STUDIES ON THE ECOLOGY OF ALDROVANDA VESICULOSA L. II. ORGANIC SUBSTANCES, PHYSICAL AND BIOTIC FACTORS AND THE GROWTH AND DEVELOPMENT OF A. VESICULOSA

EKOLOGIA POLSKA 35: 591-609 (1987)

Ryszard KAMIŃSKI

Botanic Garden, University of Wrocław, Sienkiewicza 23, PL 50-335 Wrocław, Poland 

ABSTRACT: The influence of accompanying plants and animal plankton on the growth of Aldrovanda was investigated in a natural habitat and in experimental cultures. The influence of humic acids and temperature on the wintering of turions of plants examined and their development in spring were also determined experimentally.

KEY WORDS: Aldrovanda vesiculosa, humic acids, allelopathy, wintering of turions.

1. INTRODUCTION

Autecological investigations of the influence of chemical factors on A. vesiculosa population differentiation (K a m i ń s k i  1987) confirmed also indirectly the significant influence of biotic and physical factors on the growth of Aldrovanda. Organic substances, in the form of humic acids, together with temperature influenced not only the growth of plants examined but also their development. On the basis of reports of other scientists it can be assumed that the influence of accompanying plants is differentiated and depends on their species composition. Thus studies were conducted on natural localities and experimentally in order to explain:

(1) The effect of organic substances on the development of Aldrovanda, i.e., their role in turions' wintering and in the initiation of plant growth.

(2) The allelopathic activity of accompanying plants occurring most frequently with Aldrovanda.

Such information would allow to determine with greater precision the best habitats for this plant and factors which decide first of all about its growth and development. This is of great significance in preservative cultivation of Aldrovanda or when transferring it into substitute habitats. The Botanic Garden in Wrocław conducts also such investigations. The present ones were conducted within the Central Programme of Basic Investigation No. 04.05.

2. METHODS OF INVESTIGATIONS

2.1. GENERAL

Chemical analyses of water and plants, and statistical calculations were made using the general methods specified in part I (K a m i ń s k i   1987).

2.2. SELECTION OF INDIVIDUAL AND GROUP CHARACTERS OF PLANTS AND THEIR MEASUREMENTS

For studies on the influence of accompanying plants on A. vesiculosa, locality VII on Lake Miklaszówek was chosen, where it occurred quite abundantly in different plant associations, i.e., Hydrocharitetum morsus-ranae Langendonck 1935 (microhabitat 1), Caricetum rostratae Rübel 1912 (microhabitat 2), Thelypteridii-Phragmitetum Kuiper 1957 (microhabitat 3). In each microhabitat plant samples were taken from three 1.0 m² experimental areas, each with 30 plants.

Biometrical analysis covered the characters showing the best the ecological constitution of the species, i.e., plant length, mean distance between whorls, length of leaves, number of lateral shoots, number of buds, biomass of 100 plants and biotic potential of the population.

2.3. EXPERIMENTS IN CULTURES IN VITRO

The experimental material consisted of turions of Aldrovanda collected in autumn from the locality at Nowa Kuźnia (experiment 1) and Lake Miklaszówek (experiments 2, 3) and top plant sections 30 mm long from Lake Kruglak (see part I - Kamiński 1987).

E x p e r i m e n t  1. It was conducted between September 20, 1983, and May 26, 1984 to determine the effect of temperature and organic substances on the wintering and development of turions. The organic substance used was an extract of bottom sediments from natural localities of Aldrovanda, in which 90% of carbon is that of humin and fulvic acids, called together humic acids. The experiment was made in two series. In series A turions were placed in aquaria with 10 l of tap water, whereas in series B, about 10000 microg C.l^-1 humic acids were added to tap water. Water reaction was determined as pH 6.5 - 7.

Plants were measured every 20 days when first growth symptoms were noticed, i.e., from January 25, 1984. The range of the experiment was limited because of lack of sufficient material. Two aquaria from each series, each with 10 turions, were placed in: (1) in a cool chamber at 10°C for 4 months and then in a greenhouse at 10-12°C, (2) in a cold greenhouse at 5 - 8°C in the first period of the experiment and in the following 4 months at 10-12°C, (3) in a greenhouse at 12-15°C and in the final stage of the experiment up to 25°C.

