Osmotic potential of Zinnia elegans plant material affects the yield and morphology of tracheary elements produced in vitro

The Zinnia elegans cell suspension culture is excellent for xylogenesis studies at the cellular and molecular level, due to the high and synchronous in vitro differentiation of tracheary elements (TEs). The percentage TE differentiation (%TE) in the culture is, however, influenced by a number of factors before and during cell differentiation. One of the factors that is potentially important but has not gotten much attention is the initial osmolarity of the plant material. To examine whether the growth conditions that determine leaf osmolarity (LO) affect the final %TE, we used three light intensities (50, 70 and 100 mu mol.m(-2)s(-1)) and three electrical conductivity (EC) levels (EC 2, 4 and 6 dS.m(-1)) in hydroponic systems to induce different osmolarities in leaf materials from two cultivars (cvs) of Z. elegans, Envy and Purple Prince. The isolated leaf mesophyll cells were subsequently cultured in a liquid medium (300 mOsm extracellular osmolarity) containing alpha-naphthalene acetic acid (NAA) (1 mg.l(-1)) and benzylaminopurine (BA) (1 mg.l(-1)). The LO increased in both Zinnia cvs with increasing light intensity and increasing EC during growth. Mesophyll cell size correlated negatively with EC, but the correlation was positive with light intensity in both Zinnia cvs. There was an overall positive correlation between % TE and LO although the degree of % TE change versus LO differed between light and EC treatments and also between the two Zinnia cvs. Envy cv is the best known Z. elegans cv for establishing xylogenic cultures. However, it turned out that by subjecting the plants to different growth conditions, the Purple Prince cv produces a higher % TE as compared to the Envy cv. At EC4 the TE differentiation for the Purple Prince cv was 75%, a level that is 25 to 60% higher than those earlier reported. We conclude that light intensity and EC of the root environment affect the LO of Z. elegans which in turn influences the development and therefore dimensions of TEs in an in vitro xylogenic culture. Thus, proper optimization of the growth conditions for the Zinnia plants prior to establishment of xylogenic cultures leads to enhancement of in vitro TE formation

Osmotic potential of Zinnia elegans plant material affects the yield and morphology of tracheary elements produced in vitro

The Zinnia elegans cell suspension culture is excellent for xylogenesis studies at the cellular and molecular level, due to the high and synchronous in vitro differentiation of tracheary elements (TEs).The percentage TE differentiation (%TE) in the culture is, however, influenced by a number of factors before and during cell differentiation. One of the factors that is potentially important but has not gotten much attention is the initial osmolarity of the plant material. To examine whether the growth conditions that determine leaf osmolarity (LO) affect the final %TE, we used three light intensities (50, 70 and 100 μmol.m-2s-1) and three electrical conductivity (EC) levels (EC 2, 4 and 6 dS.m-1 ) in hydroponic systems to induce different osmolarities in leaf materials from two cultivars (cvs) of Z. elegans, Envy and Purple Prince. The isolated leaf mesophyll cells were subsequently cultured in a liquid medium (300 mOsm extracellular osmolarity) containing α-naphthalene acetic acid (NAA) (1 mg.l-1) and benzylaminopurine (BA) (1 mg.l-1). The LO increased in both Zinnia cvs with increasing light intensity and increasing EC during growth. Mesophyll cell size correlated negatively with EC, but the correlation was positive with light intensity in both Zinnia cvs. There was an overall positive correlation between %TE and LO although the degree of %TE change versus LO differed between light and EC treatments and also between the two Zinnia cvs. Envy cv is the best known Z. elegans cv for establishing xylogenic cultures. However, it turned out that by subjecting the plants to different growth conditions, the Purple Prince cv produces a higher %TE as compared to the Envy cv. At EC4 the TE differentiation for the Purple Prince cv was 75%, a level that is 25 to 60% higher than those earlier reported. We conclude that light intensity and EC of the root environment affect the LO of Z. elegans which in turn influences the development and therefore dimensions of TEs in an in vitro xylogenic culture. Thus, proper optimization of the growth conditions for the Zinnia plants prior to establishment of xylogenic cultures leads to enhancement of in vitro TE formation.Keywords: Electrical conductivity, in vitro culture, leaf osmolarity, light intensity, osmotic potential, tracheary element, xylogenesis, Zinnia elegans

