The aim of this work is the most detailed investigation of the morphological variability of Nymphaea alba s.l. in the European Russia on the fresh material.
We consider as population all Nymphaea plants from one reservoir or water-stream; we consider as metapopulation a part of plants from current popolation, that are clearly separated spatially. We considered as one plant an isolated group of leaves and flowers.
We investigated 42 metapopulations of Nymphaea from 39 reservoirs and water-streams from 8 regions of European Russia. We registered main characteristics of investigated reservoirs and water-streams and also gathered hydrobiological samples for the detection the organic nutrients contents in the water.
We registered in field 9 qualitative and 6 quantitative macromorphological characters for each of investigated plants. These characters were used as diagnostic in the majority of keys and floras. We investigated 239 plants totally.
The investigation of exine sculpture by light microscope (referred hereafter as LM) doesn’t let us clearly attribute the majority of examined pollen grains to one of the types, that are traditionally distinguished in Nymphaea genus by systematics and palinologists (Komarov, 1937; Kupriyanova, 1976; Dubyhna, 1982; Uotilla, 2001). That’s why we continued the investigation of exine sculpture by scanning electronic microscope (referred hereafter as SEM). We investigated 368 pollen grains by LM and made 272 micrographs by SEM.
Visual analysis of SEM-micrographs showed that exine sculpture isn’t uniform on the whole surface of the pollen grain. The operculum sculpture (distal part of the pollen grain) doesn’t demonstrate discrete variability. We can see verrucae of different size, that become larger to the operculum’s margins. We distinguish five main types of exine sculpture on the proximal part of pollen grains:
The forth type of exine sculpture of proximal part of pollen grain is typical for herbarium specimens of N. tetragona from locus typica and was registred for plants from two populations with typical for N. candida (N. alba subsp. candida) macromorphology. The third of exine sculpture is typical for herbarium specimens of N. candida and N. alba s. str. from locus typica, and also for many populations with combinatorial combinations of macromorphological characters values, that are typical for all three Nymphaea species. Thus, our data don’t support the opinion of L.A. Kupriyanova (1976) about the possibility of clear distinguishing of N. candida and N. alba s. str. on the exine sculpture.
Our investigations have shown, that Nymphaea’s morphology changes essentially after traditional treatments of fresh material. This fact had been fairly noticed by several scientists (Komarov, 1937; Uotilla, 2001; Lisitsyhna, 2003), although quantitative investigations of Nymphaea’s macromorphology after herbarisation on concrete specimen were performed for the first time in the current work. Besides the loss of important diagostic characters (for example, color and shape of the style disc), non-predictable changes of leaf blade’s size and shape take place after herbarisation. The size of leaf blade decreases approx. in 1,5 times. The degree of transversal deformation of the shape doesn’t correlate significantly with the degree of longitudinal deformation (r=0.3; p=0.1). The size of pollen grains essentially changes after SEM-treatment. The values of small equatorial diameter essentially decrease (t-test: p<<0.01), whereas the values of big equatorial diameter don’t change significantly (t-test: p=0.56). That’s why pollen grains on the SEM-micrographs seem more streched, then before SEM-treatment (quartile range of big equatorial diameter to small equatorial diameter ratio 1.0-1.1 before SEM-treatment and 1.2-1.5 after SEM-treatment), these differences are highly significant (t-test: p<<0.01).
Complete investigation of exine sculpture without SEM is impossible. Acetolysis treatment, from the one hand, doesn’t change essentially the size of pollen grains and, from the other hand, doesn’t facilitate vitally the analysis of exine sculpture. Thus, the application of laborious methods of acetolysis for the investigations of Nymphaea’s pollen grains isn’t necessary.
We haven’t revealed any significant dependence of size characteristics of Nymphaea plants on contents of organic nutrients in water, that doesn’t support the common opinion (Komarov, 1937; Heslop-Harrison, 1955; Kupriyanova, 1976; Dubyhna, 1982; Papchenkov, 2003).
We revealed clear separation of the investigated Nymphaea populations according the size of pollen grains: populations with “petty pollen” (big equatorial diameter 32-40 mkm, small — 30-38 mkm) and with “large pollen” (44-52 mkm and 40-50 mkm correspondingly). These size classes corresponds to the size of pollen grains for as N. alba s. str. (“petty pollen ”) and for N. candida (“large pollen ”), published by L.A. Kupriyanova (1976). Only two investigated populations are characterized by intermediate size of pollen grains (41-46 and 36-43 mkm correspondingly). This separation corresponds to plant’s differences only by complex of macromorphological characters (MANOVA: p<0.001), but not by separate characters. This fact lets us work out the hypothesis about the existence of two chromosomal races of Nymphaea on the investigated territory. Our hypotheses agrees with data about straight connection of pollen size with ploidy-level (Poddubnaya-Arnol’di, 1976) and about greatly scattered chromosome numbers that were counted for the European Nymphaea (Heslop-Harrison, 1955; Dubyhna, 1982).
According to our data, one can’t separate the variety of Nymphaea’s morphotypes on the investigated territory into more or less discrete groups. Separate marginal morphotypes of existing morphological continuum can be treated as N. alba s. str. and N. tetragona, and specimen with intermediate morphology between imagined continuum center (typical N. candida) and its marginal morphotypes – as hybrids (N. alba x N. candida = N. x borealis è N. tetragona x N. candida = N. x sundvickii). This approach had been brought to its logical end by V.G. Papchenkov (2003). We should notice, that this conception doesn’t correspond the generally accepted species concept and so can’t be considered fair.
We can make the following conclusions, based of the results of the current work:
We should widen the geography of investigations and estimate ploidy-level of examined plants to clear the taxonomical significance of morphological variance of Nymphaea in the European Russia.
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