E x p e r i m e n t  2. It lasted from October 29, 1984 to January 28, 1985 in order to determine the optimum contents of humin and fulvic acids in the habitat where turions winter. Five Aldrovanda turions were placed in test tubes with tap water containing trace concentrations of these acids - 2000, 4000, 6000, 40000 microg C.l^-1 and kept at 4°C. On January 20, 1985 they were moved to room temperature in order to observe the influence of organic substances on plant development. There were three replicas of the experiment.

E x p e r i m e n t  3. The effect of organic substance on plant growth in the initial development stage was examined between March 20 and April 15, 1985. It confirmed indirectly the results of experiments 1 and 2. Turions coming to the end of dormant period, i.e., showing no signs of development but chosen from experimental material, in which very few turions began to develop, were used in the experiment. Ten turions (in three series) were placed in each test tube with tap water of a pH about 6, containing 0, 2000, 5000, 10000, 50000, 100000, 150000 microg C of organic substance per 1 litre of water. It was conducted at room temperature and at day light.

E x p e r i m e n t  4. The preliminary experiment (A) between August 12 and September 2, 1986 was followed by the basic experiment (B) determining the influence of most frequently occurring plants on the growth of Aldrovanda. Thirty mm plant tops were placed in glass flasks containing mineral-organic medium (analogous to the basic one in experiment 1 - K a m i ń s k i  1987). Each flask contained (in three replicas) 10 A. vesiculosa plants together with: (a) 5 young Hydrocharis morsus-ranae L. plants, (b) young Stratiotes aloides L. plant, (c) 2 germinant rhizomes of Carex sp.

E x p e r i m e n t  5. It was conducted to find out whether accompanying plants or zooplankton in the habitat have a greater influence on the growth of A. vesiculosa. Between June 18 and July 14, 1986, under analogous conditions as in experiment 4 B, into each aquarium with 10 Aldrovanda plants, were added: (a) zooplankton (Daphnia, Cyclops), (b) two germinant rhizomes of Carex sp., (c) plankton and rhizomes together. There were three replicas of the experiment.

3. RESULTS

3.1. FIELD INVESTIGATIONS

In order to determine the influence of accompanying plants on the Aldrovanda vesiculosa growth in field investigations, water had to be analysed in particular microhabitats as well as nutrient content in plants examined, individual and group characters of plants had to be measured. The results are given in Tables 1-3.

Table 1. Characteristics of Aldrovanda vesiculosa microhabitats in Lake Miklaszówek

^a Where: * - *** = F_calculated > F_tabular value of the F Snedecor statistics.

Although water was sampled from a relatively small area (about 300 m along the shore) the contents of inorganic and organic substances varied (Table 1). Statistical differentiation was significant but absolute differences were small. The most significant differentiation concerned the contents of sodium, which were the highest in microhabitat 1 (4.83 mg.l^-1) and the lowest in microhabitat 3 (3.03 mg.l^-1), iron (from 0.39 mg.l^-1 in microhabitat 3 to 0.19 mg.l^-1 in microhabitats 1 and 2), and sulphates (from 25.2 mg.l^-1 in microhabitat 1 to 18.66 mg.l^-1 in microhabitat 2). Contents of nitrates, ammonia, phosphates and humic acids were less significantly differentiated. The nitrates were most abundant in water from microhabitat 2 (0.21 mg.l^-1) and the least abundant in microhabitat 1 (0.15 mg.l^-1). Ammonia nitrogen was the most abundant in microhabitat 2 (1.92 mg.l^-1) and the least in microhabitat 1 (0.51 mg.l^-1), whereas phosphates were the most abundant in microhabitat 3 (0.061 mg.l^-1) and the least in microhabitat 2 (0.033 mg.l^-1). The contents of organic humin and fulvic acids were the highest in water of microhabitat 3 (1658 microg C.l^-1), and the lowest in microhabitat 2 (852 microg C.l^-1). The contents of other inorganic compounds did not differ significantly.

