Spatiotemporal Distribution of Homogalacturonans and Hemicelluloses in the Placentas, Ovules and Female Gametophytes of Utricularia nelumbifolia during Pollination

Individual architecture and photosynthetic performance of the submerged form of Drosera intermedia Hayne

Drosera intermedia grows in acidic bogs in parts of valleys that are flooded in winter, and that often dry out in summer. It is also described as the sundew of the most heavily hydrated habitats in peatlands, and it is often found in water and even underwater. This sundew is the only one that can tolerate long periods of submersion, and more importantly produces a typical submerged form that can live in such conditions for many years. Submerged habitats are occupied by D. intermedia relatively frequently. The aim of the study was to determine the environmental conditions and architecture of individuals in the submerged form of D. intermedia. The features of the morphological and anatomical structure and chlorophyll a fluorescence of this form that were measured were compared with analogous ones in individuals that occurred in emerged and peatland habitats. The submerged form occurred to a depth of 20 cm. Compared to the other forms, its habitat had the highest pH (4.71-4.92; Me = 4.71), the highest temperature and substrate hydration, and above all, the lowest photosynthetically active radiation (PAR; 20.4-59.4%). This form differed from the other forms in almost all of the features of the plant's architecture. It is particularly noteworthy that it had the largest main axis height among all of the forms, which exceeded 18 cm. The number of living leaves in a rosette was notable (18.1 ± 8.1), while the number of dead leaves was very low (6.9 ± 3.8). The most significant differences were in the shape of its submerged leaves, in which the length of the leaf blade was the lowest of all of the forms (0.493 ± 0.15 mm; p < 0.001) and usually the widest. The stem cross-sectional area was noticeably smaller in the submerged form than in the other forms, the xylem was less developed and collaterally closed vascular bundles occurred. Our analysis of the parameters of chlorophyll fluorescence in vivo revealed that the maximum quantum yield of the primary photochemistry of photosystem II is the highest for the submerged form (Me = 0.681), the same as the maximum quantum yield of the electron transport (Me φE0 = 0.183). The efficiency of energy use per one active reaction center of photosystem II (RC) was the lowest in the submerged form (Me = 2.978), same as the fraction of energy trapped by one active RC (Me = 1.976) and the non-photochemical energy dissipation (DI0/RC; Me = 0.916). The ET0/RC parameter, associated with the efficiency of the energy utilization for electron transport by one RC, in the submerged plant reached the highest value (Me = 0.489). The submerged form of D. intermedia clearly differed from the emerged and peatland forms in its plant architecture. The submerged plants had a thinner leaf blade and less developed xylem than the other forms, however, their stems were much longer. The relatively high photosynthetic efficiency of the submerged forms suggests that most of the trapped energy is utilized to drive photosynthesis with a minimum energy loss, which may be a mechanism to compensate for the relatively small size of the leaf blade.

Syncytia in Utricularia: Origin and Structure

In animals and plants, multinucleate cells (syncytia and coenocytes) are essential in ontogeny and reproduction. Fuso-morphogenesis is the formation of multinucleated syncytia by cell-cell fusion, but coenocytes are formed as a result of mitosis without cytokinesis. However, in plants, coenocytes are more widespread than true syncytia. Except for articulated laticifers, most plant syncytia have a trophic function. Here, we summarize the results of histological, histochemical, and ultrastructural analyses of syncytia in the Utricularia species from the Lentibulariaceae family. Utricularia syncytia, known only from a few species, are heterokaryotic because the syncytium possesses nuclei from two different sources: cells of maternal sporophytic nutritive tissue (placenta) and endosperm haustorium. Thus, syncytium contains both maternal and paternal genetic material. In species from section Utricularia, syncytia are highly active structures (with hypertrophied nuclei, cell wall ingrowths, and extensive cytoskeleton) that exist only during embryo development. They serve as an example of evolutionary unique trophic structures in the plant kingdom.

Immunocytochemical Analysis of Bifid Trichomes in Aldrovanda vesiculosa L. Traps

The two-armed bifids (bifid trichomes) occur on the external (abaxial) trap surface, petiole, and stem of the aquatic carnivorous plant Aldrovanda vesiculosa (Droseracee). These trichomes play the role of mucilage trichomes. This study aimed to fill the gap in the literature concerning the immunocytochemistry of the bifid trichomes and compare them with digestive trichomes. Light and electron microscopy was used to show the trichome structure. Fluorescence microscopy revealed the localization of carbohydrate epitopes associated with the major cell wall polysaccharides and glycoproteins. The stalk cells and the basal cells of the trichomes were differentiated as endodermal cells. Cell wall ingrowths occurred in all cell types of the bifid trichomes. Trichome cells differed in the composition of their cell walls. The cell walls of the head cells and stalk cells were enriched with arabinogalactan proteins (AGPs); however, they were generally poor in both low- and highly-esterified homogalacturonans (HGs). The cell walls in the trichome cells were rich in hemicelluloses: xyloglucan and galactoxyloglucan. The cell wall ingrowths in the basal cells were significantly enriched with hemicelluloses. The presence of endodermal cells and transfer cells supports the idea that bifid trichomes actively transport solutes, which are polysaccharide in nature. The presence of AGPs (which are considered plant signaling molecules) in the cell walls in these trichome cells indicates the active and important role of these trichomes in plant function. Future research should focus on the question of how the molecular architecture of trap cell walls changes in cells during trap development and prey capture and digestion in A. vesiculosa and other carnivorous plants.

Editorial for Special Issue: Research on Plant Cell Wall Biology

Plant cells are surrounded by extracellular matrixes [...].