Diversity and host recurrence of fungi associated with the bleached leaf litter in a subtropical forest

Fungi that selectively remove lignin cause extensive bleaching of leaf litter, which results in the acceleration of litter decomposition. The taxonomic diversity and host recurrence of saprotrophic fungi associated with bleached leaf litter were investigated in a subtropical forest in southern Japan. A total of 211 fungal isolates and sporocarps were obtained from bleached portions of leaf litter of 33 plant species in 18 families and were classified into 83 operational taxonomic units (OTUs) at the 97% similarity level of the ITS rDNA sequence. These fungal OTUs belonged to Rhytismataceae and Xylariaceae in the Ascomycota, and Marasmiaceae, Mycenaceae, Lachnocladiaceae, and Physalacriaceae in the Basidiomycota. OTUs in Rhytismataceae and Marasmiaceae showed a significantly higher degree of recurrence for plant species than simulated networks where partners were associated randomly. In contrast, OTUs in Xylariaceae and Mycenaceae showed no significant recurrence for plant species. Such differing degrees of recurrence for plant species implied different roles of fungal families in leaf litter decomposition.     

The adaptive value of young leaves being tightly folded or rolled on monocotyledons in tropical lowland rain forest: an hypothesis in two parts

In tropical lowland rain forest, we find that species with the leaves tightly folded or rolled until they reach at least 50% of final length occur in 10 of the 15 monocot families with >100 species, and in 12 of the 24 monocot families with <100 species, but in only seven of the 212 dicot families (eudicots and magnoliids). Earlier researchers have described how examples of tightly folded and rolled leaves develop, but most have not considered the potentially adaptive value of this pattern of growth. We hypothesize that it is a protection against herbivorous invertebrates. For tropical and temperate dicots, the young leaves have been found to suffer much smaller losses to herbivores while folded and rolled than after they are unfolded or unrolled. Being folded or rolled until a late stage involves an ‘opportunity cost’ in the loss of photosynthesis. Among dicots, defences involving such a cost (notably late development of photosynthetic systems in pendent soft young leaves) are typical of shade-tolerant species, which have longer-lived leaves than light-demanders. In contrast, among monocots late folding and rolling are found in both shade-tolerators and light-demanders. We hypothesize that late folding and rolling bring a net advantage to monocots in general, whether shade-tolerant or light-demanding, despite the opportunity cost, because they mostly have fewer leaves per plant of a given size, and therefore an individual leaf is relatively more valuable to the plant. As a coda, we suggest that the ‘sleep movements’ of some tropical plants, and the circinate vernation of ferns and some cycads, provide protection against invertebrate herbivores through the apposition of two or more layers of leaf.     

Triterpenoids and triterpenoid saponins from the aerial parts of Fagonia indica Burm

As part of our search of new bioactive compounds from indigenous medicinal plants, phytochemical investigation of the aerial parts of Fagonia indica Burm led to the isolation of seven compounds including two new compounds, namely, indicacin (1) and fagonicin (2), and five known compounds (3–7) from the methanol extract. Compounds 6 and 7 are hitherto unreported from this plant. The structures of the new compounds were elucidated from their spectral data, mainly HREIMS, 1D NMR (¹H, ¹³C NMR, and DEPT) and 2D NMR (COSY, NOESY, HSQC and HMBC), and by comparison with the literature data. The new compounds 1 and 2 were assayed for their cytotoxicity against human colorectal cancer cell line H-29. Compound 1 exhibited 51.40% cytotoxicity at 6.25 μM/mL dose whereas compound 2 demonstrated 39.3% cytotoxicity at the same dose.     

Proteins as a potential nitrogen storage compound in bark and leaves of several softwoods

Summary The occurrence of vegetative storage proteins in the leaf and bark tissues of several softwood species during overwintering was investigated by sodium dodecyl sulphate polyacrylamide electrophoresis. Monthly protein profiles from leaves and bark of six evergreen softwood species (Pinus strobus, P. sylvestris, Picea abies, P. glauca, Abies balsamea, and Thuja occidentalis) and the bark of one deciduous softwood species (Larix decidua) suggest that storage proteins are present in bark tissues of L. decidua, Pinus sylvestris, and P. strobus. The remaining species did not show similar specific proteins. However, the total soluble protein content which was determined during active growth and during overwintering in the same tissues indicated that protein levels were higher in the winter compared to the summer in the bark of all species and in the leaves of Pinus spp. and T. occidentalis. While vegetative storage proteins do not appear prevalent in all softwood species, proteins may constitute a major form of overwintering nitrogen storage for many species.     

Maintenance and constructive respiration in various organs ofHelianthus annuus L. andZinnia elegans L.

Maintenance and constructive respiration were examined in leaves, stems and roots of sunflower seedlings and in detached leaves of zinnia. Maintenance and constructive respiratory coefficients in sunflower leaves were smaller than those in stems and roots, and zinnia leaves. It was suggested that matter accumulation influenced maintenance respiratory coefficient.     

光周期对光敏核不育水稻RNA水平上诱导效应的初步研究

本文以PGMR农垦58为材料,在PGMR育性转换临界期进行不同光周期处理,分析了叶片总RNA的含量和电泳特征。结果表明:叶片总RNA含量在长日照处理下明显减少,光周期对PGMR育性转换和表达在转录水平上可能有一定的调控作用,似乎属于阻遏调控类型。在育性转换期,长日照处理有1个特异的小分子和大分子RNA组份,这些特异RNA组份是否为PGMR的特异阻遏产物还有待进一步研究。