Nitrogen fertigation of greenhouse-grown cucumber

Summary This greenhouse study investigated the response of trickle-irrigated cucumber (Cucumis sativa cv. ‘Petita’) to three N levels applied with every irrigation via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. Water containing 5.8, 11.8, or 17.8 mmol N/l, and uniformly supplied with 2.0 and 3.9 mmol/l of P and K, respectively, was applied two to three times daily. In all treatments of 0.3 leaching fraction was allowed. The resulting total N applications were 15.7, 31., and 47.2 g N/plant. The total amount of water applied was 1851/plant. Total N and NO₃-N, in lajinae and petioles, increased with increasing N level whereas P and K in generated decreased. Although different NO₃/NH₄ ratios in the treatments may have influeced the response to N, it could be concluded that the highest yield was obtained with 11.8 mmol N/1 due to increased number of fruit. In the root volume of this treatment the NO₃-N concentration in the soil solution was aroun 7 mmol/1 for most of the growing season. The dry matter concentration of fruits was not affected by the N levels. It was concluded that 11.8 mmol N/1 applied with every irrigation via the irrigation stream is adequate to cover the needs of greenhous-grown cucumber for higher yield (9.42 kg/plant over a harvesting period of 93 days).     

Evaluation of acute and chronic toxicity of selected compounds in higher plants using cell culture

Summary The feasibility of using plant cell culture to measure toxicity was determined by investigating the toxicological effects of three chemical compounds, allyl alcohol, propargylglycine, and cadmium chloride, on cell cultures ofCatharanthus roseus G. Don (Madagascar periwinkle). Suspension cultures ofC. roseus were maintained in modified B5 medium and transferred every 5 d. Five-day-old cell cultures were exposed to various concentrations (10,3,1,0.3,0.1,0.03,0.01,0.003,0.001,0.0003,0.0001, 0.00003, and 0.0 mM) of the toxicants in both acute and chronic toxicity tests. In the acute test, cells were exposed to the toxicant for 24 h, washed three times with sterile medium, and plated in petri plates with an equal volume of 1.4% agar medium. Cells in the chronic test were plated with an equal volume of 1.4% agar medium containing various concentrations of the toxicant. Cells were incubated 28 d at 30°C in the dark. The colonies were counted and the results plotted as percent survival versus toxicant concentration. The results indicate, at the concentrations tested, thatC. roseus assay may be feasible in that it fulfills the criteria for a practical assay (e.g., rapid, simple, quantifiable, and reproducible). This work was submitted to the faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Environmental Science, Institute of Environmental Sciences.     

Micropropagation of Rollinia mucosa (JACQ.) baill

Summary A protocol for in vitro propagation of Rollinia mucosa, an important medicinal plant, was developed. The presence of 500 mg l⁻¹ polyvinylpyrrolidone (PVP) during explant excision was important to avoid browning. Axillary buds, adventitious buds, and shoot cluster proliferation were achieved from epicotyl and hypocotyl explants from nursery-grown seedlings. The highest direct organogenesis percentage from hypocotyl explants was obtained upon culture of explants on Murashige and Skoog medium supplemented with 2.2 μM benzyladenine (BA) plus 2.32 μM kinetin. Epicotyl explants display highest regeneration frequency on a medium containing 8.8 μM BA and 0.54 μM naphthaleneacetic acid. Gibberellic acid was necessary for shoot elongation. Root induction was observed when shoots were pretreated with activated charcoal for 7 d in the dark before culture on Woody Plant Medium supplemented with 49.21 μM indolebutyric acid for 10 d. Root development was observed when 20 g l⁻¹ sucrose was used. Rooted plantlets were acclimatized and grown in the greenhouse.     

Photosynthesis,Transpiration, and Water Use Efficiency of Vegetative and Reproductive Shoots of Grassland Species from North-Eastern China

The differences in net photosynthetic rate (P _N), transpiration rate (E), and water use efficiency (WUE) between the vegetative and reproductive shoots of three native grass species from the grassland of northeastern China [grey-green and yellow green populations of Leymus chinensis (Trin.) Tzvel., Puccinellia tenuiflora (Griseb) Scrib & Merr, Puccinellia chinampoensis Ohwi] were compared. The two type shoots experienced similar habitats, but differed in leaf life-span and leaf area. The leaf P _N and WUE for the vegetative shoots were significantly higher than those for the reproductive shoots in the grasses, while their E were remarked lower in the dry season. Relative lower leaf P _N and WUE for the reproductive shoots of grassland grasses may explain the facts of lower seed production and the subordinate role of seed in the grassland renewal in north-eastern China.     

Understanding plant reproductive diversity

Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology.     

