Fungicide treatment significantly increased germination rate of maize seed in cold test conditions and constant low temperature. Fungicide treatment of soybean seed significantly enhanced germination only at constant low temperature and aged seed. Biostimulant applicaton did not enhanced germination rate but increased dry matter content in normally developed hypocotyls, both in fresh and aged soybean seed. Proline treatment did not show expected stimulative effect on seed germination.

THE EFFECTS OF LIGHT REGIME AND SUBSTRATE ON FLOWER PRODUCTIVITY AND LEAF MINERAL COMPOSITION IN TWO GERBERA CULTIVARS

This research evaluates the influence of light regime and substrate composition on the flower productivity and leaf macronutrient content of two gerbera cultivars (‘Ruby Red’ and ‘Vino’) grown in a greenhouse. A special emphasis was given to macro-element ratios in gerbera leaf. The results confirm positive influence of supplemental lighting on flower yield in both gerbera cultivars. Also, mixed substrate (coco fiber + rice husks) resulted with higher flower yield. Cultivar ‘Vino’ showed better productivity and significantly lower concentration of nitrogen (N), potassium (K), and magnesium (Mg) as compared to ‘Ruby Red’. The total flower productivity per plant correlated with some of the tested macronutrients in gerbera leaf (N, K, Mg) only in natural light conditions. Among all calculated leaf nutrient ratios, only P/Mg was significantly and positively correlated to flower yield, based on data from both light variants.

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees: I. Hydrogen peroxide level, antioxidative responses and photosynthetic pigments

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees: I. Hydrogen peroxide level, antioxidative responses and photosynthetic pigments Essential signaling processes such as changes in calcium mobilization, protein phosphorylation and gene expression are known to be modulated by hydrogen peroxide (H2O2). A lot of silver maple trees in the city of Osijek (Croatia) were noticed to have bleached leaves by early summer as well as during the whole vegetation season. In this study we aimed to investigate the processes that regulate H2O2 levels in healthy (green) and prematurely aged (bleached) leaves. For that purpose, photosynthetic performance and antioxidative response of green and bleached silver maple leaves were studied. Bleached leaves had higher hydrogen peroxide level, a three-fold level of total soluble proteins as well as a lower level of ascorbic acid. Concentrations of chlorophyll a, chlorophyll b, total chlorophylls and total carotenoids as well as maximum quantum yield of photosystem II were lower in bleached leaves. This indicated their impaired photosynthetic performance. Further more, bleached leaves were characterized by lower specific activities of the main antioxidative enzymes, which influenced their reactive oxygen species scavenging capability. The higher level of H2O2 content in bleached leaves as the consequence of reduced antioxidative enzyme specific activities as well as ascorbic acid level could be the reason for the down-regulation of photosynthetic performance and premature aging of those leaves.

Assessment of the influence of different sample processing and cold storage duration on plant free proline content analyses

INTRODUCTION A method which is widely accepted for the analysis of free proline content in plant tissues is based on the use of 3% sulfosalicylic acid as an extractant, followed by spectrophotometric quantification of a proline-ninhydrin complex in toluene. However, sample preparation and storage may influence the proline actually measured. This may give misleading or difficult to compare data. OBJECTIVE AND METHODOLOGY To evaluate free proline levels fresh and frozen strawberry (Fragaria × ananassa Duch.) leaves and soybean [Glycine max (L.) Merr.] hypocotyl tissues were used. These were ground with or without liquid nitrogen and proline extracted with sulfosalicylic acid. A particular focus was the influence of plant sample cold storage duration (1, 4 and 12 weeks at -20°C) on tissue proline levels measured. RESULTS The free proline content analyses, carried out in leaves of Fragaria × ananassa Duch. as well as in hypocotyls of Glycine max (L.) Merr., showed a significant influence of the sample preparation method and cold storage period. Long-term storage of up to 12 weeks at -20°C led to a significant increase in the measured proline in all samples analysed. CONCLUSION The observed changes in proline content in plant tissue samples stored at -20°C indicate the likelihood of the over-estimation of the proline content if the proline analyses are delayed. Plant sample processing and cold storage duration seem to have an important influence on results of proline analyses. Therefore it is recommended that samples should be ground fresh and analysed immediately.

Influence of different nitrogen form application on the incidence of ber and elementary composition of bell peppers

Calcium is a very important nutrient in highly productive growing such as glasshouse-grown sweet pepper, but inadequate Ca supply manifests with clear symptoms, such as, for example, local decay of pepper fruits (blossom-end rot = BER. The aim of this study was to compare the effect of different N forms on incidence of BER, yield and fruit quality of pepper fruits of the Cecil F1 cultivar in the region of East Croatia.

Alternative Substrate Use in Geranium Transplants Production (Pelargonium peltatum L. and Pelargonium zonale L.)

Container production of horticultural plants on alternative substrates is becoming popular. Agricultural producers choose this way of production due to the high cost of commercial substrates as well as their lack of accessibility on the market. When selecting an alternative substrate, care should be taken to have all the characteristics necessary for the unimpeded growth and development of plants (pH value, nutrients). Our work is based on two years research of the possibilities and effectiveness of alternative substrates utilization spent mushroom substrate (button mushroom Agaricus bisporus) and impact on growth and development of roots and aboveground parts of seasonal flowers transplants. As an initial planting materials rooted cuttings Pelargonium peltatum L. and Pelargonium zonale L were used. Measurements of morphological parameters of growth and development of plants (plant height, number of leaves, buds, flowers and flower branches) were performed, as well as determination of fresh and dry weight of roots and above-ground parts of transplants. Application of spent mushroom substrate (as alternative substrate) in the production of geraniums Pelargonium peltatum L. und Pelargonium zonale L. positively influenced growth and development of morphological parameters and the fresh and dry weight of roots and above-ground parts of treated plants compared to non-tretated plants during two growing seasons.

Seed Germination of Some Flower Species Under Influence of Different Light Conditions

The aim of this study was to examine germination energy and seed germination rate of some flower species under influence of different light conditions. Seeds of Zinnia elegans Jacq., Dianthus caryophyllus L. and Callistephus chinensis (L.) Nees that were used in the research were purchased in local store. Experiment was set up in three replicates for each light treatment and each flower species. Petri dishes with seeds were placed in growth chamber under artificial white and blue light under 12hL/12hD photoperiod. Results showed no significant difference in germination energy and total germination of investigated flower species in respect of light. Zinnia seedlings were significantly longer on white light, while Dianthus seedlings were longer on blue light. Both, length and fresh weight of Callistephus seedlings were greater on white light. The absence of significant differences between measured parameters under examined light regimes suggests that germination of Zinnia, Dianthus and Callistephus is not photosensitive.