Nutrient contents in plants of microhabitats in Lake Miklaszówek varied (Table 2). Phosphorus, sodium and iron contents were most differentiated, nitrogen and potassium contents were less differentiated and calcium and ash contents were the least differentiated. There were no statistically significant differences in magnesium and sulphur contents. Plants from microhabitat 1 had the highest nitrogen and phosphorus contents, and average ones of other elements. Plants from microhabitat 2 had the smallest contents of nitrogen, phosphorus, calcium and magnesium and the highest ones of potassium, sodium and iron. Plants from microhabitat 3 had the highest contents of calcium and magnesium and the smallest contents of potassium and sulphur. Unfortunately the lack of differentiation of potassium and calcium contents and small differentiation of iron and sulphur in particular microhabitats did not confirm the earlier positive correlations between the contents of these macroelements in water and in plants.

Table 3 shows individual and group characters of A. vesiculosa population in different plant associations from Lake Miklaszówek. Coenopopulations examined from different plant associations differed significantly in shoot length, length of leaves and biomass. There were less significant differences in the mean length of internodes. As in relations between populations the number of buds in whorls was not very significantly differentiated, there were no differences in populations examined in the number of lateral shoots and biotic potential.

'The best specimens of Aldrovanda were found in microhabitat 2, where it belonged to the association Caricetum rostratae Rűbel 1912. The highest percentage in that association had Carex rostrata Stokes ex Withering, Stratiotes aloides, Hydrocharis morsus ranae and Carex pseudocyperus L.

Worse specimens of Aldrovanda were in microhabitat 3, where they belonged to the association Thelypteridii-Phragmitetum Kuiper 1957. Dominant there were Thelypteris thelypteroides (Michaux fil.) Holub, Carex riparia Curbs, C. rostrata, Stratiotes aloides, Hydrocharis morsus ranae and Typha latifolia L. The worst Aldrovanda specimens were in the association Hydrocharitetum morsus-ranae Langendonck 1935. Hydrocharis morsus- ranae formed there almost monospecific patches. However, there was no explicit answer whether the differences in plant growth in particular microhabitats depended more on accompanying plants or on water chemistry and nutrient contents in plants examined. But the additional multiple correlations between plant length and its contents of particular nutrients obtained earlier (K a m i ń s k i   1987) were true in this case.

Table 2. Contents of macroelements in Aldrovanda vesiculosa plants from several microhabitats. For explanation of symbols see Table 1.

Table 3. Characteristics of individual and group characters of Aldrovanda vesiculosa from several microhabitats in Lake Miklaszówek. For explanation of symbols see Table I.

3.2. EXPERIMENT 1

Experiment 1 confirms more precisely what has been known about the influence of organic substance and temperature on wintering of turions, their development and A. vesiculosa growth (Maisonneuve 1859, Schoenefeld 1860, Ashida 1934, 1935, Sculthorpe 1971, Haldi 1974).

Organic substances (humin and fulvic acids) have a double effect on wintering of turions and on plant growth (Table 4). At higher contents of humic acids in water the wintering of turions was worse and plants developed from a smaller number of turions, especially at a higher temperature. Higher contents of humic acids delayed the beginning of the development, but the growth rate of plants was higher, especially at moderate temperature 10-12°C (Fig. 1). The effect of temperature varied according to the development stage of plants. Turions showed small resistance to low temperatures (100% of turions died at temperatures below -10°C) and did not tolerate well those above +12°C. At 20-25°C plants began to develop earlier, their growth rate was higher, but they were subtle, etiolized and poorly.

The plants grew the best at 10-12°C in water with higher contents of humic acids. Worse wintering of turions and a delay in their development was recompensed by quick plant growth, their better condition and greater increment of lateral shoots.

In aquaria with higher humic acid content some turions fell to the bottom when wintering, whereas in spring they floated towards the surface. This was not observed in aquaria with tap water without additional amounts of organic components. This is an important fact as under natural conditions turions are thus protected against freezing and vegetative reproduction of A. vesiculosa is continued.

Fig. 1. The effect of humic acids and temperature on the growth of Aldrovanda vesiculosa in a culture in vitro.

Table 4. Influence of humic acids and temperature on wintering and development of Aldrovanda vesiculosa turions cultured in vitro (experiment I). A - no humic acids added, B - with humic acids added.