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Controlling the supramolecular organization of pigment molecules will provide innovative materials that exhibit variable optical properties. In nature, photosynthetic systems employ chlorophyllous supramolecules in which each pigment molecule is suitably organized in proteins, and their properties are adequately optimized by changing the structures of the surrounding amino acid residues. Here, we report a strategy for varying the aggregation behavior of a chlorophyll derivative by using a phase-transition phenomenon of lipid bilayers. Methyl pyropheophorbide a (MPP) was employed as a chlorophyllous pigment in our artificial system, and synthetic phosphatidylcholines with saturated acyl chain(s) were also used. The MPP molecules successfully accumulated within the lipid bilayer of liposomes without changing the vesicular structure. When the lipid bilayer was in a gel form (under the phase-transition temperature, T m ), the embedded MPP aggregated to yield a dimeric form showing red-shifted absorption bands and circular dichroism signals. When the solutions of MPP-containing liposomes were heated to higher temperatures than their T m , MPP disaggregated to monomeric form as the absorption spectrum changed into its original fashion in dichloromethane. The reversible thermochromic (dis)aggregation of the MPP molecules had good cyclability. Additional careful examination of the phase transition in the MPP−lipid co-assemblies clarified that the critical temperatures of the MPP (dis)aggregation were in good agreement with the phase-transition temperatures of the pigment-containing bilayers. The reversible MPP aggregation in the lipid bilayers occurred in a wide range of temperatures (around 10−55 °C) by changing the length of the diacyl side chains of phospholipids. The reversible thermochromism of the chlorophyllous system was established by varying the nature of the surrounding lipid bilayer. This study can provide a useful strategy for making variable tetrapyrrolic aggregate systems induced by mild extrinsic stimuli.

This study was conducted to determine the reproductive characteristics of Barbarea vulgaris under different disturbance regimes (mowing and tilling) in two different habitats: a levee and a wheat field. On the levee, 77 of the 114 individuals that had had their floral stalks removed by the first mowing produced new rosettes at the basal part of the stem during the same growing season. The plants that were mowed four times per year had a significantly greater survival rate than the plants that were mowed twice per year. The levee population that was mowed without tillage was largely maintained by vegetative reproduction.These results suggest that mowing the levees promotes the vegetative reproduction of B. vulgaris and helps it to compete with tall-growing plants, thus facilitating its survival as a perennial. In spite of the high sprouting ability of the plant's root fragments, most of the root fragments did not regenerate when buried or when exposed to high soil moisture conditions in tilled wheat fields. The population of B. vulgaris in tilled wheat fields was maintained almost entirely by sexual reproduction. Barbarea vulgaris can survive under two different management regimes by altering its mode of reproduction.

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