Developmental anatomy and immunocytochemistry reveal the neo-ontogenesis of the leaf tissues of Psidium myrtoides (Myrtaceae) towards the globoid galls of Nothotrioza myrtoidis (Triozidae).

KEY MESSAGE: The temporal balance between hyperplasia and hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient that determines the gall globoid shape. Plant galls develop by the redifferentiation of new cell types originated from those of the host plants, with new functional and structural designs related to the composition of cell walls and cell contents. Variations in cell wall composition have just started to be explored with the perspective of gall development, and are herein related to the histochemical gradients previously detected on Psidium myrtoides galls. Young and mature leaves of P. myrtoides and galls of Nothotrioza myrtoidis at different developmental stages were analysed using anatomical, cytometrical and immunocytochemical approaches. The gall parenchyma presents transformations in the size and shape of the cells in distinct tissue layers, and variations of pectin and protein domains in cell walls. The temporal balance between tissue hyperplasia and cell hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient, which determines the globoid shape of the gall. The distribution of cell wall epitopes affected cell wall flexibility and rigidity, towards gall maturation. By senescence, it provided functional stability for the outer cortical parenchyma. The detection of the demethylesterified homogalacturonans (HGAs) denoted the activity of the pectin methylesterases (PMEs) during the senescent phase, and was a novel time-based detection linked to the increased rigidity of the cell walls, and to the gall opening. Current investigation firstly reports the influence of immunocytochemistry of plant cell walls over the development of leaf tissues, determining their neo-ontogenesis towards a new phenotype, i.e., the globoid gall morphotype.

Bacteriostatic effect of Piper betle and Psidium guajava extracts on dental plaque bacteria.

In this study, the bacteriostatic effect of Piper betle and Psidium guajava extracts on selected early dental plaque bacteria was investigated based on changes in the doubling time (g) and specific growth rates (micro). Streptococcus sanguinis, Streptococcus mitis and Actinomyces sp. were cultured in Brain Heart Infusion (BHI) in the presence and absence of the extracts. The growth of bacteria was monitored periodically every 15 min over a period of 9 h to allow for a complete growth cycle. Growth profiles of the bacteria in the presence of the extracts were compared to those in the absence and deviation in the g and micro were determined and analyzed. It was found that the g and mu were affected by both extracts. At 4 mg mL(-1) of P. betle the g-values for S. sanguinis and S. mitis were increased by 12.0- and 10.4-fold, respectively (p < 0.05). At similar concentration P. guajava increased the g-value by 1.8- and 2.6 -fold, respectively (p < 0.05). The effect on Actinomyces sp. was observed at a much lower magnitude. It appears that P. betle and P. guajava extracts have bacteriostatic effect on the plaque bacteria by creating a stressed environment that had suppressed the growth and propagation of the cells. Within the context of the dental plaque, this would ensure the attainment of thin and healthy plaque. Thus, decoctions of these plants would be suitable if used in the control of dental plaque.