Comparison of geranylgeranyl and phytyl substituted methylquinols in the tocopherol synthesis of spinach chloroplasts

Geranylgeranyl substituted methylquinols are shown to be precursors of tocopherol biosynthesis in spinach chloroplasts as well as phytyl substituted ones. The geranylgeranyl substituted quinols are methylated even to a greater extent than the phytyl substituted ones. The connection to the so far known biosynthetic origin of -tocopherol is probably -tocotrienol which is hydrogenated to γ-tocopherol and then further methylated to -tocopherol

2-Methyl-6-phytylquinol and 2,3-dimethyl-5-phytylquinol as precursors of tocopherol synthesis in spinach chloroplasts

The incorporation of [Me-14C] from SAM-[Me-14C] into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) → 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a)→,γ-tocopherol (5a)→-tocopherol (6). 1a is particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phylquinol (2b) to 6 via β-tocopherol (5b). Trimethylphytylquinol (3) is not an intermediate in the formation of 6. All reactions are independent of light

Osmotically driven pipe flows and their relation to sugar transport in plants

In plants, osmotically driven flows are believed to be responsible for translocation of sugar in the pipe-like phloem cell network, spanning the entire length of the plant. In this paper, we present an experimental and theoretical study of transient osmotically driven flows through pipes with semipermeable walls. We extend the experimental work of Eschrich, Evert and Young \cite[]{Eschrich:1972} by providing a more accurate version of their experiment allowing for better comparison with theory. In the experiments we measure the dynamics and structure of a "sugar front", i.e. the transport and decay of a sudden loading of sugar in a pipe which is closed in both ends. We include measurements of pressure inside the membrane tube allowing us to compare the experiments directly with theory and, in particular, to confirm quantitatively the exponential decay of the front in a closed tube.In a novel setup we are able to measure the entire concentration profile as the sugar front moves. In contrast to previous studies we find very good agreement between experiment and theory. In the limit of low axial resistance (valid in our experiments as well as in many cases in plants) we show that the equations can be solved exactly by the method of characteristics yielding, in general, an implicit solution. Further we show that under more general conditions the equations of motion can be rewritten as a single integro-differential equation, which can be readily solved numerically. The applicability of our results to plants is discussed and it is shown that it is probable that the pressure-flow hypothesis can account for short distance transport of sugar in plants.Comment: 34 pages, Submitted to Journal of Fluid Mechanics on May 28, 200

Tocopherol and plastoquinone synthesis in spinach chloroplasts subfractions

Subfractions isolated from intact purified spinach chloroplasts are able to prenylate the aromatic moiety of -tocopherol and plastoquinone-9 precursors. The biosynthesis of -tocopherol and plastoquinone-9 is a compartmentalized process. The chloroplast envelope membranes are the only site of the enzymatic prenylation in -tocopherol synthesis whereas the thylakoid membrane is also involved in the prenylation and methylation sequence of plastoquinone-9 biosynthesis. A very active kinase which forms phytyl-PP is localized in the stroma. Phytol but not geranylgeraniol is the polyprenol precursor of the side chain of -tocopherol in spinach chloroplasts

Phytol synthesis from geranylgeraniol in spinach chloroplasts

The reduction of /2-14C/-geranylgeranylpyrophosphate to phytylpyrophosphosphate is shown for the first time in chloroplasts. The esterification of exogenous /2-14C/-geranylgeranylpyrophosphate with endogenous chlorophyllide and the stepwise reduction of the pigment bound geranylgeraniol to phytol was also proved for spinach chloroplasts for the first time

Probing the link between biodiversity-related knowledge and self-reported pro-conservation behaviour in a global survey of zoo visitors

Many environmental communication interventions are built on the assumption that increased knowledge will lead to changes in proenvironment behaviors. Our study probes the link between biodiversity-related knowledge and self-reported proconservation behavior, based on the largest and most international study of zoo visitors ever conducted. In total, 6,357 visitors to 30 zoos from 19 countries around the globe participated in the study. Biodiversity understanding and knowledge of actions to help protect biodiversity were significantly related, but only 0.6% of the variation in knowledge of actions to help protect biodiversity could be explained by those same respondents’ biodiversity understanding. Biodiversity understanding was only the sixth most important variable in significantly predicting knowledge of actions to help protect biodiversity. Moreover, biodiversity understanding was the least important variable of those that were significantly related to self-reported proconservation behavior. Our study indicates that knowledge is a real, but relatively minor, factor in predicting whether members of the public – zoo visitors in this case – will know about specific proenvironment behaviors they can take, let alone whether they will actually undertake such behaviors