The apical control of lateral bud development in excised shoot tips of Cuscuta reflexa cultured in vitro

Excised shoot tips of Cuscuta reflexa Roxb. (dodder), a rootless and leafless angiospermic plant parasite, were cultured in vitro for the study of the control of lateral bud development by the apex. In a chemically defined medium lacking hormones, the basal bud alone developed into a shoot. The addition of coconut milk to the growth medium induced the activation of multiple lateral buds, but only a single bud developed further into a shoot. The decapitation of this shoot induced the development of another shoot and the process could be repeated. This showed the controlling effect of the apex in correlative control of bud development. Application of indole-3-acetic acid to the shoot tip explant delayed the development of the lateral bud. Gibberellic acid A₃ induced a marked elongation growth of the explant and reinforced apical dominance. The direct application of cytokinin to an inhibited bud relieved it from apical dominance. A basipetally decreasing concentration gradient of auxin may prevail at the nodes. Bud outgrowth is probably stimulated by cytokinin produced locally in the bud.     

Abscisic acid and apical dominance in Phaseolus coccineus L.

Abscisic acid (ABA) in lanolin, applied to the internode of decapitated runner bean plants enhances the outgrowth of lateral buds. The optimum concentration of the paste is 10^-5 M. The effect of ABA is counteracted by indoleacetic acid (IAA) but not by gibberellic acid (GA₃). There is no effect when ABA is applied to the apical bud or lateral buds of intact plants. However, 13.2 ng given to the lateral buds of decapitated plants stimulate their growth, whereas higher concentrations are inhibitory. Consequently, ABA enhances growth of lateral buds directly, but only when apical dominance is already weakened. The growth of the decapitated 2^nd internode was not affected by ABA. Radioactivity from [2-¹⁴C] ABA, applied to nonelongating 2^nd internode stumps of decapitated runner bean plants moves to the lateral buds, whereas [1-¹⁴C]IAA-and [³H]GA₁-translocation is much weaker. ABA transport is inhibited if IAA or [³H]GA₁ is applied simultaneously. In elongating internodes [¹⁴C]ABA is almost completely immobile. [¹⁴C]IAA-and [³H]GA₁-translocation is not affected by ABA. The amount of radioactivity from labelled ABA, translocated to the lateral buds, is highest during the early stages of bud outgrowth.Abbreviations ABA 2,4-cis, trans-(+)-abscisic acid - GA gibberellic acid - IAA indoleacetic acid - p.l. plain lanolin     

Formative and proliferative cell divisions,cell differentiation,and developmental changes in the meristem of Azolla roots

The root of the water fern Azolla is a compact higher-plant organ, advantageous for studies of cell division, cell differentiation, and morphogenesis. The cell complement of A. filiculoides Lam. and A. pinnata R.Br. roots is described, and the lineages of the cell types, all derived ultimately from a tetrahedral apical cell, are characterised in terms of sites and planes of cell division within the formative zone, where the initial cells of the cell files are generated. Subsequent proliferation of the initial cells is highly specific, each cell type having its own programme of divisions prior to terminal differentiation. Both formative and proliferative divisions (but especially the former) occur in regular sequences. Two enantiomorphic forms of root develop, with the dispositions of certain types of cell correlating with the direction, dextrorse or sinistrorse, of the cell-division sequence in the apical cells. Root growth is determinate, the apical cell dividing about 55 times, and its cell-cycle duration decreasing from an initial 10 h to about 4 h during the major phase of root development. Sites of proliferation progress acropetally during aging, but do not penetrate into the zone of formative divisions. The detailed portrait of root development that was obtained is discussed with respect to genetic and epigenetic influences; quantal and non-quantal cell cycles; variation in cell-cycle durations; relationships between cell expansion and cell division: the role of the apical cell; and the limitation of the total number of mitotic cycles during root formation.     

Herbivoran impact on phytoplankton community structure

An enclosure experiment was conducted to assess the effects of a zooplankton elimination on the structure of a phytoplankton community. Phytoplankton biomass and production were higher in grazer-free enclosures, while the productivity per unit biovolume was lower. Exclusion of zooplankton favoured the majority of algal species, especially chrysophyceans (Dinobryon spp.) and the diatom Rhizosolenia, while mucilagineous green-algae were disfavoured. Middle sized algae (ESD 15–50 µm) and those with the largest Surface Area/Volume ratio were proportionally most favoured by the elimination of grazers.These differences in phytoplankton community structure are discussed in relation to effects of direct selective grazing and nutrient recycling by zooplankton. Some differences, as the immediate positive response of Dinobryon and Rhizosolenia, are probably caused by grazing release, while others, e.g. the response of mucilagineous species, might be caused by changed competitive relationships between the algae.     

