Victorin’s gentian COSEWIC assessment and status report: chapter 6
Biology
General
Victorin’s gentian is an annual or biennial that flowers from mid-July to mid-September. The flowers exhibit periodic “sleep movements” in which they remain closed on dark days and when submerged by tides (Rousseau, 1932) and open when conditions are more favourable, such as bright sunny days. Pollination is by various insects. Fruiting begins in August and continues until October, and the seeds are dispersed by water.
Reproduction
No signs of clonal reproduction have been observed. Reproduction thus appears to be by seed production. The observation of various insects on the flowers (Figure 6) suggests that they are pollinators. Because the anthers are no more than two-thirds the length of the pistil and because the flower is always erect, insects are needed to pollinate the plants. The nectar secreted at the base of the stamens attracts primarily bumble bees (Bremus terricola, etc.), which sometimes become trapped for the night (Rousseau, 1932; Marie-Victorin, 1995). Bouillé (1996) reported that the periodic sleep movements resulting in flower closure could hinder pollination by insects because they limited their access to the flowers.
Figure 6. Pollinators in a Victorin’s gentian flower.
Survival
Victorin’s gentian appears to be intolerant of competition and is unable to survive in areas of dense herbaceous cover. Thus, part of the Saint-Augustin-de-Desmaures population can vary considerably because it occurs in denuded areas in the upper littoral zone or surrounding area. These areas may, over several years, become relatively densely vegetated, thereby becoming unfavourable to Victorin’s gentian.
No predators have been observed, but Bouillé (1996) reported a lepidopteran larva inside an ovary of a specimen from Beaumont. She indicated that the seeds of the flower were very small and dark compared to other seeds from the same individual, suggesting the possible impact of predation by insects on reproduction. She also reported that the periodic closure of the flowers could hinder pollination by insects because it limits their access to the floral parts.
ATV traffic in the littoral zone is the primary cause of plant mortality.
Physiology
Victorin’s gentian populations downstream from Quebec City flower and fruit earlier than populations upstream. This phenomenon is strange, because the climate is generally harsher and colder downstream from Quebec City. No other information is available on the physiology of this species.
Movements/dispersal
Caldwell and Crow (1992) studied the dynamics of estuarine environments and found three factors that contribute significantly to plant community structure. The duration of flooding by tides is the most important factor, followed by the presence of life forms and physical disturbances caused by ice boulders. Plants having the most success in such fluctuating environments are annuals, such as Victorin’s gentian, and highly rhizomatous perennials. Rhizome proliferation allows these plants to maintain an equilibrium between sedimentation and constant erosion and to store nutrient reserves in order to emerge and grow quickly. The seeds of annuals, such as Victorin’s gentian, are produced in large quantities and find protection in marsh surface microrelief. In addition, ice boulders stir up sediments and even vegetation cover, which can be carried over large distances and redeposited along the stream, thereby contributing to the dispersal of these species.
Victorin’s gentian seeds are heavier than water, but can float due to the papillae covering them, which act as floats. They are carried offshore by tidal and wave action. When the papillae are imbibed, the seeds sink with the slightest movement of the water (Rousseau, 1932; Marie Victorin, 1995). According to Rousseau (1932), this property contributes little to the spread of the species. Locally, hydrochory (water dispersal) is most likely, but it is plausible that the seeds are dispersed over large distances by “epiornithochory” (Brouillet et al., 1996), whereby seeds are transported in mud stuck to birds’ feet.
Behaviour/adaptability
According to the data from the Montreal Botanical Garden, Victorin’s gentian was cultivated for at least two years. There have been at least eight attempts to germinate seeds, but despite the various cultural methods used, virtually all of the attempts failed.
Teusher (1941) reported that the following treatment was successfully applied to Victorin’s gentian. Seeds that were to be sown in the spring were first placed in the refrigerator at 35°F for approximately three months (seeds can also be sown in the fall and overwintered in a cold frame). The plantings were relatively dense in a 5-inch clay pot, and when the first 2 or 3 leaves appeared, they were thinned, keeping only 10 plants, which is much better than transplanting seedlings. The pots were kept moist by placing them in a saucer of water throughout the entire growing season. Vigorous rosettes formed the first year. After overwintering in a cold frame, they flowered abundantly the following summer.
In 1996, seeds were sent to the environmental cytology and phytogenetic resources laboratory (Laval University – Quebec Department of Environment and Wildlife) for a chromosome count. Gervais and Trahan (1996) succeeded in germinating only the seeds from Pointe Platon. The protocol used is as follows: the seeds are rinsed with 70% ethyl alcohol for three minutes, then rinsed with distilled water and placed on a piece of moist filter paper in a petri dish. They are left for two weeks at ambient temperature and then placed in the refrigerator for one month (Coursol, 1998).
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