Photosynthetic functions of leaves affected by the bibenzyl batatasin-III

In northern Sweden, Empetrum hermaphroditum Hagerup dominates the ground layer vegetation in post fire successions by suppressing other plant species. Previous studies suggest that this negative effect by E. hermaphroditum may be explained, at least in part, by the release of phenolic compounds, particularly batatasin-III, from foliage to soil. In this pilot study, we evaluated the effect of batatasin-III on photosynthesis by applying the compound (0.1, 1.0, or 2.8 mM) directly to the transpiration stream of intact Spinacia oleracea L. (spinach) and Betula pendula L. (birch) leaves. Within the concentration range used, batatasin-III had a small, but significant, effect on photosynthesis. The strongest effect was found on CO2 assimilation, but there were also significant effects on respiration and on maximum quantum yield of chlorophyll fluorescence (Fv / Fm). In spinach leaves treated with 2.8 mM of batatasin-III, a 14 % decrease in Fv / Fm-685 coincided with a 30 % inhibition of CO2 assimilation rates. It is possible, that the inhibition of photosynthesis by batatasin-III was caused by direct effects on chloroplast membrane energization processes and subsequent control on the primary photochemistry of PSII. The variable fluorescence kinetics indicated that maximum quantum yield of variable fluorescence of PSII was depressed while continued upstream transported allowed oxidation of the primary electron acceptor

Novel technique shows different hydrophobic chemical signatures of exotic and indigenous plant soils with similar effects of extracts on indigenous species seedling growth

Changes to ecosystem abiotic parameters are regarded as possible mechanisms facilitating plant invasion and community composition shifts. This study compared the hydrophobic chemical signatures of soil from exotic bitou bush (Chrysanthemoides monilifera spp. rotundata) invaded, indigenous acacia (Acacia longifolia var. sophorae) dominated and bare sand (unvegetated) habitats using a novel, rapid, capturing technique which utilised Amberlite® XAD4 resin filled bags that were placed in situ. The hydrophobic chemical signature of the bitou bush soil extract was significantly different to the acacia soil and bare sand extracts. High concentrations of 18 sesquiterpenes dominated the hydrophobic signature of the bitou bush extract. Low concentrations of all three extracts did not significantly affect the seedling growth of three indigenous test species under laboratory conditions, however, at higher concentrations, the extracts from soil inhabited by plants, whether exotic or indigenous, similarly inhibited the seedling growth of two species, while seedling growth of the third species was inhibited by extracts from all three soil types. These results do not support the hypothesis that exotic invasive species are more likely to exhibit allelopathic effects than indigenous plant species.12 page(s