J. B. Drossopoulos

Bio: J. B. Drossopoulos is an academic researcher from Agricultural University of Athens. The author has contributed to research in topics: Dry weight & Explant culture. The author has an hindex of 12, co-authored 18 publications receiving 436 citations.

Designing synthetic polymers as soil conditioners

Abstract: This work focuses on synthetic polymeric materials that are designed to function as soil conditioners. A classification of the various polymeric soil conditioners is given and a historical review is attempted. One hundred and three examples are examined, covering the period from 1950 up to today. The routes followed for the preparation of a synthetic polymeric soil conditioner are discussed. In this way, materials and/or properties are tailored for certain applications. Water‐soluble, water‐insoluble (crosslinked or hydrophobic), ionic, or non‐ionic conditioners are examined and pictures of their shapes are given. Finally, a discussion on the combination(s) of materials and/or properties outlines the future trends of this topic. Interpenetrating networks, blends of soil conditioning polymers, polymers combined with slow‐releasing compounds as well as transformable materials are included by examining certain works that are concerned with such materials presenting combined properties that are used ...

Effect of vitamins and inorganic micronutrients on callus growth and somatic embryogenesis from leaves of chilli pepper

Abstract: The effect of different vitamins and inorganic micronutrients on callus growth and the induction and proliferation of somatic embryos from young mature, fully expanded leaves of chilli pepper (Capsicum annuum L.) was investigated. Explants were cultured on a solid Murashige and Skoog (MS) medium supplemented with 8% (w/v) sucrose, 12.9 μM 6-benzyladenine, 9 μM 2,4-dichlorophenoxyacetic acid and 0.5 mg l−1 thiamin.HCl in various combinations of eleven different vitamins. Alternatively, explants were cultured onto a solid medium containing MS macro- and micronutrients except for the salts of Mn, Zn, I, Cu and Co which were added at either the standard MS concentration or at a tenfold increased (Cu, Co) or decreased (Mn, Zn, I) concentration. The results indicated that somatic embryogenesis from pepper leaves is favoured by the addition of nicotinic acid to the culture medium and the increase of copper concentration (an average induction of 70.2 globular embryos/mm2 of explant surface, 9.2% higher than control), without reducing embryo maturation and germination.

Growth regulator pretreatment improves somatic embryogenesis from leaves of squash (Cucurbita pepo l.) and melon (Cucumis melo l.)

Abstract: Leaf explants of squash (Cucurbita pepo L.) and melon (Cucumis melo L.) were pretreated initially with 113.1, 226.2 or 452.4 µM 2,4-dichlorophenoxyacetic acid (2,4-D), 46.5, 93 or 186 µM kinetin or a combination of both at the above concentrations, for 6, 24 or 48 h. After pretreatment, explants were transferred to an agar-solidified medium that was not supplemented with growth regulators or to a species-specific standard induction medium. Control explants from each species were incubated directly on the species-specific standard induction medium. Initial pretreatment of squash explants with 186 µM kinetin and of melon explants with 226.2 µM 2,4-D for 48 h significantly promoted the formation of somatic embryos which developed further to the torpedo-shape stage and germinated. Under these conditions at least four plants can be regenerated per square centimeter of explant surface, thus achieving an increase over non-pretreated cultures of 143% and 130% for squash and melon, respectively.

Some characteristics of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue

Abstract: The effectiveness of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue was examined through the evaluation of some of its physical and chemical characteristics. The concentration of 25% w/w of this material into the conditioner‐soil mixtures appears to be the maximum level for the cultivation of tomato plants. The plants grown on this conditioner‐soil mixture were 1.52±8.5% times larger than those grown on a sandy loam soil. The pure conditioner cannot be used as a substrate for the growth of tomato plants. The water‐holding capacity of the conditioner was almost two times higher than that of the pure soil and remained almost stable for temperatures between 8–40°C. The apparent density of the conditioner was 0.5 times smaller than that of the pure soil. With increased application rate of the conditioner to the soil, there was a decrease in the pH, an increase in the specific conductivity, and an increase in the ammonium‐nitrogen (NH4‐N) and...

Die and let live: leaf senescence contributes to plant survival under drought stress

Abstract: Leaf senescence is a highly regulated physiological process that leads to leaf death and is, as such, the last developmental stage of the leaf. Plant aging and environmental stresses may induce the process of senescence. Here we will focus on the role of leaf senescence in field-grown plants as a response to adverse climatic conditions and, more specifically, on how it contributes to plant survival under drought stress. Drought induces several responses in plants including leaf senescence, which plays a major role in the survival of several species. Drought-induced leaf senescence contributes to nutrient remobilisation during stress, thus allowing the rest of the plant (i.e. the youngest leaves, fruits or flowers) to benefit from the nutrients accumulated during the life span of the leaf. In addition, drought-induced leaf senescence, especially when accompanied by leaf abscission, avoids large losses through transpiration, thus contributing to the maintenance of a favourable water balance of the whole plant. Drought-induced leaf senescence occurs gradually and is characterised by specific macroscopic, cellular, biochemical and molecular changes. Leaf yellowing (i.e. chlorophyll degradation) and specific changes in cell ultrastructure (e.g. chromatin condensation, thylakoid swelling, plastoglobuli accumulation), metabolism (e.g.protein degradation, lipid peroxidation) and gene expression occur during leaf senescence in drought-stressed plants. Cytokinins and ABA have been shown to be involved in the regulation of drought-induced leaf senescence, although the possible role of other plant hormones should not be excluded. Reactive oxygen species, whose concentrations increase during drought-induced leaf senescence, are also known to be regulators of this process. The complex mechanisms of regulation of leaf senescence in drought-stressed plants are discussed, and attention is drawn to those aspects that still require investigation.

Polyacrylamide in agriculture and environmental land management

Abstract: Anionic polyacrylamide (PAM) has been sold since 1995 to reduce irrigation‐induced erosion and enhance infiltration. Its soil stabilizing and flocculating properties improve runoff water quality by reducing sediments, N, dissolved reactive phosphorus (DRP) and total P, chemical oxygen demand (COD), pesticides, weed seeds, and microorganisms in runoff. PAM used for erosion control is a large (12–15 Mg mol −1 ) water‐soluble (non‐cross‐linked) anionic molecule, containing by PAM or can be slightly reduced. Typical seasonal application totals in furrow irrigation vary from 3 to 7 kg ha −1 . Research has shown little or no consistent adverse effect on soil microbial populations. Some evidence exists for PAM‐related yield increases where infiltration was crop‐limiting, especially in field portions having irregular slopes, where erosion prevention eliminated deep furrow cutting that deprives shallow roots of adequate water delivery. Modified water management with PAM shows great promise for water conservation. High effectiveness and low cost of PAM for erosion control and infiltration management, coupled with easier implementation than traditional conservation measures, has resulted in rapid adoption. About 800,000 ha of US irrigated land use PAM for erosion and/or infiltration management. In recent years, PAM has been deployed for uses beyond agricultural erosion control, including construction site erosion control, use in storm water runoff ponds to accelerate water clarification, soil stabilization and dust prevention in helicopter‐landing zones, and various other high‐traffic military situations. Among the newest topics being researched is the use of PAM to reduce ditch, canal, and pond seepage, using specific application protocols that take advantage of its increase of water viscosity at higher concentrations.