How are pollinators guided by colourful floral structures? A commentary on: ‘The role of pollinator preference in the maintenance of pollen colour variation’

This article comments on: Jennifer L. Ison, Elizabeth S. L. Tuan, Matthew H. Koski, Jack S. Whalen and Laura F. Galloway. 2019. The role of pollinator preference in the maintenance of pollen colour variation. Annals of Botany 123(6): 951–960.

Spores and Pollen Colour Changes and Thermal Maturation of Mid-Cretaceous Lacustrine Organic-rich Sediments in the Mamfe Basin, S.W. Cameroon

Repeated palynological analyses of samples collected from lacustrine black organic rich shales and carbonate rocks which are abound in the Mamfe Basin have consistently yielded extremely low count of palynomorphs. Geochemical analysis of the same rocks revealed very high Total Organic Carbon (TOC) content of up to 16.10wt%, whereas similar rocks elsewhere as expected, yielded high abundance and diversity of palynomorphs. Several geologic factors involved in the burial history of sedimentary rocks may account for this low sporomorphs count, however, microscopic analyses of the changes in their colour, provides a quick and relatively cheap approach by which the thermal alteration of the sediments can be reconstructed. Palynomorphs data from this and previous studies of the same sediments were compared and confirmed to be very poor in abundance however, the few recognizable species undoubtedly permitted the assignment of an Albian-Turonian age to these sediments under study. Spore-pollen colour variation (Munsell colour standards) has proven to have a positive correlation with thermal alteration hence, sediments and organic matter maturation. Using a three sporomorph group (SG) that include: (1) leiotrilete spores of the genera Cyathidites, Deltoidospora, Dictyophyllidites, Gleicheniidites, and Leiotriletes (SG-1) with sporoderm thicknesses <1μm, 1–1.5μm and >1.5μm, respectively); (2) trilete, regulate spores of the genus Lycopodiacidites (SG-2); (3) trilete, striate spores of the genus Cicatricosisporites (SG-3); and (4) the gymnosperm-pollen taxon Classopollis torosus (SG-4). Results show here that the colour index varied from 2.5 to 5.0, indicating low to high maturity with Kerogen types I, II and III corresponding to a paloetemparature range of 60 to 140oC for an estimated stratigraphic interval of 1000 to 3000m in the Mamfe Basin.

Comparative flower structure of three species of sundew (Drosera anglica, Drosera linearis, and Drosera rotundifolia) in relation to breeding system

Whereas much attention has been given to the fascinating prey-trapping leaves of carnivorous plants, less research has been conducted on their flower structure and breeding systems. Accordingly, a comparative study of the floral morphology and anatomy of the three species of sundews (Droseraceae: Drosera anglica Huds., Drosera linearis Goldie, and Drosera rotundifolia L.) in Saskatchewan was performed to ascertain the presence of floral rewards for potential pollinators and to obtain pollen to ovule ratios, an indicator of breeding system. Utilizing light and scanning electron microscopy, differences between the three species were apparent in length of styles, number of placentas, anther and pollen colour, and structure of glandular trichomes on sepals. The occurrence of features unique to each species does not support the concept of D. anglica as a hybrid of the other two species. Flowers of all three species lack nectaries, although clusters of papillate cells that were reminiscent of secretory tissue were observed at the apices of anthers and at the summits of ovaries. Pollen to ovule ratios were low for all species, ranging from 9.0 to 18.7 in D. rotundifolia and D. linearis, respectively, suggesting an autogamous breeding system for each species.Key words: Drosera anglica, Drosera linearis, Drosera rotundifolia, Droseraceae, comparative flower structure, pollen to ovule ratios, breeding system.

A NOTE ON THE INHERITANCE OF POLLEN COLOUR IN SAFFLOWER (CARTHAMUS L.)

Two pollen colours are found in the genus Carthamus, namely, white and yellow. Pollen colour has been used to differentiate between species belonging to different sections particularly tetraploid and hexaploid species. A hypothetical model is suggested to explain the inheritance of this character in interspecific hybrids. It seems that pollen colour is governed by a single locus with three alleles.