Aspects of aerobic mineralization during spring in Lake Vechten with special reference to the 14C-labelling technique

Aerobic mineralization, i.e. seston respiration, microbial breakdown of detritus and microbial assimilation-dissimilation of photosynthetically derived D(issolved) O(rganic) C(arbon) was measured in concentrated samples from the pelagic zone of Lake Vechten. The samples were described by cell numbers of dominant algae prior to concentrating by centrifuge with continuous rotor. The concentrated samples were incubated in the laboratory at in situ temperature and a light intensity of 30 W · m^–2 for measuring primary production and photosynthetically derived DOC. After filtration the particulate fraction was incubated in unlabelled lake water far measuring respiratory production of DI¹⁴C. Portions of the same particulate fraction were sterilized and incubated in unlabelled sample concentrate for measuring microbial breakdown of detritus. The seston respiration amounted to 19–30% loss of the particulate fraction over 15–45 h. Microbial breakdown of detritus amounted to 28–40% loss of the particulate fraction over 24–168 h. In both cases P(articulate) O(rganic) ¹⁴C(arbon) was transformed to mainly DI¹⁴C. Microbial assimilation-dissimilatioh of photosynthetically derived DOC could not be measured reliably.     

EFFECTS OF VARIATIONS IN LIGHT INTENSITY ON THE EFFICIENCY OF GROWTH OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN A CYCLOSTAT1

The relative importance of respiration and organic carbon release to the efficiency of carbon specific growth of Skeletonema costatum (Grev.) Clave was evaluated over a light range from 1500–15 μE · m^?2· s^?1. Net growth efficiency ranged from 0.45–0.69 with a maximum at 130 μE · m^?2· s^?1. Respiration was 93% or more of the variations in growth efficiency. Organic carbon release ranged from 0–7% of gross production and increased with light intensity. Carbon specific particulate production was a hyperbolic function of incident light intensity and was related exponentially to particulate carbon production per unit chlorophyll a. Full sunlight conditions, 1500 μE · m^?2· s^?1, did not induce photoinhibition of gross production. Variations in the efficiency of growth of S. costatum were minimized over a wide range of light intensities mainly because of variations in cellular pigments which permitted the efficient utilization of available light energy, and a reduction in the losses of carbon which increases the growth rate, possibly as a consequence of the recycling of respired carbon within the cell.     

Direct Recycling of Spent NCM Cathodes through Ionothermal Lithiation

Ionic liquids (ILs) are a family of nonconventional molten salts that offer many advantages, such as negligible vapor pressures, negligible flammability, wide liquidus ranges, good thermal stability, and much synthesis flexibility. The unique solvation environment of these ILs provides new reaction or flux media for controlling formation of solid‐state materials with a minimum perturbation of morphologies. A successful lithiation via ionothermal synthesis using a cost‐effective Li halide as Li source and recyclable ILs as solvents is reported here for the direct recycling of LiNi_1/3Co_1/3Mn_1/3O₂ (NCM 111) cathodes. In addition, the ionic liquids can be readily recycled and reused after ionothermal lithiation. The lithiation of spent cathodes can enable the direct recycling of spent cathode materials in lithium‐ion batteries.     

Crumbs proteins stabilize the cone mosaics of photoreceptors and improve vision in zebrafish

Although the unique organization of vertebrate cone mosaics was first described long ago,both their underlying molecular basis and physiological significance are largely unknown.Here,we demonstrate that Crumbs proteins,the key regulators of epithelial apical polarity,establish the planar cellular polarity of photoreceptors in zebrafish.Via heterophilic Crb2a-Crb2b interactions,the apicobasal polarity protein Crb2b restricts the asymmetric planar distribution of Crb2a in photoreceptors.The planar polarized Crumbs proteins thus balance intercellular adhesions and tension between photoreceptors,thereby stabilizing the geometric organization of cone mosaics.Notably,loss of Crb2b in zebrafish induces a nearsightedness-like phenotype in zebrafish accompanied by an elongated eye axis and impairs zebrafish visual perception for predation.These data reveal a detailed mechanism for cone mosaic homeostasis via previously undiscovered apical-planar polarity coordination and propose a pathogenic mechanism for nearsightedness.     

Extended Producer Responsibility in the United States

Extended producer responsibility (EPR) is a policy approach that requires manufacturers to finance the costs of recycling or safely disposing of products consumers no longer want. This article describes the evolution of EPR policies in the United States, focusing on the role of states as policy actors. For their part, federal lawmakers have not embraced EPR policies except to remove some barriers to state‐level initiatives. In the two‐decade period from 1991 to 2011, U.S. states enacted more than 70 EPR laws. In addition, manufacturers have implemented voluntary programs to collect and recycle products, but those efforts have proven largely ineffective in capturing significant quantities of waste products. With the help of new coalitions of diverse interest groups, recently states have renewed efforts to establish effective EPR programs, enacting 40 laws in the period 2008–2011. Several state initiatives suggest a more promising future for EPR.