Pollination biology from micro-morphological adaptations to community ecology of plant-pollinator interactions

Functional Diversity of Nectary Structure and Nectar Composition in the Genus Fritillaria (Liliaceae)

Fritillaria is a genus consisting of 130 to 140 species of bulbous plants, native to temperate regions of the northern hemisphere. Generally viewed as an insect pollinated genus with the exception of two North American species, Fritillaria gentneri and F. recurva, which are described as hummingbird-pollinated and the Asian species, F. imperialis, described as passerine-pollinated. These pollinator shifts are possibly the result of adaptive changes to the structure and morphology of the nectary, as well as a change in the nectar concentration and composition. A study was conducted in a target group of 56 Fritillaria species, based on the morphology of their nectaries and nectar composition to assess the significance of pollination mode as well as its predisposition for the evolution of bird pollination. All species studied had nectaries located at their tepal base and produced nectar, but their size, shape, color, and composition all varied. Most fritillaries had hexose-rich nectar, in easily accessible and unprotected nectaries. Scanning electron microscope (SEM) analysis revealed that the surface of the nectaries of most Fritillaria species was flat and clearly distinct from that of the surrounding tissues, which might be regarded as an adaptation for insect-pollination. Nectaries of F. imperialis were considerably larger and had dilute nectar without sucrose, which was produced profusely, thereby fulfilling the criteria characteristic of ornithophilous flowers. The copious nectar of presumed hummingbird-pollinated species was rather balanced and of medium sugar concentration. Their large lanceolate nectaries contrasted sharply with the tessellated background of their tepals. These characters might indicate a mixed pollination system that engages both birds and insects. Floral anatomy and microstructure and nectar composition for Fritillaria species in subgenera Korolkowia and Liliorhiza are studied for the first time.

An Unexplored Side of Regeneration Niche: Seed Quantity and Quality Are Determined by the Effect of Temperature on Pollen Performance

In 1977, Peter Grubb introduced the regeneration niche concept, which assumes that a plant species cannot persist if the environmental conditions are only suitable for adult plant growth and survival, but not for seed production, dispersal, germination, and seedling establishment. During the last decade, this concept has received considerable research attention as it helps to better understand community assembly, population dynamics, and plant responses to environmental changes. Yet, in its present form, it focuses too much on the post-fertilization stages of plant sexual reproduction, neglecting the fact that the environment can operate as a constraint at many points in the chain of processes necessary for successful regeneration. In this review, we draw the attention of the plant ecology research community to the pre-fertilization stages of plant sexual reproduction, an almost ignored but important aspect of the regeneration niche, and their potential consequences for successful seed production. Particularly, we focus on how temperature affects pollen performance and determines plant reproduction success by playing an important role in the temporal and spatial variations in seed quality and quantity. We also review the pollen adaptations to temperature stresses at different levels of plant organization and discuss the plasticity of the performance of pollen under changing temperature conditions. The reviewed literature demonstrates that pre-fertilization stages of seed production, particularly the extreme sensitivity of male gametophyte performance to temperature, are the key determinants of a species' regeneration niche. Thus, we suggest that previous views stating that the regeneration niche begins with the production of seeds should be modified to include the preceding stages. Lastly, we identify several gaps in pollen-related studies revealing a framework of opportunities for future research, particularly how these findings could be used in the field of plant biology and ecology.