Dynamic and Reversible Aggregation of the Human CAP Superfamily Member GAPR-1 in Protein Inclusions in Saccharomyces cerevisiae

Many proteins that can assemble into higher order structures termed amyloids can also concentrate into cytoplasmic inclusions via liquid–liquid phase separation. Here, we study the assembly of human Golgi-Associated plant Pathogenesis Related protein 1 (GAPR-1), an amyloidogenic protein of the Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-related 1 proteins (CAP) protein superfamily, into cytosolic inclusions in Saccharomyces cerevisiae. Overexpression of GAPR-1-GFP results in the formation GAPR-1 oligomers and fluorescent inclusions in yeast cytosol. These cytosolic inclusions are dynamic and reversible organelles that gradually increase during time of overexpression and decrease after promoter shut-off. Inclusion formation is, however, a regulated process that is influenced by factors other than protein expression levels. We identified N-myristoylation of GAPR-1 as an important determinant at early stages of inclusion formation. In addition, mutations in the conserved metal-binding site (His54 and His103) enhanced inclusion formation, suggesting that these residues prevent uncontrolled protein sequestration. In agreement with this, we find that addition of Zn²⁺ metal ions enhances inclusion formation. Furthermore, Zn²⁺ reduces GAPR-1 protein degradation, which indicates stabilization of GAPR-1 in inclusions. We propose that the properties underlying both the amyloidogenic properties and the reversible sequestration of GAPR-1 into inclusions play a role in the biological function of GAPR-1 and other CAP family members.     

Host gall size and oviposition success by the parasitoid Eurytoma gigantea

Abstract. 1. Eurytoma gigantea Walsh is a specialist parasitoid of the tephritid gallmaker Eurosta solidaginis (Fitch).
2. In the natural environment the incidence of parasitism by Eurytoma is greater in small galls than in large ones.
3. Laboratory experiments demonstrated that small galls are not more frequently discovered; however, oviposition attempts on small galls were more likely to be successful.
4. Eurytoma spends much time probing galls too big to penetrate; this leads to a decrease in foraging efficiency when many large galls are present.
5. The chance of successfully penetrating a gall depends on the thickness of the gall wall and the length of the parasitoid's ovipositor.
6. A simulation model was constructed which shows that a gallmak-er's chance of being parasitized depends on gall size, the number of parasitoids that discover the gall, and their ovipositor lengths.     

Haploid plant regeneration from unpollinated ovule cultures of niger (<Emphasis Type="Italic">Guizotia abyssinica</Emphasis> (L. f.) Cass.)

Haploid plants were regenerated in vitro from unpollinated ovules of niger (Guizotia abyssinica (L. f.) (Cass.) on Murashige and Skoog nutrient medium (MS) supplemented with 10 μM naphthaleneacetic acid or 10 μM NAA + 1.5 μM kinetin and 30 g/l sucrose. Gamborg (B5) medium was the best for plant regeneration (in comparison with MS, Nitsch and Nitsch (NN), and Chu (N6) media) from cultured ovules, and 6.66 and 7.33 ovules of JNC-6 and Ootacamund cultivars were involved in direct plant regeneration on this medium. Matured ovules (ovules collected one day before anthesis or on the day of anthesis) only responded to cultural regimes and involved in direct plantlet development. Cytological preparation of root tips and chloroplast counts in the guard cells of leaf stomata of regenerated plants confirmed their haploid nature. This text was submitted by the authors in English.     

Promotion by phloroglucinol of micropropagation of Minuartia valentina, an endangered and endemic Spanish plant

Tissue culture techniques for the propagation and conservation of endemic or threatened plants can be used to complement the methods usually applied in ex situ conservation. Thus, Minuartia valentina (Caryophyllaceae), an endangered plant species endemic to the Valencia Community (Eastern Spain), was successfully regenerated through shoot proliferation from wild plants growing in their natural area. Nodal segments, 10~mm long, were cut from rametes of adult material, sterilised and established in vitro. Equally successful shoot multiplication was achieved on Murashige and Skoog (MS) medium with 80 mg l-1 phloroglucinol in combination with either 1 mg l-1 6-benzylaminopurine or 1 mg l-1 kinetin. Excised shoots were rooted in MS medium supplemented with an auxin (indole acetic acid, indole-3-butyric acid, or napththalene acetic acid). Shoots rooted well (96–100%) within three weeks in all auxin treatments. However, the use of napththalene acetic acid was discarded because this auxin delayed root differentiation, and induced adventitious root malformation. Rooted plantlets were transferred to pots and 85% of them acclimatized successfully four weeks after transfer to greenhouse conditions, where they exhibited normal morphology and growth.