One for all and all for one: retention of colour-unchanged old flowers increases pollinator attraction in a hermaphroditic plant.

Long-lived flowers increase pollen transfer rates, but these entail high water and carbon maintenance costs. The retention of pollinated and reward-free old flowers enhances pollinator visitation to young receptive flowers by increasing floral display size. This mechanism is associated with acropetal inflorescences or changes in flower colour and openness, but the retention of unchanging solitary flowers remains overlooked. We examined pollination-dependent variation in floral longevity and determined stigmatic receptivity, pollen viability and pollen removal rates among flower ages in Kielmeyera regalis, a Neotropical savanna shrub. We also evaluated the effects of floral display size on pollinator visitation rates. Lastly, we determined whether old flowers are unvisited and exclusively increase pollinator attraction to young flowers through flower removal experiments. Regardless of pollination treatment, flowers lasted fully open with no detectable physical changes for 3 days. Over time, stigmas remained receptive but >95% of pollen was removed. Pollinator visitation significantly increased with floral display size and intermediate percentages (15-30%) of newly opened flowers. Accordingly, the retention of reward-free and unvisited old flowers increased young flower-pollinator interaction. Our results reveal the importance of a prolonged floral longevity in increasing pollinator attraction toward newly opened receptive flowers without changes in flower colour and form. We conclude that the retention of pollinated, reward-free and unvisited colour-unchanged old flowers in K. regalis is a strategy that counteracts the water use costs associated with the maintenance of large flowers with increased mate opportunities in a pollen-limited scenario.

CD4 T-cell hyporesponsiveness induced by schistosome larvae is not dependent upon eosinophils but may involve connective tissue mast cells.

In areas endemic for schistosomiasis, people can often be in contact with contaminated water resulting in repeated exposures to infective Schistosoma mansoni cercariae. Using a murine model, repeated infections result in IL-10-dependent CD4(+) T-cell hyporesponsiveness in the skin-draining lymph nodes (sdLN), which could be caused by an abundance of eosinophils and connective tissue mast cells at the skin infection site. Here, we show that whilst the absence of eosinophils did not have a significant effect on cytokine production, MHC-II(+) cells were more numerous in the dermal cell exudate population. Nevertheless, the absence of dermal eosinophils did not lead to an increase in the responsiveness of CD4(+) T cells in the sdLN, revealing that eosinophils in repeatedly exposed skin did not impact on the development of CD4(+) T-cell hyporesponsiveness. On the other hand, the absence of connective tissue mast cells led to a reduction in dermal IL-10 and to an increase in the number of MHC-II(+) cells infiltrating the skin. There was also a small but significant alleviation of hyporesponsiveness in the sdLN, suggesting that mast cells may have a role in regulating immune responses after repeated exposures of the skin to S. mansoni cercariae.

Dental enamel EPR dosimetry: comparative testing of the spectra processing methods for determination of radiation-induced signal amplitude.

The aim of this investigation is to find out the optimal algorithm for mathematical processing of the EPR spectra of irradiated tooth enamel for estimating the amplitude of the radiation-induced signal, which is used for determination of the absorbed dose in enamel for retrospective individual dosimetry. A recently developed analytical model, which takes into account the line shape variation of the enamel EPR spectral components registered at different microwave power, was applied to spectra processing in various operation modes to simulate spectra processing techniques differing by the number of fitted parameters. The precision of dose determination at spectra processing was assessed by the root mean square deviation between experimental and nominal doses for sets of spectra of enamel samples irradiated in different doses and measured at different microwave power. It is shown that in the case of pooled enamel samples prepared as a mixture from different teeth, the higher precision of spectra processing is obtained using a model with fixed native background signal line shape (characterized by width and asymmetry parameters). In case of individual samples prepared each from a different tooth, better results are obtained using a model with variable background signal line shape.