Pollenkitt of some monocotyledons: lipid composition and implications for pollen germination.

The composition of pollenkitt and its role in the progamic phase of reproduction are poorly understood. With the aim of extending knowledge on these topics, we chose to study two monocotyledons rich in pollenkitt, with bi-celled and long-lived pollen and dry-type stigma: Crocus vernus Hill subsp. vernus and Narcissus poeticus L. Fatty acids of pollenkitt were assayed with gas chromatography. Germination tests were performed in vivo by pollinating the stigmas with a beard hair under a stereomicroscope, and in vitro in liquid culture medium using pollen, either treated or not, with carbon disulphide to remove pollenkitt. The pollen tube percentages were evaluated using fluorescence microscopy techniques. Scanning electron microscopy was used to examine pollen and to follow the early post-pollination stages. Pollenkitt forms bridges between pollen grains but not between grains and stigma papillae. It consists of a mixture of 25 fatty acids, most with long and unsaturated chains, among which are some omega acids. The same acids with different percentages persist on the peritapetal membrane. After its removal, the pollen loses adhesiveness and dries quickly, but retains full capacity for germination on the papillae and can even trigger germination in contiguous pollen grains that do not touch the papillae. The results, while confirming the key role of pollenkitt in protecting pollen and favouring pollination, suggest secondary roles in the progamic phase, and highlight the interactive ability of the pollen regardless of lipid shell. The predominance of fatty acids with 18:3 and 16:0, as already noted in Brassica napus pollenkitt, suggests their hierarchy independent of plant species.

Influence of sensory quality on preferences for apples of primary school children.

In this research work, sensorial features of four varieties of fresh apples have been investigated by children aged 6-10 years (n = 336) of the Centre-East region of Italy (Abruzzo). The examined sensory properties were visual appealing, aromatic flavour, sourness, sweetness, firmness and crunchiness. Statistical analysis was performed by means of principal component analysis which underlined the differences and similarities between the examined fruits and the most responsive variables. Results are very interesting and allow to better understand the most important descriptors which influence the appreciation of the different tested varieties. Furthermore, it has been noted that different varieties influence each other for the perception of some sensory characteristics. Thus, improving the knowledge of the most appreciated organoleptic properties of apples by young consumers would be very useful and it might stimulate the development of new and more appealing cultivars in the future.

Hydrolysis of Oleuropein by Lactobacillus plantarum Strains Associated with Olive Fermentation.

Oleuropein (Chemical Abstracts Service registry number 32619-42-4), a bitter-tasting secoiridoid glucoside commonly found in leaves of the olive tree as well as in olives (Olea europaea L.), was found to be hydrolyzed by the beta-glucosidase (EC 3.2.1.2.1) produced by oleuropeinolytic Lactobacillus plantarum-type strains. Three strains, designated B17, B20, and B21, were isolated from the brine of naturally ripe olives not treated with alkali. These strains were rod-shaped forms, grown at a pH 3.5 limit, and tolerated 1% oleuropein and 8% NaCl in the growth medium. The beta-glucosidase produced hydrolyzed 5-bromo-4-chloro-3-indolyl-beta-d-glucopy-ranoside as well as oleuropein. The presence of 2% glucose in the medium inhibited activity by 40 to 50%, depending on the bacterial strain. Chromatographic analysis of the trimethylsilyl derivatives of the products obtained after 7 days of incubation at 30 degrees C of strain B21 showed all the hydrolysis products of oleuropein, i.e., aglycone, iridoid monoterpen, and 3,4-dihydroxyphenylethanol (hydroxytyrosol). Oleuropein and its aglycone after 21 days of incubation decreased to trace levels with the simultaneous increase in concentration of beta-3,4-dihydroxyphenylethanol.

Truffle melanogenesis: correlation with reproductive differentiation and ascocarp ripening.

The present work uses histochemical techniques to investigate the correlation between reproductive differentiation and age of truffles (Tuber aestivum and Tuber melanosporum) with melanin synthesis. The dopa oxidase and tyrosine hydroxylase activities of tyrosinase have been localized within the ascocarp and melanin localization was performed by the Schmorl's reaction. A true tyrosinase is present in truffles, able to oxidize both l-tyrosine and l-dopa. The tyrosinase activity is on in the young ascocarps (in the peridium, hypothecium, and fertile veins) and off in the ripe ones, thus it appears correlated with the age and differentiation of the sporogenic hyphae that arise from the hypothecium; a similar correlation has been previously described in Neurospora crassa, which is an ascomycete as well as the truffles.