Mineral Acquisition from Clay by Budongo Forest Chimpanzees

Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay consumed indicates that it takes the form of kaolinite. We discuss the contribution of clay geophagy to the mineral intake of the Sonso chimpanzees and show that clay eaten using leaf sponges is particularly rich in minerals. We show that termite mound soil, also regularly consumed, is rich in minerals. We discuss the frequency of clay and termite soil geophagy in the context of the disappearance from Budongo Forest of a formerly rich source of minerals, the decaying pith of Raphia farinifera palms

Caspase inhibitors affect the kinetics and dimensions of tracheary elements in xylogenic Zinnia (Zinnia elegans) cell cultures

<p>Abstract</p> <p>Background</p> <p>The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented.</p> <p>Results</p> <p>Confocal microscopic images revealed the consecutive stages of TE formation in Zinnia cells during trans-differentiation. Application of the caspase inhibitors Z-Asp-CH2-DCB, Ac-YVAD-CMK and Ac-DEVD-CHO affected the kinetics of formation and the dimensions of the TEs resulting in a significant delay of TE formation, production of larger TEs and in elimination of the 'two-wave' pattern of TE production. DNA breakdown and appearance of TUNEL-positive nuclei was observed in xylogenic cultures and this was suppressed in the presence of caspase inhibitors.</p> <p>Conclusions</p> <p>To the best of our knowledge this is the first report showing that caspase inhibitors can modulate the process of trans-differentiation in Zinnia xylogenic cell cultures. As caspase inhibitors are closely associated with cell death inhibition in a variety of plant systems, this suggests that the altered TE formation results from suppression of PCD. The findings presented here are a first step towards the use of appropriate PCD signalling modulators or related molecular genetic strategies to improve the hydraulic properties of xylem vessels in favour of the quality and shelf life of plants or plant parts.</p

Reconstructing Climate Policy: How Best to Engage China and Other Developing Countries?

Duke University organized the International Conference on Reconstructing Climate Policy: Moving Beyond the Kyoto Impasse, May 2003. The organizer invited me to specifically address the following two issues at the conference: 1) Whether is the proposal for joint accession by the U.S. and China in the interest of China?, and 2) Even if participating a global cap-and-trade regime is so beneficial to China as many economic studies suggest, why has China consistently refused in international negotiations even to discuss its participation in it?. In this paper, we look at the first issue from the following perspectives: a) how does China value importance of maintaining unity of the Group of 77?; b) what lessons has China learned from bilateral negotiations with the U.S. to work out the terms for China to get accession to the WTO?; c) what is the legitimacy of the U.S. insistence that it re-joins the Kyoto Protocol only if major developing countries join?; d) what are implications of the U.S. strikingly reversed position on the commitments of developing countries in New Delhi for initiating discussions on joint accession by the U.S. and China?; and e) how would joint accession by the U.S. and China be perceived?. We then address the second issue from the following perspectives: a) from the point of view of fairness, how do developing countries including China and India perceive emissions caps in the first place?; b) why have China and India been sceptical to international emissions trading?; c) how is an inflow of CDM investment in China perceived politically in comparison with the exports of emissions permits to the U.S.?; d) what are the implications of “lock in” to emissions cap, in particular no rules and principles for setting emissions targets for the commitment periods subsequent to Kyoto?; e) how to address the complex undertaking of setting emissions caps for developing countries, which must be linked to future, unobserved levels in comparison with the historically observed levels for industrialized countries?. Finally, the paper touches on the likely path forward

The plight of the sense-making ape

This is a selective review of the published literature on object-choice tasks, where participants use directional cues to find hidden objects. This literature comprises the efforts of researchers to make sense of the sense-making capacities of our nearest living relatives. This chapter is written to highlight some nonsensical conclusions that frequently emerge from this research. The data suggest that when apes are given approximately the same sense-making opportunities as we provide our children, then they will easily make sense of our social signals. The ubiquity of nonsensical contemporary scientific claims to the effect that humans are essentially--or inherently--more capable than other great apes in the understanding of simple directional cues is, itself, a testament to the power of preconceived ideas on human perception